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Gerber-Tichet E, Blanchet FP, Majzoub K, Kremer EJ. Toll-like receptor 4 - a multifunctional virus recognition receptor. Trends Microbiol 2024:S0966-842X(24)00171-9. [PMID: 39179422 DOI: 10.1016/j.tim.2024.07.001] [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: 02/28/2024] [Revised: 05/30/2024] [Accepted: 07/02/2024] [Indexed: 08/26/2024]
Abstract
Since the initial description of Toll receptors in Drosophila and their mammalian counterparts Toll-like receptors (TLRs), numerous fundamental and applied studies have explored their crucial role as sensors of pathogen-associated molecular patterns (PAMPs). Among the ten human TLRs, TLR4 is particularly well known for its ability to detect lipopolysaccharides (LPS), a component of the Gram-negative bacterial cell wall. In addition to its archetypal functions, TLR4 is also a versatile virus sensor. This review provides a background on the discovery of TLR4 and how this knowledge laid a foundation for characterization of its diverse roles in antiviral responses, examined through genetic, biochemical, structural, and immunological approaches. These advances have led to a deeper understanding of the molecular functions that enable TLR4 to orchestrate multi-nodal control by professional antigen-presenting cells (APCs) to initiate appropriate and regulated antiviral immune responses.
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Affiliation(s)
- Elina Gerber-Tichet
- Institut de Génétique Moléculaire de Montpellier, Université de Montpellier, CNRS UMR 5535, 34090 Montpellier, France
| | - Fabien P Blanchet
- Institut de Recherche en Infectiologie de Montpellier, Université de Montpellier, CNRS UMR 9004, 34090 Montpellier, France
| | - Karim Majzoub
- Institut de Génétique Moléculaire de Montpellier, Université de Montpellier, CNRS UMR 5535, 34090 Montpellier, France
| | - Eric J Kremer
- Institut de Génétique Moléculaire de Montpellier, Université de Montpellier, CNRS UMR 5535, 34090 Montpellier, France.
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2
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Park A, Lee JY. Adenoviral Vector System: A Comprehensive Overview of Constructions, Therapeutic Applications and Host Responses. J Microbiol 2024; 62:491-509. [PMID: 39037484 DOI: 10.1007/s12275-024-00159-4] [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: 05/15/2024] [Revised: 06/26/2024] [Accepted: 07/04/2024] [Indexed: 07/23/2024]
Abstract
Adenoviral vectors are crucial for gene therapy and vaccine development, offering a platform for gene delivery into host cells. Since the discovery of adenoviruses, first-generation vectors with limited capacity have evolved to third-generation vectors flacking viral coding sequences, balancing safety and gene-carrying capacity. The applications of adenoviral vectors for gene therapy and anti-viral treatments have expanded through the use of in vitro ligation and homologous recombination, along with gene editing advancements such as CRISPR-Cas9. Current research aims to maintain the efficacy and safety of adenoviral vectors by addressing challenges such as pre-existing immunity against adenoviral vectors and developing new adenoviral vectors from rare adenovirus types and non-human species. In summary, adenoviral vectors have great potential in gene therapy and vaccine development. Through continuous research and technological advancements, these vectors are expected to lead to the development of safer and more effective treatments.
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Affiliation(s)
- Anyeseu Park
- The Laboratory of Viromics and Evolution, Korea Zoonosis Research Institute, Jeonbuk National University, Iksan, 54531, Republic of Korea
| | - Jeong Yoon Lee
- The Laboratory of Viromics and Evolution, Korea Zoonosis Research Institute, Jeonbuk National University, Iksan, 54531, Republic of Korea.
