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Background and Objectives: Multiple sclerosis (MS) is a chronic immune-mediated demyelinating disease of the CNS. Highlighted by the success of B-cell-depleting therapies such as the monoclonal anti-CD20 antibodies rituximab, ocrelizumab, and ofatumumab, B cells have been shown to play a central role in the immunopathology of the disease. Yet, the target antigens of the pathogenic B-cell response in MS remain unclear., Methods: We combined polyclonal B-cell stimulation of peripheral blood mononuclear cells with a human proteome-wide protein microarray to identify target antigens of MS by comparing samples from 20 patients with MS with 9 age-matched and sex-matched healthy controls. Results were verified by enzyme-linked immunosorbent assay (ELISA) in 3 independent validation cohorts (N = 47 patients with MS in remission; N = 20 patients with MS during relapse; N = 25 HCs; N = 30 patients with other noninflammatory neurologic diseases; N = 9 patients with other inflammatory neurologic diseases). Experimental autoimmune encephalomyelitis (EAE) was used as an animal model to evaluate the pathogenicity of the antibodies of choice., Results: Our results corroborate the existing concept of a highly diverse autoimmune response in MS. Yet, a significantly elevated antibody response against the membrane protein modulator of VRAC current 1 (MLC1) was noted in B-cell culture supernatants and serum samples of patients with MS. Furthermore, significantly elevated titers to MLC1 were observed in the CSF of patients with neuroinflammatory diseases other than MS. Neurons and astrocytes were identified as the main cell types expressing MLC1 in the brain of a patient with MS. Injection of anti-MLC1 antibodies into mice with EAE led to strong in vivo binding to cerebral cortical neurons and to the death of 4 of the 7 injected mice., Discussion: Future studies will have to address the diagnostic and prognostic value of MLC1-specific antibodies in neuroinflammatory disorders such as MS and characterize the functional role of MLC1 expression in neurons and astrocytes., Trial Registration Information: The study has been registered in the German Clinical Trials Register (study number DRKS00015528).

Background and Objectives: Levels of activated complement proteins in the CSF are increased in people with multiple sclerosis (MS) and are associated with clinical disease severity. In this study, we determined whether complement activation profiles track with quantitative MRI metrics and liquid biomarkers indicative of disease activity and progression., Methods: Complement components and activation products (Factor H and I, C1q, C3, C4, C5, Ba, Bb, C3a, C4a, C5a, and sC5b-9) and liquid biomarkers (neurofilament light chain, glial fibrillary acidic protein [GFAP], CXCL-13, CXCL-9, and IL-12b) were quantified in the CSF of 112 patients with clinically isolated syndromes and 127 patients with MS; longitudinal MRIs according to a standardized protocol of the Swiss MS cohort were assessed. We used multivariable models to analyze associations of the 12 complement parameters as individual independent variables and longitudinal brain volumes, T2-weighted (T2w) lesion volumes, contrast-enhancing (CELs) and paramagnetic rim lesions (PRLs), and molecular biomarkers as dependent variables, respectively., Results: Strongest associations with accelerated brain atrophy were found for C4a: doubling of C4a CSF levels was associated with an additional brain volume loss of -0.24% (95% CI -0.31% to -0.16%; p < 0.0001) per year, followed by Ba and C3a (-0.22% [-0.29% to -0.15%]) and -0.13% ([-0.21 to -0.06]; both p < 0.001). Doubling of C3a, Ba, and C4a levels correlated with 2.2- (1.6-3.0; p < 0.0001), 2.0- (1.3-3.1; p = 0.0038), and 1.8-fold (1.2-2.6; p = 0.0029) increased longitudinal T2w lesion volumes; C3a and Ba were associated with 2.5- (1.4-4.6; p = 0.0022) and 3.3-fold (1.5-7.2; p = 0.0024) higher odds for CELs and 2.6- (1.7-4.0; p < 0.0001) and 2.3-fold (1.3-4.3; p = 0.006) increased PRL incidence rates. C1q, C3a, and C4a were associated with higher GFAP levels, and CXCL-13, CXCL-9, and IL-12b analyses showed consistent patterns with strongest associations for C1q, followed by Ba, C3a, and C4a., Discussion: Intrathecal complement activation is consistently associated with MRI metrics and liquid biomarkers indicative for MS disease activity and progression. Our results demonstrate that aberrant complement activation is strongly associated with structural brain damage in MS. Therapeutic targeting of the complement system might limit disability accumulation due to MS.

Background and Objectives: Histopathologic studies have identified immunoglobulin (Ig) deposition and complement activation as contributors of CNS tissue damage in multiple sclerosis (MS). Intrathecal IgM synthesis is associated with higher MS disease activity and severity, and IgM is the strongest complement-activating immunoglobulin. In this study, we investigated whether complement components (CCs) and complement activation products (CAPs) are increased in persons with MS, especially in those with an intrathecal IgM synthesis, and whether they are associated with disease severity and progression., Methods: CC and CAP levels were quantified in plasma and CSF of 112 patients with clinically isolated syndrome (CIS), 127 patients with MS (90 relapsing-remitting, 14 primary progressive, and 23 secondary progressive), 31 inflammatory neurologic disease, and 44 symptomatic controls from the Basel CSF databank study. Patients with CIS/MS were followed in the Swiss MS cohort study (median 6.3 years). Levels of CC/CAP between diagnosis groups were compared; in CIS/MS, associations of CC/CAP levels with intrathecal Ig synthesis, baseline Expanded Disability Status Scale (EDSS) scores, MS Severity Score (MSSS), and neurofilament light chain (NfL) levels were investigated by linear regression, adjusted for age, sex, and albumin quotient., Results: CSF (but not plasma) levels of C3a, C4a, Ba, and Bb were increased in patients with CIS/MS, being most pronounced in those with an additional intrathecal IgM production. In CIS, doubling of C3a and C4a in CSF was associated with 0.31 (CI 0.06-0.56; p = 0.016) and 0.32 (0.02-0.62; p = 0.041) increased EDSS scores at lumbar puncture. Similarly, doubling of C3a and Ba in CIS/MS was associated with 0.61 (0.19-1.03; p < 0.01) and 0.74 (0.18-1.31; p = 0.016) increased future MSSS. In CIS/MS, CSF levels of C3a, C4a, Ba, and Bb were associated with increased CSF NfL levels, e.g., doubling of C3a was associated with an increase of 58% (Est. 1.58; CI 1.37-1.81; p < 0.0001)., Discussion: CNS-compartmentalized activation of the classical and alternative pathways of complement is increased in CIS/MS and associated with the presence of an intrathecal IgM production. Increased complement activation within the CSF correlates with EDSS, future MSSS, and NfL levels, supporting the concept that complement activation contributes to MS pathology and disease progression. Complement inhibition should be explored as therapeutic target to attenuate disease severity and progression in MS.

