CD4 and CD8 T cells have redundant but not identical roles in virus-induced demyelination

A chronic demyelinating disease results from murine infection with the neurotropic strain JHM of mouse hepatitis virus (MHV-JHM), Demyelination is largely immune mediated. In this study, the individual roles of CD4 and CD8 T cells in MHV-induced demyelination were investigated using recombination-activating gene 1(-/-) (RAG1(-/-)) mice infected with an attenuated strain of MHV-JHM. These animals develop demyelination only after adoptive transfer of splenocytes front mice previously immunized to MHV, In this study, we show that, following adoptive transfer, virus-specific CD4 and CD8 T cells rapidly infiltrate the CNS of MIN-JHM-infected RAG1(-/-) mice. Adoptive transfer of CD4 T cell-enriched donors resulted in more severe clinical disease accompanied by less demyelination than was detected in the recipients of undepleted cells. Macrophage infiltration into the gray matter of CD4 T cell-enriched recipients was greater than that observed in mice receiving undepleted splenocytes, In contrast, CD8 T cell-enriched recipients developed delayed disease with extensive demyelination of the spinal cord. MHV-JHM-infected RAG1(-/-) mice receiving donors depleted of both CD4 and CD8 T cells did not develop demyelination, These results demonstrate that the development of demyelination following MHV infection may be initiated by either CD4 or CD8 T cells. Furthermore, they show that CD4 T cells contribute more prominently than CD8 T cells to the severity of clinical disease, and that this correlates with increased macrophage infiltration into the gray matter.