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3
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Rivera CE, Zhou Y, Chupp DP, Yan H, Fisher AD, Simon R, Zan H, Xu Z, Casali P. Intrinsic B cell TLR-BCR linked coengagement induces class-switched, hypermutated, neutralizing antibody responses in absence of T cells. SCIENCE ADVANCES 2023; 9:eade8928. [PMID: 37115935 PMCID: PMC10146914 DOI: 10.1126/sciadv.ade8928] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Accepted: 03/23/2023] [Indexed: 05/03/2023]
Abstract
Maturation of antibody responses entails somatic hypermutation (SHM), class-switch DNA recombination (CSR), plasma cell differentiation, and generation of memory B cells, and it is thought to require T cell help. We showed that B cell Toll-like receptor 4 (TLR4)-B cell receptor (BCR) (receptor for antigen) coengagement by 4-hydroxy-3-nitrophenyl acetyl (NP)-lipopolysaccharide (LPS) (Escherichia coli lipid A polysaccharide O-antigen) or TLR5-BCR coengagement by Salmonella flagellin induces mature antibody responses to NP and flagellin in Tcrβ-/-Tcrδ-/- and NSG/B mice. TLR-BCR coengagement required linkage of TLR and BCR ligands, "linked coengagement." This induced B cell CSR/SHM, germinal center-like differentiation, clonal expansion, intraconal diversification, plasma cell differentiation, and an anamnestic antibody response. In Tcrβ-/-Tcrδ-/- mice, linked coengagement of TLR4-BCR by LPS or TLR5-BCR by flagellin induced protective antibodies against E. coli or Salmonella Typhimurium. Our findings unveiled a critical role of B cell TLRs in inducing neutralizing antibody responses, including those to microbial pathogens, without T cell help.
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Affiliation(s)
- Carlos E. Rivera
- Department of Microbiology, Immunology & Molecular Genetics, University of Texas Long School of Medicine, UT Health Science Center, San Antonio, TX 78229, USA
| | - Yulai Zhou
- Department of Microbiology, Immunology & Molecular Genetics, University of Texas Long School of Medicine, UT Health Science Center, San Antonio, TX 78229, USA
| | - Daniel P. Chupp
- Department of Microbiology, Immunology & Molecular Genetics, University of Texas Long School of Medicine, UT Health Science Center, San Antonio, TX 78229, USA
| | - Hui Yan
- Department of Microbiology, Immunology & Molecular Genetics, University of Texas Long School of Medicine, UT Health Science Center, San Antonio, TX 78229, USA
| | - Amanda D. Fisher
- Department of Microbiology, Immunology & Molecular Genetics, University of Texas Long School of Medicine, UT Health Science Center, San Antonio, TX 78229, USA
| | - Raphael Simon
- Center for Vaccine Development, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Hong Zan
- Department of Microbiology, Immunology & Molecular Genetics, University of Texas Long School of Medicine, UT Health Science Center, San Antonio, TX 78229, USA
| | - Zhenming Xu
- Department of Microbiology, Immunology & Molecular Genetics, University of Texas Long School of Medicine, UT Health Science Center, San Antonio, TX 78229, USA
| | - Paolo Casali
- Department of Microbiology, Immunology & Molecular Genetics, University of Texas Long School of Medicine, UT Health Science Center, San Antonio, TX 78229, USA
- Department of Medicine, University of Texas Long School of Medicine, UT Health Science Center, San Antonio, TX 78229, USA
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Provine NM, Klenerman P. Adenovirus vector and mRNA vaccines: Mechanisms regulating their immunogenicity. Eur J Immunol 2022:10.1002/eji.202250022. [PMID: 36330560 PMCID: PMC9877955 DOI: 10.1002/eji.202250022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2022] [Revised: 09/05/2022] [Accepted: 11/02/2022] [Indexed: 11/06/2022]
Abstract
Replication-incompetent adenovirus (Ad) vector and mRNA-lipid nanoparticle (LNP) constructs represent two modular vaccine platforms that have attracted substantial interest over the past two decades. Due to the COVID-19 pandemic and the rapid development of multiple successful vaccines based on these technologies, there is now clear real-world evidence of the utility and efficacy of these platforms. Considerable optimization and refinement efforts underpin the successful application of these technologies. Despite this, our understanding of the specific pathways and processes engaged by these vaccines to stimulate the immune response remains incomplete. This review will synthesize our current knowledge of the specific mechanisms by which CD8+ T cell and antibody responses are induced by each of these vaccine platforms, and how this can be impacted by specific vaccine construction techniques. Key gaps in our knowledge are also highlighted, which can hopefully focus future studies.
