Epstein-Barr virus (EBV) infection of B cells is associated with increased multiple sclerosis (MS) susceptibility. Recently, we found that CXCR3-expressing B cells preferentially infiltrate the central nervous system of MS patients. In chronic virus-infected mice, these types of B cells are sustained and show increased antiviral responsiveness. How EBV persistence in B cells influences their development remains unclear. First, we analyzed ex vivo B-cell subsets from MS patients who received autologous bone marrow transplantation (n=9), which is often accompanied by EBV reactivation. The frequencies of non-class-switched and class-switched memory B cells were reduced at 3-7 months, while only class-switched B cells returned back to baseline at 24-36 months post-transplantation. At these time points, EBV DNA load positively correlated to the frequency of CXCR3+ , and not CXCR4+ or CXCR5+ , class-switched B cells. Second, for CXCR3+ memory B cells trapped within the blood of MS patients treated with natalizumab (anti-VLA-4 antibody n=15), latent EBV infection corresponded to enhanced in vitro formation of anti-EBNA1 IgG-secreting plasma cells under germinal center-like conditions. These findings imply that EBV persistence in B cells potentiates brain-homing and antibody-producing CXCR3+ subsets in MS. This article is protected by copyright. All rights reserved.