Intramuscular vaccination against SARS-CoV-2 transiently induces neutralizing IgG rather than IgA in the saliva.

The mucosal immunity is crucial for restricting SARS-CoV-2 at its entry site. Intramuscularly applied vaccines against SARS-CoV-2 stimulate high levels of neutralizing Abs in serum, but the impact of these intramuscular vaccinations on features of mucosal immunity is less clear. Here, we analyzed kinetic and functional properties of anti-SARS-CoV-2 Abs in the saliva after vaccination with BNT162b2. We analyzed a total of 24 healthy donors longitudinally for up to 16 months. We found that specific IgG appeared in the saliva after the second vaccination, declined thereafter and reappeared after the third vaccination. Adjusting serum and saliva for the same IgG concentration revealed a strong correlation between the reactivity in these two compartments. Reactivity to VoCs correlated strongly as seen by ELISAs against RBD variants and by live-virus neutralizing assays against replication-competent viruses. For further functional analysis, we purified IgG and IgA from serum and saliva. In vaccinated donors we found neutralizing activity towards authentic virus in the IgG, but not in the IgA fraction of the saliva. In contrast, IgA with neutralizing activity appeared in the saliva only after breakthrough infection. In serum, we found neutralizing activity in both the IgA and IgG fractions. Together, we show that intramuscular mRNA vaccination transiently induces a mucosal immunity that is mediated by IgG and thus differs from the mucosal immunity after infection. Waning of specific mucosal IgG might be linked to susceptibility for breakthrough infection.

Single-cell profiling reveals preferential reduction of memory B cell subsets in cladribine patients that correlates with treatment response.

Background: Cladribine is a highly effective immunotherapy that is applied in two short-term courses over 2 years and reduces relapse rate and disease progression in patients with relapsing multiple sclerosis (MS). Despite the short treatment period, cladribine has a long-lasting effect on disease activity even after recovery of lymphocyte counts, suggesting a yet undefined long-term immune modulating effect. Objectives: Our aim was to provide a more profound understanding of the detailed effects of cladribine, also with regard to the patients' therapy response. Design: We performed an open-labeled, explorative, prospective, single-arm study, in which we examined the detailed lymphocyte subset development of MS patients who received cladribine treatment over 2 years. Methods: We performed in-depth profiling of the effects of cladribine on peripheral blood lymphocytes by flow cytometry, bulk RNA sequencing of sorted CD4+ T cells, CD8+ T cells, and CD19+ B cells as well as single-cell RNA sequencing of peripheral blood mononuclear cells in a total of 23 MS patients before and at different time points up to 24 months after cladribine treatment. Data were correlated with clinical and cranial magnetic resonance imaging (MRI) disease activity. Results: Flow cytometry revealed a predominant and sustained reduction of memory B cells compared to other B cell subsets after cladribine treatment, whereas T cell subsets were slightly reduced in a more uniform pattern. The overall transcriptional profile of total blood B cells exhibited reduced expression of proinflammatory and T cell activating genes, while single-cell transcriptomics revealed that gene expression within each B cell cluster did not change over time. Stable patients displayed stronger reductions of selected memory B cell clusters as compared to patients with clinical or cerebral MRI disease activity. Conclusion: We describe a pronounced and sustained effect of cladribine on the memory B cell compartment, and the resulting change in B cell subset composition causes a significant alteration of B cell transcriptional profiles resulting in reduced proinflammatory and T cell activating capacities. The extent of reduction in selected memory B cell clusters by cladribine may predict treatment response.

Features of Isoforms of Human Soluble TACI.

