# The cytokine signature in multiple sclerosis: a study during the SARS-CoV-2 pandemic

## TL;DR

This study compares immune responses in people with multiple sclerosis who developed the disease during the SARS-CoV-2 pandemic versus before, finding distinct immune patterns linked to pandemic conditions.

## Contribution

The study identifies a unique cytokine signature in pandemic-era MS cases, suggesting peripheral immune activation influenced by pandemic-related environmental changes.

## Key findings

- CXCL13 and BAFF were elevated in both MS and pandemic MS, indicating B-cell involvement.
- Pandemic MS showed elevated peripheral IL-7, PDGF-BB, and CCL2, with serum and CSF CCL2 correlation unique to this group.
- Logistic regression distinguished pandemic MS from pre-pandemic MS using CXCL13, CCL4, and PDGF-BB.

## Abstract

Multiple sclerosis (MS) is a multifactorial autoimmune disorder resulting from the interplay of genetic susceptibility and environmental exposures. Viral infections, particularly Epstein–Barr virus (EBV), have been implicated in disease pathogenesis through mechanisms such as molecular mimicry. The SARS-CoV-2 pandemic provided a unique opportunity to explore whether large-scale viral exposure influenced early MS immunopathogenesis.

In this cross-sectional study, we compared cytokine profiles in patients with first MS onset during 2020 (pandMS, n = 36) with age-, sex-, and disease duration-matched pre-pandemic MS cases (MS, n = 20) and a reference cohort of individuals with other non-inflammatory neurological diseases (ONIND, n = 20). Paired cerebrospinal fluid (CSF) and serum samples were analyzed for 45 cytokines, along with neurofilament light (NfL) chain, BAFF, and CXCL13. Intrathecal cytokine synthesis was estimated using CSF/serum quotients and indices. Magnetic resonance imaging (MRI) and clinical evaluations, including Expanded Disability Status Scale (EDSS), were conducted in a patient subset. Statistical analyses included correlation, logistic regression, and multivariate modelling.

CXCL13 and BAFF were elevated in both MS and pandMS, consistent with B-cell recruitment and survival. A second cytokine cluster (marked by CCL4) indicative of astrocyte–microglia activation increased exclusively in MS. In pandMS, peripheral IL-7, PDGF-BB, and CCL2 were selectively elevated. Notably, serum and CSF CCL2 correlated only in pandMS, and serum CCL2 associated with white matter lesion burden. Logistic regression distinguished pandMS from MS based on CXCL13 index, CCL4 index, and serum PDGF-BB (r² = 0.65). MRI lesion counts and clinical parameters did not differ between groups.

While core MS-associated cytokines remain temporally stable, the pandemic period was associated with a shift toward peripheral immune activation at disease onset in pandMS. These findings likely reflect environmental and behavioral changes during the SARS-CoV-2 pandemic rather than direct viral effects. Our results highlight the dynamic interplay between central and peripheral immune mechanisms in early MS and reinforce the potential role of environmental exposures in modulating disease immunopathogenesis.