A cross-sectional study of MRI features and the gut microbiome in pediatric-onset multiple sclerosis

OBJECTIVE

To identify gut microbiome features associated with MRI lesion burden in persons with pediatric-onset multiple sclerosis (symptom onset <18 years).

METHODS

A cross-sectional study involving the Canadian Paediatric Demyelinating Disease Network study participants. Gut microbiome features (alpha diversity, phylum- and genus-level taxa) were derived using 16S rRNA sequencing from stool samples. T1- and T2-weighted lesion volumes were measured on brain MRI obtained within 6 months of stool sample procurement. Associations between the gut microbiota and MRI metrics (cube-root-transformed) were assessed using standard and Lasso regression models.

RESULTS

Thirty-four participants were included; mean ages at symptom onset and MRI were 15.1 and 19.0 years, respectively, and 79% were female. The T1- and T2-weighted lesion volumes were not significantly associated with alpha diversity (age and sex-adjusted p > 0.08). At the phylum level, high Tenericutes (relative abundance) was associated with higher T1 and T2 volumes (β coefficient = 0.25, 0.37) and high Firmicutes, Patescibacteria or Actinobacteria with lower lesion volumes (β coefficient = -0.30 to -0.07). At the genus level, high Ruminiclostridium, whereas low Coprococcus 3 and low Erysipelatoclostridium were associated with higher lesion volumes.

INTERPRETATION

Our study characterized the gut microbiota features associated with MRI lesion burden in pediatric-onset MS, shedding light onto possible pathophysiological mechanisms.

Short-chain fatty acid producers in the gut are associated with pediatric multiple sclerosis onset

OBJECTIVE

The relationship between multiple sclerosis and the gut microbiome has been supported by animal models in which commensal microbes are required for the development of experimental autoimmune encephalomyelitis. However, observational study findings in humans have only occasionally converged when comparing multiple sclerosis cases and controls which may in part reflect confounding by comorbidities and disease duration. The study of microbiome in pediatric-onset multiple sclerosis offers unique opportunities as it is closer to biological disease onset and minimizes confounding by comorbidities and environmental exposures.

METHODS

A multicenter case-control study in which 35 pediatric-onset multiple sclerosis cases were 1:1 matched to healthy controls on age, sex, self-reported race, ethnicity, and recruiting site. Linear mixed effects models, weighted correlation network analyses, and PICRUSt2 were used to identify microbial co-occurrence networks and for predicting functional abundances based on marker gene sequences.

RESULTS

Two microbial co-occurrence networks (one reaching significance after adjustment for multiple comparisons; q < 0.2) were identified, suggesting interdependent bacterial taxa that exhibited association with disease status. Both networks indicated a potentially protective effect of higher relative abundance of bacteria observed in these clusters. Functional predictions from the significant network suggested a contribution of short-chain fatty acid producers through anaerobic fermentation pathways in healthy controls. Consistent family-level findings from an independent Canadian-US study (19 case/control pairs) included Ruminococaccaeae and Lachnospiraceae (p < 0.05). Macronutrient intake was not significantly different between cases and controls, minimizing the potential for dietary confounding.

INTERPRETATION

Our results suggest that short-chain fatty acid producers may be important contributors to multiple sclerosis onset.

SARS-CoV-2 vaccination and infection in ozanimod-treated participants with relapsing multiple sclerosis

OBJECTIVE

To investigate the serologic response, predictors of response, and clinical outcomes associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination and infection in ozanimod-treated participants with relapsing multiple sclerosis (RMS) from DAYBREAK.

METHODS

DAYBREAK (ClinicalTrials.gov-NCT02576717), an open-label extension study of oral ozanimod 0.92 mg, enrolled participants aged 18-55 years with RMS who completed phase 1-3 ozanimod trials. Participants who were fully vaccinated against SARS-CoV-2 with mRNA or non-mRNA vaccines, were unvaccinated, and/or had COVID-19-related adverse events (AEs, with or without vaccination) and postvaccination serum samples were included (n = 288). Spike receptor binding domain (RBD) antibody levels (seroconversion: ≥0.8 U/mL) and serologic evidence of SARS-CoV-2 infection (nucleocapsid IgG: ≥1 U/mL) were assessed (Roche Elecsys/Cobas e411 platform).

