Background

Glial fibrillar acidic protein (GFAP) autoimmunity is a recently identified disease, at the frontier of auto-immune encephalitis and gliopathies. Clinical features associated to this new entity are still not fully evaluated; especially the risk of relapse and the disability outcome.

Objectives

To report the clinical, biological, imaging features, and the clinical course of a French cohort of patients with GFAP autoantibodies.

Methods

We retrospectively included all patients tested positive for GFAP antibodies since 2017, from two French referral centers (auto-immune encephalitis and rare inflammatory disorders of the brain and the spinal cord). GFAP autoantibodies were detected exclusively in the CSF, by immunohistochemistry and their specificity confirmed by cell-based assay using cells expressing human GFAPα.

Results

We identified 46 patients with GFAP antibodies. Median age at onset was 43 years and men were more affected (30/46). Infectious prodromal symptoms were found in 82% of cases. Other autoimmune diseases were found in 22% of cases and coexisting neural autoantibodies in 11% of cases, including MOG-IgG and AQP4-IgG positive cases. Tumors were present in 24%, and T cell dysfunction in 23% of cases, respectively. The most frequent presentation was acute/subacute menigoencephalitis (85%) with cerebellar dysfunction in 57% of cases. Other/associated clinical presentation included: myelitis (30%), visual tract involvement (35%) and peripheral nervous system involvement (28%). CSF showed pleocytosis (98%), oligoclonal bands (77%) and low glucose level (15%). MRI findings were heterogeneous: radial enhancement was found in 26%, periventricular diffuse T2 hyperintensity in 39%, brainstem involvement in 33%, leptomeningeal enhancement in 23%, and reversible splenial lesions in 4 cases.

39/46 patients have a monophasic course, associated to a good outcome at last follow-up (Rankin Score≤2: 89% at 15,5 months), despite a frequently severe clinical presentation (intensive care unit hospitalization: 42%). Seventy patients were treated with immunotherapy. 11/22 patients showed negativation of GFAP antibodies (median time: 2 months).

Conclusions

GFAP autoimmunity was generally associated to a good outcome and a low risk of relapse. Identification of factors associated to risk of relapse or disability, to monitor immunotherapy, is needed.

Background

In PREVENT, eculizumab was associated with a significant reduction in relapse risk versus placebo and was well tolerated. In total, 46 patients (26/96 in the eculizumab arm, 20/47 in the placebo arm) were previously treated with the monoclonal antibody rituximab.

Objectives

To describe the efficacy and safety of eculizumab in patients in the PREVENT trial (NCT01892345) who had previously received rituximab.

Methods

Adults with aquaporin-4 immunoglobulin G-positive neuromyelitis optica spectrum disorder received eculizumab (maintenance dose, 1200 mg/2 weeks) or placebo with/without concomitant immunosuppressive treatment (except rituximab/mitoxantrone). A post hoc descriptive analysis was performed using data from patients with any prior rituximab treatment (within the previous year only for review of adverse events [AEs]) recorded more than 3 months before randomization.

Results

Baseline characteristics of the prior-rituximab subgroup were similar to those of the total PREVENT population; however, the subgroup included a lower proportion of Asian patients (10.9% vs 36.4% in total PREVENT) and greater representation from the Americas (58.7% vs 30.8%). In the subgroup, median times from last dose of rituximab to meningococcal vaccination and to first dose of study treatment were 31.7 and 38.7 weeks, respectively. Adjudicated relapses occurred in 1/26 patients (3.8%) and 7/20 patients (35.0%) in the eculizumab and placebo arms (hazard ratio: 0.093; 95% confidence interval: 0.011–0.755; p = 0.0055), respectively. Rates of AEs for eculizumab and placebo were 1025.8 and 1029.1 events/100 patient-years (100% of patients), respectively, and rates of serious AEs were 46.9 and 66.0 events/100 patient-years (38.9% and 47.1% of patients), respectively. Serious infections/infestations were recorded in 2/18 patients (11.1%) and 2/17 patients (11.8%) in the eculizumab and placebo arms, respectively.

