Effect of ganciclovir on murine cytomegalovirus-induced reactivation of toxoplasma pneumonia.

Active cytomegalovirus (CMV) infection induces immunosuppression and predisposes to the development of life-threatening superinfections in immunocompromised patients. We have described a mouse model in which acute murine CMV (MCMV) infection reactivates previously dormant Toxoplasma gondii infection, manifested as pneumonia. To determine whether therapy with ganciclovir might prevent MCMV-induced reactivation of T. gondii pneumonia, we administered ganciclovir to mice starting 1 day before to 2 days after MCMV infection and continuing for 14 days. When ganciclovir was begun early (before, on the day of, or 1 day after MCMV infection), the severity of T. gondii pneumonia reactivated by MCMV was significantly reduced. However, when therapy was delayed, no beneficial effect of ganciclovir was observed and the severity of MCMV-induced reactivation of T. gondii pneumonia was comparable to that seen in untreated animals. We conclude that ganciclovir therapy can attenuate but not eliminate MCMV-induced reactivation of T. gondii pneumonia and that prophylactic or very early administration of the drug is necessary to achieve protection.