Abstract
Multiple sclerosis (MS) is a chronic autoimmune disease targeting the central nervous system (CNS). MS develops almost exclusively in individuals previously infected with Epstein-Barr virus (EBV)(1), yet the mechanisms linking EBV infection to MS pathogenesis remain incompletely defined. Here we characterized EBV-infected B cells in MS and demonstrated that EBV directly infects autoreactive anti-CNS antigen B cells and reprograms them into pro-inflammatory antigen-presenting cells (APCs). EBV(+) B cells in MS were enriched within the CD27(+)CD21(low) memory B-cell subset and exhibited upregulated B cell activation and APC transcriptional programs. Recombinant antibodies derived from MS blood and cerebrospinal fluid (CSF) EBV(+) B cells bound brain tissue, and several cross-bound both MS-associated autoantigens and Epstein-Barr virus nuclear antigen-1 (EBNA1). In vitro, EBV(+) B cells functioned as APCs that stimulated T peripheral helper cells, with associated activation of EBV(-) anti-CNS antigen B cells. Collectively, these findings support a mechanistic framework in which EBV infects and transcriptionally reprograms autoreactive anti-CNS antigen B cells into APCs that drive pathogenic anti-CNS antigen T cell and EBV(-) B cell responses in MS.