Conclusions

In patients in PREVENT who had previously received rituximab, the risk of adjudicated relapse was significantly lower with eculizumab than with placebo. Rates of serious infections were similarly low with eculizumab and placebo.

Background

Alemtuzumab is an anti-CD52 monoclonal antibody therapy approved for treating RRMS. Although alemtuzumab is associated with non–MS-related secondary autoimmune events, the role pre-existing non-MS autoimmunity plays in secondary autoimmunity is unclear.

Objectives

To assess the impact of 1) pre-existing non-MS autoimmunity and 2) post-alemtuzumab thyroid autoimmunity on subsequent onset of new autoimmunity up to 9 years after initiating alemtuzumab.

Methods

In clinical trials (NCT00050778, NCT00530348, NCT00548405, NCT00930553, NCT02255656), patients were monitored for autoimmune adverse events (AEs). All patient- and investigator-reported AEs were recorded. An autoimmune event was pre-existing if it occurred prior to initiating alemtuzumab or was in the medical history database.

Results

A total of 1216 patients from the alemtuzumab clinical development program who received alemtuzumab 12 mg were included in the analysis. Ninety-six had pre-existing non-MS autoimmunity. Up to 9 years after alemtuzumab initiation, the percentage of patients with new autoimmune disease was similar in those with (35.4%) versus without (35.3%) pre-existing autoimmunity; similar percentages of patients with versus without pre-existing autoimmunity had ≥2 new autoimmune events (5.2% vs 8.2%, respectively). Most patients with thyroid disorders at baseline did not experience new autoimmunity after alemtuzumab. Treatment-emergent thyroid autoimmunity after alemtuzumab Course 1 was not associated with subsequent nonthyroid autoimmunity after Course 2 (0% of patients with vs 3.0% of patients without thyroid autoimmunity after Course 1). Similarly, thyroid autoimmunity after Course 2 did not predict nonthyroid autoimmunity after Course 3 (1.8% vs 2.0%, respectively). Among 25,292 patients treated with alemtuzumab in the postmarketing setting as of 31 March 2019, additional events (occurring 18–36 months post treatment) included autoimmune hepatitis (10.7 in 10,000) and hemophagocytic lymphohistiocytosis (2.7 in 10,000).

Conclusions

Over 9 years after alemtuzumab initiation, pre-existing non-MS autoimmunity was not associated with subsequent new autoimmune disease. Emergence of thyroid autoimmunity after Courses 1 and 2 does not appear to predict subsequent serious autoimmune disease.

STUDY SUPPORT: Sanofi and Bayer HealthCare Pharmaceuticals.

Background

DMF is a well-established therapy for relapsing forms of multiple sclerosis (RMS); data from ENDORSE, an extension to phase 3 studies DEFINE and CONFIRM, has enabled >10 years follow-up.

Objectives

We report safety/efficacy of DMF in patients with RMS treated with DMF and followed for 13 years in ENDORSE (NCT00835770) (2 years DEFINE/CONFIRM, and >10 years ENDORSE).

Methods

Incidence of serious AEs (SAEs), discontinuations due to AEs, annualized relapse rate (ARR) and Expanded Disability Status Scale (EDSS) score were assessed. Patients were treated with DMF 240 mg BID: placebo (PBO)/DMF (PBO, years 0–2 /DMF, years 3–10) or continuously (DMF/DMF). Efficacy outcomes were assessed in patients up to 10 years due to sample size considerations. For lymphocyte analysis, data from first DMF exposure were analysed for patients in DEFINE/CONFIRM/ENDORSE.