Objective: To determine whether serum neurofilament light chain (sNfL) levels are associated with recent MRI activity in patients with relapsing-remitting MS (RRMS)., Methods: This observational study included 163 patients (405 samples) with early RRMS from the Study of Early interferon-beta1a (IFN-β1a) Treatment (SET) cohort and 179 patients (664 samples) with more advanced RRMS from the Genome-Wide Association Study of Multiple Sclerosis (GeneMSA) cohort. Based on annual brain MRI, we assessed the ability of sNfL cutoffs to reflect the presence of combined unique active lesions, defined as new/enlarging lesion compared with MRI in the preceding year or contrast-enhancing lesion. The probability of active MRI lesions among patients with different sNfL levels was estimated with generalized estimating equations models., Results: From the sNfL samples ≥90th percentile, 81.6% of the SET (OR = 3.4, 95% CI = 1.8-6.4) and 48.9% of the GeneMSA cohort samples (OR = 2.6, 95% CI = 1.7-3.9) was associated with radiological disease activity on MRI. The sNfL level between the 10th and 30th percentile was reflective of negligible MRI activity: 1.4% (SET) and 6.5% (GeneMSA) of patients developed ≥3 active lesions, 5.8% (SET) and 6.5% (GeneMSA) developed ≥2 active lesions, and 34.8% (SET) and 11.8% (GeneMSA) showed ≥1 active lesion on brain MRI. The sNfL level <10th percentile was associated with even lower MRI activity. Similar results were found in a subgroup of clinically stable patients., Conclusions: Low sNfL levels (≤30th percentile) help identify patients with MS with very low probability of recent radiologic disease activity during the preceding year. This result suggests that in future, sNfL assessment may substitute the need for annual brain MRI monitoring in considerable number (23.1%-36.4%) of visits in clinically stable patients., (Copyright © 2020 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.)

Objective: To assess whether serum concentrations of the anti-inflammatory cytokine growth differentiation factor 15 (GDF-15) differ in patients with highly active multiple sclerosis (MS) vs patients with stable MS and healthy controls (HCs)., Methods: GDF-15 concentrations were measured by ELISA in serum and CSF in a cross-sectional cohort of patients with MS, patients with other inflammatory neurologic diseases (OIND), patients with noninflammatory neurologic diseases (NIND), and healthy controls (HC). Serum GDF-15 concentrations were measured in a longitudinally sampled cohort of clinically and radiologically well-characterized patients with MS and corresponding controls., Results: Cross-sectionally measured median serum GDF-15 concentrations were significantly higher in patients with OIND (n = 42) (600 pg/mL, interquartile range [IQR] = 320-907 pg/mL) compared with HCs (n = 29) (325 pg/mL, IQR = 275-419 pg/mL; p = 0.0007), patients with NIND (n = 46) (304 pg/mL, IQR = 245-493 pg/mL; p = 0.0002), or relapsing MS (n = 42) (356 pg/mL, IQR = 246-460 pg/mL; p = 0.0002). CSF and serum concentrations of GDF-15 were correlated (r = 0.41, 95% CI = 0.25-0.56, p < 0.0001). In a longitudinally sampled cohort of patients with MS (n = 48), deeply phenotyped with quantitative clinical and MRI assessments, mean GDF-15 concentrations were significantly higher in patients with a stable disease course (405 pg/mL, SD = 202) than in patients with intermittent MRI activity (333 pg/mL, SD = 116; p = 0.02)., Conclusions: Serum GDF-15 concentrations are increased in patients with MS with a stable disease course. These data suggest that GDF-15 may serve as a biomarker for disease stability in MS., (Copyright © 2020 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.)

Objective: To explore the repertoire of glycan-specific immunoglobulin G (IgG) antibodies in treatment-naive patients with relapsing-remitting multiple sclerosis (RRMS)., Methods: A systems-level approach combined with glycan array technologies was used to determine specificities and binding reactivities of glycan-specific IgGs in treatment-naive patients with RRMS compared with patients with noninflammatory and other inflammatory neurologic diseases., Results: We identified a unique signature of glycan-binding IgG in MS with high reactivities to the dietary xenoglycan N-glycolylneuraminic acid (Neu5Gc) and the self-glycan N-acetylneuraminic acid (Neu5Ac). Increased reactivities of serum IgG toward Neu5Gc and Neu5Ac were additionally observed in an independent, treatment-naive cohort of patients with RRMS., Conclusion: Patients with MS show increased IgG reactivities to structurally related xenogeneic and human neuraminic acids. The discovery of these glycan-specific epitopes as immune targets and potential biomarkers in MS merits further investigation., (Copyright © 2020 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.)