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He M, Zhou X, Wang X. Glycosylation: mechanisms, biological functions and clinical implications. Signal Transduct Target Ther 2024; 9:194. [PMID: 39098853 DOI: 10.1038/s41392-024-01886-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2023] [Revised: 05/25/2024] [Accepted: 06/07/2024] [Indexed: 08/06/2024] Open
Abstract
Protein post-translational modification (PTM) is a covalent process that occurs in proteins during or after translation through the addition or removal of one or more functional groups, and has a profound effect on protein function. Glycosylation is one of the most common PTMs, in which polysaccharides are transferred to specific amino acid residues in proteins by glycosyltransferases. A growing body of evidence suggests that glycosylation is essential for the unfolding of various functional activities in organisms, such as playing a key role in the regulation of protein function, cell adhesion and immune escape. Aberrant glycosylation is also closely associated with the development of various diseases. Abnormal glycosylation patterns are closely linked to the emergence of various health conditions, including cancer, inflammation, autoimmune disorders, and several other diseases. However, the underlying composition and structure of the glycosylated residues have not been determined. It is imperative to fully understand the internal structure and differential expression of glycosylation, and to incorporate advanced detection technologies to keep the knowledge advancing. Investigations on the clinical applications of glycosylation focused on sensitive and promising biomarkers, development of more effective small molecule targeted drugs and emerging vaccines. These studies provide a new area for novel therapeutic strategies based on glycosylation.
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Affiliation(s)
- Mengyuan He
- Department of Hematology, Shandong Provincial Hospital, Shandong University, Jinan, Shandong, 250021, China
| | - Xiangxiang Zhou
- Department of Hematology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong, 250021, China.
- National Clinical Research Center for Hematologic Diseases, the First Affiliated Hospital of Soochow University, Suzhou, 251006, China.
| | - Xin Wang
- Department of Hematology, Shandong Provincial Hospital, Shandong University, Jinan, Shandong, 250021, China.
- Department of Hematology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong, 250021, China.
- National Clinical Research Center for Hematologic Diseases, the First Affiliated Hospital of Soochow University, Suzhou, 251006, China.
- Taishan Scholars Program of Shandong Province, Jinan, Shandong, 250021, China.
- Branch of National Clinical Research Center for Hematologic Diseases, Jinan, Shandong, 250021, China.
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2
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Wei SJ, Xiong Q, Yao H, He QM, Yu PL. Is systemic lupus erythematosus linked to Immunoglobulin G4 Autoantibodies? Hum Immunol 2024; 85:110826. [PMID: 38954949 DOI: 10.1016/j.humimm.2024.110826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2023] [Revised: 04/26/2024] [Accepted: 05/21/2024] [Indexed: 07/04/2024]
Abstract
Systemic lupus erythematosus (SLE) is a systemic autoimmune disorder characterized by a hyperactive immune system with multiple abnormalities in B-cell proliferation, antibody production, T-cell regulation, and immune complex (IC) formation. In humans, Immunoglobulin (Ig) G is found in four subclasses. IgG1-IgG4, which are distinguished by both structural and biological differences. Fab-arm Exchange (FAE), specific biases in the IgG4 response repertoire, and a decreased capacity to induce effector functions mediated by interactions in the fragment crystallizable (Fc) region are just a few of the distinctive characteristics of IgG4. The recent finding of the presence of double-stranded DNA (dsDNA) and antinuclear antibody (ANA)-IgG4 has raised attention to this IgG subclass and its possible role in SLE. IgG4 was previously believed to just have anti-inflammatory effects by inhibiting immune responses, but recent studies have shown that these antibodies can also play a role in the onset and development of some clinical disorders. To consider the clinical effects of IgG4 presence, it is necessary to discuss its characteristics, which could underlie the potential role it can play in SLE. Therefore, this study aimed to comprehensively review the role of IgG4 in SLE to elucidate the collective incidence of high IgG4 levels reported in some SLE patients.
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Affiliation(s)
- Shu-Jun Wei
- Sichuan Police College, Longtouguan Road, Jiangyang District, Luzhou City, Sichuan Province, China
| | - Qian Xiong
- Chongqing Key Laboratory of Development and Utilization of Genuine Medicinal Materials in Three Gorges Reservoir Area, Chongqing Three Gorges Medical College, China
| | - Huan Yao
- Chengdu University of Traditional Chinese Medicine, Chengdu, 610072, Sichuan, China; Sichuan Provincial Engineering Research Center of Innovative Re-development of Famous Classical Formulas, Pengzhou 611930, China
| | - Qing-Man He
- Affiliated Hospital of Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Peng-Long Yu
- Chongqing Key Laboratory of Development and Utilization of Genuine Medicinal Materials in Three Gorges Reservoir Area, Chongqing Three Gorges Medical College, China.
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Koneczny I, Macher S, Hutterer M, Seifert-Held T, Berger-Sieczkowski E, Blaabjerg M, Breu M, Dreyhaupt J, Dutra LA, Erdler M, Fae I, Fischer G, Frommlet F, Heidbreder A, Högl B, Klose V, Klotz S, Liendl H, Nissen MS, Rahimi J, Reinecke R, Ricken G, Stefani A, Süße M, Teive HAG, Weis S, Berger T, Sabater L, Gaig C, Lewerenz J, Höftberger R. HLA dependency and possible clinical relevance of intrathecally synthesized anti-IgLON5 IgG4 in anti-IgLON5 disease. Front Immunol 2024; 15:1376456. [PMID: 38827736 PMCID: PMC11141242 DOI: 10.3389/fimmu.2024.1376456] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Accepted: 04/15/2024] [Indexed: 06/04/2024] Open
Abstract
Background Anti-IgLON5 disease is a rare chronic autoimmune disorder characterized by IgLON5 autoantibodies predominantly of the IgG4 subclass. Distinct pathogenic effects were described for anti-IgLON5 IgG1 and IgG4, however, with uncertain clinical relevance. Methods IgLON5-specific IgG1-4 levels were measured in 46 sera and 20 cerebrospinal fluid (CSF) samples from 13 HLA-subtyped anti-IgLON5 disease patients (six females, seven males) using flow cytometry. Intervals between two consecutive serum or CSF samplings (31 and 10 intervals, respectively) were categorized with regard to the immunomodulatory treatment active at the end of the interval, changes of anti-IgLON5 IgG1 and IgG4 levels, and disease severity. Intrathecal anti-IgLON5 IgG4 synthesis (IS) was assessed using a quantitative method. Results The median age at onset was 66 years (range: 54-75), disease duration 10 years (range: 15-156 months), and follow-up 25 months (range: 0-83). IgLON5-specific IgG4 predominance was observed in 38 of 46 (83%) serum and 11 of 20 (55%) CSF samples. Anti-IgLON5 IgG4 levels prior clinical improvement in CSF but not serum were significantly lower than in those prior stable/progressive disease. Compared to IgLON5 IgG4 levels in serum, CSF levels in HLA-DRB1*10:01 carriers were significantly higher than in non-carriers. Indeed, IgLON5-specific IgG4 IS was demonstrated not only in four of five HLA-DRB1*10:01 carriers but also in one non-carrier. Immunotherapy was associated with decreased anti-IgGLON5 IgG serum levels. In CSF, lower anti-IgLON5 IgG was associated with immunosuppressive treatments used in combination, that is, corticosteroids and/or azathioprine plus intravenous immunoglobulins or rituximab. Conclusion Our findings might indicate that CSF IgLON5-specific IgG4 is frequently produced intrathecally, especially in HLA-DRB1*10:01 carriers. Intrathecally produced IgG4 may be clinically relevant. While many immunotherapies reduce serum IgLON5 IgG levels, more intense immunotherapies induce clinical improvement and may be able to target intrathecally produced anti-IgLON5 IgG. Further studies need to confirm whether anti-IgLON5 IgG4 IS is a suitable prognostic and predictive biomarker in anti-IgLON5 disease.
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Affiliation(s)
- Inga Koneczny
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Stefan Macher
- Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Markus Hutterer
- Department of Neurology, Johannes Kepler University Linz, Linz, Austria
- Department of Neurology with Stroke Unit and Acute Geriatrics, Saint John of God Hospital Linz, Linz, Austria
| | - Thomas Seifert-Held
- Department of Neurology, Medical University of Graz, Graz, Austria
- Department of Neurology, Landeskrankenhaus (LKH) Murtal, Standort Knittelfeld, Austria
| | | | - Morten Blaabjerg
- Department of Neurology, Odense University Hospital, Odense, Denmark
| | - Markus Breu
- Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Jens Dreyhaupt
- Institute for Epidemiology and Medical Biometry, Ulm University, Ulm, Germany
| | | | - Marcus Erdler
- Department of Neurology and Karl Landsteiner Institute for Neuroimmunological and Neurodegenerative Disorders Klinik Donaustadt, Vienna, Austria
| | - Ingrid Fae
- Department of Blood Group Serology and Transfusion Medicine, Medical University of Vienna, Vienna, Austria
| | - Gottfried Fischer
- Department of Blood Group Serology and Transfusion Medicine, Medical University of Vienna, Vienna, Austria
| | - Florian Frommlet
- Center of Medical Data Science, Medical University of Vienna, Vienna, Austria
| | - Anna Heidbreder
- Department of Neurology, Johannes Kepler University Linz, Linz, Austria
- Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria
| | - Birgit Högl
- Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria
| | - Veronika Klose
- Department of Neurology, University Hospital Ulm, Ulm, Germany
| | - Sigrid Klotz
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Herburg Liendl
- Department of Neurology, Landeskrankenhaus (LKH) Murtal, Standort Knittelfeld, Austria
| | - Mette S. Nissen
- Department of Neurology, Odense University Hospital, Odense, Denmark
| | - Jasmin Rahimi
- Department of Neurology and Karl Landsteiner Institute for Neuroimmunological and Neurodegenerative Disorders Klinik Donaustadt, Vienna, Austria
| | - Raphael Reinecke
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Gerda Ricken
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Ambra Stefani
- Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria
| | - Marie Süße
- Department of Neurology, University Medicine Greifswald, Greifswald, Germany
| | - Helio A. G. Teive
- Movement Disorders Unit, Neurology Service, Internal Medicine Department, Hospital de Clínicas, Federal University of Paraná, Curitiba, PR, Brazil
| | - Serge Weis
- Division of Neuropathology, Department of Pathology and Molecular Pathology, Johannes Kepler University Linz, Linz, Austria
| | - Thomas Berger
- Department of Neurology, Medical University of Vienna, Vienna, Austria
- Comprehensive Center for Clinical Neurosciences and Mental Health, Medical University of Vienna, Vienna, Austria
| | - Lidia Sabater
- Fundació de recerca clínic-Institut d’Investigacions Biomèdiques August Pi i Sunyer (FCRB-IDIBAPS), Caixa Research Institute (CRI), Universitat de Barcelona, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
| | - Carles Gaig
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
- Department of Neurology, Hospital Clínic, Barcelona, Spain
| | - Jan Lewerenz
- Department of Neurology, University Hospital Ulm, Ulm, Germany
| | - Romana Höftberger
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
- Comprehensive Center for Clinical Neurosciences and Mental Health, Medical University of Vienna, Vienna, Austria
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Herbst R, Huijbers MG, Oury J, Burden SJ. Building, Breaking, and Repairing Neuromuscular Synapses. Cold Spring Harb Perspect Biol 2024; 16:a041490. [PMID: 38697654 PMCID: PMC11065174 DOI: 10.1101/cshperspect.a041490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/05/2024]
Abstract
A coordinated and complex interplay of signals between motor neurons, skeletal muscle cells, and Schwann cells controls the formation and maintenance of neuromuscular synapses. Deficits in the signaling pathway for building synapses, caused by mutations in critical genes or autoantibodies against key proteins, are responsible for several neuromuscular diseases, which cause muscle weakness and fatigue. Here, we describe the role that four key genes, Agrin, Lrp4, MuSK, and Dok7, play in this signaling pathway, how an understanding of their mechanisms of action has led to an understanding of several neuromuscular diseases, and how this knowledge has contributed to emerging therapies for treating neuromuscular diseases.
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Affiliation(s)
- Ruth Herbst
- Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, 1090 Vienna, Austria
| | - Maartje G Huijbers
- Department of Human Genetics, Leiden University Medical Centre LUMC, 2300 RC Leiden, the Netherlands
- Department of Neurology, Leiden University Medical Centre LUMC, 2333 ZA Leiden, the Netherlands
| | - Julien Oury
- Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, NYU School of Medicine, New York, New York 10016, USA
| | - Steven J Burden
- Neurology Department, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA
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5
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Koneczny I, Mané-Damas M, Zong S, De Haas S, Huda S, van Kruining D, Damoiseaux J, De Rosa A, Maestri M, Guida M, Molenaar P, Van Damme P, Fichtenbaum A, Perkmann T, De Baets M, Lazaridis K, Zouvelou V, Tzartos S, Ricciardi R, Losen M, Martinez-Martinez P. A retrospective multicenter study on clinical and serological parameters in patients with MuSK myasthenia gravis with and without general immunosuppression. Front Immunol 2024; 15:1325171. [PMID: 38715598 PMCID: PMC11074957 DOI: 10.3389/fimmu.2024.1325171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Accepted: 03/25/2024] [Indexed: 06/19/2024] Open
Abstract
Introduction Muscle-specific kinase (MuSK)- myasthenia gravis (MG) is caused by pathogenic autoantibodies against MuSK that correlate with disease severity and are predominantly of the IgG4 subclass. The first-line treatment for MuSK-MG is general immunosuppression with corticosteroids, but the effect of treatment on IgG4 and MuSK IgG4 levels has not been studied. Methods We analyzed the clinical data and sera from 52 MuSK-MG patients (45 female, 7 male, median age 49 (range 17-79) years) from Italy, the Netherlands, Greece and Belgium, and 43 AChR-MG patients (22 female, 21 male, median age 63 (range 2-82) years) from Italy, receiving different types of immunosuppression, and sera from 46 age- and sex-matched non-disease controls (with no diagnosed diseases, 38 female, 8 male, median age 51.5 (range 20-68) years) from the Netherlands. We analyzed the disease severity (assessed by MGFA or QMG score), and measured concentrations of MuSK IgG4, MuSK IgG, total IgG4 and total IgG in the sera by ELISA, RIA and nephelometry. Results We observed that MuSK-MG patients showed a robust clinical improvement and reduction of MuSK IgG after therapy, and that MuSK IgG4 concentrations, but not total IgG4 concentrations, correlated with clinical severity. MuSK IgG and MuSK IgG4 concentrations were reduced after immunosuppression in 4/5 individuals with before-after data, but data from non-linked patient samples showed no difference. Total serum IgG4 levels were within the normal range, with IgG4 levels above threshold (1.35g/L) in 1/52 MuSK-MG, 2/43 AChR-MG patients and 1/45 non-disease controls. MuSK-MG patients improved within the first four years after disease onset, but no further clinical improvement or reduction of MuSK IgG4 were observed four years later, and only 14/52 (26.92%) patients in total, of which 13 (93.3%) received general immunosuppression, reached clinical remission. Discussion We conclude that MuSK-MG patients improve clinically with general immunosuppression but may require further treatment to reach remission. Longitudinal testing of individual patients may be clinically more useful than single measurements of MuSK IgG4. No significant differences in the serum IgG4 concentrations and IgG4/IgG ratio between AChR- and MuSK-MG patients were found during follow-up. Further studies with larger patient and control cohorts are necessary to validate the findings.