Results

At 23 January 2020, 1736 patients enrolled/received ≥1 dose DMF. Of 1736 patients, 760 completed. Patients were followed for a median (min,max) of 6.76(0.04,10.98) years in ENDORSE, and 2 years in DEFINE/CONFIRM. Overall, 551 (32%) patients experienced SAEs; most were MS relapse and fall. There was one case of PML in this study. There was no increased incidence of other infections or serious infections. Sixteen percent (n=282) patients discontinued due to AEs; 2% relapse, 2% disease progression, and 4% GI disorders. ALC decreased over the first 48 weeks, and then remained generally stable for the majority of the study. The proportion of patients with other AEs of special interest (including opportunistic infection, malignancy, and serious herpes zoster) was similar regardless of ALC. For patients continuously treated (n=501), overall ARR remained low (0.141[95% CI, 0.119,0.167]), while for PBO/DMF patients (n=249) ARR decreased after initiating DMF (ARR 0–2 years, 0.330[95% CI, 0.266,0.408]; ARR overall, 0.149[95% CI, 0.116,0.190]). Overall, 60% of DMF/DMF and 66% of PBO/DMF patients remained relapse-free; 20% and 17% of patients had 1 relapse, respectively. Walking abilities were maintained throughout the study; the number of patients with EDSS scores ≤3.5 was 413/479(86%) DMF/DMF (179/217[82%] PBO/DMF) at Year 2, and 173/226(77%) DMF/DMF (67/90[74%] PBO/DMF) at Year 10. Seventy-two percent and 73% of DMF/DMF and PBO/DMF patients, respectively, had no 24-week confirmed disability progression over 10 years.

Conclusions

These safety and efficacy data in patients followed for 13 years, support DMF as a long-term option for patients with RMS.

Background

In multiple sclerosis (MS), thalamic integrity is affected both directly by demyelination, neuronal loss and increasing iron concentration, and indirectly by remote gray and white matter lesions affecting neural projections into and out of the thalamus. Thalamic atrophy may therefore reflect a large fraction of MS-related brain damage and thus represent a useful marker of overall damage and therapeutic efficacy.

Objectives

To assess the efficacy of ocrelizumab (OCR) in patients switching to or maintaining OCR therapy on thalamic atrophy in patients with relapsing MS (RMS) and primary progressive MS (PPMS), participating in the OPERA I/II (NCT01247324/NCT01412333) and ORATORIO (NCT01194570) Phase III trials, respectively.

Methods

At the end of the double-blind controlled treatment period in OPERA I/II, patients entered the open‑label extension (OLE), and either continued to receive OCR (OCR-OCR) or switched from interferon β-1a (IFN β-1a) to OCR (IFN β-1a-OCR). In ORATORIO, patients entered the OLE ~3–9 months after the double-blind period cut-off and either continued OCR (OCR-OCR) or switched from placebo (PBO) to OCR (PBO-OCR). Changes in thalamic volume from the core trial baseline were computed using Jacobian integration and analyzed using a mixed-effect repeated measurement model, adjusted for baseline volume, age, baseline gadolinium-enhancing lesions (presence/absence), baseline T2 lesion volume, region (US vs rest of the world), Expanded Disability Status Scale category (<4, ≥4), week, treatment, treatment and time interaction, and treatment and baseline volume interaction.

Results

In the OLE of OPERA I/II, changes (%) in thalamic volume from baseline at OLE Week 46, 94, 142, 190, and 238, were: –2.88/–2.12 (p<0.001), –3.31/–2.36 (p<0.001), –3.61/–2.78 (p<0.001), –3.68/–3.03 (p<0.001), and –4.07/–3.41 (p<0.001), for IFN β-1a-OCR/OCR-OCR patients, respectively. During the OLE of ORATORIO, changes in thalamic volume at OLE Day 1, Week 48, 96, and 144, were: –3.46/–2.44 (p<0.001), –3.93/–2.61 (p<0.001), –4.30/–3.25 (p<0.001), and –4.86/–3.62 (p<0.001), for PBO-OCR/OCR-OCR patients, respectively.

Conclusions

In the OLE, patients with RMS and PPMS who were initially randomized to ocrelizumab experienced less thalamic volume loss compared with those initiating ocrelizumab later.

Background

Obesity is increasingly recognized as a risk for multiple sclerosis (MS). While the underlying mechanisms remain undetermined, reduced vitamin D bioavailability and altered levels of the immunomodulatory cytokines adiponectin and leptin have been proposed.

