Activation and Impaired Accessory Cell Function of Human Monocytes in Vitro by Cytomegalovirus
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Monocytes are believed to participate in the host response to cytomegalovirus (CMV), a DNA virus which may exist in a latent form or may cause severe organ pathology depending on the immune competence of the host. To investigate monocyte-CMV interaction, the effect of CMV on monocyte phenotype and function was explored. Purified monocytes were inoculated at a multiplicity of infection of 1.0-2.0 with an isolate of CMV, laboratory propogated strain AD-169. The monocytes did not exhibit cytopathic changes or release virions into the culture supernatant. However, they did express immediate-early (IE) and early antigen (EA) viral proteins as detected by immunoperoxidase staining using monoclonal antibodies against IE and EA. Activation studies revealed that the CMV-infected monocytes spontaneously secreted increased amounts of H2 02 and expressed high levels of surface interleukin 2 and HLA-DR receptors. However, the CMV-infected monocytes secreted significantly less H2 02 following stimulation with lipopolysaccharide, muramyl dipeptide, or phorbol myristate acetate. Similarly, studies of the accessory cell functions of CMV-infected monocytes showed a marked decrease in ability to present antigen and mitogen for lymphocyte proliferation. These findings suggest that CMV infection alters monocyte function and may contribute to immunosuppression in vivo.