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Affiliation(s)
- Inga Koneczny
- Research Group Neuroinflammation and Autoimmunity, Department of Psychiatry and Neuropsychology, School for Mental Health and Neuroscience, Maastricht University, Maastricht, Netherlands
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Marina Mané-Damas
- Research Group Neuroinflammation and Autoimmunity, Department of Psychiatry and Neuropsychology, School for Mental Health and Neuroscience, Maastricht University, Maastricht, Netherlands
| | - Shenghua Zong
- Research Group Neuroinflammation and Autoimmunity, Department of Psychiatry and Neuropsychology, School for Mental Health and Neuroscience, Maastricht University, Maastricht, Netherlands
| | - Sander De Haas
- Research Group Neuroinflammation and Autoimmunity, Department of Psychiatry and Neuropsychology, School for Mental Health and Neuroscience, Maastricht University, Maastricht, Netherlands
| | - Saif Huda
- Neurosciences Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
- Department of Neurology, Walton Centre National Health Service (NHS) Foundation Trust, Liverpool, United Kingdom
| | - Daan van Kruining
- Department of Psychiatry and Neuropsychology, Maastricht University, Maastricht, Netherlands
| | - Jan Damoiseaux
- Central Diagnostic Laboratory, Maastricht University Medical Center, Maastricht, Netherlands
| | - Anna De Rosa
- Department of Clinical and Experimental Medicine, Neurology Unit, University of Pisa, Pisa, Italy
| | - Michelangelo Maestri
- Department of Clinical and Experimental Medicine, Neurology Unit, University of Pisa, Pisa, Italy
| | - Melania Guida
- Department of Clinical and Experimental Medicine, Neurology Unit, University of Pisa, Pisa, Italy
| | - Peter Molenaar
- Research Group Neuroinflammation and Autoimmunity, Department of Psychiatry and Neuropsychology, School for Mental Health and Neuroscience, Maastricht University, Maastricht, Netherlands
| | - Philip Van Damme
- Neurology Department, University Hospital, Leuven, Belgium
- Department of Neurosciences, Center for Brain & Disease Research, VIB, Leuven, Belgium
| | - Andreas Fichtenbaum
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
- Department of Laboratory Medicine, Medical University of Vienna, Vienna, Austria
| | - Thomas Perkmann
- Department of Laboratory Medicine, Medical University of Vienna, Vienna, Austria
| | - Marc De Baets
- Research Group Neuroinflammation and Autoimmunity, Department of Psychiatry and Neuropsychology, School for Mental Health and Neuroscience, Maastricht University, Maastricht, Netherlands
| | | | - Vasiliki Zouvelou
- 1stNeurology Department, National and Kapodistrian University of Athens, Athens, Greece
| | - Socrates Tzartos
- Department of Immunology, Hellenic Pasteur Institute, Athens, Greece
- Department of Neuroimmunology, Tzartos NeuroDiagnostics, Athens, Greece
| | - Roberta Ricciardi
- Department of Clinical and Experimental Medicine, Neurology Unit, University of Pisa, Pisa, Italy
- Cardio Thoracic and Vascular Surgery Department, University of Pisa, Pisa, Italy
| | - Mario Losen
- Research Group Neuroinflammation and Autoimmunity, Department of Psychiatry and Neuropsychology, School for Mental Health and Neuroscience, Maastricht University, Maastricht, Netherlands
| | - Pilar Martinez-Martinez
- Research Group Neuroinflammation and Autoimmunity, Department of Psychiatry and Neuropsychology, School for Mental Health and Neuroscience, Maastricht University, Maastricht, Netherlands
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Ünlü S, Sánchez Navarro BG, Cakan E, Berchtold D, Meleka Hanna R, Vural S, Vural A, Meisel A, Fichtner ML. Exploring the depths of IgG4: insights into autoimmunity and novel treatments. Front Immunol 2024; 15:1346671. [PMID: 38698867 PMCID: PMC11063302 DOI: 10.3389/fimmu.2024.1346671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Accepted: 02/29/2024] [Indexed: 05/05/2024] Open
Abstract
IgG4 subclass antibodies represent the rarest subclass of IgG antibodies, comprising only 3-5% of antibodies circulating in the bloodstream. These antibodies possess unique structural features, notably their ability to undergo a process known as fragment-antigen binding (Fab)-arm exchange, wherein they exchange half-molecules with other IgG4 antibodies. Functionally, IgG4 antibodies primarily block and exert immunomodulatory effects, particularly in the context of IgE isotype-mediated hypersensitivity reactions. In the context of disease, IgG4 antibodies are prominently observed in various autoimmune diseases combined under the term IgG4 autoimmune diseases (IgG4-AID). These diseases include myasthenia gravis (MG) with autoantibodies against muscle-specific tyrosine kinase (MuSK), nodo-paranodopathies with autoantibodies against paranodal and nodal proteins, pemphigus vulgaris and foliaceus with antibodies against desmoglein and encephalitis with antibodies against LGI1/CASPR2. Additionally, IgG4 antibodies are a prominent feature in the rare entity of IgG4 related disease (IgG4-RD). Intriguingly, both IgG4-AID and IgG4-RD demonstrate a remarkable responsiveness to anti-CD20-mediated B cell depletion therapy (BCDT), suggesting shared underlying immunopathologies. This review aims to provide a comprehensive exploration of B cells, antibody subclasses, and their general properties before examining the distinctive characteristics of IgG4 subclass antibodies in the context of health, IgG4-AID and IgG4-RD. Furthermore, we will examine potential therapeutic strategies for these conditions, with a special focus on leveraging insights gained from anti-CD20-mediated BCDT. Through this analysis, we aim to enhance our understanding of the pathogenesis of IgG4-mediated diseases and identify promising possibilities for targeted therapeutic intervention.
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Affiliation(s)
- Selen Ünlü
- Koç University Research Center for Translational Medicine (KUTTAM), İstanbul, Türkiye
- Koç University School of Medicine, Istanbul, Türkiye
| | - Blanca G. Sánchez Navarro
- Department of Neurology with Experimental Neurology, Integrated Myasthenia Gravis Center, Neuroscience Clinical Research Center, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Elif Cakan
- Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology and Harvard University, Cambridge, MA, United States
| | - Daniel Berchtold
- Department of Neurology with Experimental Neurology, Integrated Myasthenia Gravis Center, Neuroscience Clinical Research Center, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Rafael Meleka Hanna
- Department of Neurology with Experimental Neurology, Integrated Myasthenia Gravis Center, Neuroscience Clinical Research Center, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Secil Vural
- Koç University Research Center for Translational Medicine (KUTTAM), İstanbul, Türkiye
- Department of Dermatology and Venereology, Koç University School of Medicine, İstanbul, Türkiye
| | - Atay Vural
- Koç University Research Center for Translational Medicine (KUTTAM), İstanbul, Türkiye
- Department of Neurology, Koç University School of Medicine, İstanbul, Türkiye
| | - Andreas Meisel
- Department of Neurology with Experimental Neurology, Integrated Myasthenia Gravis Center, Neuroscience Clinical Research Center, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Miriam L. Fichtner
- Koç University Research Center for Translational Medicine (KUTTAM), İstanbul, Türkiye
- Department of Neurology with Experimental Neurology, Integrated Myasthenia Gravis Center, Neuroscience Clinical Research Center, Charité Universitätsmedizin Berlin, Berlin, Germany
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7
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Dziadkowiak E, Baczyńska D, Waliszewska-Prosół M. MuSK Myasthenia Gravis-Potential Pathomechanisms and Treatment Directed against Specific Targets. Cells 2024; 13:556. [PMID: 38534400 DOI: 10.3390/cells13060556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Revised: 03/17/2024] [Accepted: 03/19/2024] [Indexed: 03/28/2024] Open
Abstract
Myasthenia gravis (MG) is an autoimmune disease in which autoantibodies target structures within the neuromuscular junction, affecting neuromuscular transmission. Muscle-specific tyrosine kinase receptor-associated MG (MuSK-MG) is a rare, often more severe, subtype of the disease with different pathogenesis and specific clinical features. It is characterized by a more severe clinical course, more frequent complications, and often inadequate response to treatment. Here, we review the current state of knowledge about potential pathomechanisms of the MuSK-MG and their therapeutic implications as well as ongoing research in this field, with reference to key points of immune-mediated processes involved in the background of myasthenia gravis.
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Affiliation(s)
- Edyta Dziadkowiak
- Department of Neurology, Wroclaw Medical University, Borowska 213, 50-556 Wroclaw, Poland
| | - Dagmara Baczyńska
- Department of Molecular and Cellular Biology, Wroclaw Medical University, Borowska 211A, 50-556 Wroclaw, Poland
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8
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Motta RV, Culver EL. IgG4 autoantibodies and autoantigens in the context of IgG4-autoimmune disease and IgG4-related disease. Front Immunol 2024; 15:1272084. [PMID: 38433835 PMCID: PMC10904653 DOI: 10.3389/fimmu.2024.1272084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Accepted: 01/25/2024] [Indexed: 03/05/2024] Open
Abstract
Immunoglobulins are an essential part of the humoral immune response. IgG4 antibodies are the least prevalent subclass and have unique structural and functional properties. In this review, we discuss IgG4 class switch and B cell production. We review the importance of IgG4 antibodies in the context of allergic responses, helminth infections and malignancy. We discuss their anti-inflammatory and tolerogenic effects in allergen-specific immunotherapy, and ability to evade the immune system in parasitic infection and tumour cells. We then focus on the role of IgG4 autoantibodies and autoantigens in IgG4-autoimmune diseases and IgG4-related disease, highlighting important parallels and differences between them. In IgG4-autoimmune diseases, pathogenesis is based on a direct role of IgG4 antibodies binding to self-antigens and disturbing homeostasis. In IgG4-related disease, where affected organs are infiltrated with IgG4-expressing plasma cells, IgG4 antibodies may also directly target a number of self-antigens or be overexpressed as an epiphenomenon of the disease. These antigen-driven processes require critical T and B cell interaction. Lastly, we explore the current gaps in our knowledge and how these may be addressed.
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Affiliation(s)
- Rodrigo V. Motta
- Translational Gastroenterology and Liver Unit, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Emma L. Culver
- Translational Gastroenterology and Liver Unit, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
- Department of Gastroenterology and Hepatology, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom
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9
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Iorio R. Myasthenia gravis: the changing treatment landscape in the era of molecular therapies. Nat Rev Neurol 2024; 20:84-98. [PMID: 38191918 DOI: 10.1038/s41582-023-00916-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/06/2023] [Indexed: 01/10/2024]
Abstract
Myasthenia gravis (MG) is an autoimmune disorder that affects the neuromuscular junction, leading to muscle weakness and fatigue. MG is caused by antibodies against the acetylcholine receptor (AChR), the muscle-specific kinase (MuSK) or other AChR-related proteins that are expressed in the postsynaptic muscle membrane. The standard therapeutic approach for MG has relied on acetylcholinesterase inhibitors, corticosteroids and immunosuppressants, which have shown good efficacy in improving MG-related symptoms in most people with the disease; however, these therapies can carry a considerable burden of long-term adverse effects. Moreover, up to 15% of individuals with MG exhibit limited or no response to these standard therapies. The emergence of molecular therapies, including monoclonal antibodies, B cell-depleting agents and chimeric antigen receptor T cell-based therapies, has the potential to revolutionize the MG treatment landscape. This Review provides a comprehensive overview of the progress achieved in molecular therapies for MG associated with AChR antibodies and MuSK antibodies, elucidating both the challenges and the opportunities these therapies present to the field. The latest developments in MG treatment are described, exploring the potential for personalized medicine approaches.
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Affiliation(s)
- Raffaele Iorio
- Department of Neuroscience, Università Cattolica del Sacro Cuore, Rome, Italy.
- Neurology Unit, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy.
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10
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Liu Y, Wang Y, Hu M, Xu S, Jiang F, Han Y, Liu Z. The role of IgG4 in systemic lupus erythematosus: Implications for pathogenesis and therapy. J Biochem Mol Toxicol 2024; 38:e23626. [PMID: 38229315 DOI: 10.1002/jbt.23626] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Revised: 11/16/2023] [Accepted: 12/14/2023] [Indexed: 01/18/2024]
Abstract
Immunoglobulin (Ig) G4 has a distinctive nature, and its involvement in autoimmune disorders is a subject of ongoing debate and uncertainty. A growing body of evidence indicates that IgG4 may play a pathogenic role in the development of systemic lupus erythematosus (SLE). The IgG4 autoantibodies have the capability to bind autoantigens in a competitive manner with other Ig classes, thereby forming immune complexes (ICs) that are noninflammatory in nature. This is due to the low affinity of IgG4 for both the Fc receptors and the C1 complement molecule, which results in a diminished inflammatory response in individuals with SLE. The present study aims to elucidate the significance of IgG4 in SLE. The present discourse pertains to the nascent and suggested modalities through which IgG4 might participate in the pathogenesis of SLE and the potential ramifications for therapeutic interventions in SLE.
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Affiliation(s)
- Yanyan Liu
- Department of Blood Transfusion, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Yingjian Wang
- Department of Blood Transfusion, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Mengsi Hu
- Department of Blood Transfusion, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Shoufang Xu
- Department of Blood Transfusion, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Feiyu Jiang
- Department of Blood Transfusion, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Yetao Han
- Department of Blood Transfusion, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Zhiwei Liu
- Department of Blood Transfusion, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
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11
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Tannemaat MR, Huijbers MG, Verschuuren JJGM. Myasthenia gravis-Pathophysiology, diagnosis, and treatment. HANDBOOK OF CLINICAL NEUROLOGY 2024; 200:283-305. [PMID: 38494283 DOI: 10.1016/b978-0-12-823912-4.00026-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/19/2024]
Abstract
Myasthenia gravis (MG) is an autoimmune disease characterized by dysfunction of the neuromuscular junction resulting in skeletal muscle weakness. It is equally prevalent in males and females, but debuts at a younger age in females and at an older age in males. Ptosis, diplopia, facial bulbar weakness, and limb weakness are the most common symptoms. MG can be classified based on the presence of serum autoantibodies. Acetylcholine receptor (AChR) antibodies are found in 80%-85% of patients, muscle-specific kinase (MuSK) antibodies in 5%-8%, and <1% may have low-density lipoprotein receptor-related protein 4 (Lrp4) antibodies. Approximately 10% of patients are seronegative for antibodies binding the known disease-related antigens. In patients with AChR MG, 10%-20% have a thymoma, which is usually detected at the onset of the disease. Important differences between clinical presentation, treatment responsiveness, and disease mechanisms have been observed between these different serologic MG classes. Besides the typical clinical features and serologic testing, the diagnosis can be established with additional tests, including repetitive nerve stimulation, single fiber EMG, and the ice pack test. Treatment options for MG consist of symptomatic treatment (such as pyridostigmine), immunosuppressive treatment, or thymectomy. Despite the treatment with symptomatic drugs, steroid-sparing immunosuppressants, intravenous immunoglobulins, plasmapheresis, and thymectomy, a large proportion of patients remain chronically dependent on corticosteroids (CS). In the past decade, the number of treatment options for MG has considerably increased. Advances in the understanding of the pathophysiology have led to new treatment options targeting B or T cells, the complement cascade, the neonatal Fc receptor or cytokines. In the future, these new treatments are likely to reduce the chronic use of CS, diminish side effects, and decrease the number of patients with refractory disease.
