The role of host responses in the recovery of mice from Sendai virus infection.

The antiviral responses in mice to intranasal inoculation with Sendai virus are described. To investigate the relative importance of the humoral, cell-mediated and interferon responses, the pathogenesis of this infection was studied in animals which were immunocompetent, T cell-deprived or immunosuppressed with cyclophosphamide. Treatment with cyclophosphamide converted the mild, self-limiting infection observed in immunocompetent mice into a severe and frequently lethal pneumonic disease. This was associated with an enhanced interferon response but no detectable antibody or cell-mediated immune response. T cell-deprived mice suffer an infection of intermediate severity associated with an increased interferon response, a normal humoral immune response and no cell-mediated immune response. The implications of these results in relation to the role of the antiviral responses in recovery from Sendai virus infection are discussed.