Neuroantigen-specific regulatory CD8+ T cell responses as a therapy for relapsing autoimmune demyelinating disease

Abstract

Abstract Multiple Sclerosis (MS) is an autoimmune demyelinating disease of the central nervous system (CNS). We have shown that CNS-specific CD8+ T cells possess a disease suppressive function in MS and its animal model, experimental autoimmune encephalomyelitis (EAE). In humans, this suppressive function of CD8+ T cells is deficient during MS relapses. We thus evaluated the role of CD8+ T cells in the context of the relapsing-remitting model (RR-EAE), using SJL mice. We demonstrate here that PLP178–191- and MBP84–104-specific CD8+ T cells ameliorated disease severity in an antigen-specific manner. Moreover, PLP178–191 CD8+ T cells reduced the number of relapses in PLP178–191-induced disease, even when transferred during ongoing disease. We were further able to ascertain that the suppressor population of CD8+ T cells express CD25, and show that a very low number of CD25+ CD8+ T cells are sufficient to suppress RR-EAE. We also probed the role of endogenously generated CNS-specific CD8+ T cell responses by using Listeria monocytogenes (LM) encoding CNS antigens to preferentially prime suppressive CD8+ T cells in vivo. Using this system, we show infection with LM expressing PLP175–194 endogenously induced disease suppressive CD8+ T cells that protected and treated PLP178–191 disease. Importantly, a combination of CD8+ T cell transfer boosted by LM infection also successfully treated ongoing disease induced by a non-cognate peptide (PLP139–151), indicating that this approach could be effective even in the context of epitope spreading. These studies support a potential immunotherapeutic strategy using LM vaccination to prime disease regulatory CD8+ T cells.