The BAFF/APRIL-system with the two cytokines BAFF and APRIL and their three receptors, transmembrane activator and CAML interactor (TACI), BAFF receptor, and B-cell maturation Ag, is important for B cell maintenance. The BAFF/APRIL system is a therapeutic target in B cell-derived malignancies and autoimmune diseases. However, unexpected outcomes of clinical trials with atacicept (TACI-Fc) underline our incomplete understanding of this system. Shedding of the three receptors is one important regulatory element. In humans, TACI exists in two isoforms generated through alternative splicing in their extracellular portion: TACI-long (l) has two cysteine-rich domains, whereas TACI-short (s) lacks the first low-affinity one. In this study, we discriminated soluble (s) forms of TACI-l and TACI-s with newly generated mAbs and found that both were spontaneously released from activated human B cells, with a predominance of sTACI-l. Furthermore, sTACI-l was also the dominant isoform in human serum. Vaccination with the mRNA vaccine from BioNTech does not significantly affect the serum levels of sTACI-l. Both TACI-s and TACI-l were shed by a disintegrin and metalloproteinase domain-containing protein 10. TACI-l and TACI-s formed homo- and hetero-oligomers in soluble and membrane-bound forms. Both sTACI-l and sTACI-s acted as decoy receptors for BAFF, but only sTACI-l also efficiently inhibited APRIL. Dimerization of sTACI-l enhanced its decoy functions only slightly. Together, we extend our knowledge of the complexity of the BAFF/APRIL system by identifying and characterizing the two soluble isoforms of TACI.

Ublituximab: A new FDA-approved anti-CD20 mAb for relapsing forms of multiple sclerosis.

Ublituximab, an intravenous glycoengineered chimeric anti-CD20 IgG1 monoclonal antibody (mAb), is a new FDA-approved treatment for relapsing forms of Multiple Sclerosis (MS). Reassembling the other three anti-CD20 mAbs already in use for MS (rituximab, ocrelizumab and ofatumumab), ublituximab leads to depletion of B cells but spars long-lived plasma cells. Here, we discuss the main findings obtained during the phase 3 clinical trials (ULTIMATE I and II) for ublituximab versus teriflunomide. The current emergence and approval of new anti-CD20 mAbs with different dose regimens, routes of application, glycoengineering and mechanisms of action may contribute to different clinical outcomes.

Dissection of complement and Fc-receptor-mediated pathomechanisms of autoantibodies to myelin oligodendrocyte glycoprotein.

Autoantibodies against myelin oligodendrocyte glycoprotein (MOG) have recently been established to define a new disease entity, MOG-antibody-associated disease (MOGAD), which is clinically overlapping with multiple sclerosis. MOG-specific antibodies (Abs) from patients are pathogenic, but the precise effector mechanisms are currently still unknown and no therapy is approved for MOGAD. Here, we determined the contributions of complement and Fc-receptor (FcR)-mediated effects in the pathogenicity of MOG-Abs. Starting from a recombinant anti-MOG (mAb) with human IgG1 Fc, we established MOG-specific mutant mAbs with differential FcR and C1q binding. We then applied selected mutants of this MOG-mAb in two animal models of experimental autoimmune encephalomyelitis. First, we found MOG-mAb-induced demyelination was mediated by both complement and FcRs about equally. Second, we found that MOG-Abs enhanced activation of cognate MOG-specific T cells in the central nervous system (CNS), which was dependent on FcR-, but not C1q-binding. The identification of complement-dependent and -independent pathomechanisms of MOG-Abs has implications for therapeutic strategies in MOGAD.

Antibodies Against Glutamic Acid Decarboxylase 65 Are Locally Produced in the CSF and Arise During Affinity Maturation.

BACKGROUND AND OBJECTIVES: Antibodies (Abs) against the cytoplasmic protein glutamic acid decarboxylase 65 (GAD65) are detected in patients with neurologic syndromes together referred to as GAD65-Ab spectrum disorders. The response of some of these patients to plasma exchange or immunoglobulins indicates that GAD65-Abs could contribute to disease pathogenesis at least at some stages of disease. However, the involvement of GAD65-reactive B cells in the CNS is incompletely understood. METHODS: We studied 7 patients with high levels of GAD65-Abs and generated monoclonal Abs (mAbs) derived from single cells in the CSF. Sequence characteristics, reactivity to GAD65, and the role of somatic hypermutations of the mAbs were analyzed. RESULTS: Twelve CSF-derived mAbs were generated originating from 3 patients with short disease duration, and 7/12 of these mAbs (58%) were GAD65 reactive in at least 1 detection assay. Four of 12 (33%) were definitely positive in all 3 detection assays. The intrathecal anti-GAD65 response was polyclonal. GAD65-Abs were mostly of the IgG1 subtype and had undergone affinity maturation. Reversion of 2 GAD65-reactive mAbs to their corresponding germline-encoded unmutated common ancestors abolished GAD65 reactivity. DISCUSSION: GAD65-specific B cells are present in the CNS and represent a sizable fraction of CSF B cells early in the disease course. The anti-GAD65 response in the CSF is polyclonal and shows evidence of antigen-driven affinity maturation required for GAD65 recognition. Our data support the hypothesis that the accumulation of GAD65-specific B cells and plasma cells in the CSF is an important feature of early disease stages.