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Affiliation(s)
- Nicholas M. Provine
- Translational Gastroenterology UnitNuffield Department of MedicineUniversity of OxfordOxfordUK
| | - Paul Klenerman
- Translational Gastroenterology UnitNuffield Department of MedicineUniversity of OxfordOxfordUK,Peter Medawar Building for Pathogen ResearchUniversity of OxfordOxfordUK
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Salih F, Schönborn L, Endres M, Greinacher A. Immunvermittelte Sinus- und Hirnvenenthrombosen: VITT und
prä-VITT als Modellerkrankung. AKTUEL RHEUMATOL 2022. [DOI: 10.1055/a-1936-3123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
ZusammenfassungIn diesem Übersichtsartikel beschreiben wir die klinischen und
paraklinischen Charakteristika der Vakzin-induzierten immunthrombotischen
Thrombozytopenie (VITT) und fassen den gegenwärtigen Kenntnisstand zur
Pathogenese zusammen. Bei der VITT bilden sich 5–20 Tage nach einer
Impfung mit einem Adenovirus-vektorbasiertem SARS-CoV-2-Vakzin (AstraZeneca oder
Johnson & Johnson) lebensbedrohliche Thrombosen aus, vor allem in den
zerebralen Sinus und Hirnvenen. Laborchemisch zeigt sich eine typische
Thrombozytopenie mit erhöhten D-Dimeren. Der Pathogenese liegen
immunologische Prozesse zugrunde, die Ähnlichkeiten mit der
Heparin-induzierten Thrombozytopenie aufweisen: so geht die VITT mit
hochtitrigem Immunoglobulin G gegen das thrombozytäre Protein
Plättchenfaktor 4 (PF4) einher. Durch die Interaktion mit dem Impfstoff
wird PF4 so verändert, dass es von Antikörper-produzierenden
Zellen des Immunsystems erkannt wird. Die so produzierten
Anti-PF4-Antikörper führen über thrombozytäre
FcγIIa-Rezeptoren zu einer Plättchenaktivierung. Der Nachweis
plättchenaktivierender Anti-PF4-Antikörper bestätigt die
Diagnose einer VITT. Antikoagulanzien, die die Bildung von Thrombin oder
Thrombin selbst blockieren und hochdosiertes i. v.-Immunglobulin G, das
die Fcγ-Rezeptor-vermittelte Zellaktivierung inhibiert, stellen die
wirksame und kausale Behandlung der VITT dar. Bei Patienten mit katastrophalem
Verlauf kann ein Plasmaaustausch versucht werden. Bei einigen Patienten ist ein
prä-VITT Syndrom als Prodromalstadium zu beoachten, das sich
typischerweise mit Kopfschmerzen manifestieren kann und dessen frühe
Behandlung hilft, thrombotische Komplikationen zu vermeiden. Die spezifische
Dynamik der VITT-assozierten Immunreaktion entspricht einer transienten,
sekundären Immunantwort. Aktuelle Studien gehen der Frage nach, wie PF4
an unterschiedliche adenovirale Proteine bindet und beleuchten die Rolle von
anderen Impfstoff-Bestandteilen als potentielle Liganden für die
PF4-Bindung. Einige dieser Faktoren sind auch an der Etablierung eines
proinflammatorischen Milieus („danger signal“) beteiligt, das
unmittelbar nach der Impfung die 1. Phase der VITT-Pathogenese triggert. Sobald
in der 2. Phase der VITT-Pathogenese hohe Titer von Anti-PF4-Antikörper
gebildet sind, aktivieren diese neben Thrombozyten auch Granulozyten. In einem
als NETose (von „neutrophil extracellular traps“) bezeichneten
Prozess setzen aktivierte Granulozyten dabei DNA frei, mit der PF4 weitere
Komplexe bildet, an die Anti-PF4-Antikörper binden. Dies
verstärkt die Fcγ-Rezeptor-vermittelte Zellaktivierung weiter
mit der Folge einer ausgeprägten Thrombin-Bildung. Zum Ende des Artikels
geben wir einen Ausblick, welchen Einfluss die bisherigen Erkenntnisse zur VITT
auf weitere globale Impfkampagnen gegen SARS-CoV-2 haben und beleuchten, wie
Anti-PF4-Antikörper jenseits von VITT und HIT auch eine Rolle bei
seltenen Erkrankungen spielen, die mit rezidivierenden venösen und
arteriellen Thrombosen einhergehen.
