Effects of stress on the immune response to theiler's virus - implications for virus-induced autoimmunity

Psychological stress is an important factor in susceptibility to many diseases. Our laboratory has been investigating the impact of stress on the susceptibility to Theiler's virus-induced demyelination (TVID), a mouse model of multiple sclerosis. Using immunodominant viral peptides specific for identification of either CD4⁺ or CD8⁺ T cells, stress reduced IFN-γ-producing virus-specific CD4⁺ and CD8⁺ T cells in the spleen and CD8⁺ T cells in the CNS. Expression of mRNA for the Th1 transcription factor T-bet and the Th2 transcription factor GATA-3 were decreased in spleen cells isolated from stressed mice. Cytokine production by cells isolated from the CNS or spleens following stimulation with virus indicated that stress decreased both type 1 and type 2 responses. The adverse effects of stress were partially reversed by concurrent RU486 administration but mimicked by dexamethasone, indicating a major role for glucocorticoids. Global stress-induced immunosuppression resulted in higher levels of virus replication and dissemination. The higher viral load subsequently led to an earlier disease onset and more severe clinical and histological signs of demyelinating disease. Our results have important implications for understanding the pathogenesis of MS, and suggest that stressful events during early infection with an agent capable of inducing demyelination may result in immunosuppression and failure to eliminate the pathogen, which in turn may lead to the development of MS.