T-lymphocyte effects on murine cytomegalovirus pulmonary infection.

Cytomegalovirus (CMV) infections were induced in male BALB/c mice treated with rat monoclonal antibodies (MAb) to deplete selectively CD8 and CD4 cell populations in vivo. The animals were then inoculated intraperitoneally with murine CMV and the infection was monitored virologically and histologically. High concentrations of virus were found in the lungs of mice depleted of CD4 or both CD4 and CD8 cells. These animals developed pulmonary infections that persisted for at least 49 days after inoculation. In contrast, immunologically intact mice and those administered anti-CD8 MAb experienced only a transient infection of the lungs. Focal interstitial infiltrates of mononuclear cells were demonstrated in pulmonary tissues of CD4 MAb-treated animals, but not in normal mice and those receiving the CD8 MAb. Adoptive transfer of CD4 cells to animals (rendered immune-incompetent by thymectomy and irradiation) protected against pulmonary infection and the development of interstitial pneumonia. Mice treated with CD4 MAb failed to produce specific CMV antibody, whereas the depletion of CD8 cells had no effect on antibody elaboration. Administration of anti-CD4 and CD8 MAb did not affect virus replication in the salivary glands, the preferential site for CMV infection in the mouse. Induction of pulmonary infection and interstitial pneumonia by CMV in BALB/c mice is mediated by CD4 T cells.