Anti-MOG autoantibodies pathogenicity in children and macaques demyelinating diseases

In Silico Modeling of Myelin Oligodendrocyte Glycoprotein Disulfide Bond Reduction by Phosphine-Borane Complexes

BACKGROUND

Neurodegenerative diseases can cause vision loss by damaging retinal ganglion cells in the optic nerve. Novel phosphine-borane compounds (PBs) can protect these cells from oxidative stress via the reduction of disulfide bonds. However, the specific targets of these compounds are unknown. Proteomic evidence suggests that myelin oligodendrocyte glycoprotein (MOG) is a potential target. MOG is of significant interest due to its role in anti-MOG optic neuritis syndrome.

METHODS

We used in silico modeling to explore the structural consequences of cleaving the extracellular domain MOG disulfide bond, both in isolation and in complex with anti-MOG antibodies. The potential binding of PBs to this bond was examined using molecular docking.

RESULTS

Cleaving the disulfide bond of MOG altered the structure of MOG dimers and reduced their energetic favorability by 46.13 kcal/mol. The energy profiles of anti-MOG antibody complexes were less favorable when the disulfide bond of MOG was reduced in the monomeric state by 55.21 kcal/mol, but the reverse was true in the dimeric state. PBs exhibited reducing capabilities with the MOG extracellular disulfide bond, with this best-scoring compound binding with an energy of -28.54 kcal/mol to the MOG monomer and -24.97 kcal/mol to the MOG dimer.

CONCLUSIONS

These findings suggest that PBs can affect the structure of MOG dimers and the formation of antibody complexes by reducing the MOG disulfide bond. Structural changes in MOG could have implications for neurodegenerative diseases and anti-MOG syndrome.

Contributions of CSF interleukin-6 elevation to the pathogenesis of myelin oligodendrocyte glycoprotein antibody-associated disease

BACKGROUND

Myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) is a rare neuroinflammatory disorder characterized by acute episodes of central nervous system (CNS) demyelination. Previous studies have reported elevated interleukin (IL)-6 in cerebrospinal fluid (CSF) of MOGAD patients.

OBJECTIVE

We examined if CSF IL-6 level increase is associated with clinical parameters in MOGAD.

METHODS

IL-6 levels were measured using 44 CSF samples during the acute phase and 6 samples during recovery from 34 MOGAD patients, as well as 65 CSF samples from 45 aquaporin-4 antibody-positive neuromyelitis optica spectrum disorder (AQP4Ab + NMOSD), 107 samples from 76 multiple sclerosis patients, and 45 samples from neurodegenerative disease patients. Associations between IL-6 levels and clinical parameters in MOGAD were also evaluated.

RESULTS

CSF IL-6 levels were significantly comparably elevated during acute-phase in MOGAD and AQP4Ab + NMOSD, but declined following the acute phase. Among MOGAD patients, CSF IL-6 level was significantly correlated with CSF cell count, greater in patients with brain lesions than spinal cord lesions, and higher in CSF than serum, suggesting that excessive IL-6 is produced predominantly in CNS. Neurological recovery was tended to be poorer in MOGAD patients with higher CSF IL-6 level.

CONCLUSION

CSF IL-6 may play important roles in the pathogenesis of MOGAD, especially in CNS inflammation.

Frequency and clinical relevance of MOG-antibodies in CSF in pediatric patients with MOG antibody-associated diseases

OBJECTIVE

This retrospective study aimed to describe a cohort of 38 pediatric patients with MOGAD and to investigate the clinical differences between patients with CSF-negativity and CSF-positivity for MOG-abs.

METHODS

The clinical and laboratory characteristics of pediatric patients with MOGAD were retrospectively studied. Demographics, clinical characteristics, CSF analysis, treatments and prognosis of patients were recorded. All patients' serums and CSF were tested for MOG-IgG by live cell-based assays (CBA). The data were statistically analysed.

RESULTS

A total of 38 pediatric MOGAD patients were enrolled in the study, including 22 (57.9 %) females and 16 male (42.1 %) with a mean age of 8.4 ± 4.0 years at disease onset. Twenty-seven (71.7 %) patients were CSF-positive for MOG-abs while 11 (28.9 %) patients were CSF-negative for MOG-abs. The median follow-up was 25.5 months (IQR 5.5-73.25). Seventeen (44.7 %) patients presented a relapsing disease course, and the majority of these patients was CSF positive with a significant difference between the two groups (p = 0.038) in terms of recurrent diseases. CSF-positive patients presented more often an increased white cell count (p = 0.043), and in this cohort clinical phenotypes with spinal involvement were more frequent while encephalitis-like phenotypes were more frequent in the CSF negative cohort (p = 0.019).

