Poliovirus infection of cyclophosphamide-treated mice results in persistence and late paralysis: I. Clinical, pathologic, and immunologic studies.

An attenuated human poliovirus infection of cyclophosphamide (CY)-treated mice was developed as a model of persistent CNS enterovirus infections and as an investigation of the interaction of virus with motor neurons during persistence. Ten percent of mice inoculated intracerebrally with undiluted virus developed clinical disease by day 90, but of those treated with CY, 80% developed disease. At higher virus dilutions plus CY there was a marked increase in the incubation period. The latest onset of clinical disease occurred on day 146. Only paralyzed animals had pathologic changes in the spinal cord and virus antigen in anterior horn cells. Neutralizing antibodies were suppressed by CY, as were humoral and cellular immune responses to other antigens.