T cell responses to COVID-19 infection and vaccination in patients with multiple sclerosis receiving disease-modifying therapy

Background: Multiple sclerosis (MS) is a neurological disorder marked by accumulating immune-mediated damage to the central nervous system. The dysregulated immune system in MS combined with immune effects of disease-modifying therapies (DMTs) used in MS treatment could alter responses to infections, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes coronavirus disease 2019 (COVID-19). Most of the literature on immune response to SARS-CoV-2 infection and COVID-19 vaccination, in both the general population and patients with MS on DMTs, has focused on humoral immunity. However, immune response to COVID-19 involves multiple lines of defense, including T cells. Objective and Methods: We review innate and adaptive immunity to COVID-19 and expand on the role of T cells in mediating protective immunity against SARS-CoV-2 infection and in responses to COVID-19 vaccination in MS. Results: Innate, humoral, and T cell immune responses combat COVID-19 and generate protective immunity. Assays detecting cytokine expression by T cells show an association between SARS-CoV-2-specific T cell responses and milder/asymptomatic COVID-19 and protective immune memory. Conclusion: Studies of COVID-19 immunity in people with MS on DMTs should ideally include comprehensive assessment of innate, humoral, and T cell responses.