Humoral signatures of MOG-antibody-associated disease track with age and disease activity.

Myelin oligodendrocyte glycoprotein (MOG)-antibody (Ab)-associated disease (MOGAD) is an inflammatory demyelinating disease of the CNS. Although MOG is encephalitogenic in different mammalian species, the mechanisms by which human MOG-specific Abs contribute to MOGAD are poorly understood. Here, we use a systems-level approach combined with high-dimensional characterization of Ab-associated immune features to deeply profile humoral immune responses in 123 patients with MOGAD. We show that age is a major determinant for MOG-antibody-related immune signatures. Unsupervised clustering additionally identifies two dominant immunological endophenotypes of MOGAD. The pro-inflammatory endophenotype characterized by increased binding affinities for activating Fcγ receptors (FcγRs), capacity to activate innate immune cells, and decreased frequencies of galactosylated and sialylated immunoglobulin G (IgG) glycovariants is associated with clinically active disease. Our data support the concept that FcγR-mediated effector functions control the pathogenicity of MOG-specific IgG and suggest that FcγR-targeting therapies should be explored for their therapeutic potential in MOGAD.

Ocrelizumab Treatment Modulates B-Cell Regulating Factors in Multiple Sclerosis.

BACKGROUND AND OBJECTIVES: Antibodies to CD20 efficiently reduce new relapses in multiple sclerosis (MS), and ocrelizumab has been shown to be effective also in primary progressive MS. Although anti-CD20 treatments efficiently deplete B cells in blood, some B cells and CD20- plasma cells persist in lymphatic organs and the inflamed CNS; their survival is regulated by the B cell-activating factor (BAFF)/A proliferation-inducing ligand (APRIL) system. The administration of a soluble receptor for BAFF and APRIL, atacicept, unexpectedly worsened MS. Here, we explored the long-term effects of ocrelizumab on immune cell subsets as well as on cytokines and endogenous soluble receptors comprising the BAFF-APRIL system. METHODS: We analyzed immune cell subsets and B cell-regulating factors longitudinally for up to 2.5 years in patients with MS treated with ocrelizumab. In a second cohort, we determined B-cell regulatory factors in the CSF before and after ocrelizumab. We quantified the cytokines BAFF and APRIL along with their endogenous soluble receptors soluble B-cell maturation antigen (sBCMA) and soluble transmembrane activator and calcium-modulator and cyclophilin ligand (CAML) interactor (sTACI) using enzyme-linked immunosorbent assays (ELISAs). In addition, we established an in-house ELISA to measure sTACI-BAFF complexes. RESULTS: Ocrelizumab treatment of people with MS persistently depleted B cells and CD20+ T cells. This treatment enhanced BAFF and reduced the free endogenous soluble receptor and decoy sTACI in both serum and CSF. Levels of sTACI negatively correlated with BAFF levels. Reduction of sTACI was associated with formation of sTACI-BAFF complexes. DISCUSSION: We describe a novel effect of anti-CD20 therapy on the BAFF-APRIL system, namely reduction of sTACI. Because sTACI is a decoy for APRIL, its reduction may enhance local APRIL activity, thereby promoting regulatory IgA+ plasma cells and astrocytic interleukin (IL)-10 production. Thus, reducing sTACI might contribute to the beneficial effect of anti-CD20 as exogenous sTACI (atacicept) worsened MS. CLASSIFICATION OF EVIDENCE: This study provides Class IV evidence that endogenous sTACI in blood and CSF is decreased after ocrelizumab treatment.

Anti-pan-neurofascin antibodies induce subclass-related complement activation and nodo-paranodal damage.

