Mouse Hepatitis Virus (MHV) Infection in Thymectomized C₃H Mice

MHV(PRI) virus produced a non-fatal immunizing infection in adult C₃H mice over a greater than 6.0 log₁₀ unit range but a uniformly fatal infection in adult Princeton (PRI) mice. Neonatally thymectomized 4-6 week old C₃H mice died by day 10 after inoculation with MHV(PRI). Intact and thymectomized C₃H mice had comparable virus titers in their livers until day 7 postinfection after which time virus was undetectable in intact C₃H mice but remained at high titers in thymectomized C₃H mice. The liver pathology was similar in both groups until day 6 post infection after which time resolving lesions were seen in livers of intact C₃H mice whereas thymectomized C₃H mice developed fulminant fatal hepatitis. In in vitro tests, the macrophages of the thymectomized C₃H mice did not support growth of MHV(PRI) virus to any greater extent than the macrophages of nonthymectomized C₃H mice. Although infection with MHV(PRI) was fatal for both PRI and thymectomized C₃H mice, the course of infection was much more rapid in PRI mice. C₃Hss mice which are congenic with C₃H mice but have macrophages which support growth of MHV(PRI) responded to MHV(PRI) infection with a rapidly fatal illness in the same way as PRI mice. These data suggest that macrophages resistant to viral multiplication and intact thymic function are both necessary for resistance to the lethal effects of MHV(PRI) virus. This research was supported in part by National Science Foundation Grant No. GB 31479.