CONCLUSIONS

CSF-status appears to identify two subgroups in this pediatric MOGAD population; thus, CSF-status requires further studies in pediatric patients with MOGAD.

Classification of Myelin Oligodendrocyte Glycoprotein Antibody-Related Disease and Its Mimicking Acute Demyelinating Syndromes in Children Using MRI-Based Radiomics: From Lesion to Subject

RATIONALE AND OBJECTIVES

To develop MRI-based radiomics models from the lesion level to the subject level and assess their value for differentiating myelin oligodendrocyte glycoprotein antibody-related disease (MOGAD) from non-MOGAD acute demyelinating syndromes in pediatrics.

MATERIALS AND METHODS

66 MOGAD and 66 non-MOGAD children were assigned to the training set (36/35), internal test set (14/16), and external test set (16/15), respectively. At the lesion level, five single-sequence models were developed alongside a fusion model (combining these five sequences). The radiomics features of each lesion were quantified as the lesion-level radscore (LRS) using the best-performing model. Subsequently, a lesion-typing function was employed to classify lesions into two types (MOGAD-like or non-MOGAD-like), and the average LRS of the predominant type lesions in each subject was considered as the subject-level radscore (SRS). Based on SRS, a subject-level model was established and compared to both clinical models and radiologists' assessments.

RESULTS

At the lesion level, the fusion model outperformed the five single-sequence models in distinguishing MOGAD and non-MOGAD lesions (0.867 and 0.810 of area under the curve [AUC] in internal and external testing, respectively). At the subject level, the SRS model showed superior performance (0.844 and 0.846 of AUC in internal and external testing, respectively) compared to clinical models and radiologists' assessments for distinguishing MOGAD and non-MOGAD.

CONCLUSION

MRI-based radiomics models have potential clinical value for identifying MOGAD from non-MOGAD. The fusion model and SRS model can distinguish between MOGAD and non-MOGAD at the lesion level and subject level, respectively, providing a differential diagnosis method for these two diseases.

Delimiting MOGAD as a disease entity using translational imaging

The first formal consensus diagnostic criteria for myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) were recently proposed. Yet, the distinction of MOGAD-defining characteristics from characteristics of its important differential diagnoses such as multiple sclerosis (MS) and aquaporin-4 antibody seropositive neuromyelitis optica spectrum disorder (NMOSD) is still obstructed. In preclinical research, MOG antibody-based animal models were used for decades to derive knowledge about MS. In clinical research, people with MOGAD have been combined into cohorts with other diagnoses. Thus, it remains unclear to which extent the generated knowledge is specifically applicable to MOGAD. Translational research can contribute to identifying MOGAD characteristic features by establishing imaging methods and outcome parameters on proven pathophysiological grounds. This article reviews suitable animal models for translational MOGAD research and the current state and prospect of translational imaging in MOGAD.

Complement-dependent cytotoxicity of human autoantibodies against myelin oligodendrocyte glycoprotein

Background

The autoantibody to myelin oligodendrocyte glycoprotein (MOG), a component of the central nervous system myelin, has been identified in a subset of demyelinating diseases. However, there is no convincing evidence to support the direct pathogenic contribution of this autoantibody.

Objective

To elucidate the role of anti-MOG autoantibodies in human demyelinating disorders, we assessed the effect of autoantibodies on MOG-expressing cells.

Methods

Mammalian cells expressing the human MOG protein reacted with human anti-MOG autoantibodies in the presence or absence of complement. Sera from 86 patients and 11 healthy sera were used. We analyzed anti-MOG antibody titers, IgG subclass, and their cytotoxic ability in sera from patients with various neurological diseases. Membrane attack complex (MAC) formation was examined by detection of complement C9 or C9neo with western blot or flow cytometry.

Results

Among 86 patients, 40 were determined to be MOG-IgG-positive and 46 were negative. Anti-MOG-positive sera, but not -negative sera, caused cell death in MOG-expressing cells. This cytotoxic effect was disappeared after heat inactivation of sera. Importantly, anti-MOG IgG and externally added complement were necessary for sufficient cytotoxic effects. Anti-MOG autoantibodies were histologically colocalized with complement and formed a membrane attack complex consisting of anti-MOG IgG and complement factors.