Autoimmune neuropathy associated with antibodies against pan-neurofascin is a new subtype of nodo-paranodopathy. It is relevant because it is associated with high morbidity and mortality. Affected patients often require intensive care unit treatment for several months, and data on the reversibility and long-term prognosis are limited. The pathogenicity including IgG subclass-associated mechanisms has not been unravelled, nor directly compared to anti-neurofascin-155 IgG4-related pathology. Understanding the underlying pathology might have a direct impact on treatment of these severely affected patients. By a multicentre combined prospective and retrospective approach, we provide clinical data of a large cohort of patients with anti-neurofascin-associated neuropathy (n = 18) including longitudinal titre and neurofilament light chain assessment via Ella® and relate clinical data to in vitro pathogenicity studies of anti-neurofascin antibodies. We assessed antibody binding characteristics and the pathogenic effects of anti-pan-neurofascin versus neurofascin-155 antibodies on living myelinating dorsal root ganglia co-cultures. Additionally, we analysed the IgG subclass profile and the complement binding capacity and effector functions considering the effects of intravenous immunoglobulin preparations via enzyme-linked immunosorbent and cell-based assays. In contrast to chronic neurofascin-155 IgG4-associated neuropathy, anti-pan-neurofascin-associated disease presented with a high morbidity and mortality, but as a monophasic and potentially reversible disorder. During follow-up, antibodies were no longer detectable in 8 of 11 patients. Anti-pan-neurofascin had direct access to the nodes of Ranvier in myelinating cultures titre-dependently, most probably inducing this severe phenotype. Antibody preincubation led to impaired paranode formation, destruction of paranodal architecture and alterations on paranodal myelin and sensory neurons in the cultures, with more severe effects than neurofascin-155 antibodies. Besides IgG4, subclass IgG3 was detected and associated with complement binding and cytotoxic effects in vitro. As a possible correlate of axonal damage in vivo, we detected highly increased serum neurofilament light chain levels (sNF-L), correlating to serum C3a. Still, sNF-L was not identified as a marker for poor prognosis, but rather as an intra- and interindividual marker for acuteness, severity and course, with a strong decrease during recovery. Our data provide evidence that anti-pan-neurofascin antibodies directly attack the node and induce severe and acute, but potentially reversible, nodo-paranodal pathology, possibly involving complement-mediated mechanisms. Screening for autoantibodies thus is crucial to identify this subset of patients who benefit from early antibody-depleting therapy. Titre and sNF-L might serve as valuable follow-up parameters. The prospect of a favourable outcome has high relevance for physicians, patients and relatives during months of critical care.

Pathomechanisms in demyelination and astrocytopathy: autoantibodies to AQP4, MOG, GFAP, GRP78 and beyond.

PURPOSE OF REVIEW: The purpose of this review is to highlight the recently emerging pathomechanisms of diseases associated with autoantibodies to AQP4, MOG, GFAP, GRP78 and further novel targets. We discuss novel biomarkers and therapeutic approaches. RECENT FINDINGS: Although complement-mediated cytotoxicity (CDC) is regarded as the major effector mechanism for AQP4-IgG in neuromyelitis optica spectrum disorders (NMOSD), recent studies helped to understand the relevance of complement-independent effector mechanisms. For MOG-IgG mediated diseases the role of CDC is less clear. MOG-IgG may trigger a tightly controlled FcR and BTK-driven microglia proliferative response in MOG-antibody-associated diseases. Differences of antibody-mediated tissue damage may reflect differential response to therapy. In addition, antibodies to GFAP, GRP78 and further novel targets have been implicated in demyelination and astrocytopathy. SUMMARY: Elucidating the whole spectrum of effector functions in diseases mediated by AQP4-IgG and MOG-IgG and understanding the role of additional novel autoantibodies involved in demyelination and astrocytopathy may guide further novel treatment decisions.

FK506-Binding Protein 11 Is a Novel Plasma Cell-Specific Antibody Folding Catalyst with Increased Expression in Idiopathic Pulmonary Fibrosis.