Objectives

To determine the roles of vitamin D, adiponectin and leptin levels in explaining the effect of obesity on MS, using a Mendelian randomization (MR) mediation framework.

Methods

Independent genetic estimates for body mass index (BMI), 25-hydroxyvitamin D (25OHD), adiponectin and leptin levels were obtained from from large-scale genome-wide association studies and the UK Biobank, totalling over 800,000 participants. The effect on MS was measured using summary genetic data on 14,802 MS cases and 26,703 controls from the International MS Genetics Consortium (IMSGC). To avoid bias from population stratification, all participants were of European ancestry. We estimated the odds of MS for each of the exposures, and the proportion of the effect of BMI explained by potential mediators significantly associated with MS, using the product of coefficients method in a two-step MR framework.

Results

Each standard deviation (SD) increase in BMI was associated with a 40% increase in the odds of MS (95% CI 1.16 to 1.67, P=3.1x10^-4). Similarly, a SD increase in standardized log transformed 25OHD levels reduced the odds of MS by 28% (95% CI 0.60-0.87, P=6.2x10^-4). In contrast, we observed no notable effect of adiponectin (OR=1.05, 95% CI 0.74-1.49, P=0.78) or leptin (OR=1.18, 95% CI 0.59-2.36, P=0.64) on the odds of MS. In MR mediation analysis, we estimate that the reduction in 25OHD levels only explains 5.4% of the effect of increased BMI on the risk of MS (95% CI 0.4% to 30.5%). Sensitivity analyses showed that these estimates were robust to potential bias from pleiotropy.

Conclusions

This study found that only a minority of the increased risk of MS conferred by obesity is mediated by lowered vitamin D levels, while leptin and adiponectin had no measurable effect. This suggests that vitamin D supplementation would only modestly reverse the effect of obesity on MS, the majority of which remains unexplained.

Background

Glial fibrillary acidic protein (GFAP) is released into the cerebrospinal fluid and blood upon astroglial injury and activation, one of the hallmarks of progressive multiple sclerosis (PMS). It is unclear whether blood GFAP levels are associated with disability accumulation in secondary progressive MS (SPMS).

Objectives

To explore GFAP as a prognostic biomarker of disability worsening in patients with active and/or non-active SPMS (aSPMS and/or naSPMS) in the Phase 3 EXPAND study.

Methods

In this post-hoc analysis from the EXPAND study, baseline (BL) GFAP was quantified in EDTA plasma samples using Single Molecule Array technology. GFAP was categorized as high/low based on the gender stratified 80 percentile. The effect of GFAP on time to Expanded Disability Status Scale [EDSS] 7 (wheelchair restricted) was assessed using a Cox regression model adjusted for age, gender, disease duration, treatment, relapses in the 24 months prior to study start, and BL EDSS. Subgroup analyses were conducted in patients with aSPMS/naSPMS (with/without relapses ≤24 months prior to study entry, and/or gadolinium-enhancing T1 lesions at BL) and were also stratified by gender.

Results

Samples were available for 1405 of the 1651 patients randomized in the EXPAND study; median GFAP levels (pg/mL) were 119.6 (male) and 141.4 (female). Overall, the risk of reaching EDSS 7 was higher in patients with high BL GFAP (96%: high vs low GFAP, [34/281, 12.1%] vs [54/1117, 4.8%]; HR 1.96 [1.27; 3.03]; p=0.0024). Interestingly, the increased risk of reaching EDSS 7 was mainly seen in females (23/169; 13.6%] vs [34/673; 5.1%]; HR 2.22 [1.30; 3.80]; p=0.0035), and not significant in males ([11/112, 9.8%] vs [20/444, 4.5%]; HR 1.45 [0.67; 3.12]; p=0.3457). Increase in risk of reaching EDSS 7 was mainly observed in naSPMS patients (high GFAP [14/133; 10.5%] vs low GFAP [22/570; 3.9%]; HR 3.40 [1.71; 6.75]; p=0.0005) and was not significant in aSPMS patients (high GFAP [20/144; 13.9%] vs low GFAP [30/521; 5.8%]; HR 1.58 [0.88; 2.82]; p=0.1250). However, associations between BL GFAP levels and time to 6-months confirmed disability progression showed similar trends, but were less pronounced.

