Effect of acyclovir treatment on acute and chronic murine cytomegalovirus infection

Murine cytomegalovirus (MCMV) is inhibited in vitro by 1 to 2 microM acyclovir. Therapy of a systemic MCMV infection in weanling mice with acyclovir was only minimally effective when drug was administered intraperitoneally, while oral administration by addition of acyclovir to the drinking water was highly efficacious in mice with disseminated MCMV. Effective therapy was characterized by reduction of virus titers in lung, liver, spleen, and kidney. In mice chronically infected with MCMV, treatment for 30 days with oral acyclovir eliminated or reduced virus titers in all target organs except the salivary gland. Therapeutic efficacy in this model infection using oral administration of acyclovir could be correlated with the achievement of acyclovir levels in the plasma of experimental animals two to 10 times greater than the mean inhibitory concentration for MCMV in vitro throughout treatment. The lack of efficacy observed when drug was administered intraperitoneally was associated with acyclovir levels exceeding 1 microM for one to three hours after each dose.