Antibodies are central effectors of the adaptive immune response, widespread used therapeutics, but also potentially disease-causing biomolecules. Antibody folding catalysts in the plasma cell are incompletely defined. Idiopathic pulmonary fibrosis (IPF) is a fatal chronic lung disease with increasingly recognized autoimmune features. We found elevated expression of FK506-binding protein 11 (FKBP11) in IPF lungs where FKBP11 specifically localized to antibody-producing plasma cells. Suggesting a general role in plasma cells, plasma cell-specific FKBP11 expression was equally observed in lymphatic tissues, and in vitro B cell to plasma cell differentiation was accompanied by induction of FKBP11 expression. Recombinant human FKBP11 was able to refold IgG antibody in vitro and inhibited by FK506, strongly supporting a function as antibody peptidyl-prolyl cis-trans isomerase. Induction of ER stress in cell lines demonstrated induction of FKBP11 in the context of the unfolded protein response in an X-box-binding protein 1 (XBP1)-dependent manner. While deficiency of FKBP11 increased susceptibility to ER stress-mediated cell death in an alveolar epithelial cell line, FKBP11 knockdown in an antibody-producing hybridoma cell line neither induced cell death nor decreased expression or secretion of IgG antibody. Similarly, antibody secretion by the same hybridoma cell line was not affected by knockdown of the established antibody peptidyl-prolyl isomerase cyclophilin B. The results are consistent with FKBP11 as a novel XBP1-regulated antibody peptidyl-prolyl cis-trans isomerase and indicate significant redundancy in the ER-resident folding machinery of antibody-producing hybridoma cells.

Persistence of functional memory B cells recognizing SARS-CoV-2 variants despite loss of specific IgG.

Although some COVID-19 patients maintain SARS-CoV-2-specific serum immunoglobulin G (IgG) for more than 6 months postinfection, others eventually lose IgG levels. We assessed the persistence of SARS-CoV-2-specific B cells in 17 patients, 5 of whom had lost specific IgGs after 5-8 months. Differentiation of blood-derived B cells in vitro revealed persistent SARS-CoV-2-specific IgG B cells in all patients, whereas IgA B cells were maintained in 11. Antibodies derived from cultured B cells blocked binding of viral receptor-binding domain (RBD) to the cellular receptor ACE-2, had neutralizing activity to authentic virus, and recognized the RBD of the variant of concern Alpha similarly to the wild type, whereas reactivity to Beta and Gamma were decreased. Thus, differentiation of memory B cells could be more sensitive for detecting previous infection than measuring serum antibodies. Understanding the persistence of SARS-CoV-2-specific B cells even in the absence of specific serum IgG will help to promote long-term immunity.

Myelin-oligodendrocyte glycoprotein antibody-associated disease.

Myelin-oligodendrocyte glycoprotein antibody-associated disease (MOGAD) is a recently identified autoimmune disorder that presents in both adults and children as CNS demyelination. Although there are clinical phenotypic overlaps between MOGAD, multiple sclerosis, and aquaporin-4 antibody-associated neuromyelitis optica spectrum disorder (NMOSD) cumulative biological, clinical, and pathological evidence discriminates between these conditions. Patients should not be diagnosed with multiple sclerosis or NMOSD if they have anti-MOG antibodies in their serum. However, many questions related to the clinical characterisation of MOGAD and pathogenetic role of MOG antibodies are still unanswered. Furthermore, therapy is mainly based on standard protocols for aquaporin-4 antibody-associated NMOSD and multiple sclerosis, and more evidence is needed regarding how and when to treat patients with MOGAD.

Effects of Natalizumab Therapy on Intrathecal Immunoglobulin G Production Indicate Targeting of Plasmablasts.

OBJECTIVES: To evaluate the long-term effects of natalizumab (NTZ) on different features of intrathecal immunoglobulin (Ig) synthesis in patients with multiple sclerosis (MS) and to quantify the expression of α4-integrin in stages of B-cell maturation. METHODS: We combined a cross-sectional (49 NTZ-treated MS patients, mean treatment duration 5.1 years, and 47 untreated MS patients) and a longitudinal study (33 patients with MS before and during NTZ, mean treatment duration: 4.8 years), analyzing paired serum and CSF samples for IgG, IgA, and IgM levels, reactivity against selected viruses (measles virus, rubella virus, and varicella zoster virus [MRZ] reaction), and oligoclonal bands (OCBs). Banding patterns before and after therapy were directly compared by isoelectric focusing in 1 patient. In addition, we determined the expression of α4-integrin by FACS analysis on blood-derived B-cell subsets (plasmablasts, memory B cells, and naive B cells) of healthy controls. RESULTS: In serum, NTZ decreased IgM and IgG, but not IgA, levels. IgM hypogammaglobulinemia occurred in 28% of NTZ-treated patients. In CSF, NTZ treatment resulted in a strong reduction of intrathecally produced IgG and, to a lesser extent, IgA, whereas IgM indices [(Ig CSF/Serum)/(Albumin CSF/Serum)] remained largely unchanged. Reduction of the IgG index correlated with NTZ treatment duration, as did serum IgM and IgA levels. MRZ reaction was unchanged and OCB persisted. Direct comparison of OCB pattern before and after NTZ revealed the persistence of individual bands. α4-Integrin expression was highest on plasmablasts (CD19+CD38+CD27+). CONCLUSION: Our data indicate that NTZ reduces short-lived plasmablasts in the CNS compartment but has little effect on locally persisting long-lived plasma cells.