Conclusions

Blood GFAP appears to be a prognostic biomarker of disability worsening. The relevance of the gender difference and the stronger correlations found in SPMS patients with non-active versus active disease needs further investigation.

Background

We recently showed that 7T MRI leptomeningeal enhancement (LME) is common in relapsing-remitting multiple sclerosis (RRMS) and is related to gray matter (cortical/thalamic) and white matter (WMLs) lesions.

Objectives

To investigate the dynamics of LME longitudinal change and relationship to subsequent lesion accumulation using 7T MRI.

Methods

25 RRMS subjects [age 44.5±11.2 years (mean±SD), 68% women, Expanded Disability Status Scale (EDSS) 2.0±1.5, 92% on disease-modifying therapy-DMT] and 12 healthy controls (HC) underwent brain 3D MP2RAGE and FLAIR 7T MRI with 0.7 mm³ voxels at baseline and ~1 year. Gadolinium-enhanced 3D-FLAIR was evaluated for LME. WMLs, cortical lesions (CLs) and thalamic lesions (TLs) were expert-quantified. Wilcoxon rank-sum, two-sample t-tests and Spearman’s correlations were investigated.

Results

LME was found in 17/25 (68%) RRMS subjects at baseline and 18/25 (72%) at follow-up vs. a single stable focus in 1/12 HC (8.3%). In the RRMS group, 42 LME foci [mean 2.5±1.1 (range 1-5) per LME+ subject] were identified at baseline versus 48 foci [2.7±1.2 (1-5)] at follow-up. LME foci number at follow-up was unchanged in 18 (72%) RRMS subjects, increased in 6 (24%), decreased in 1 (4%). All 6 subjects with increased LME foci were on treatment [glatiramer acetate, interferon-β (2), rituximab, ocrelizumab, fingolimod]. The subject with LME resolution was treated with ocrelizumab. LME+ subjects had an on-study increase in volume of WMLs (baseline 11.0±14.4 vs. follow-up 12.6±16.3 ml, p<0.001), CLs (0.85±1.2 vs. 1.0±1.4 ml, p=0.002) and TLs (0.103±0.093 vs. 0.117±0.099 ml, p=0.005), whereas LME- subjects had an increase only in WML volume (2.7±2.3 vs. 3.3±2.6 ml, p=0.023). Baseline LME foci number correlated with 1-year change in CL (r=0.36, p=0.078) and WML (r=0.50, p=0.010) volumes. Minimal EDSS change over 1 year was noted. We used these data as the basis for a sample size calculation for a hypothetical trial of a putative therapy that would reduce the rate of MRI lesion accrual by 80% over 1 year. For a single-arm study with 1-year run-in on standard therapy and 1 year on new treatment to achieve 80% power, sample sizes of n=46, n=56 and n=79 were calculated for CL volume, TL volume and LME foci number, respectively.

Conclusions

The evolution of cerebral LME may be a dynamic process in the short term in RRMS, providing a monitoring tool, with about one quarter of patients showing new foci at one year. LME may pose a risk for the subsequent development of new lesions in widespread brain regions, implicating meningeal involvement as a marker or mediator of increased disease severity.

Abstract

Several experimental and clinical observations have suggested the presence of elevated inflammation, diffuse or organized in lymphoid structures that resemble secondary lymphoid organs, tertiary lymphoid structures (TLS), in the leptomeninges of either experimental animal model or post-mortem multiple sclerosis (MS) central nervous system (CNS), both in the brain and in the spinal cord. This feature, named lymphoid neogenesis, has been suggested to have a relevant role in maintaining intrathecal immune response in MS, as well as previosly shown in other chronic inflammatory diseases.