Conclusion

The human MOG antibody specifically killed MOG-expressing cells in vitro in the presence of externally added complement. Membrane attack complexes were formed on the cells, indicating that this autoantibody activated complement-mediated cytotoxicity. Further studies in larger numbers of patients are needed to characterize the role of complement in MOGAD.

BioSimia, France CNRS network for nonhuman primate biomedical research in infectiology, immunology, and neuroscience

Research and developments based on nonhuman primate models have a specific place in biomedical sciences, and nonhuman primate species also have a specific place in the public opinion on the use of animal in research. While nonhuman primates are used in very limited number compared to other animal models, they are rightly the focus of deep ethical concerns. The importance of nonhuman primates in neuroscientific fundamental and preclinical discoveries together with the targeting of such research by activist groups well illustrate this fact. Nonhuman primates also highly contribute to other biomedical fields including immunology, virology, or metabolic and respiratory physiology. In all these fields, researchers, engineers and technicians face similar matters and share the same needs for optimal animal welfare, handling, and veterinary care, the same quest for first-rate research infrastructure and funding, and the same yearning for more public understanding and support. In this article, we give an overview of the evolution of human-animal relationships and public attitudes to animal research in France, and we recount the creation of BioSimia, France network for nonhuman primate biomedical research which now links all academic laboratories nationwide in all the domains for which nonhuman primates remain essential. We explain the principles as well as the outcomes of networking across disciplines. As a perspective, we outline the potential benefits of extending such network to a European scale.

Serum Neurofilament Light Chain Levels and Myelin Oligodendrocyte Glycoprotein Antibodies in Pediatric Acquired Demyelinating Syndromes

Introduction: The relationship between serum neurofilament light chain (sNfL) and myelin oligodendrocyte glycoprotein antibody (MOG-Ab) status has not been yet investigated in children with the acquired demyelinating syndrome (ADS).

Objective and Methods: The sNfL levels and MOG-Abs were measured by ultrasensitive single-molecule array and cell-based assay in a cohort of 37 children with ADS and negativity for serum anti-aquaporin 4 (AQP4) antibodies. The sNfL levels were compared in MOG-Ab+/MOG-Ab– and in two subgroups MOG-Ab+ with/without encephalopathy.

Results: About 40% ADS resulted in MOG-Ab+. MOG-Ab+ were younger at sampling (median = 9.8; range = 2.17–17.5 vs. 14.7/9–17; p = 0.002) with lower frequency of cerebrospinal fluid oligoclonal bands positivity (27% vs. 70%; p = 0.013) compared to MOG-Ab–. About 53% of MOG-Ab+ presented encephalopathy at onset, 1/22 of MOG-Ab– (p = 0.0006). Higher sNfL levels (p = 0.0001) were found in MOG-Ab+ (median/range = 11.11/6.8–1,129) and MOG-Ab– (median/range = 11.6/4.3–788) compared to age-matched controls (median/range = 2.98/1–4.53), without significant difference. MOG-Ab+ with encephalopathy resulted significantly younger at sampling (median/range: 4.5/2.17–11.17 vs. 14.16/9.8–17.5; p = 0.004), had higher sNfL levels (median/range:75.24/9.1–1,129 vs. 10.22/6.83–50.53; p = 0.04), and showed a trend for higher MOG-Ab titer (0.28/0.04–0.69 vs. 0.05/0.04–0.28; p = 0.1) in comparison to those without encephalopathy.

Discussion: We confirmed high sNfL levels in pediatric ADS independently from the MOG-Ab status. Encephalopathy at onset is associated more frequently with MOG Ab+ children with higher sNfL levels and MOG titer. These findings suggest a role of acute demyelination in association with axonal damage in the pathogenesis of encephalopathy in pediatric ADS.