RESULTS

In fully vaccinated participants (n = 148), spike RBD antibody seroconversion occurred in 90% (n = 98/109) of those without serologic evidence of prior SARS-CoV-2 exposure (100% [n = 80/80] seroconversion after mRNA vaccination) and in 100% (n = 39/39) of participants with serologic evidence of viral exposure. mRNA vaccination predicted higher spike RBD antibody levels, whereas absolute lymphocyte count (ALC), age, body mass index, and sex did not. COVID-19-related AEs were reported in 10% (n = 15/148) of fully vaccinated participants-all were nonserious and not severe; all participants recovered.

INTERPRETATION

Most ozanimod-treated participants with RMS mounted a serologic response to SARS-CoV-2 vaccination and infection, regardless of participant characteristics or ALC levels. In this analysis, all COVID-19-related AEs post-full vaccination in participants taking ozanimod were nonserious and not severe.

"Ependymal-in" Gradient of Thalamic Damage in Progressive Multiple Sclerosis

Leptomeningeal and perivenular infiltrates are important contributors to cortical grey matter damage and disease progression in multiple sclerosis (MS). Whereas perivenular inflammation induces vasculocentric lesions, leptomeningeal involvement follows a subpial "surface-in" gradient. To determine whether similar gradient of damage occurs in deep grey matter nuclei, we examined the dorsomedial thalamic nuclei and cerebrospinal fluid (CSF) samples from 41 postmortem secondary progressive MS cases compared with 5 non-neurological controls and 12 controls with other neurological diseases. CSF/ependyma-oriented gradient of reduction in NeuN⁺ neuron density was present in MS thalamic lesions compared to controls, greatest (26%) in subventricular locations at the ependyma/CSF boundary and least with increasing distance (12% at 10 mm). Concomitant graded reduction in SMI31⁺ axon density was observed, greatest (38%) at 2 mm from the ependyma/CSF boundary and least at 10 mm (13%). Conversely, gradient of major histocompatibility complex (MHC)-II⁺ microglia density increased by over 50% at 2 mm at the ependyma/CSF boundary and only by 15% at 10 mm and this gradient inversely correlated with the neuronal (R = -0.91, p < 0.0001) and axonal (R = -0.79, p < 0.0001) thalamic changes. Observed gradients were also detected in normal-appearing thalamus and were associated with rapid/severe disease progression; presence of leptomeningeal tertiary lymphoid-like structures; large subependymal infiltrates, enriched in CD20⁺ B cells and occasionally containing CXCL13⁺ CD35⁺ follicular dendritic cells; and high CSF protein expression of a complex pattern of soluble inflammatory/neurodegeneration factors, including chitinase-3-like-1, TNFR1, parvalbumin, neurofilament-light-chains and TNF. Substantial "ependymal-in" gradient of pathological cell alterations, accompanied by presence of intrathecal inflammation, compartmentalized either in subependymal lymphoid perivascular infiltrates or in CSF, may play a key role in MS progression. SUMMARY FOR SOCIAL MEDIA: Imaging and neuropathological evidences demonstrated the unique feature of "surface-in" gradient of damage in multiple sclerosis (MS) since early pediatric stages, often associated with more severe brain atrophy and disease progression. In particular, increased inflammation in the cerebral meninges has been shown to be strictly associated with an MS-specific gradient of neuronal, astrocyte, and oligodendrocyte loss accompanied by microglial activation in subpial cortical layers, which is not directly related to demyelination. To determine whether a similar gradient of damage occurs in deep grey matter nuclei, we examined the potential neuronal and microglia alterations in the dorsomedial thalamic nuclei from postmortem secondary progressive MS cases in combination with detailed neuropathological characterization of the inflammatory features and protein profiling of paired CSF samples. We observed a substantial "subependymal-in" gradient of neuro-axonal loss and microglia activation in active thalamic lesions of progressive MS cases, in particular in the presence of increased leptomeningeal and cerebrospinal fluid (CSF) inflammation. This altered graded pathology was found associated with more severe and rapid progressive MS and increased inflammatory degree either in large perivascular subependymal infiltrates, enriched in B cells, or within the paired CSF, in particular with elevated levels of a complex pattern of soluble inflammatory and neurodegeneration factors, including chitinase 3-like-1, TNFR1, parvalbumin, neurofilament light-chains and TNF. These data support a key role for chronic, intrathecally compartmentalized inflammation in specific disease endophenotypes. CSF biomarkers, together with advance imaging tools, may therefore help to improve not only the disease diagnosis but also the early identification of specific MS subgroups that would benefit of more personalized treatments. ANN NEUROL 2022;92:670-685.