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Affiliation(s)
- Martijn R Tannemaat
- Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands
| | - Maartje G Huijbers
- Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands; Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
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12
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Hayashi M. Pathophysiology of Childhood-Onset Myasthenia: Abnormalities of Neuromuscular Junction and Autoimmunity and Its Background. PATHOPHYSIOLOGY 2023; 30:599-617. [PMID: 38133144 PMCID: PMC10747330 DOI: 10.3390/pathophysiology30040043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2023] [Revised: 11/28/2023] [Accepted: 11/29/2023] [Indexed: 12/23/2023] Open
Abstract
The pathophysiology of myasthenia gravis (MG) has been largely elucidated over the past half century, and treatment methods have advanced. However, the number of cases of childhood-onset MG is smaller than that of adult MG, and the treatment of childhood-onset MG has continued to be based on research in the adult field. Research on pathophysiology and treatment methods that account for the unique growth and development of children is now desired. According to an epidemiological survey conducted by the Ministry of Health, Labour and Welfare of Japan, the number of patients with MG by age of onset in Japan is high in early childhood. In recent years, MG has been reported from many countries around the world, but the pattern of the number of patients by age of onset differs between East Asia and Western Europe, confirming that the Japanese pattern is common in East Asia. Furthermore, there are racial differences in autoimmune MG and congenital myasthenic syndromes according to immunogenetic background, and their pathophysiology and relationships are gradually becoming clear. In addition, treatment options are also recognized in different regions of the world. In this review article, I will present recent findings focusing on the differences in pathophysiology.
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Affiliation(s)
- Masatoshi Hayashi
- Department of Pediatrics, Uwajima City Hospital, Uwajima 798-8510, Japan
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13
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Rispens T, Huijbers MG. The unique properties of IgG4 and its roles in health and disease. Nat Rev Immunol 2023; 23:763-778. [PMID: 37095254 PMCID: PMC10123589 DOI: 10.1038/s41577-023-00871-z] [Citation(s) in RCA: 36] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/20/2023] [Indexed: 04/26/2023]
Abstract
IgG4 is the least abundant subclass of IgG in human serum and has unique functional features. IgG4 is largely unable to activate antibody-dependent immune effector responses and, furthermore, undergoes Fab (fragment antigen binding)-arm exchange, rendering it bispecific for antigen binding and functionally monovalent. These properties of IgG4 have a blocking effect, either on the immune response or on the target protein of IgG4. In this Review, we discuss the unique structural characteristics of IgG4 and how these contribute to its roles in health and disease. We highlight how, depending on the setting, IgG4 responses can be beneficial (for example, in responses to allergens or parasites) or detrimental (for example, in autoimmune diseases, in antitumour responses and in anti-biologic responses). The development of novel models for studying IgG4 (patho)physiology and understanding how IgG4 responses are regulated could offer insights into novel treatment strategies for these IgG4-associated disease settings.
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Affiliation(s)
- Theo Rispens
- Department of Immunopathology, Sanquin Research and Landsteiner Laboratory, Amsterdam, The Netherlands
| | - Maartje G Huijbers
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands.
- Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands.
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14
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Cao M, Liu WW, Maxwell S, Huda S, Webster R, Evoli A, Beeson D, Cossins JA, Vincent A. IgG1-3 MuSK Antibodies Inhibit AChR Cluster Formation, Restored by SHP2 Inhibitor, Despite Normal MuSK, DOK7, or AChR Subunit Phosphorylation. NEUROLOGY(R) NEUROIMMUNOLOGY & NEUROINFLAMMATION 2023; 10:e200147. [PMID: 37582613 PMCID: PMC10427144 DOI: 10.1212/nxi.0000000000200147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 06/07/2023] [Indexed: 08/17/2023]
Abstract
BACKGROUND AND OBJECTIVES Up to 50% of patients with myasthenia gravis (MG) without acetylcholine receptor antibodies (AChR-Abs) have antibodies to muscle-specific kinase (MuSK). Most MuSK antibodies (MuSK-Abs) are IgG4 and inhibit agrin-induced MuSK phosphorylation, leading to impaired clustering of AChRs at the developing or mature neuromuscular junction. However, IgG1-3 MuSK-Abs also exist in MuSK-MG patients, and their potential mechanisms have not been explored fully. METHODS C2C12 myotubes were exposed to MuSK-MG plasma IgG1-3 or IgG4, with or without purified agrin. MuSK, Downstream of Kinase 7 (DOK7), and βAChR were immunoprecipitated and their phosphorylation levels identified by immunoblotting. Agrin and agrin-independent AChR clusters were measured by immunofluorescence and AChR numbers by binding of 125I-α-bungarotoxin. Transcriptomic analysis was performed on treated myotubes. RESULTS IgG1-3 MuSK-Abs impaired AChR clustering without inhibiting agrin-induced MuSK phosphorylation. Moreover, the well-established pathway initiated by MuSK through DOK7, resulting in βAChR phosphorylation, was not impaired by MuSK-IgG1-3 and was agrin-independent. Nevertheless, the AChR clusters did not form, and both the number of AChR microclusters that precede full cluster formation and the myotube surface AChRs were reduced. Transcriptomic analysis did not throw light on the pathways involved. However, the SHP2 inhibitor, NSC-87877, increased the number of microclusters and led to fully formed AChR clusters. DISCUSSION MuSK-IgG1-3 is pathogenic but seems to act through a noncanonical pathway. Further studies should throw light on the mechanisms involved at the neuromuscular junction.
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Affiliation(s)
- Michelangelo Cao
- From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy
| | - Wei-Wei Liu
- From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy
| | - Susan Maxwell
- From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy
| | - Saif Huda
- From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy
| | - Richard Webster
- From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy
| | - Amelia Evoli
- From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy
| | - David Beeson
- From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy
| | - Judith A Cossins
- From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy
| | - Angela Vincent
- From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy.
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15
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Berger-Sieczkowski E, Endmayr V, Haider C, Ricken G, Jauk P, Macher S, Pirker W, Högl B, Heidbreder A, Schnider P, Bradley-Zechmeister E, Mariotto S, Koneczny I, Reinecke R, Kasprian G, Weber C, Bergmann M, Milenkovic I, Berger T, Gaig C, Sabater L, Graus F, Gelpi E, Höftberger R. Analysis of inflammatory markers and tau deposits in an autopsy series of nine patients with anti-IgLON5 disease. Acta Neuropathol 2023; 146:631-645. [PMID: 37646790 PMCID: PMC10499680 DOI: 10.1007/s00401-023-02625-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 08/11/2023] [Accepted: 08/13/2023] [Indexed: 09/01/2023]
Abstract
Anti-IgLON5 disease is a rare neurological, probably autoimmune, disorder associated in many cases with a specific tauopathy. Only a few post-mortem neuropathological studies have been reported so far. Little is known about the pathogenic mechanisms that result in neurodegeneration. We investigated the neuropathology of anti-IgLON5 disease and characterized cellular and humoral inflammation. We included nine cases (six of them previously published). Median age of patients was 71 years (53-82 years), the median disease duration was 6 years (0.5-13 years), and the female to male ratio was 5:4. Six cases with a median disease duration of 9 years presented a prominent tauopathy. Five of them had a classical anti-IgLON5-related brainstem tauopathy and another presented a prominent neuronal and glial 4-repeat tauopathy, consistent with progressive supranuclear palsy (PSP). Three cases with short disease duration (median 1.25 years) only showed a primary age-related neurofibrillary pathology. Inflammatory infiltrates of T and B cells were mild to moderate and did not significantly differ between anti-IgLON5 disease cases with or without tauopathy. In contrast, we found an extensive neuropil deposition of IgG4 in the tegmentum of the brainstem, olivary nucleus, and cerebellar cortex that was most prominent in two patients with short disease duration without the typical IgLON5-related tauopathy. The IgG4 deposits were particularly prominent in the cerebellar cortex and in these regions accompanied by mild IgG1 deposits. Activated complement deposition (C9neo) was absent. Our study indicates that IgLON5-related tau pathology occurs in later disease stages and may also present a PSP-phenotype with exclusively 4-repeat neuronal and glial tau pathology. The prominent deposition of anti-IgLON5 IgG4 at predilection sites for tau pathology suggests that anti-IgLON5 antibodies precede the tau pathology. Early start of immunotherapy might prevent irreversible neuronal damage and progression of the disease, at least in a subgroup of patients.
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Affiliation(s)
- Evelyn Berger-Sieczkowski
- Department of Neurology, Medical University of Vienna, Vienna, Austria
- Comprehensive Center for Clinical Neurosciences and Mental Health, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
| | - Verena Endmayr
- Comprehensive Center for Clinical Neurosciences and Mental Health, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
| | - Carmen Haider
- Comprehensive Center for Clinical Neurosciences and Mental Health, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
| | - Gerda Ricken
- Comprehensive Center for Clinical Neurosciences and Mental Health, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
| | - Philipp Jauk
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
| | - Stefan Macher
- Department of Neurology, Medical University of Vienna, Vienna, Austria
- Comprehensive Center for Clinical Neurosciences and Mental Health, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
| | - Walter Pirker
- Department of Neurology, Klinik Ottakring, Vienna, Austria
| | - Birgit Högl
- Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria
| | - Anna Heidbreder
- Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria
| | - Peter Schnider
- Department of Neurology, Landesklinikum Wiener Neustadt, Wiener Neustadt, Austria
| | | | - Sara Mariotto
- Neurology Unit, Department of Neurosciences, Biomedicine, and Movement Sciences, University of Verona, Verona, Italy
| | - Inga Koneczny
- Comprehensive Center for Clinical Neurosciences and Mental Health, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
| | - Raphael Reinecke
- Comprehensive Center for Clinical Neurosciences and Mental Health, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
| | - Gregor Kasprian
- Comprehensive Center for Clinical Neurosciences and Mental Health, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
- Division of Neuroradiology and Musculoskeletal Radiology, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Austria
| | - Corinna Weber
- Department of Neurology, Medical University of Vienna, Vienna, Austria
- Comprehensive Center for Clinical Neurosciences and Mental Health, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
| | - Melanie Bergmann
- Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria
| | - Ivan Milenkovic
- Department of Neurology, Medical University of Vienna, Vienna, Austria
- Comprehensive Center for Clinical Neurosciences and Mental Health, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
| | - Thomas Berger
- Department of Neurology, Medical University of Vienna, Vienna, Austria
- Comprehensive Center for Clinical Neurosciences and Mental Health, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria
| | - Carles Gaig
- Neurology Service, Hospital Clínic of Barcelona, Barcelona, Spain
- Neuroimmunology Laboratory-Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | - Lidia Sabater
- Neuroimmunology Laboratory-Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | - Francesc Graus
- Neuroimmunology Laboratory-Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | - Ellen Gelpi
- Comprehensive Center for Clinical Neurosciences and Mental Health, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria.
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria.
- Neurological Tissue Bank of the Biobanc-Hospital Clinic-IDIBAPS, Barcelona, Spain.
| | - Romana Höftberger
- Comprehensive Center for Clinical Neurosciences and Mental Health, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria.
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria.
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16
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Oh S, Mao X, Manfredo-Vieira S, Lee J, Patel D, Choi EJ, Alvarado A, Cottman-Thomas E, Maseda D, Tsao PY, Ellebrecht CT, Khella SL, Richman DP, O'Connor KC, Herzberg U, Binder GK, Milone MC, Basu S, Payne AS. Precision targeting of autoantigen-specific B cells in muscle-specific tyrosine kinase myasthenia gravis with chimeric autoantibody receptor T cells. Nat Biotechnol 2023; 41:1229-1238. [PMID: 36658341 PMCID: PMC10354218 DOI: 10.1038/s41587-022-01637-z] [Citation(s) in RCA: 38] [Impact Index Per Article: 38.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Accepted: 12/08/2022] [Indexed: 01/21/2023]
Abstract
Muscle-specific tyrosine kinase myasthenia gravis (MuSK MG) is an autoimmune disease that causes life-threatening muscle weakness due to anti-MuSK autoantibodies that disrupt neuromuscular junction signaling. To avoid chronic immunosuppression from current therapies, we engineered T cells to express a MuSK chimeric autoantibody receptor with CD137-CD3ζ signaling domains (MuSK-CAART) for precision targeting of B cells expressing anti-MuSK autoantibodies. MuSK-CAART demonstrated similar efficacy as anti-CD19 chimeric antigen receptor T cells for depletion of anti-MuSK B cells and retained cytolytic activity in the presence of soluble anti-MuSK antibodies. In an experimental autoimmune MG mouse model, MuSK-CAART reduced anti-MuSK IgG without decreasing B cells or total IgG levels, reflecting MuSK-specific B cell depletion. Specific off-target interactions of MuSK-CAART were not identified in vivo, in primary human cell screens or by high-throughput human membrane proteome array. These data contributed to an investigational new drug application and phase 1 clinical study design for MuSK-CAART for the treatment of MuSK autoantibody-positive MG.
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Affiliation(s)
- Sangwook Oh
- Department of Dermatology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Xuming Mao
- Department of Dermatology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Silvio Manfredo-Vieira
- Department of Dermatology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | | | | | - Eun Jung Choi
- Department of Dermatology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | | | | | - Damian Maseda
- Department of Dermatology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Patricia Y Tsao
- Department of Dermatology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Christoph T Ellebrecht
- Department of Dermatology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Sami L Khella
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - David P Richman
- Department of Neurology, University of California - Davis, Davis, CA, USA
| | - Kevin C O'Connor
- Departments of Neurology and Immunobiology, Yale School of Medicine, New Haven, CT, USA
| | | | | | - Michael C Milone
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | | | - Aimee S Payne
- Department of Dermatology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
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17
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Vakrakou AG, Karachaliou E, Chroni E, Zouvelou V, Tzanetakos D, Salakou S, Papadopoulou M, Tzartos S, Voumvourakis K, Kilidireas C, Giannopoulos S, Tsivgoulis G, Tzartos J. Immunotherapies in MuSK-positive Myasthenia Gravis; an IgG4 antibody-mediated disease. Front Immunol 2023; 14:1212757. [PMID: 37564637 PMCID: PMC10410455 DOI: 10.3389/fimmu.2023.1212757] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Accepted: 07/05/2023] [Indexed: 08/12/2023] Open
Abstract
Muscle-specific kinase (MuSK) Myasthenia Gravis (MG) represents a prototypical antibody-mediated disease characterized by predominantly focal muscle weakness (neck, facial, and bulbar muscles) and fatigability. The pathogenic antibodies mostly belong to the immunoglobulin subclass (Ig)G4, a feature which attributes them their specific properties and pathogenic profile. On the other hand, acetylcholine receptor (AChR) MG, the most prevalent form of MG, is characterized by immunoglobulin (Ig)G1 and IgG3 antibodies to the AChR. IgG4 class autoantibodies are impotent to fix complement and only weakly bind Fc-receptors expressed on immune cells and exert their pathogenicity via interfering with the interaction between their targets and binding partners (e.g. between MuSK and LRP4). Cardinal differences between AChR and MuSK-MG are the thymus involvement (not prominent in MuSK-MG), the distinct HLA alleles, and core immunopathological patterns of pathology in neuromuscular junction, structure, and function. In MuSK-MG, classical treatment options are usually less effective (e.g. IVIG) with the need for prolonged and high doses of steroids difficult to be tapered to control symptoms. Exceptional clinical response to plasmapheresis and rituximab has been particularly observed in these patients. Reduction of antibody titers follows the clinical efficacy of anti-CD20 therapies, a feature implying the role of short-lived plasma cells (SLPB) in autoantibody production. Novel therapeutic monoclonal against B cells at different stages of their maturation (like plasmablasts), or against molecules involved in B cell activation, represent promising therapeutic targets. A revolution in autoantibody-mediated diseases is pharmacological interference with the neonatal Fc receptor, leading to a rapid reduction of circulating IgGs (including autoantibodies), an approach already suitable for AChR-MG and promising for MuSK-MG. New precision medicine approaches involve Chimeric autoantibody receptor T (CAAR-T) cells that are engineered to target antigen-specific B cells in MuSK-MG and represent a milestone in the development of targeted immunotherapies. This review aims to provide a detailed update on the pathomechanisms involved in MuSK-MG (cellular and humoral aberrations), fostering the understanding of the latest indications regarding the efficacy of different treatment strategies.
