Murine cytomegalovirus pneumonia. Description of a model and investigation of pathogenesis.

Pneumonitis was produced in CD-1 mice by intratracheal instillation of murine cytomegalovirus. Lethal pneumonia occurred after instillation of virus derived from partially purified salivary gland homogenates, whereas virus attenuated by serial passage in cell culture caused mild disease and no mortality, even though both virulent and attenuated strains achieved comparable peak titers in lung homogenates. Virulence was characterized by rapid association of virus with pulmonary macrophages and early spread of virus from macrophages to susceptible parenchymal cells. This resulted in enhanced viral growth and cellular destruction during the first 5 days of infection. Delay in the early growth of murine cytomegalovirus in pulmonary parenchyma may diminish the destructive effects of virus on the lung and prevent mortality.