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Affiliation(s)
- Farid Salih
- Klinik für Neurologie mit Experimenteller Neurologie,
Charité Universitätsmedizin Berlin, Berlin,
Germany
| | - Linda Schönborn
- Institut für Transfusionsmedizin, Universitätsmedizin
Greifswald, Greifswald, Germany
| | - Matthias Endres
- Klinik für Neurologie mit Experimenteller Neurologie,
Charité Universitätsmedizin Berlin, Berlin,
Germany
| | - Andreas Greinacher
- Institut für Transfusionsmedizin, Universitätsmedizin
Greifswald, Greifswald, Germany
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Araújo NM, Rubio IGS, Toneto NPA, Morale MG, Tamura RE. The use of adenoviral vectors in gene therapy and vaccine approaches. Genet Mol Biol 2022; 45:e20220079. [PMID: 36206378 PMCID: PMC9543183 DOI: 10.1590/1678-4685-gmb-2022-0079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2022] [Accepted: 07/12/2022] [Indexed: 11/04/2022] Open
Abstract
Adenovirus was first identified in the 1950s and since then this pathogenic group
of viruses has been explored and transformed into a genetic transfer vehicle.
Modification or deletion of few genes are necessary to transform it into a
conditionally or non-replicative vector, creating a versatile tool capable of
transducing different tissues and inducing high levels of transgene expression.
In the early years of vector development, the application in monogenic diseases
faced several hurdles, including short-term gene expression and even a fatality.
On the other hand, an adenoviral delivery strategy for treatment of cancer was
the first approved gene therapy product. There is an increasing interest in
expressing transgenes with therapeutic potential targeting the cancer hallmarks,
inhibiting metastasis, inducing cancer cell death or modulating the immune
system to attack the tumor cells. Replicative adenovirus as vaccines may be even
older and date to a few years of its discovery, application of non-replicative
adenovirus for vaccination against different microorganisms has been
investigated, but only recently, it demonstrated its full potential being one of
the leading vaccination tools for COVID-19. This is not a new vector nor a new
technology, but the result of decades of careful and intense work in this
field.
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Affiliation(s)
- Natália Meneses Araújo
- Universidade Federal de São Paulo, Laboratório de Biologia Molecular
do Câncer, São Paulo, SP, Brazil.
| | - Ileana Gabriela Sanchez Rubio
- Universidade Federal de São Paulo, Laboratório de Biologia Molecular
do Câncer, São Paulo, SP, Brazil. ,Universidade Federal de São Paulo, Departamento de Ciências
Biológicas, Diadema, SP, Brazil. ,Universidade Federal de São Paulo, Laboratório de Ciências
Moleculares da Tireóide, Diadema, SP, Brazil.
| | | | - Mirian Galliote Morale
- Universidade Federal de São Paulo, Laboratório de Biologia Molecular
do Câncer, São Paulo, SP, Brazil. ,Universidade Federal de São Paulo, Departamento de Ciências
Biológicas, Diadema, SP, Brazil. ,Universidade Federal de São Paulo, Laboratório de Ciências
Moleculares da Tireóide, Diadema, SP, Brazil.
| | - Rodrigo Esaki Tamura
- Universidade Federal de São Paulo, Laboratório de Biologia Molecular
do Câncer, São Paulo, SP, Brazil. ,Universidade Federal de São Paulo, Departamento de Ciências
Biológicas, Diadema, SP, Brazil.