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Affiliation(s)
- Aigli G. Vakrakou
- First Department of Neurology, Medical School, National and Kapodistrian University of Athens, Athens, Greece
| | - Eleni Karachaliou
- Second Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Elisabeth Chroni
- Department of Neurology, School of Medicine, University of Patras, Patras, Greece
| | - Vasiliki Zouvelou
- First Department of Neurology, Medical School, National and Kapodistrian University of Athens, Athens, Greece
| | - Dimitrios Tzanetakos
- Second Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Stavroula Salakou
- Second Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Marianna Papadopoulou
- Second Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece
- Department of Physiotherapy, University of West Attica, Athens, Greece
| | - Socrates Tzartos
- Tzartos NeuroDiagnostics, Athens, Greece
- Department of Neurobiology, Hellenic Pasteur Institute, Athens, Greece
- Department of Pharmacy, University of Patras, Patras, Greece
| | - Konstantinos Voumvourakis
- Second Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Constantinos Kilidireas
- First Department of Neurology, Medical School, National and Kapodistrian University of Athens, Athens, Greece
- Department of Neurology, Henry Dunant Hospital Center, Athens, Greece
| | - Sotirios Giannopoulos
- Second Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Georgios Tsivgoulis
- Second Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece
- Department of Neurology, The University of Tennessee Health Science Center, Memphis, TN, United States
| | - John Tzartos
- Second Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece
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Lim JL, Augustinus R, Plomp JJ, Roya-Kouchaki K, Vergoossen DLE, Fillié-Grijpma Y, Struijk J, Thomas R, Salvatori D, Steyaert C, Blanchetot C, Vanhauwaert R, Silence K, van der Maarel SM, Verschuuren JJ, Huijbers MG. Development and characterization of agonistic antibodies targeting the Ig-like 1 domain of MuSK. Sci Rep 2023; 13:7478. [PMID: 37156800 PMCID: PMC10167245 DOI: 10.1038/s41598-023-32641-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Accepted: 03/30/2023] [Indexed: 05/10/2023] Open
Abstract
Muscle-specific kinase (MuSK) is crucial for acetylcholine receptor (AChR) clustering and thereby neuromuscular junction (NMJ) function. NMJ dysfunction is a hallmark of several neuromuscular diseases, including MuSK myasthenia gravis. Aiming to restore NMJ function, we generated several agonist monoclonal antibodies targeting the MuSK Ig-like 1 domain. These activated MuSK and induced AChR clustering in cultured myotubes. The most potent agonists partially rescued myasthenic effects of MuSK myasthenia gravis patient IgG autoantibodies in vitro. In an IgG4 passive transfer MuSK myasthenia model in NOD/SCID mice, MuSK agonists caused accelerated weight loss and no rescue of myasthenic features. The MuSK Ig-like 1 domain agonists unexpectedly caused sudden death in a large proportion of male C57BL/6 mice (but not female or NOD/SCID mice), likely caused by a urologic syndrome. In conclusion, these agonists rescued pathogenic effects in myasthenia models in vitro, but not in vivo. The sudden death in male mice of one of the tested mouse strains revealed an unexpected and unexplained role for MuSK outside skeletal muscle, thereby hampering further (pre-) clinical development of these clones. Future research should investigate whether other Ig-like 1 domain MuSK antibodies, binding different epitopes, do hold a safe therapeutic promise.
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Affiliation(s)
- Jamie L Lim
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, The Netherlands
| | - Roy Augustinus
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, The Netherlands
| | - Jaap J Plomp
- Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands
| | - Kasra Roya-Kouchaki
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, The Netherlands
| | - Dana L E Vergoossen
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, The Netherlands
| | - Yvonne Fillié-Grijpma
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, The Netherlands
| | - Josephine Struijk
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, The Netherlands
| | - Rachel Thomas
- Department PDC-Pathologie, Leiden University Medical Center, Leiden, The Netherlands
| | - Daniela Salvatori
- Veterinary Faculty, Department Clinical Sciences, Universiteit Utrecht, Utrecht, The Netherlands
| | | | | | | | | | - Silvère M van der Maarel
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, The Netherlands
| | - Jan J Verschuuren
- Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands
| | - Maartje G Huijbers
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, The Netherlands.
- Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands.
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19
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Prömer J, Barresi C, Herbst R. From phosphorylation to phenotype - Recent key findings on kinase regulation, downstream signaling and disease surrounding the receptor tyrosine kinase MuSK. Cell Signal 2023; 104:110584. [PMID: 36608736 DOI: 10.1016/j.cellsig.2022.110584] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Revised: 12/16/2022] [Accepted: 12/31/2022] [Indexed: 01/04/2023]
Abstract
Muscle-specific kinase (MuSK) is the key regulator of neuromuscular junction development. MuSK acts via several distinct pathways and is responsible for pre- and postsynaptic differentiation. MuSK is unique among receptor tyrosine kinases as activation and signaling are particularly tightly regulated. Initiation of kinase activity requires Agrin, a heparan sulphate proteoglycan derived from motor neurons, the low-density lipoprotein receptor-related protein-4 (Lrp4) and the intracellular adaptor protein Dok-7. There is a great knowledge gap between MuSK activation and downstream signaling. Recent studies using omics techniques have addressed this knowledge gap, thereby greatly contributing to a better understanding of MuSK signaling. Impaired MuSK signaling causes severe muscle weakness as described in congenital myasthenic syndromes or myasthenia gravis but the underlying pathophysiology is often unclear. This review focuses on recent advances in deciphering MuSK activation and downstream signaling. We further highlight latest break-throughs in understanding and treatment of MuSK-related disorders and discuss the role of MuSK in non-muscle tissue.
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Affiliation(s)
- Jakob Prömer
- Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna, Austria
| | - Cinzia Barresi
- Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna, Austria
| | - Ruth Herbst
- Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna, Austria.
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Behbehani R. Ocular Myasthenia Gravis: A Current Overview. Eye Brain 2023; 15:1-13. [PMID: 36778719 PMCID: PMC9911903 DOI: 10.2147/eb.s389629] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Accepted: 01/24/2023] [Indexed: 02/05/2023] Open
Abstract
Ocular myasthenia gravis (OMG) is a neuromuscular disease characterized by autoantibody production against post-synaptic proteins in the neuromuscular junction. The pathophysiological auto-immune mechanisms of myasthenia are diverse, and this is governed primarily by the type of autoantibody production. The diagnosis of OMG relies mainly on clinical assessment, the use of serological antibody assays for acetylcholine receptors (AchR), muscle-specific tyrosine kinase (MusK), and low-density lipoprotein 4 (LPR4). Other autoantibodies against post-synaptic proteins, such as cortactin and agrin, have been detected; however, their diagnostic value and pathogenic effect are not yet clearly defined. Clinical tests such as the ice test and electrophysiologic tests, particularly single-fiber electromyography, have a valuable role in diagnosis. The treatment of OMG is primarily through cholinesterase inhibitors (pyridostigmine), and steroids are frequently required in cases of ophthalmoplegia. Other immunosuppressive therapies include antimetabolites (azathioprine, mycophenolate mofetil, methotrexate) and biological agents such as B-cell depleting agents (Rituximab) and complement inhibitors (eculizumab). Evidence is scarce on the effect of immunosuppressive therapy on altering the natural course of OMG. Clinicians must be vigilant of a myasthenic syndrome in patients using immune-check inhibitors. Reliable and consistent biomarkers are required to assess disease severity and response to therapy to optimize the management of OMG. The purpose of this review is to summarize the current trends and the latest developments in diagnosing and treating OMG.
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Affiliation(s)
- Raed Behbehani
- Neuroophthalmology Unit, Ibn Sina Hospital, Kuwait City, Kuwait,Correspondence: Raed Behbehani, Ibn Sina Hospital, P.O Box 1180, Tel +965 2224 2999, Fax +965 2249 2406, Email
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21
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Quinn L, Nguyen B, Menard-Katcher C, Spencer L. IgG4+ cells are increased in the gastrointestinal tissue of pediatric patients with active eosinophilic gastritis and duodenitis and decrease in remission. Dig Liver Dis 2023; 55:53-60. [PMID: 36064648 PMCID: PMC9885790 DOI: 10.1016/j.dld.2022.08.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Revised: 08/11/2022] [Accepted: 08/14/2022] [Indexed: 02/05/2023]
Abstract
BACKGROUND Recent studies have shown that IgG4 is increased in the esophageal tissue of eosinophilic esophagitis patients, including the presence of IgG4+ plasma cells. AIMS Our aim was to determine whether IgG4 is elevated in the gastric or duodenal tissue of pediatric patients with eosinophilic gastritis or duodenitis (EoG or EoD). METHODS This was a retrospective single center study. Pediatric patients were characterized as having active EoG, EoD, or as controls based on clinical symptoms and histologic features. Immunohistochemistry for IgG4 was performed in gastric and duodenal tissue, and peak IgG4+ cells were compared between groups and after treatment. RESULTS The frequency of IgG4+ cells was significantly higher in patients with EoG and EoD compared to controls in the stomach [EoG 6.5 cells/hpf (3.6-10.9), control 0 cells/hpf (0-0.7), p<0.0001] and duodenum [EoD 7.5 cells/hpf (2.8-37), control 0.5 cells/hpf (0.3-1.3), p<0.001)] respectively, and positively correlated with eosinophil counts (stomach: r 0.74, p<0.0001; duodenum: r 0.57, p<0.0001). The amount of tissue IgG4 was significantly decreased in patients in remission but not in persistently active disease. CONCLUSIONS These data suggest local tissue production of IgG4 may be a universal feature of eosinophilic gastrointestinal disease that tracks with disease activity.
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Affiliation(s)
- Laura Quinn
- Department of Pediatrics, Section of Pediatric Gastroenterology, Hepatology & Nutrition, Gastrointestinal Eosinophilic Diseases Program, and the Digestive Health Institute; Children's Hospital Colorado and University of Colorado School of Medicine, Aurora, CO, USA.
| | - Brian Nguyen
- Department of Pathology, Children's Hospital Colorado, University of Colorado School of Medicine, Aurora, CO, USA
| | - Calies Menard-Katcher
- Department of Pediatrics, Section of Pediatric Gastroenterology, Hepatology & Nutrition, Gastrointestinal Eosinophilic Diseases Program, and the Digestive Health Institute; Children's Hospital Colorado and University of Colorado School of Medicine, Aurora, CO, USA
| | - Lisa Spencer
- Department of Pediatrics, Section of Pediatric Gastroenterology, Hepatology & Nutrition, Gastrointestinal Eosinophilic Diseases Program, and the Digestive Health Institute; Children's Hospital Colorado and University of Colorado School of Medicine, Aurora, CO, USA
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22
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Harsini S, Rezaei N. Autoimmune diseases. Clin Immunol 2023. [DOI: 10.1016/b978-0-12-818006-8.00001-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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23
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Sánchez-Tejerina D, Sotoca J, Llaurado A, López-Diego V, Juntas-Morales R, Salvado M. New Targeted Agents in Myasthenia Gravis and Future Therapeutic Strategies. J Clin Med 2022; 11:6394. [PMID: 36362622 PMCID: PMC9658349 DOI: 10.3390/jcm11216394] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Revised: 10/25/2022] [Accepted: 10/26/2022] [Indexed: 08/22/2023] Open
Abstract
Myasthenia gravis (MG) is a chronic autoimmune disease for which multiple immunomodulatory therapies are available. Nevertheless, MG has a significant impact on patient quality of life. In recent years, experts' main efforts have focused on optimizing treatment strategies, since disease burden is considerably affected by their safety and tolerability profiles, especially in patients with refractory phenotypes. This article aims to offer neurologists caring for MG patients an overview of the most innovative targeted drugs specifically designed for this disease and summarizes the recent literature and more recent evidence on agents targeting B cells and plasmablasts, complement inhibitors, and neonatal fragment crystallizable receptor (FcRn) antagonists. Positive clinical trial results have been reported, and other studies are ongoing. Finally, we briefly discuss how the introduction of these novel targeted immunological therapies in a changing management paradigm would affect not only clinical outcomes, disease burden, safety, and tolerability, but also health spending in a condition that is increasingly managed based on a patient-centred model.
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Affiliation(s)
| | | | | | | | | | - Maria Salvado
- Clinic of Neuromuscular Disorders and Rare Diseases, Neurology Department, Hospital Universitari Vall d’Hebron, Vall d’Hebron Research Institute, European Reference Network for Neuromuscular and Rare Diseases EURO-NMD, 08035 Barcelona, Spain
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24
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Payet CA, You A, Fayet OM, Dragin N, Berrih-Aknin S, Le Panse R. Myasthenia Gravis: An Acquired Interferonopathy? Cells 2022; 11:cells11071218. [PMID: 35406782 PMCID: PMC8997999 DOI: 10.3390/cells11071218] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 03/23/2022] [Accepted: 03/28/2022] [Indexed: 01/12/2023] Open
Abstract
Myasthenia gravis (MG) is a rare autoimmune disease mediated by antibodies against components of the neuromuscular junction, particularly the acetylcholine receptor (AChR). The thymus plays a primary role in AChR-MG patients. In early-onset AChR-MG and thymoma-associated MG, an interferon type I (IFN-I) signature is clearly detected in the thymus. The origin of this chronic IFN-I expression in the thymus is not yet defined. IFN-I subtypes are normally produced in response to viral infection. However, genetic diseases called interferonopathies are associated with an aberrant chronic production of IFN-I defined as sterile inflammation. Some systemic autoimmune diseases also share common features with interferonopathies. This review aims to analyze the pathogenic role of IFN-I in these diseases as compared to AChR-MG in order to determine if AChR-MG could be an acquired interferonopathy.