MS meningeal inflammation, particularly enriched in B cells and compartmentalized within cerebral sulci, is specifically linked to elevated demyelination and damage of the adjacent subpial cortical grey matter. In particular, elevated meningeal inflammationis associated with substantial “surface-in” gradient of cortical neuronal loss and microglia activation highest in the outer cortical layers, close to the cerebrospinal fluid (CSF)/pia boundary, compared to the inner ones.

The strict correlation between meningeal molecular profiling and paired CSF protein one in post-mortem MS cases with elevated cortical lesion load and aggressive disease course has suggested that meningeal infiltrates may represent one of the main intrathecal sources of inflammatory and cytotoxic factors that released in the CSF might orchestrate and/or exacerbate chronic local inflammation and following cortical pathology.

Similar intrathecal inflammatory pattern detected in naïve MS patients was able to predict 89% of the variance in cortical lesion volume and number at time of diagnosis and to distinguish patients at high risk of disease activity after 4 years follow-up.

Abstract

Background/Purpose: Inflammation in the meninges is increasingly recognized as a critical component of the underlying pathophysiology of multiple sclerosis (MS). Histopathologic data suggests direct links between meningeal inflammation and both local and distant cortical demyelination and axonal loss. Neuroimaging studies of leptomeningeal enhancement (LME), a possible surrogate of meningeal inflammation, show a relationship between LME and cortical atrophy, although findings relating LME to cortical lesions (CLs) have been more inconsistent. In this study, we aimed to evaluate the interrelationship between LME, CLs, and more distant neuronal atrophy through evaluation of retinal thickness by optical coherence tomography (OCT).

Methods: Forty participants with MS underwent whole brain 7T imaging on a Philips Achieva scanner with a volume transmit/32 channel receive head coil and optical coherence tomography on a Heidelberg Engineering Spectralis spectral domain OCT scanner at baseline, along with annual follow up OCT images. 7T scans involved pre- and post-contrast acquisition of magnetization prepared 2 rapid acquisition gradient echo (MP2RAGE) sequences acquired at 0.7 mm x 0.688 mm x 0.68 mm resolution and a magnetization prepared fluid attenuated inversion recovery (MPFLAIR) image at 0.7mm³ isotropic resolution. MRI images were reviewed for LME and CLs and processed for segmented volumes. OCT images underwent segmentation for individual retinal layers. MRI and OCT data were evaluated using correlation testing and mixed models regression, adjusted for age, sex, treatment status, and optic neuritis history.

Results: The cohort consisted of 26 (65%) females and were mostly of the relapsing-remitting phenotype (30/40 (75%). Thirty-two (80%) subjects had at least one focus of LME and all had CLs on 7T MRI. Baseline ganglion cell/inner plexiform (GCIP) layer and average macular thickness (AMT) correlated with normalized CL volume (r = -0.45, p = 0.006 and r = -0.34, p = 0.049 respectively). Macular RNFL (mRNFL) and GCIP thickness and AMT were -4.60 (-7.85, -1.35) μm, -8.12 (-14.16, -2.08) μm, and 15.073 (-28.61, -1.54) μm thinner, respectively, if LME was present (p = 0.006, 0.009, and 0.030, respectively). In subjects in whom spread/fill-sulcal pattern LME was present at baseline, mRNFL thickness declined -0.84 (-1.61, -0.07) μm/year faster (p = 0.033) and OPL thickness declined -1.23 (-2.33, -0.13) μm/year faster (p = 0.029).

Conclusion: This study provides support for a relationship between MRI findings of cortical pathology and LME and thinning of retinal layers as measured by OCT. These associations suggest meningeal inflammation may be a common link resulting in widespread demyelination, neuronal loss, and axonal degeneration throughout the CNS and the retina.

Background

Commensal gut microbes are known to affect host immune function and may be modifiable. Recent work suggests gut microbiota composition contributes to onset of MS; however, little is known about its contribution to MS disease activity.

Objectives

Estimate the association between gut microbiota and subsequent disease activity among individuals with pediatric-onset MS (pedMS) from the U.S. Network of Pediatric MS Centers.

