CD4⁺ T cells reactive to Epstein-Barr virus late lytic antigens are enriched in individuals with multiple sclerosis

Multiple sclerosis (MS) pathogenesis is linked to Epstein-Barr virus (EBV), but the underlying immune mechanisms remain unclear. Using an optimized T cell assay, we demonstrate that CD4⁺ T cells from individuals with MS predominantly target EBV viral particle components, specifically the late lytic capsid and glycoprotein antigens, rather than latent antigens. In contrast, the Epstein-Barr nuclear antigen 1 (EBNA1) primarily activated CD8⁺ T cells. EBV-specific CD4⁺ T cell responses were twofold higher in individuals with untreated MS compared with healthy controls, whereas responses to other herpesviruses remained similar. Anti-CD20 therapy initiation in treatment-naïve participants reduced these responses, a finding validated in an independent cohort, and eliminated viral shedding in saliva. Our results establish preferential CD4⁺ T cell reactivity to EBV late lytic antigens as a key feature of MS, providing a framework for developing EBV-targeted therapies, including vaccines and antivirals.