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Affiliation(s)
- Cloé A Payet
- Sorbonne University, INSERM, Institute of Myology, Center of Research in Myology, F-75013 Paris, France
| | - Axel You
- Sorbonne University, INSERM, Institute of Myology, Center of Research in Myology, F-75013 Paris, France
| | - Odessa-Maud Fayet
- Sorbonne University, INSERM, Institute of Myology, Center of Research in Myology, F-75013 Paris, France
| | - Nadine Dragin
- Sorbonne University, INSERM, Institute of Myology, Center of Research in Myology, F-75013 Paris, France
| | - Sonia Berrih-Aknin
- Sorbonne University, INSERM, Institute of Myology, Center of Research in Myology, F-75013 Paris, France
| | - Rozen Le Panse
- Sorbonne University, INSERM, Institute of Myology, Center of Research in Myology, F-75013 Paris, France
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25
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Dalakas MC. Autoimmune Neurological Disorders with IgG4 Antibodies: a Distinct Disease Spectrum with Unique IgG4 Functions Responding to Anti-B Cell Therapies. Neurotherapeutics 2022; 19:741-752. [PMID: 35290608 PMCID: PMC9294117 DOI: 10.1007/s13311-022-01210-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/18/2022] [Indexed: 11/26/2022] Open
Abstract
The main IgG4 antibody-mediated neurological disorders (IgG4-ND) include MuSK myasthenia; CIDP with nodal/paranodal antibodies to Neurofascin-155, contactin-1/caspr-1, or pan-neurofascins; anti-LGI1 and CASPR2-associated limbic encephalitis, Morvan syndrome, or neuromyotonia; and several cases of the anti-IgLON5 and anti-DPPX-spectrum CNS diseases. The paper is centered on the clinical spectrum of IgG4-ND and their immunopathogenesis highlighting the unique functional effects of the IgG4 subclass compared to IgG1-3 antibody subclasses. The IgG4 antibodies exert pathogenic effects on their targeted antigens by blocking enzymatic activity or disrupting protein-protein interactions affecting signal transduction pathways, but not by activating complement, binding to inhibitory FcγRIIb receptor or engaging in cross-linking of the targeted antigen with immune complex formation as the IgG1-IgG3 antibody subclasses do. IgG4 can even inhibit the classical complement pathway by affecting the affinity of IgG1-2 subclasses to C1q binding. Because the IgG4 antibodies do not trigger inflammatory processes or complement-mediated immune responses, the conventional anti-inflammatory therapies, especially with IVIg, immunosuppressants, and plasmapheresis, are ineffective or not sufficiently effective in inducing long-term remissions. In contrast, aiming at the activated plasmablasts connected with IgG4 antibody production is a meaningful therapeutic target in IgG4-ND. Indeed, data from large series of patients with MuSK myasthenia, CIDP with nodal/paranodal antibodies, and anti-LGI1 and CASPR2-associated syndromes indicate that B cell depletion therapy with rituximab exerts long-lasting clinical remissions by targeting memory B cells and IgG4-producing CD20-positive short-lived plasma cells. Because IgG4 antibody titers seem reduced in remissions and increased in exacerbation, they may serve as potential biomarkers of treatment response supporting further the pathogenic role of self-reacting B cells. Controlled trials are needed in IgG4-ND not only with rituximab but also with the other anti-B cell agents that target CD19/20, especially those like obexelimab and obinutuzumab, that concurrently activate the inhibitory FcγRIIb receptors which have low binding affinity to IgG4, exerting a more prolonged anti-B cell action affecting also antigen presentation and cytotoxic T cells. Antibody therapies targeting FcRn, testing those anti-FcRn inhibitors that effectively catabolize the IgG4 antibody subclass, may be especially promising.
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Affiliation(s)
- Marinos C Dalakas
- Department of Neurology, Thomas Jefferson University, Philadelphia, PA, USA.
- Neuroimmunology Unit National and Kapodistrian University of Athens Medical School, Athens, Greece.
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26
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Koneczny I, Tzartos J, Mané-Damas M, Yilmaz V, Huijbers MG, Lazaridis K, Höftberger R, Tüzün E, Martinez-Martinez P, Tzartos S, Leypoldt F. IgG4 Autoantibodies in Organ-Specific Autoimmunopathies: Reviewing Class Switching, Antibody-Producing Cells, and Specific Immunotherapies. Front Immunol 2022; 13:834342. [PMID: 35401530 PMCID: PMC8986991 DOI: 10.3389/fimmu.2022.834342] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 02/28/2022] [Indexed: 12/24/2022] Open
Abstract
Organ-specific autoimmunity is often characterized by autoantibodies targeting proteins expressed in the affected tissue. A subgroup of autoimmunopathies has recently emerged that is characterized by predominant autoantibodies of the IgG4 subclass (IgG4-autoimmune diseases; IgG4-AID). This group includes pemphigus vulgaris, thrombotic thrombocytopenic purpura, subtypes of autoimmune encephalitis, inflammatory neuropathies, myasthenia gravis and membranous nephropathy. Although the associated autoantibodies target specific antigens in different organs and thus cause diverse syndromes and diseases, they share surprising similarities in genetic predisposition, disease mechanisms, clinical course and response to therapies. IgG4-AID appear to be distinct from another group of rare immune diseases associated with IgG4, which are the IgG4-related diseases (IgG4-RLD), such as IgG4-related which have distinct clinical and serological properties and are not characterized by antigen-specific IgG4. Importantly, IgG4-AID differ significantly from diseases associated with IgG1 autoantibodies targeting the same organ. This may be due to the unique functional characteristics of IgG4 autoantibodies (e.g. anti-inflammatory and functionally monovalent) that affect how the antibodies cause disease, and the differential response to immunotherapies of the IgG4 producing B cells/plasmablasts. These clinical and pathophysiological clues give important insight in the immunopathogenesis of IgG4-AID. Understanding IgG4 immunobiology is a key step towards the development of novel, IgG4 specific treatments. In this review we therefore summarize current knowledge on IgG4 regulation, the relevance of class switching in the context of health and disease, describe the cellular mechanisms involved in IgG4 production and provide an overview of treatment responses in IgG4-AID.
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Affiliation(s)
- Inga Koneczny
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
- *Correspondence: Inga Koneczny,
| | - John Tzartos
- Neuroimmunology, Tzartos NeuroDiagnostics, Athens, Greece
- 2nd Department of Neurology, “Attikon” University Hospital, School of Medicine, National and Kapodistrian University of Athens, Athens, Greece
| | - Marina Mané-Damas
- Research Group Neuroinflammation and Autoimmunity, Department of Psychiatry and Neuropsychology, Faculty of Health, Medicine and Life Sciences, Maastricht University, Maastricht, Netherlands
| | - Vuslat Yilmaz
- Department of Neuroscience, Aziz Sancar Institute of Experimental Medicine, Istanbul University, Istanbul, Turkey
| | - Maartje G. Huijbers
- Department of Human Genetics, Leiden University Medical Center, Leiden, Netherlands
- Department of Neurology, Leiden University Medical Center, Leiden, Netherlands
| | - Konstantinos Lazaridis
- Department of Immunology, Laboratory of Immunology, Hellenic Pasteur Institute, Athens, Greece
| | - Romana Höftberger
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Erdem Tüzün
- Department of Neuroscience, Aziz Sancar Institute of Experimental Medicine, Istanbul University, Istanbul, Turkey
| | - Pilar Martinez-Martinez
- Research Group Neuroinflammation and Autoimmunity, Department of Psychiatry and Neuropsychology, Faculty of Health, Medicine and Life Sciences, Maastricht University, Maastricht, Netherlands
| | - Socrates Tzartos
- Neuroimmunology, Tzartos NeuroDiagnostics, Athens, Greece
- Department of Neurobiology, Hellenic Pasteur Institute, Athens, Greece
| | - Frank Leypoldt
- Neuroimmunology, Institute of Clinical Chemistry and Department of Neurology, UKSH Kiel/Lübeck, Kiel University, Kiel, Germany
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27
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Huijbers MG, Marx A, Plomp JJ, Le Panse R, Phillips WD. Advances in the understanding of disease mechanisms of autoimmune neuromuscular junction disorders. Lancet Neurol 2022; 21:163-175. [DOI: 10.1016/s1474-4422(21)00357-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 09/15/2021] [Accepted: 10/06/2021] [Indexed: 01/19/2023]
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28
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Jiao L, Li H, Guo S. Eculizumab treatment for myasthenia gravis subgroups: 2021 update. J Neuroimmunol 2022; 362:577767. [PMID: 34823117 DOI: 10.1016/j.jneuroim.2021.577767] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 11/01/2021] [Accepted: 11/13/2021] [Indexed: 01/21/2023]
Abstract
Eculizumab is a recombinant humanized monoclonal antibody that targets the complement protein C5, inhibiting its cleavage into C5a and C5b and ultimately preventing the formation of C5b-9 membrane attack complex (MACs), thereby protecting the neuromuscular junction from the damage of complement activation. In 2017, eculizumab became the second FDA-approved medication for AchR-positive generalized myasthenia gravis (gMG) patients based on the successful results of a randomized, double-blinded, placebo-controlled, phase 2, phase 3 study (the REGAIN trial) and its open-label extension study. Despite the efficacy of eculizumab in treating AchR antibody-positive refractory gMG was demonstrated in the REGAIN study, there is few information on its efficacy in other subgroup of MG patients including seronegative MG, thymoma-associated MG and MG crisis. This narrative review summarizes current clinical studies of eculizumab in these refractory gMG patients, with a focus on the therapeutic efficacy and tolerability in different subgroup of MG.
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Affiliation(s)
- Li Jiao
- Department of Neurology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jing Wu Road, Huaiyin District, Jinan 250021, Shandong, China
| | - Honghao Li
- Department of Neurology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jing Wu Road, Huaiyin District, Jinan 250021, Shandong, China
| | - Shougang Guo
- Department of Neurology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jing Wu Road, Huaiyin District, Jinan 250021, Shandong, China.
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Endmayr V, Tunc C, Ergin L, De Rosa A, Weng R, Wagner L, Yu TY, Fichtenbaum A, Perkmann T, Haslacher H, Kozakowski N, Schwaiger C, Ricken G, Hametner S, Klotz S, Dutra LA, Lechner C, de Simoni D, Poppert KN, Müller GJ, Pirker S, Pirker W, Angelovski A, Valach M, Maestri M, Guida M, Ricciardi R, Frommlet F, Sieghart D, Pinter M, Kircher K, Artacker G, Höftberger R, Koneczny I. Anti-Neuronal IgG4 Autoimmune Diseases and IgG4-Related Diseases May Not Be Part of the Same Spectrum: A Comparative Study. Front Immunol 2022; 12:785247. [PMID: 35095860 PMCID: PMC8795769 DOI: 10.3389/fimmu.2021.785247] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Accepted: 12/15/2021] [Indexed: 12/18/2022] Open
Abstract
Background IgG4 is associated with two emerging groups of rare diseases: 1) IgG4 autoimmune diseases (IgG4-AID) and 2) IgG4-related diseases (IgG4-RLD). Anti-neuronal IgG4-AID include MuSK myasthenia gravis, LGI1- and Caspr2-encephalitis and autoimmune nodo-/paranodopathies (CNTN1/Caspr1 or NF155 antibodies). IgG4-RLD is a multiorgan disease hallmarked by tissue-destructive fibrotic lesions with lymphocyte and IgG4 plasma cell infiltrates and increased serum IgG4 concentrations. It is unclear whether IgG4-AID and IgG4-RLD share relevant clinical and immunopathological features. Methods We collected and analyzed clinical, serological, and histopathological data in 50 patients with anti-neuronal IgG4-AID and 19 patients with IgG4-RLD. Results A significantly higher proportion of IgG4-RLD patients had serum IgG4 elevation when compared to IgG4-AID patients (52.63% vs. 16%, p = .004). Moreover, those IgG4-AID patients with elevated IgG4 did not meet the diagnostic criteria of IgG4-RLD, and their autoantibody titers did not correlate with their serum IgG4 concentrations. In addition, patients with IgG4-RLD were negative for anti-neuronal/neuromuscular autoantibodies and among these patients, men showed a significantly higher propensity for IgG4 elevation, when compared to women (p = .005). Last, a kidney biopsy from a patient with autoimmune paranodopathy due to CNTN1/Caspr1-complex IgG4 autoantibodies and concomitant nephrotic syndrome did not show fibrosis or IgG4+ plasma cells, which are diagnostic hallmarks of IgG4-RLD. Conclusion Our observations suggest that anti-neuronal IgG4-AID and IgG4-RLD are most likely distinct disease entities.
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Affiliation(s)
- Verena Endmayr
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Cansu Tunc
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Lara Ergin
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Anna De Rosa
- Department of Clinical and Experimental Medicine, Neurology Unit, University of Pisa, Pisa, Italy
| | - Rosa Weng
- Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Lukas Wagner
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Thin-Yau Yu
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Andreas Fichtenbaum
- Department of Laboratory Medicine, Medical University of Vienna, Vienna, Austria
| | - Thomas Perkmann
- Department of Laboratory Medicine, Medical University of Vienna, Vienna, Austria
| | - Helmuth Haslacher
- Department of Laboratory Medicine, Medical University of Vienna, Vienna, Austria
| | | | - Carmen Schwaiger
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Gerda Ricken
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Simon Hametner
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Sigrid Klotz
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Lívia Almeida Dutra
- Department of Neurology and Neurosurgery, Hospital Israelita Albert Einstein, São Paulo, Brazil
| | - Christian Lechner
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
- Pediatric Neurology, Department of Pediatric and Adolescent Medicine, Medical University of Innsbruck, Innsbruck, Austria
| | - Désirée de Simoni
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
- Department of Neurology, University Hospital St. Poelten, St. Poelten, Austria
| | - Kai-Nicolas Poppert
- Department of Neurology, Christian Doppler University Hospital, Paracelsus Medical University, Salzburg, Austria
| | - Georg Johannes Müller
- Department of Neurology and Karl Landsteiner Institute for Neuroimmunological and Neurodegenerative Disorders, Klinik Donaustadt, Vienna, Austria
| | - Susanne Pirker
- Department of Neurology, Klinik Hietzing, Vienna, Austria
| | - Walter Pirker
- Department of Neurology, Klinik Ottakring, Vienna, Austria
| | | | - Matus Valach
- Department of Pathology, Klinik Landstrasse, Vienna, Austria
| | - Michelangelo Maestri
- Department of Clinical and Experimental Medicine, Neurology Unit, University of Pisa, Pisa, Italy
| | - Melania Guida
- Department of Clinical and Experimental Medicine, Neurology Unit, University of Pisa, Pisa, Italy
| | - Roberta Ricciardi
- Department of Clinical and Experimental Medicine, Neurology Unit, University of Pisa, Pisa, Italy
| | - Florian Frommlet
- Center for Medical Statistics, Informatics and Intelligent Systems, Section for Medical Statistics, Medical University of Vienna, Vienna, Austria
| | - Daniela Sieghart
- Division of Rheumatology, Department of Internal Medicine III, Medical University of Vienna, Vienna, Austria
| | - Miklos Pinter
- Wiener Privatklinik – Health Center, Vienna, Austria
| | - Karl Kircher
- Department of Ophthalmology, Medical University of Vienna, Vienna, Austria
| | - Gottfried Artacker
- Department of Pediatrics and Adolescent Medicine, Klinik Donaustadt, Vienna, Austria
| | - Romana Höftberger
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Inga Koneczny
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
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Schneider-Gold C, Gilhus NE. Advances and challenges in the treatment of myasthenia gravis. Ther Adv Neurol Disord 2022; 14:17562864211065406. [PMID: 34987614 PMCID: PMC8721395 DOI: 10.1177/17562864211065406] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Accepted: 11/18/2021] [Indexed: 01/04/2023] Open
Abstract
Myasthenia gravis (MG) is a chronic autoimmune disease with fluctuating muscle weakness and fatigability. Standard immunomodulatory treatment may fail to achieve sufficient improvement with minimal symptom expression or remission of myasthenic symptoms, despite adequate dosing and duration of treatment. Treatment-resistant MG poses a challenge for both patients and treating neurologists and requires new therapeutic approaches. The spectrum of upcoming immunotherapies that more specifically address distinct targets of the main immunological players in MG pathogenesis includes T-cell directed monoclonal antibodies that block the intracellular cascade associated with T-cell activation, monoclonal antibodies directed against key B-cell molecules, as well as monoclonal antibodies against the fragment crystallizable neonatal receptor (FcRn), cytokines and transmigration molecules, and also drugs that inhibit distinct elements of the complement system activated by the pathogenic MG antibodies. The review gives an overview on new drugs being evaluated in still ongoing or recently finished controlled clinical trials and drugs of potential benefit in MG due to their mechanisms of action and positive effects in other autoimmune disorders. Also, the challenges associated with the new therapeutic options are discussed briefly.