Endogenous soluble receptors sBCMA and sTACI: biomarker, immunoregulator and hurdle for therapy in multiple myeloma.

BAFF and APRIL regulate B cell homeostasis by binding to their three receptors BAFFR, BCMA and TACI. The complexity of this system is further increased by shedding of these three receptors; this reduces signaling due to the display of less surface receptors. Further, soluble forms, sBCMA and sTACI, were detected in body fluids and serve as biomarker in malignancies, autoimmune diseases and immunodeficiencies. sBCMA and sTACI function as decoys blocking BAFF and APRIL. BCMA is a promising therapeutic target in multiple myeloma, but sBCMA may reduce therapeutic activity of CAR T cells, bispecific antibodies, and antibody-drug conjugates. Insights into the biochemical mechanism of shedding of BCMA can be harnessed to improve BCMA-directed therapy by blocking its shedding with a γ-secretase inhibitor.

Modeling compartmentalized chronic immune-mediated demyelinating CNS disease in the Biozzi ABH mouse.

We explored whether experimental autoimmune encephalomyelitis (EAE) in Biozzi mice recapitulates temporal dynamics of tissue injury, immune-pathogenesis and CNS compartmentalization occurring in progressive multiple sclerosis (MS). Chronic EAE exhibited relapsing and progressing disease, partial closure of BBB, reduced tissue inflammatory activity, and development of meningeal ectopic lymphoid tissue, directly opposing (potentially driving) spinal subpial demyelinated plaques. A T cell predominant disease during relapses transformed into a B cell predominant disease in late chronic EAE, with high serum anti-MOG reactivity. Thus, late chronic Biozzi EAE recapitulates essential features of progressive MS, and is suitable for developing disease modifying and regenerative therapies.

Features of MOG required for recognition by patients with MOG antibody-associated disorders.

Antibodies to myelin oligodendrocyte glycoprotein (MOG-Abs) define a distinct disease entity. Here we aimed to understand essential structural features of MOG required for recognition by autoantibodies from patients. We produced the N-terminal part of MOG in a conformationally correct form; this domain was insufficient to identify patients with MOG-Abs by ELISA even after site-directed binding. This was neither due to a lack of lipid embedding nor to a missing putative epitope at the C-terminus, which we confirmed to be an intracellular domain. When MOG was displayed on transfected cells, patients with MOG-Abs recognized full-length MOG much better than its N-terminal part with the first hydrophobic domain (P < 0.0001). Even antibodies affinity-purified with the extracellular part of MOG recognized full-length MOG better than the extracellular part of MOG after transfection. The second hydrophobic domain of MOG enhanced the recognition of the extracellular part of MOG by antibodies from patients as seen with truncated variants of MOG. We confirmed the pivotal role of the second hydrophobic domain by fusing the intracellular part of MOG from the evolutionary distant opossum to the human extracellular part; the chimeric construct restored the antibody binding completely. Further, we found that in contrast to 8-18C5, MOG-Abs from patients bound preferentially as F(ab')2 rather than Fab. It was previously found that bivalent binding of human IgG1, the prominent isotype of MOG-Abs, requires that its target antigen is displayed at a distance of 13-16 nm. We found that, upon transfection, molecules of MOG did not interact so closely to induce a Förster resonance energy transfer signal, indicating that they are more than 6 nm apart. We propose that the intracellular part of MOG holds the monomers apart at a suitable distance for bivalent binding; this could explain why a cell-based assay is needed to identify MOG-Abs. Our finding that MOG-Abs from most patients require bivalent binding has implications for understanding the pathogenesis of MOG-Ab associated disorders. Since bivalently bound antibodies have been reported to only poorly bind C1q, we speculate that the pathogenicity of MOG-Abs is mostly mediated by other mechanisms than complement activation. Therefore, therapeutic inhibition of complement activation should be less efficient in MOG-Ab associated disorders than in patients with antibodies to aquaporin-4 .