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Ren Z, Yang F, Yao S, Bi L, Jiang G, Huang J, Tang Y. Effects of low molecular weight peptides from monkfish (Lophius litulon) roe on immune response in immunosuppressed mice. Front Nutr 2022; 9:929105. [PMID: 36211506 PMCID: PMC9532971 DOI: 10.3389/fnut.2022.929105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Accepted: 09/05/2022] [Indexed: 11/16/2022] Open
Abstract
This study aimed to investigate the immunomodulatory activation of low-molecular-weight peptides from monkfish (Lophius litulon) roe (named MRP) on cyclophosphamide (CTX)-induced immunosuppressed mice. Our results indicated that MRP (100 mg/kg/d BW) could significantly increase the body weight and immune organ index, and improve the morphological changes in the spleen and thymus of mice. These effects subsequently enhance the serum levels of interleukin (IL)-6, IL-1β, tumor necrosis factor (TNF)-α, and immunoglobulin (Ig) A, IgM, and IgG. Furthermore, MRP could also improve CTX-induced oxidative stress, and activate the NF-κB and MAPK pathways in the spleen tissues. The findings reported herein indicate that MRP has a good immunomodulatory activation toward immunosuppressed mice, hence can potentially be developed as an immune adjuvant or functional food.
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Affiliation(s)
- Zhexin Ren
- Zhejiang Provincial Engineering Technology Research Center of Marine Biomedical Products, School of Food and Pharmacy, Zhejiang Ocean University, Zhoushan, China
| | - Fei Yang
- Hangzhou Women's Hospital (Hangzhou Maternity and Child Health Care Hospital), Neonatal Intensive Care Unit, Hangzhou, China
| | - Sijia Yao
- Zhejiang Provincial Engineering Technology Research Center of Marine Biomedical Products, School of Food and Pharmacy, Zhejiang Ocean University, Zhoushan, China
| | - Lijun Bi
- College of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, China
| | - Guanqin Jiang
- Zhejiang Provincial Engineering Technology Research Center of Marine Biomedical Products, School of Food and Pharmacy, Zhejiang Ocean University, Zhoushan, China
| | - Ju Huang
- Zhejiang Provincial Engineering Technology Research Center of Marine Biomedical Products, School of Food and Pharmacy, Zhejiang Ocean University, Zhoushan, China
- Key Laboratory of Health Risk Factors for Seafood of Zhejiang Province, Zhejiang Ocean University, Zhoushan, China
- *Correspondence: Ju Huang
| | - Yunping Tang
- Zhejiang Provincial Engineering Technology Research Center of Marine Biomedical Products, School of Food and Pharmacy, Zhejiang Ocean University, Zhoushan, China
- Yunping Tang
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Greinacher A, Schönborn L, Siegerist F, Steil L, Palankar R, Handtke S, Reder A, Thiele T, Aurich K, Methling K, Lalk M, Völker U, Endlich N. Pathogenesis of vaccine-induced immune thrombotic thrombocytopenia (VITT). Semin Hematol 2022; 59:97-107. [PMID: 35512907 PMCID: PMC8863951 DOI: 10.1053/j.seminhematol.2022.02.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2022] [Accepted: 02/16/2022] [Indexed: 02/06/2023]
Abstract
Vaccine-induced immune thrombotic thrombocytopenia (VITT; synonym, thrombosis with thrombocytopenia syndrome, is associated with high-titer immunoglobulin G antibodies directed against platelet factor 4 (PF4). These antibodies activate platelets via platelet FcγIIa receptors, with platelet activation greatly enhanced by PF4. Here we summarize the current concepts in the pathogenesis of VITT. We first address parallels between heparin-induced thrombocytopenia and VITT, and provide recent findings on binding of PF4 to adenovirus particles and non-assembled adenovirus proteins in the 2 adenovirus vector-based COVID-19 vaccines, ChAdOx1 nCoV-19 and Ad26.COV2.S. Further, we discuss the potential role of vaccine constituents such as glycosaminoglycans, EDTA, polysorbate 80, human cell-line proteins and nucleotides as potential binding partners of PF4. The immune response towards PF4 in VITT is likely triggered by a proinflammatory milieu. Human cell-line proteins, non-assembled virus proteins, and potentially EDTA may contribute to the proinflammatory state. The transient nature of the immune response towards PF4 in VITT makes it likely that-as in heparin-induced thrombocytopenia -marginal zone B cells are key for antibody production. Once high-titer anti-PF4 antibodies have been formed 5 to 20 days after vaccination, they activate platelets and granulocytes. Activated granulocytes undergo NETosis and the released DNA also forms complexes with PF4, which fuels the Fcγ receptor-dependent cell activation process, ultimately leading to massive thrombin generation. Finally, we summarize our initial observations indicating that VITT-like antibodies might also be present in rare patients with recurrent venous and arterial thrombotic complications, independent of vaccination.