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Affiliation(s)
- Christiane Schneider-Gold
- Department of Neurology, St. Josef Hospital, Ruhr-University of Bochum, Gudrunstrasse 56, Bochum D-44791, Germany
| | - Nils Erik Gilhus
- Department of Clinical Medicine, University of Bergen, Bergen, NorwayDepartment of Neurology, Haukeland University Hospital, Bergen, Norway
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Dalakas MC. IgG4-Mediated Neurologic Autoimmunities: Understanding the Pathogenicity of IgG4, Ineffectiveness of IVIg, and Long-Lasting Benefits of Anti-B Cell Therapies. NEUROLOGY(R) NEUROIMMUNOLOGY & NEUROINFLAMMATION 2022; 9:9/1/e1116. [PMID: 34845096 PMCID: PMC8630661 DOI: 10.1212/nxi.0000000000001116] [Citation(s) in RCA: 33] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Accepted: 10/08/2021] [Indexed: 12/15/2022]
Abstract
BACKGROUND AND OBJECTIVES Describe the unique functions of immunoglobulin G4 (IgG4) in IgG4-neurologic disorders (IgG4-ND) and explain why, in contrast to their IgG1-counterparts, they respond poorly to intravenous immune globulin (IVIg) but effectively to anti-B cell therapies. METHODS The IgG4 structure and isotype switch, B cells and plasmablasts relevant to IgG4 production, and IgG4-induced disruption of the targeted antigens are reviewed and compared with IgG1-mediated autoimmune ND, where IVIg inhibits IgG1-triggered inflammatory effects. RESULTS The main IgG4-ND include muscle-specific kinase myasthenia; nodal/paranodal chronic inflammatory demyelinating polyradiculoneuropathy with antibodies to neurofascin-155, contactin-1/caspr-1, or pan-neurofascins; antileucine-rich, glioma-inactivated-1 and contactin-associated protein-like 2 associated-limbic encephalitis, Morvan syndrome, or neuromyotonia; and anti-IgLON5 disorder. The IgG4, because of its unique structural features in the hinge region, has noninflammatory properties being functionally monovalent and bispecific, unable to engage in cross-linking and internalization of the targeted antigen. In contrast to IgG1 subclass which is bivalent and monospecific, IgG4 does not activate complement and cannot bind to inhibitory Fcγ receptor (FcγRIIb) to activate cellular and complement-mediated immune responses, the key functions inhibited by IVIg. Because IVIg contains only 0.7%-2.6% IgG4, its idiotypes are of IgG1 subclass and cannot effectively neutralize IgG4 or sufficiently enhance IgG4 catabolism by saturating FcRn. In contrast, rituximab, by targeting memory B cells and IgG4-producing CD20-positive short-lived plasma cells, induces long-lasting clinical benefits. DISCUSSION Rituximab is the preferred treatment in IgG4-ND patients with severe disease by effectively targeting the production of pathogenic IgG-4 antibodies. In contrast, IVIG is ineffective because it inhibits immunoinflammatory functions irrelevant to the mechanistic effects of IgG4 and contains IgG-1 idiotypes that cannot sufficiently neutralize or possibly catabolize IgG4. Controlled studies with anti-CD19/20 monoclonals that also activate FcγRIIb may be more promising in treating IgG4-ND.
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Affiliation(s)
- Marinos C Dalakas
- From Thomas Jefferson University, Philadelphia, PA; and the University of Athens Medical School, Greece.
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32
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Zhao S, Zhang K, Ren K, Lu J, Ma C, Zhao C, Li Z, Guo J. Clinical features, treatment and prognosis of MuSK antibody-associated myasthenia gravis in Northwest China: a single-centre retrospective cohort study. BMC Neurol 2021; 21:428. [PMID: 34732168 PMCID: PMC8567678 DOI: 10.1186/s12883-021-02439-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 10/14/2021] [Indexed: 01/18/2023] Open
Abstract
BACKGROUND AND PURPOSE To summarize the clinical characteristics of patients with muscle-specific kinase antibody-associated myasthenia gravis (MuSK-MG) and to evaluate the therapeutic responses to different treatment regimes. METHODS Eighteen MuSK-MG patients admitted in our department between October 2017 and September 2020 were included. Clinical parameters were collected and the responses to different immunosuppressive drugs were assessed by MGFA Postintervention Status (MGFA-PIS). Meanwhile, the correlation between QMG scores and MuSK antibody titers were analyzed and MuSK antibody (MuSK-ab) titers were compared before and after therapy based on different immunosuppressive treatment regimes. RESULTS Female predominance (ratio of females to males, 15:3) was evident in the study population, with the average onset age of (40.28 ± 18.57) years and the median disease course of 30.50 months (interquartile range [IQR], 17.50-44.75 months). Ocular manifestation was the most common onset symptom (11/18; 61.11%), and mild symmetrical ptosis was most frequent. Bulbar symptoms had the highest incidence of 88.89% over the entire disease course. Abnormal responses to RNS test were recorded most frequently on the musculus deltoideus (83.33%). All patients were treated with prednisone (Pred) alone or plus azathioprine (AZA), tacrolimus (TAC) or low-dose rituximab (RTX), and 17 (94.44%) of them achieved a favorable outcome defined as minimal manifestation (MM) or better. In general, an obvious positive correlation between QMG score and MuSK-ab titer (r = 0.710, P < 0.001) were found in all patients. A more significant reduction of MuSK-ab titers was observed in patients receiving TAC or RTX plus Pred than those receiving AZA plus Pred. CONCLUSIONS The prominent clinical manifestations of ocular and bulbar muscles involvements, together with abnormal RNS response mostly recorded on the musculus deltoideus and better efficacy associated with TAC or low-dose RTX plus Pred, provide a more exhaustive picture of MuSK-MG, particularly in Northwest China.
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Affiliation(s)
- Sijia Zhao
- Department of Neurology, Tangdu Hospital, Air Force Medical University, Xi'an, 710038, Shaanxi Province, China
| | - Kai Zhang
- Department of Intensive Care Unit, Xi'an No.3 Hospital, Xi'an, 710018, Shaanxi Province, China
| | - Kaixi Ren
- Department of Neurology, Tangdu Hospital, Air Force Medical University, Xi'an, 710038, Shaanxi Province, China
| | - Jiarui Lu
- Department of Neurology, Tangdu Hospital, Air Force Medical University, Xi'an, 710038, Shaanxi Province, China
| | - Chao Ma
- Department of Cardiology, Tangdu Hospital, Air Force Medical University, Xi'an, 710038, Shaanxi Province, China
| | - Cong Zhao
- Department of Neurology, Air Force Medical Center of PLA, Beijing, 100142, China
| | - Zhuyi Li
- Department of Neurology, Tangdu Hospital, Air Force Medical University, Xi'an, 710038, Shaanxi Province, China.
| | - Jun Guo
- Department of Neurology, Tangdu Hospital, Air Force Medical University, Xi'an, 710038, Shaanxi Province, China.
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Mandel-Brehm C, Fichtner ML, Jiang R, Winton VJ, Vazquez SE, Pham MC, Hoehn KB, Kelleher NL, Nowak RJ, Kleinstein SH, Wilson MR, DeRisi JL, O'Connor KC. Elevated N-Linked Glycosylation of IgG V Regions in Myasthenia Gravis Disease Subtypes. THE JOURNAL OF IMMUNOLOGY 2021; 207:2005-2014. [PMID: 34544801 DOI: 10.4049/jimmunol.2100225] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 08/10/2021] [Indexed: 02/06/2023]
Abstract
Elevated N-linked glycosylation of IgG V regions (IgG-VN-Glyc) is an emerging molecular phenotype associated with autoimmune disorders. To test the broader specificity of elevated IgG-VN-Glyc, we studied patients with distinct subtypes of myasthenia gravis (MG), a B cell-mediated autoimmune disease. Our experimental design focused on examining the B cell repertoire and total IgG. It specifically included adaptive immune receptor repertoire sequencing to quantify and characterize N-linked glycosylation sites in the circulating BCR repertoire, proteomics to examine glycosylation patterns of the total circulating IgG, and an exploration of human-derived recombinant autoantibodies, which were studied with mass spectrometry and Ag binding assays to respectively confirm occupation of glycosylation sites and determine whether they alter binding. We found that the frequency of IgG-VN-Glyc motifs was increased in the total BCR repertoire of patients with MG when compared with healthy donors. The elevated frequency was attributed to both biased V gene segment usage and somatic hypermutation. IgG-VN-Glyc could be observed in the total circulating IgG in a subset of patients with MG. Autoantigen binding, by four patient-derived MG autoantigen-specific mAbs with experimentally confirmed presence of IgG-VN-Glyc, was not altered by the glycosylation. Our findings extend prior work on patterns of Ig V region N-linked glycosylation in autoimmunity to MG subtypes.
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Affiliation(s)
- Caleigh Mandel-Brehm
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA
| | - Miriam L Fichtner
- Department of Neurology, Yale University School of Medicine, New Haven, CT.,Department of Immunobiology, Yale University School of Medicine, New Haven, CT
| | - Ruoyi Jiang
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT
| | - Valerie J Winton
- Proteomics Center of Excellence, Northwestern University, Evanston, IL
| | - Sara E Vazquez
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA
| | - Minh C Pham
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT
| | - Kenneth B Hoehn
- Department of Pathology, Yale University School of Medicine, New Haven, CT
| | - Neil L Kelleher
- Department of Chemistry, Chemistry of Life Processes Institute, Proteomics Center of Excellence at Northwestern University, Evanston, IL.,Department of Molecular Biosciences, Chemistry of Life Processes Institute, Proteomics Center of Excellence at Northwestern University, Evanston, IL
| | - Richard J Nowak
- Department of Neurology, Yale University School of Medicine, New Haven, CT
| | - Steven H Kleinstein
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT.,Department of Pathology, Yale University School of Medicine, New Haven, CT.,Interdepartmental Program in Computational Biology and Bioinformatics, Yale University, New Haven, CT
| | - Michael R Wilson
- Weill Institute for Neurosciences, Department of Neurology, University of California San Francisco, San Francisco, CA; and
| | - Joseph L DeRisi
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA.,Chan Zuckerberg Biohub, San Francisco, CA
| | - Kevin C O'Connor
- Department of Neurology, Yale University School of Medicine, New Haven, CT; .,Department of Immunobiology, Yale University School of Medicine, New Haven, CT
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Circulating Biomarkers in Neuromuscular Disorders: What Is Known, What Is New. Biomolecules 2021; 11:biom11081246. [PMID: 34439911 PMCID: PMC8393752 DOI: 10.3390/biom11081246] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 08/16/2021] [Accepted: 08/19/2021] [Indexed: 02/07/2023] Open
Abstract
The urgent need for new therapies for some devastating neuromuscular diseases (NMDs), such as Duchenne muscular dystrophy or amyotrophic lateral sclerosis, has led to an intense search for new potential biomarkers. Biomarkers can be classified based on their clinical value into different categories: diagnostic biomarkers confirm the presence of a specific disease, prognostic biomarkers provide information about disease course, and therapeutic biomarkers are designed to predict or measure treatment response. Circulating biomarkers, as opposed to instrumental/invasive ones (e.g., muscle MRI or nerve ultrasound, muscle or nerve biopsy), are generally easier to access and less “time-consuming”. In addition to well-known creatine kinase, other promising molecules seem to be candidate biomarkers to improve the diagnosis, prognosis and prediction of therapeutic response, such as antibodies, neurofilaments, and microRNAs. However, there are some criticalities that can complicate their application: variability during the day, stability, and reliable performance metrics (e.g., accuracy, precision and reproducibility) across laboratories. In the present review, we discuss the application of biochemical biomarkers (both validated and emerging) in the most common NMDs with a focus on their diagnostic, prognostic/predictive and therapeutic application, and finally, we address the critical issues in the introduction of new biomarkers.
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35
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Myasthenia Gravis: Epidemiology, Pathophysiology and Clinical Manifestations. J Clin Med 2021; 10:jcm10112235. [PMID: 34064035 PMCID: PMC8196750 DOI: 10.3390/jcm10112235] [Citation(s) in RCA: 121] [Impact Index Per Article: 40.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 05/17/2021] [Accepted: 05/17/2021] [Indexed: 12/12/2022] Open
Abstract
Myasthenia gravis (MG) is an autoimmune neurological disorder characterized by defective transmission at the neuromuscular junction. The incidence of the disease is 4.1 to 30 cases per million person-years, and the prevalence rate ranges from 150 to 200 cases per million. MG is considered a classic example of antibody-mediated autoimmune disease. Most patients with MG have autoantibodies against the acetylcholine receptors (AChRs). Less commonly identified autoantibodies include those targeted to muscle-specific kinase (MuSK), low-density lipoprotein receptor-related protein 4 (Lrp4), and agrin. These autoantibodies disrupt cholinergic transmission between nerve terminals and muscle fibers by causing downregulation, destruction, functional blocking of AChRs, or disrupting the clustering of AChRs in the postsynaptic membrane. The core clinical manifestation of MG is fatigable muscle weakness, which may affect ocular, bulbar, respiratory and limb muscles. Clinical manifestations vary according to the type of autoantibody, and whether a thymoma is present.
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36
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Gastaldi M, Scaranzin S, Businaro P, Mobilia E, Benedetti L, Pesce G, Franciotta D. Improving laboratory diagnostics in myasthenia gravis. Expert Rev Mol Diagn 2021; 21:579-590. [PMID: 33970749 DOI: 10.1080/14737159.2021.1927715] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Introduction: Myasthenia gravis (MG) is a prototypical autoimmune disease, characterized by pathogenic autoantibodies targeting structures of the neuromuscular junction. Radioimmunoprecipitation assays (RIPAs) represent the gold standard for their detection. However, new methods are emerging to complement, or overcome RIPAs, also with the perspective of eliminating the use of radioactive reagents.Areas covered: We discuss advances in laboratory methods, prompted especially by cell-based assays (CBAs), for the detection of the autoantibodies of MG diagnostics, above all those to the nicotinic acetylcholine receptor (AChR), muscle-specific kinase (MuSK), and low molecular-weight receptor-related low-density lipoprotein-4 (LRP4).Expert opinion: CBA technology makes AChRs aggregate on cell membranes, thus allowing to detect autoantibodies to clustered AChRs, with reduction of seronegative MG cases. The diagnostic relevance of RIPA/CBA-measurable LRP4 antibodies is still unclear, in Caucasian patients at least. Live CBAs for the detection of AChR, MuSK, and LRP4 antibodies might represent an alternative to RIPAs, but first require full validation. CBAs could be used as screening tests, limiting RIPAs for antibody quantification. To this end, ELISAs might be an alternative.Fixation procedures preserving enough degree of antigen conformationality could yield AChR and MuSK CBAs suitable for a wide use in clinical-chemistry laboratories.