Methods

Stool samples were collected from cases (MS symptom onset <18 years) and profiled using 16S rRNA sequencing of the V4 region. Amplicon sequence variants (ASVs) were identified using the Divisive Amplicon Denoising Algorithm-2 (DADA2). ASVs present in <20% of samples were removed. ASV clusters (modules) were identified using weighted genetic correlation network analysis (WGCNA) and sparCC transformation of ASV abundance. Cox proportional hazard recurrent event models were used to examine the relationship between individual ASVs and then ASV clusters, adjusted for age, sex, and disease modifying therapy (DMT) use.

Results

Of 53 pedMS cases, 72% were girls. At stool sample collection, the mean age was 15.5 years (SD: 2.7) and disease duration was 1.1 years (SD: 1.0). Less than half (45%) had one relapse and 30% had >1 relapse over the subsequent mean follow-up of 2.5 years (SD:1.3). Over this time, 91% used a DMT. Among 270 individual ASVs included in the analyses, 20 were nominally significant (p<0.05), e.g. the presence of Blautia stercoris was associated with higher relapse risk (hazard ratio [HR]=2.50; 95% confidence interval [CI]=1.43, 4.37). WGCNA identified 6 ASV modules. Higher values of one module’s eigengene was significantly (false discovery rate q<0.2) associated with higher relapse risk (HR=1.23, 95% CI=1.02, 1.50). Four ASVs nominally associated with higher relapse risk were in this module. These included Blautia massiliensis, Dorea longicatena, Coprococcus comes, and an unknown species in genus Subdoligranulum.

Conclusions

We found that a high relative abundance of a gut microbiota species within the Blautia genus, and its interconnected variants, was associated with a higher relapse risk in pedMS cases. While our study represents the largest of its kind in MS, findings need to be replicated. However, Blautia stercoris has been linked to disease activity in other immune-mediated diseases such as systemic lupus erythematosus.

Background

Astrocytic impairment is a common feature of neuromyelitis optica and possibly also multiple sclerosis (MS) lesions and initiates even prior to demyelination. Repopulation of early active plaques with aquaporin 4-negative astrocyte precursors has been recorded, implying astrocytic loss in pre-active lesion stages.

Objectives

Therefore, we aimed at investigating effects of a primary astrocytic loss on lesion regeneration and remyelination.

Methods

Osmolytic shifts induce severe astrocytic loss in certain CNS regions, leading to a secondary oligodendrocyte loss and demyelination, in the absence of antigen-specific lymphocyte activation. In patients, this is referred to as central pontine myelinolysis (CPM). Studying autopsy material from patients with CPM, as well as an experimental rat model, we characterized the oligodendrocyte precursor cell (OPC) activation and differentiation. Using injections of the thymidine-analogue BrdU, we traced the maturation of OPCs activated in early lesions.

Results

Animal experiments revealed rapid activation of the parenchymal NG2+ OPC reservoir in the widely astrocyte-free lesion, leading to extensive OPC proliferation. One week after lesion initiation, most cells derived from parenchymal OPCs expressed breast carcinoma amplified sequence 1 (BCAS1), indicating the transition into a pre-myelinating state. Though, cells derived from the early parenchymal response often presented a dysfunctional morphology with condensed cytoplasm and without evidence for process extension, that were sparsely found among myelin producing or mature oligodendrocytes. Correspondingly, also early human CPM lesions showed reduced astrocyte numbers and non-myelinating BCAS1+ oligodendrocytes with dysfunctional morphology. In the animal model, neural stem cells (NSCs) located in the subventricular zone (SVZ) were activated while the lesion was already repopulated with OPCs, giving rise to nestin+ progenitors that partially generated oligodendroglial lineage cells in the lesion, that was finally successively refilled with astrocytes and remyelinated. Those nestin+ stem cell-derived progenitors were absent in human CPM cases possibly contributing to the rather inefficient lesion repair.

Conclusions

The present study underpins the importance of astrocyte-oligodendrocyte interactions for remyelination, thus stressing the necessity to further determine the impact of astrocyte dysfunction on remyelination efficiency in demyelinating disorders like MS.