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Affiliation(s)
- Andreas Greinacher
- Institute of Transfusion Medicine, University Medicine Greifswald, Greifswald, Germany.
| | - Linda Schönborn
- Institute of Transfusion Medicine, University Medicine Greifswald, Greifswald, Germany
| | - Florian Siegerist
- Institute for Anatomy and Cell Biology, University Medicine Greifswald, Greifswald, Germany
| | - Leif Steil
- Interfaculty Institute of Genetics and Functional Genomics, Department Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Raghavendra Palankar
- Institute of Transfusion Medicine, University Medicine Greifswald, Greifswald, Germany
| | - Stefan Handtke
- Institute of Transfusion Medicine, University Medicine Greifswald, Greifswald, Germany
| | - Alexander Reder
- Interfaculty Institute of Genetics and Functional Genomics, Department Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Thomas Thiele
- Institute of Transfusion Medicine, University Medicine Greifswald, Greifswald, Germany
| | - Konstanze Aurich
- Institute of Transfusion Medicine, University Medicine Greifswald, Greifswald, Germany
| | - Karen Methling
- Institute of Biochemistry, University of Greifswald, Greifswald, Germany
| | - Michael Lalk
- Institute of Biochemistry, University of Greifswald, Greifswald, Germany
| | - Uwe Völker
- Interfaculty Institute of Genetics and Functional Genomics, Department Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Nicole Endlich
- Institute for Anatomy and Cell Biology, University Medicine Greifswald, Greifswald, Germany
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Toll-Like Receptor 4 Regulates Rabies Virus-Induced Humoral Immunity through Recruitment of Conventional Type 2 Dendritic Cells to Lymph Organs. J Virol 2021; 95:e0082921. [PMID: 34613801 DOI: 10.1128/jvi.00829-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Rabies, caused by rabies virus (RABV), is fatal to both humans and animals around the world. Effective clinical therapy for rabies has not been achieved, and vaccination is the most effective means of preventing and controlling rabies. Although different vaccines, such as live attenuated and inactivated vaccines, can induce different immune responses, different expressions of pattern recognition receptors (PRRs) also cause diverse immune responses. Toll-like receptor 4 (TLR4) is a pivotal PRR that induces cytokine production and bridges innate and adaptive immunity. Importantly, TLR4 recognizes various virus-derived pathogen-associated molecular patterns (PAMPs) and virus-induced damage-associated molecular patterns (DAMPs), usually leading to the activation of immune cells. However, the role of TLR4 in the humoral immune response induced by RABV has not yet been revealed. Based on TLR4-deficient (TLR4-/-) and wild-type (WT) mouse models, we report that TLR4-dependent recruitment of the conventional type 2 dendritic cells (CD8α- CD11b+ cDC2) into secondary lymph organs (SLOs) is critical for antigen presentation. cDC2-initiated differentiation of follicular helper T (Tfh) cells promotes the proliferation of germinal center (GC) B cells, the formation of GCs, and the production of plasma cells (PCs), all of which contribute to the production of RABV-specific IgG and virus-neutralizing antibodies (VNAs). Collectively, our work demonstrates that TLR4 is necessary for the recruitment of cDC2 and for the induction of RABV-induced humoral immunity, which is regulated by the cDC2-Tfh-GC B axis. IMPORTANCE Vaccination is the most efficient method to prevent rabies. TLR4, a well-known immune sensor, plays a critical role in initiating innate immune response. Here, we found that TLR4-deficient (TLR4-/-) mice suppressed the induction of humoral immune response after immunization with rabies virus (RABV), including reduced production of VNAs and RABV-specific IgG compared to that occurred in wild-type (WT) mice. As a consequence, TLR4-/- mice exhibited higher mortality than that of WT mice after challenge with virulent RABV. Importantly, further investigation found that TLR4 signaling promoted the recruitment of cDC2 (CD8α+ CD11b-), a subset of cDCs known to induce CD4+ T-cell immunity through their MHC-II presentation machinery. Our results imply that TLR4 is indispensable for an efficient humoral response to rabies vaccine, which provides new insight into the development of novel rabies vaccines.
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