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Affiliation(s)
- Matteo Gastaldi
- Neuroimmunology Laboratory, IRCCS Mondino Foundation, Pavia, Italy
| | - Silvia Scaranzin
- Neuroimmunology Laboratory, IRCCS Mondino Foundation, Pavia, Italy
| | - Pietro Businaro
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
| | - Emanuela Mobilia
- Autoimmunity Laboratory, IRCCS Ospedale Policlinico San Martino, Genova, Italy
| | - Luana Benedetti
- Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova, Genova, Italy; IRCCS Ospedale Policlinico San Martino, Genova, Italy
| | - Giampaola Pesce
- Autoimmunity Laboratory, IRCCS Ospedale Policlinico San Martino, Genova, Italy.,Department of Internal Medicine (Dimi), University of Genova, Genova, Italy
| | - Diego Franciotta
- Autoimmunity Laboratory, IRCCS Ospedale Policlinico San Martino, Genova, Italy
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Functional monovalency amplifies the pathogenicity of anti-MuSK IgG4 in myasthenia gravis. Proc Natl Acad Sci U S A 2021; 118:2020635118. [PMID: 33753489 PMCID: PMC8020787 DOI: 10.1073/pnas.2020635118] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
An expanding group of autoimmune diseases is now recognized to be hallmarked by pathogenic IgG4 autoantibodies. IgG4 has the unique ability to exchange Fab-arms, rendering it bispecific and functionally monovalent. Here we show that autoantibody functional monovalency significantly amplifies the pathogenicity of IgG4 autoantibodies using patient-derived monoclonal antibodies in an in vivo model of MuSK myasthenia gravis. Therefore, subclass switching to predominant IgG4 autoantibodies is a critical step in the development of MuSK myasthenia gravis. This new mechanism in autoimmunity is also potentially relevant to 29 other IgG4-mediated autoimmune diseases known to date, allergy and other disease settings where IgG4 antibodies contribute to pathology. Human immunoglobulin (Ig) G4 usually displays antiinflammatory activity, and observations of IgG4 autoantibodies causing severe autoimmune disorders are therefore poorly understood. In blood, IgG4 naturally engages in a stochastic process termed “Fab-arm exchange” in which unrelated IgG4s exchange half-molecules continuously. The resulting IgG4 antibodies are composed of two different binding sites, thereby acquiring monovalent binding and inability to cross-link for each antigen recognized. Here, we demonstrate that this process amplifies autoantibody pathogenicity in a classic IgG4-mediated autoimmune disease: muscle-specific kinase (MuSK) myasthenia gravis. In mice, monovalent anti-MuSK IgG4s caused rapid and severe myasthenic muscle weakness, whereas the same antibodies in their parental bivalent form were less potent or did not induce a phenotype. Mechanistically this could be explained by opposing effects on MuSK signaling. Isotype switching to IgG4 in an autoimmune response thereby may be a critical step in the development of disease. Our study establishes functional monovalency as a pathogenic mechanism in IgG4-mediated autoimmune disease and potentially other disorders.
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38
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Zou A, Ramanathan S, Dale RC, Brilot F. Single-cell approaches to investigate B cells and antibodies in autoimmune neurological disorders. Cell Mol Immunol 2021; 18:294-306. [PMID: 32728203 PMCID: PMC8027387 DOI: 10.1038/s41423-020-0510-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 07/07/2020] [Indexed: 12/18/2022] Open
Abstract
Autoimmune neurological disorders, including neuromyelitis optica spectrum disorder, anti-N-methyl-D-aspartate receptor encephalitis, anti-MOG antibody-associated disorders, and myasthenia gravis, are clearly defined by the presence of autoantibodies against neurological antigens. Although these autoantibodies have been heavily studied for their biological activities, given the heterogeneity of polyclonal patient samples, the characteristics of a single antibody cannot be definitively assigned. This review details the findings of polyclonal serum and CSF studies and then explores the advances made by single-cell technologies to the field of antibody-mediated neurological disorders. High-resolution single-cell methods have revealed abnormalities in the tolerance mechanisms of several disorders and provided further insight into the B cells responsible for autoantibody production. Ultimately, several factors, including epitope specificity and binding affinity, finely regulate the pathogenic potential of an autoantibody, and a deeper appreciation of these factors may progress the development of targeted immunotherapies for patients.
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Affiliation(s)
- Alicia Zou
- Brain Autoimmunity Group, Kids Neuroscience Centre, Kids Research at the Children's Hospital at Westmead, Sydney, NSW, Australia
- Discipline of Child and Adolescent Health, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia
| | - Sudarshini Ramanathan
- Brain Autoimmunity Group, Kids Neuroscience Centre, Kids Research at the Children's Hospital at Westmead, Sydney, NSW, Australia
- Discipline of Child and Adolescent Health, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia
| | - Russell C Dale
- Brain Autoimmunity Group, Kids Neuroscience Centre, Kids Research at the Children's Hospital at Westmead, Sydney, NSW, Australia
- Discipline of Child and Adolescent Health, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia
- Brain and Mind Centre, The University of Sydney, Sydney, NSW, Australia
| | - Fabienne Brilot
- Brain Autoimmunity Group, Kids Neuroscience Centre, Kids Research at the Children's Hospital at Westmead, Sydney, NSW, Australia.
- Discipline of Child and Adolescent Health, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia.
- Brain and Mind Centre, The University of Sydney, Sydney, NSW, Australia.
- School of Medical Sciences, Discipline of Applied Medical Science, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia.
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Koneczny I, Yilmaz V, Lazaridis K, Tzartos J, Lenz TL, Tzartos S, Tüzün E, Leypoldt F. Common Denominators in the Immunobiology of IgG4 Autoimmune Diseases: What Do Glomerulonephritis, Pemphigus Vulgaris, Myasthenia Gravis, Thrombotic Thrombocytopenic Purpura and Autoimmune Encephalitis Have in Common? Front Immunol 2021; 11:605214. [PMID: 33584677 PMCID: PMC7878376 DOI: 10.3389/fimmu.2020.605214] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 12/08/2020] [Indexed: 12/20/2022] Open
Abstract
IgG4 autoimmune diseases (IgG4-AID) are an emerging group of autoimmune diseases that are caused by pathogenic autoantibodies of the IgG4 subclass. It has only recently been appreciated, that members of this group share relevant immunobiological and therapeutic aspects even though different antigens, tissues and organs are affected: glomerulonephritis (kidney), pemphigus vulgaris (skin), thrombotic thrombocytopenic purpura (hematologic system) muscle-specific kinase (MuSK) in myasthenia gravis (peripheral nervous system) and autoimmune encephalitis (central nervous system) to give some examples. In all these diseases, patients’ IgG4 subclass autoantibodies block protein-protein interactions instead of causing complement mediated tissue injury, patients respond favorably to rituximab and share a genetic predisposition: at least five HLA class II genes have been reported in individual studies to be associated with several different IgG4-AID. This suggests a role for the HLA class II region and specifically the DRβ1 chain for aberrant priming of autoreactive T-cells toward a chronic immune response skewed toward the production of IgG4 subclass autoantibodies. The aim of this review is to provide an update on findings arguing for a common pathogenic mechanism in IgG4-AID in general and to provide hypotheses about the role of distinct HLA haplotypes, T-cells and cytokines in IgG4-AID.
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Affiliation(s)
- Inga Koneczny
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Vuslat Yilmaz
- Department of Neuroscience, Aziz Sancar Institute of Experimental Medicine, Istanbul University, Istanbul, Turkey
| | - Konstantinos Lazaridis
- Department of Immunology, Laboratory of Immunology, Hellenic Pasteur Institute, Athens, Greece
| | - John Tzartos
- Tzartos NeuroDiagnostics, Athens, Greece.,1st Department of Neurology, Eginition Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Tobias L Lenz
- Research Group for Evolutionary Immunogenomics, Max Planck Institute for Evolutionary Biology, Plön, Germany
| | - Socrates Tzartos
- Tzartos NeuroDiagnostics, Athens, Greece.,Department of Neurobiology, Hellenic Pasteur Institute, Athens, Greece
| | - Erdem Tüzün
- Department of Neuroscience, Aziz Sancar Institute of Experimental Medicine, Istanbul University, Istanbul, Turkey
| | - Frank Leypoldt
- Neuroimmunology, Institute of Clinical Chemistry and Department of Neurology, Medical Faculty, Christian-Albrechts-University Kiel, Kiel, Germany
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40
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Barrantes FJ. Possible implications of dysregulated nicotinic acetylcholine receptor diffusion and nanocluster formation in myasthenia gravis. Neural Regen Res 2021; 16:242-246. [PMID: 32859770 PMCID: PMC7896218 DOI: 10.4103/1673-5374.290880] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Myasthenia gravis is a rare and invalidating disease affecting the neuromuscular junction of voluntary muscles. The classical form of this autoimmune disease is characterized by the presence of antibodies against the most abundant protein in the neuromuscular junction, the nicotinic acetylcholine receptor. Other variants of the disease involve autoimmune attack of non-receptor scaffolding proteins or enzymes essential for building or maintaining the integrity of this peripheral synapse. This review summarizes the participation of the above proteins in building the neuromuscular junction and the destruction of this cholinergic synapse by autoimmune aggression in myasthenia gravis. The review also covers the application of a powerful biophysical technique, superresolution optical microscopy, to image the nicotinic receptor in live cells and follow its motional dynamics. The hypothesis is entertained that anomalous nanocluster formation by antibody crosslinking may lead to accelerated endocytic internalization and elevated turnover of the receptor, as observed in myasthenia gravis.
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41
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Frykman H, Kumar P, Oger J. Immunopathology of Autoimmune Myasthenia Gravis: Implications for Improved Testing Algorithms and Treatment Strategies. Front Neurol 2020; 11:596621. [PMID: 33362698 PMCID: PMC7755715 DOI: 10.3389/fneur.2020.596621] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Accepted: 11/19/2020] [Indexed: 12/13/2022] Open
Abstract
Myasthenia gravis (MG) is a heterogeneous condition, characterized by autoantibodies (Abs) that target functionally important structures within neuromuscular junctions (NMJ), thus affecting nerve-to-muscle transmission. MG patients are more often now subgrouped based on the profile of serum autoantibodies, which segregate with clinical presentation, immunopathology, and their response to therapies. The serological testing plays an essential role in confirming MG diagnosis and guiding disease management, although a small percentage of MG patients remain negative for antibodies. With the advancements in new highly effective pathophysiologically-specific immunotherapeutic options, it has become increasingly important to identify the specific Abs responsible for the pathogenicity in individual MG patients. There are several new assays and protocols being developed for the improved detection of Abs in MG patients. This review focuses on the divergent immunopathological mechanisms in MG, and discusses their relevance to improved diagnostic and treatment. We propose a comprehensive "reflex testing," algorithm for the presence of MG autoantibodies, and foresee that in the near future, the convenience and specificity of novel assays will permit the clinicians to consider them into routine systematic testing, thus stimulating laboratories to make these tests available. Moreover, adopting treatment driven testing algorithms will be crucial to identify subgroups of patients potentially benefiting from novel immunotherapies for MG.
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Affiliation(s)
- Hans Frykman
- Department of Medicine, University of British Columbia, Vancouver, BC, Canada.,BC Neuroimmunology Lab, University of British Columbia, Vancouver, BC, Canada
| | - Pankaj Kumar
- BC Neuroimmunology Lab, University of British Columbia, Vancouver, BC, Canada
| | - Joel Oger
- Department of Medicine, University of British Columbia, Vancouver, BC, Canada.,BC Neuroimmunology Lab, University of British Columbia, Vancouver, BC, Canada
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42
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Rodríguez Cruz PM, Cossins J, Beeson D, Vincent A. The Neuromuscular Junction in Health and Disease: Molecular Mechanisms Governing Synaptic Formation and Homeostasis. Front Mol Neurosci 2020; 13:610964. [PMID: 33343299 PMCID: PMC7744297 DOI: 10.3389/fnmol.2020.610964] [Citation(s) in RCA: 87] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 10/30/2020] [Indexed: 12/28/2022] Open
Abstract
The neuromuscular junction (NMJ) is a highly specialized synapse between a motor neuron nerve terminal and its muscle fiber that are responsible for converting electrical impulses generated by the motor neuron into electrical activity in the muscle fibers. On arrival of the motor nerve action potential, calcium enters the presynaptic terminal, which leads to the release of the neurotransmitter acetylcholine (ACh). ACh crosses the synaptic gap and binds to ACh receptors (AChRs) tightly clustered on the surface of the muscle fiber; this leads to the endplate potential which initiates the muscle action potential that results in muscle contraction. This is a simplified version of the events in neuromuscular transmission that take place within milliseconds, and are dependent on a tiny but highly structured NMJ. Much of this review is devoted to describing in more detail the development, maturation, maintenance and regeneration of the NMJ, but first we describe briefly the most important molecules involved and the conditions that affect their numbers and function. Most important clinically worldwide, are myasthenia gravis (MG), the Lambert-Eaton myasthenic syndrome (LEMS) and congenital myasthenic syndromes (CMS), each of which causes specific molecular defects. In addition, we mention the neurotoxins from bacteria, snakes and many other species that interfere with neuromuscular transmission and cause potentially fatal diseases, but have also provided useful probes for investigating neuromuscular transmission. There are also changes in NMJ structure and function in motor neuron disease, spinal muscle atrophy and sarcopenia that are likely to be secondary but might provide treatment targets. The NMJ is one of the best studied and most disease-prone synapses in the nervous system and it is amenable to in vivo and ex vivo investigation and to systemic therapies that can help restore normal function.
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Affiliation(s)
- Pedro M. Rodríguez Cruz
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| | - Judith Cossins
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| | - David Beeson
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| | - Angela Vincent
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
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43
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Lazaridis K, Tzartos SJ. Myasthenia Gravis: Autoantibody Specificities and Their Role in MG Management. Front Neurol 2020; 11:596981. [PMID: 33329350 PMCID: PMC7734299 DOI: 10.3389/fneur.2020.596981] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Accepted: 10/30/2020] [Indexed: 12/11/2022] Open
Abstract
Myasthenia gravis (MG) is the most common autoimmune disorder affecting the neuromuscular junction, characterized by skeletal muscle weakness and fatigability. It is caused by autoantibodies targeting proteins of the neuromuscular junction; ~85% of MG patients have autoantibodies against the muscle acetylcholine receptor (AChR-MG), whereas about 5% of MG patients have autoantibodies against the muscle specific kinase (MuSK-MG). In the remaining about 10% of patients no autoantibodies can be found with the classical diagnostics for AChR and MuSK antibodies (seronegative MG, SN-MG). Since serological tests are relatively easy and non-invasive for disease diagnosis, the improvement of methods for the detection of known autoantibodies or the discovery of novel autoantibody specificities to diminish SN-MG and to facilitate differential diagnosis of similar diseases, is crucial. Radioimmunoprecipitation assays (RIPA) are the staple for MG antibody detection, but over the past years, using cell-based assays (CBAs) or improved highly sensitive RIPAs, it has been possible to detect autoantibodies in previously SN-MG patients. This led to the identification of more patients with antibodies to the classical antigens AChR and MuSK and to the third MG autoantigen, the low-density lipoprotein receptor-related protein 4 (LRP4), while antibodies against other extracellular or intracellular targets, such as agrin, Kv1.4 potassium channels, collagen Q, titin, the ryanodine receptor and cortactin have been found in some MG patients. Since the autoantigen targeted determines in part the clinical manifestations, prognosis and response to treatment, serological tests are not only indispensable for initial diagnosis, but also for monitoring treatment efficacy. Importantly, knowing the autoantibody profile of MG patients could allow for more efficient personalized therapeutic approaches. Significant progress has been made over the past years toward the development of antigen-specific therapies, targeting only the specific immune cells or autoantibodies involved in the autoimmune response. In this review, we will present the progress made toward the development of novel sensitive autoantibody detection assays, the identification of new MG autoantigens, and the implications for improved antigen-specific therapeutics. These advancements increase our understanding of MG pathology and improve patient quality of life by providing faster, more accurate diagnosis and better disease management.