Recombinant myelin oligodendrocyte glycoprotein quality modifies evolution of experimental autoimmune encephalitis in macaques

Experimental autoimmune encephalitis (EAE) is a well-recognized model for the study of human acquired demyelinating diseases (ADD), a group of inflammatory disorders of the central nervous system (CNS) characterized by inflammation, myelin loss, and neurological impairment of variable severity. In rodents, EAE is typically induced by active immunization with a combination of myelin-derived antigen and a strong adjuvant as complete Freund's adjuvant (CFA), containing components of the mycobacterial wall, while myelin antigen alone or associated with other bacterial components, as lipopolysaccharides (LPS), often fails to induce EAE. In contrast to this, EAE can be efficiently induced in non-human primates by immunization with the recombinant human myelin oligodendrocyte glycoprotein (rhMOG), produced in Escherichia coli (E. coli), purified and formulated with incomplete Freund's adjuvant (IFA), which lacks bacterial elements. Here, we provide evidence indicating how trace amounts of bacterial contaminants within rhMOG may influence the course and severity of EAE in the cynomolgus macaque immunized with rhMOG/IFA. The residual amount of E. coli contaminants, as detected with mass spectrometry within rhMOG protein stocks, were found to significantly modulate the severity of clinical, radiological, and histologic hallmarks of EAE in macaques. Indeed, animals receiving the purest rhMOG showed milder disease severity, increased numbers of remissions, and reduced brain damage. Histologically, these animals presented a wider diversity of lesion types, including changes in normal-appearing white matter and prephagocytic lesions. Non-human primates EAE model with milder histologic lesions reflect more accurately ADD and permits to study of the pathogenesis of disease initiation and progression.

Pathogenesis of autoimmune demyelination: from multiple sclerosis to neuromyelitis optica spectrum disorders and myelin oligodendrocyte glycoprotein antibody-associated disease

Autoimmunity plays a significant role in the pathogenesis of demyelination. Multiple sclerosis (MS), neuromyelitis optica spectrum disorders (NMOSD) and myelin oligodendrocyte glycoprotein antibody‐associated disease (MOGAD) are now recognised as separate disease entities under the amalgam of human central nervous system demyelinating disorders. While these disorders share inherent similarities, investigations into their distinct clinical presentations and lesion pathologies have aided in differential diagnoses and understanding of disease pathogenesis. An interplay of various genetic and environmental factors contributes to each disease, many of which implicate an autoimmune response. The pivotal role of the adaptive immune system has been highlighted by the diagnostic autoantibodies in NMOSD and MOGAD, and the presence of autoreactive lymphocytes in MS lesions. While a number of autoantigens have been proposed in MS, recent emphasis on the contribution of B cells has shed new light on the well‐established understanding of T cell involvement in pathogenesis. This review aims to synthesise the clinical characteristics and pathological findings, discuss existing and emerging hypotheses regarding the aetiology of demyelination and evaluate recent pathogenicity studies involving T cells, B cells, and autoantibodies and their implications in human demyelination.

Regulatory T Cells Increase After rh-MOG Stimulation in Non-Relapsing but Decrease in Relapsing MOG Antibody-Associated Disease at Onset in Children

Background

Myelin oligodendrocytes glycoprotein (MOG) antibody-associated disease (MOGAD) represent 25% of pediatric acquired demyelinating syndrome (ADS); 40% of them may relapse, mimicking multiple sclerosis (MS), a recurrent and neurodegenerative ADS, which is MOG-Abs negative.

Aims

To identify MOG antigenic immunological response differences between MOGAD, MS and control patients, and between relapsing versus non-relapsing subgroups of MOGAD.

Methods

Three groups of patients were selected: MOGAD (n=12 among which 5 relapsing (MOGR) and 7 non-relapsing (MOGNR)), MS (n=10) and control patients (n=7). Peripheral blood mononuclear cells (PBMC) collected at the time of the first demyelinating event were cultured for 48 h with recombinant human (rh)-MOG protein (10 μg/ml) for a specific stimulation or without stimulation as a negative control. The T cells immunophenotypes were analyzed by flow cytometry. CD4⁺ T cells, T helper (Th) cells including Th1, Th2, and Th17 were analyzed by intracellular staining of cytokines. Regulatory T cells (T_regs, Foxp3⁺), CD45RA^-Foxp3⁺ T_regs and subpopulation naive T_regs (CD45RA⁺Foxp3^int), effector T_regs (CD45RA^-Foxp3^high) and non-suppressive T_regs (CD45RA^-Foxp3^int) proportions were determined.

