Progressive inhibition of T-cell function preceding clinical signs of cytomegalovirus infection in mice.

Groups of mice that received a predominantly lethal or a nonlethal dose of murine cytomegalovirus (CMV) were studied prospectively to correlate clinical observations with detection of virus in spleen cells and with the response of spleen cells to the thymus-derived (T-) cell mitogen concanavalin A (con A). In both groups of mice, virus was virtually cleared from spleen cells by day 8 after infection. Depression of the spleen cell response to con A preceded clinical signs of infection, was more severe in the lethally infected group, and improved as clinical signs cleared in the few surviving mice. Serum from infected mice depressed the response of uninfected spleen cells to con A. These findings support the hypothesis that clinical illness and death from CMV infection of mice are a consequence of events that follow the depression of T-cell function by CMV. This depression is at least partially mediated by a humoral mechanism.