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Affiliation(s)
| | - Socrates J Tzartos
- Tzartos NeuroDiagnostics, Athens, Greece.,Department of Neurobiology, Hellenic Pasteur Institute, Athens, Greece
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44
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Cao M, Koneczny I, Vincent A. Myasthenia Gravis With Antibodies Against Muscle Specific Kinase: An Update on Clinical Features, Pathophysiology and Treatment. Front Mol Neurosci 2020; 13:159. [PMID: 32982689 PMCID: PMC7492727 DOI: 10.3389/fnmol.2020.00159] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Accepted: 08/03/2020] [Indexed: 12/24/2022] Open
Abstract
Muscle Specific Kinase myasthenia gravis (MuSK-MG) is an autoimmune disease that impairs neuromuscular transmission leading to generalized muscle weakness. Compared to the more common myasthenia gravis with antibodies against the acetylcholine receptor (AChR), MuSK-MG affects mainly the bulbar and respiratory muscles, with more frequent and severe myasthenic crises. Treatments are usually less effective with the need for prolonged, high doses of steroids and other immunosuppressants to control symptoms. Under physiological condition, MuSK regulates a phosphorylation cascade which is fundamental for the development and maintenance of postsynaptic AChR clusters at the neuromuscular junction (NMJ). Agrin, secreted by the motor nerve terminal into the synaptic cleft, binds to low density lipoprotein receptor-related protein 4 (LRP4) which activates MuSK. In MuSK-MG, monovalent MuSK-IgG4 autoantibodies block MuSK-LRP4 interaction preventing MuSK activation and leading to the dispersal of AChR clusters. Lower levels of divalent MuSK IgG1, 2, and 3 antibody subclasses are also present but their contribution to the pathogenesis of the disease remains controversial. This review aims to provide a detailed update on the epidemiological and clinical features of MuSK-MG, focusing on the pathophysiological mechanisms and the latest indications regarding the efficacy and safety of different treatment options.
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Affiliation(s)
- Michelangelo Cao
- Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
| | - Inga Koneczny
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Angela Vincent
- Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
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45
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Koneczny I. Update on IgG4-mediated autoimmune diseases: New insights and new family members. Autoimmun Rev 2020; 19:102646. [PMID: 32801046 DOI: 10.1016/j.autrev.2020.102646] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Accepted: 03/08/2020] [Indexed: 12/23/2022]
Abstract
Antibodies of IgG4 subclass are exceptional players of the immune system, as they are considered to be immunologically inert and functionally monovalent, and as such may be part of classical tolerance mechanisms. IgG4 antibodies are found in a range of different diseases, including IgG4-related diseases, allergy, cancer, rheumatoid arthritis, helminth infection and IgG4 autoimmune diseases, where they may be pathogenic or protective. IgG4 autoimmune diseases are an emerging new group of diseases that are characterized by pathogenic, antigen-specific autoantibodies of IgG4 subclass, such as MuSK myasthenia gravis, pemphigus vulgaris and thrombotic thrombocytopenic purpura. The list of IgG4 autoantigens is rapidly growing and to date contains 29 candidate antigens. Interestingly, IgG4 autoimmune diseases are restricted to four distinct organs: 1) the central and peripheral nervous system, 2) the kidney, 3) the skin and mucous membranes and 4) the vascular system and soluble antigens in the blood circulation. The pathogenicity of IgG4 can be validated using our classification system, and is usually excerted by functional blocking of protein-protein interaction.
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Affiliation(s)
- Inga Koneczny
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Währingergürtel 18-20, 1090 Vienna, Austria.
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46
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Jiang R, Fichtner ML, Hoehn KB, Pham MC, Stathopoulos P, Nowak RJ, Kleinstein SH, O'Connor KC. Single-cell repertoire tracing identifies rituximab-resistant B cells during myasthenia gravis relapses. JCI Insight 2020; 5:136471. [PMID: 32573488 DOI: 10.1172/jci.insight.136471] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 06/11/2020] [Indexed: 12/19/2022] Open
Abstract
Rituximab, a B cell-depleting therapy, is indicated for treating a growing number of autoantibody-mediated autoimmune disorders. However, relapses can occur after treatment, and autoantibody-producing B cell subsets may be found during relapses. It is not understood whether these autoantibody-producing B cell subsets emerge from the failed depletion of preexisting B cells or are generated de novo. To further define the mechanisms that cause postrituximab relapse, we studied patients with autoantibody-mediated muscle-specific kinase (MuSK) myasthenia gravis (MG) who relapsed after treatment. We carried out single-cell transcriptional and B cell receptor profiling on longitudinal B cell samples. We identified clones present before therapy that persisted during relapse. Persistent B cell clones included both antibody-secreting cells and memory B cells characterized by gene expression signatures associated with B cell survival. A subset of persistent antibody-secreting cells and memory B cells were specific for the MuSK autoantigen. These results demonstrate that rituximab is not fully effective at eliminating autoantibody-producing B cells and provide a mechanistic understanding of postrituximab relapse in MuSK MG.
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Affiliation(s)
| | - Miriam L Fichtner
- Department of Immunobiology and.,Department of Neurology, Yale School of Medicine, New Haven, Connecticut, USA
| | - Kenneth B Hoehn
- Department of Pathology, Yale School of Medicine, New Haven, Connecticut, USA
| | | | - Panos Stathopoulos
- Department of Immunobiology and.,Department of Neurology, Yale School of Medicine, New Haven, Connecticut, USA
| | - Richard J Nowak
- Department of Neurology, Yale School of Medicine, New Haven, Connecticut, USA
| | - Steven H Kleinstein
- Department of Immunobiology and.,Interdepartmental Program in Computational Biology & Bioinformatics, Yale University, New Haven, Connecticut, USA.,Department of Pathology, Yale School of Medicine, New Haven, Connecticut, USA
| | - Kevin C O'Connor
- Department of Immunobiology and.,Department of Neurology, Yale School of Medicine, New Haven, Connecticut, USA
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47
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Vergoossen DLE, Augustinus R, Huijbers MG. MuSK antibodies, lessons learned from poly- and monoclonality. J Autoimmun 2020; 112:102488. [PMID: 32505442 DOI: 10.1016/j.jaut.2020.102488] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 04/28/2020] [Accepted: 05/06/2020] [Indexed: 11/25/2022]
Abstract
Muscle-specific kinase (MuSK) plays a critical role in establishing and maintaining neuromuscular synapses. Antibodies derived from immunizing animals with MuSK were important tools to help detect MuSK and its activity. The role of antibodies in MuSK-related research got an extra dimension when autoantibodies to MuSK were found to cause myasthenia gravis (MG) in 2001. Active immunization with MuSK or passive transfer of polyclonal purified IgG(4) fractions from patients reproduced myasthenic muscle weakness in a range of animal models. Polyclonal patient-purified autoantibodies were furthermore found to block agrin-Lrp4-MuSK signaling, explaining the synaptic disassembly, failure of neuromuscular transmission and ultimately muscle fatigue observed in vivo. MuSK autoantibodies are predominantly of the IgG4 subclass. Low levels of other subclass MuSK antibodies coexist, but their role in the pathogenesis is unclear. Patient-derived monoclonal antibodies revealed that MuSK antibody subclass and valency alters their functional effects and possibly their pathogenicity. Interestingly, recombinant functional bivalent MuSK antibodies might even have therapeutic potential for a variety of neuromuscular disorders, due to their agonistic nature on the MuSK signaling cascade. Thus, MuSK antibodies have proven to be helpful tools to study neuromuscular junction physiology, contributed to our understanding of the pathophysiology of MuSK MG and might be used to treat neuromuscular disorders. The source of MuSK antibodies and consequently their (mixed) polyclonal or monoclonal nature were important confounding factors in these experiments. Here we review the variety of MuSK antibodies described thus far, the insights they have given us and their potential for the future.
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Affiliation(s)
- Dana L E Vergoossen
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, the Netherlands
| | - Roy Augustinus
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, the Netherlands
| | - Maartje G Huijbers
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, the Netherlands; Department of Neurology, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, the Netherlands.
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48
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Takamori M. Myasthenia Gravis: From the Viewpoint of Pathogenicity Focusing on Acetylcholine Receptor Clustering, Trans-Synaptic Homeostasis and Synaptic Stability. Front Mol Neurosci 2020; 13:86. [PMID: 32547365 PMCID: PMC7272578 DOI: 10.3389/fnmol.2020.00086] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 04/28/2020] [Indexed: 12/18/2022] Open
Abstract
Myasthenia gravis (MG) is a disease of the postsynaptic neuromuscular junction (NMJ) where nicotinic acetylcholine (ACh) receptors (AChRs) are targeted by autoantibodies. Search for other pathogenic antigens has detected the antibodies against muscle-specific tyrosine kinase (MuSK) and low-density lipoprotein-related protein 4 (Lrp4), both causing pre- and post-synaptic impairments. Agrin is also suspected as a fourth pathogen. In a complex NMJ organization centering on MuSK: (1) the Wnt non-canonical pathway through the Wnt-Lrp4-MuSK cysteine-rich domain (CRD)-Dishevelled (Dvl, scaffold protein) signaling acts to form AChR prepatterning with axonal guidance; (2) the neural agrin-Lrp4-MuSK (Ig1/2 domains) signaling acts to form rapsyn-anchored AChR clusters at the innervated stage of muscle; (3) adaptor protein Dok-7 acts on MuSK activation for AChR clustering from “inside” and also on cytoskeleton to stabilize AChR clusters by the downstream effector Sorbs1/2; (4) the trans-synaptic retrograde signaling contributes to the presynaptic organization via: (i) Wnt-MuSK CRD-Dvl-β catenin-Slit 2 pathway; (ii) Lrp4; and (iii) laminins. The presynaptic Ca2+ homeostasis conditioning ACh release is modified by autoreceptors such as M1-type muscarinic AChR and A2A adenosine receptors. The post-synaptic structure is stabilized by: (i) laminin-network including the muscle-derived agrin; (ii) the extracellular matrix proteins (including collagen Q/perlecan and biglycan which link to MuSK Ig1 domain and CRD); and (iii) the dystrophin-associated glycoprotein complex. The study on MuSK ectodomains (Ig1/2 domains and CRD) recognized by antibodies suggested that the MuSK antibodies were pathologically heterogeneous due to their binding to multiple functional domains. Focussing one of the matrix proteins, biglycan which functions in the manner similar to collagen Q, our antibody assay showed the negative result in MG patients. However, the synaptic stability may be impaired by antibodies against MuSK ectodomains because of the linkage of biglycan with MuSK Ig1 domain and CRD. The pathogenic diversity of MG is discussed based on NMJ signaling molecules.
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49
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Fichtner ML, Jiang R, Bourke A, Nowak RJ, O'Connor KC. Autoimmune Pathology in Myasthenia Gravis Disease Subtypes Is Governed by Divergent Mechanisms of Immunopathology. Front Immunol 2020; 11:776. [PMID: 32547535 PMCID: PMC7274207 DOI: 10.3389/fimmu.2020.00776] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Accepted: 04/06/2020] [Indexed: 12/13/2022] Open
Abstract
Myasthenia gravis (MG) is a prototypical autoantibody mediated disease. The autoantibodies in MG target structures within the neuromuscular junction (NMJ), thus affecting neuromuscular transmission. The major disease subtypes of autoimmune MG are defined by their antigenic target. The most common target of pathogenic autoantibodies in MG is the nicotinic acetylcholine receptor (AChR), followed by muscle-specific kinase (MuSK) and lipoprotein receptor-related protein 4 (LRP4). MG patients present with similar symptoms independent of the underlying subtype of disease, while the immunopathology is remarkably distinct. Here we highlight these distinct immune mechanisms that describe both the B cell- and autoantibody-mediated pathogenesis by comparing AChR and MuSK MG subtypes. In our discussion of the AChR subtype, we focus on the role of long-lived plasma cells in the production of pathogenic autoantibodies, the IgG1 subclass mediated pathology, and contributions of complement. The similarities underlying the immunopathology of AChR MG and neuromyelitis optica (NMO) are highlighted. In contrast, MuSK MG is caused by autoantibody production by short-lived plasmablasts. MuSK MG autoantibodies are mainly of the IgG4 subclass which can undergo Fab-arm exchange (FAE), a process unique to this subclass. In FAE IgG4, molecules can dissociate into two halves and recombine with other half IgG4 molecules resulting in bispecific antibodies. Similarities between MuSK MG and other IgG4-mediated autoimmune diseases, including pemphigus vulgaris (PV) and chronic inflammatory demyelinating polyneuropathy (CIDP), are highlighted. Finally, the immunological distinctions are emphasized through presentation of biological therapeutics that provide clinical benefit depending on the MG disease subtype.
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Affiliation(s)
- Miriam L Fichtner
- Department of Neurology, School of Medicine, Yale University, New Haven, CT, United States.,Department of Immunobiology, School of Medicine, Yale University, New Haven, CT, United States
| | - Ruoyi Jiang
- Department of Immunobiology, School of Medicine, Yale University, New Haven, CT, United States
| | - Aoibh Bourke
- Trinity Hall, University of Cambridge, Cambridge, United Kingdom
| | - Richard J Nowak
- Department of Neurology, School of Medicine, Yale University, New Haven, CT, United States
| | - Kevin C O'Connor
- Department of Neurology, School of Medicine, Yale University, New Haven, CT, United States.,Department of Immunobiology, School of Medicine, Yale University, New Haven, CT, United States
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50
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Abstract
Thirty to fifty percent of patients with acetylcholine receptor (AChR) antibody (Ab)-negative myasthenia gravis (MG) have Abs to muscle specific kinase (MuSK) and are referred to as having MuSK-MG. MuSK is a 100 kD single-pass post-synaptic transmembrane receptor tyrosine kinase crucial to the development and maintenance of the neuromuscular junction. The Abs in MuSK-MG are predominantly of the IgG4 immunoglobulin subclass. MuSK-MG differs from AChR-MG, in exhibiting more focal muscle involvement, including neck, shoulder, facial and bulbar-innervated muscles, as well as wasting of the involved muscles. MuSK-MG is highly associated with the HLA DR14-DQ5 haplotype and occurs predominantly in females with onset in the fourth decade of life. Some of the standard treatments of AChR-MG have been found to have limited effectiveness in MuSK-MG, including thymectomy and cholinesterase inhibitors. Therefore, current treatment involves immunosuppression, primarily by corticosteroids. In addition, patients respond especially well to B cell depletion agents, e.g., rituximab, with long-term remissions. Future treatments will likely derive from the ongoing analysis of the pathogenic mechanisms underlying this disease, including histologic and physiologic studies of the neuromuscular junction in patients as well as information derived from the development and study of animal models of the disease.
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Affiliation(s)
| | - David P. Richman
- Department of Neurology, University of California, Davis, Davis, CA, United States
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