CD8 T-cells predominate in CNS lesions of MS patients and display oligoclonal expansion. However, the role of myelin-specific CD8 T-cells in disease remains unclear, with studies showing protective and pathogenic roles in EAE. We demonstrated a disease-suppressive function for CNS-specific CD8 T-cells in a model where the antigen is exogenously administered in vivo and used for in vitro activation. To probe the nature of the CD8 response elicited by endogenously presented myelin antigens in vivo, we developed a novel approach utilizing infection with Listeria monocytogenes (LM) encoding proteolipid protein peptide (PLP) amino acids 178-191 (LM-PLP). LM-PLP infection preferentially induced PLP-specific CD8 T-cell responses. Despite the induction of PLP-specific CD8 T-cells, LM-PLP infection did not result in disease. In fact, LM-PLP infection resulted in significant amelioration of PLP178-191-induced EAE. Disease suppression was not observed in mice deficient in CD8 T-cells, IFN-γ or perforin. DTH responses and CNS infiltration were reduced in protected mice, and their CD4 T-cells had reduced capacity to induce tissue inflammation. Importantly, infection with LM-PLP ameliorated established disease. Our studies indicate that CD8 T-cells induced by endogenous presentation of PLP178-191 attenuate CNS autoimmunity in models of EAE, implicating the potential of this approach as a novel immunotherapeutic strategy.
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