Immunosuppression and murine polyomavirus infection.

Murine polyomavirus (MPYV) infection in mice has many similarities to human infections by BK virus (BKV) and JC virus (JCV) and provides a model for the human infections. MPYV causes acute, inapparent infection with virus appearing in numerous organs, including brain and kidney, and then subsides and becomes latent. At a later time it can be reactivated by corticosteroid treatment or pregnancy (McCance and Mims, 1979, McCance, 1983). To determine the effect of prolonged immunosuppression on virus activity in brain and kidney during acute infection, mice were treated with methotrexate, cyclophosphamide, or prednisone and azathioprine and inoculated with murine polyomavirus. Prednisone/azathioprine and cyclophosphamide caused protracted kidney infection and methotrexate had no effect. In the brain, prednisone/azathioprine and cyclophosphamide had minor effects on virus titers and course of infection, but methotrexate prevented MPYV from appearing in the brain. When mice were immunosuppressed with prednisone/azathioprine one week prior to inoculation, titers were much higher in the kidneys, but virus did not appear in the brain until late in the course of infection.