Results

The mean onset age of each group, ranging from 9.9 to 13.8, and sex ratio, were similar between MOGR, MOGNR, MS and control patients as analyzed by one-way ANOVA and Chi-square test. When comparing unstimulated to rh-MOG stimulated T cells, a significant increase in the proportion of Th2 and Th17 cells was observed in MOGAD. Increase of Th17 cells was significant in MOGNR (means: 0.63 ± 0.15 vs. 1.36 ± 0.43; Wilcoxon-test p = 0.03) but not in MOGR. CD4⁺ T_regs were significantly increased in MOGNR (means: 3.51 ± 0.7 vs. 4.59 ± 1.33; Wilcoxon-test p = 0.046) while they decreased in MOGR. CD45RA^-Foxp3⁺ T_regs were significantly decreased in MOGR (means: 2.37 ± 0.23 vs. 1.99 ± 0.17; paired t-test p = 0.021), but not in MOGNR. MOGR showed the highest ratio of effector T_regs/non suppressive-T_regs, which was significantly higher than in MOGNR.

Conclusions

Our findings suggest that CD4⁺ Th2 and Th17 cells are involved in the pathophysiology of MOGAD in children. The opposite response of T_regs to rh-MOG in MOGNR, where CD4⁺ T_regs increased, and in MOGR, where CD45RA^-Foxp3⁺ T_regs decreased, suggests a probable loss of tolerance toward MOG autoantigen in MOGR which may explain relapses in this recurrent pediatric autoimmune disease.

Anti-MOG Antibody Syndrome and Cerebral Sinovenous Thrombosis: A Cause–Effect Hypothesis

Cerebral venous thrombosis is an uncommon event of stroke in childhood. Its origin is multifactorial and often it manifests with nonspecific symptoms that may overlap with underlying predisposing factors. Anti–myelin oligodendrocyte glycoprotein (MOG) antibody syndrome is a group of recently recognized acquired demyelinating diseases that occur more commonly in children, usually, with a favorable outcome. The association between cerebral venous thrombosis and demyelinating syndrome has been reported but their clinical relationship is matter of debate and various hypotheses have been advanced including intravenous (IV) steroid therapy and/or the consequence of a shared inflammatory-thrombotic process. Herein, we report the case of a child with anti-MOG antibody syndromes who developed a thrombosis of the superior sagittal sinus and of the right Trolard's vein.

Novel insights into pathophysiology and therapeutic possibilities reveal further differences between AQP4-IgG- and MOG-IgG-associated diseases

PURPOSE OF REVIEW

This review summarizes recent insights into the pathogenesis and therapeutic options for patients with MOG- or AQP4-antibodies.

RECENT FINDINGS

Although AQP4-IgG are linked to NMOSD, MOG-IgG-associated diseases (MOGAD) include a broader clinical spectrum of autoimmune diseases of the central nervous system (CNS). Details of membrane assembly of AQP4-IgG required for complement activation have been uncovered. Affinity-purified MOG-IgG from patients were shown to be pathogenic by induction of demyelination when the blood--brain barrier (BBB) was breached and by enhancement of activation of cognate T cells. A high-affinity AQP4-IgG, given peripherally, could induce NMOSD-like lesions in rats in the absence of BBB breach. Circulating AQP4-specific and MOG-specific B cells were identified and suggest differences in origin of MOG-antibodies or AQP4-antibodies. Patients with MOG-IgG show a dichotomy concerning circulating MOG-specific B cells; whether this is related to differences in clinical response of anti-CD20 therapy remains to be analyzed. Clinical trials of AQP4-IgG-positive NMOSD patients showed success with eculizumab (preventing cleavage of complement factor C5, thereby blocking formation of chemotactic C5a and membrane attack complex C9neo), inebilizumab (depleting CD19 + B cells), and satralizumab (anti-IL-6R blocking IL-6 actions).

SUMMARY

New insights into pathological mechanisms and therapeutic responses argue to consider NMOSD with AQP4-IgG and MOGAD as separate disease entities.

E.U. paediatric MOG consortium consensus: Part 3 - Biomarkers of paediatric myelin oligodendrocyte glycoprotein antibody-associated disorders

A first episode of acquired demyelinating disorder (ADS) in children is a diagnostic challenge as different diseases can express similar clinical features. Recently, antibodies against myelin oligodendrocyte glycoprotein (MOG) have emerged as a new ADS biomarker, which clearly allow the identification of monophasic and relapsing ADS forms different from MS predominantly in children. Due to the novelty of this antibody there are still challenges and controversies about its pathogenicity and best technique to detect it. In this manuscript we will discuss the recommendations and caveats on MOG antibody assays, role in the pathogenesis, and additionally discuss the usefulness of other potential new biomarkers in MOG-antibody associated disorders (MOGAD).