Cytomegalovirus inhibits CD14 expression on human alveolar macrophages

Cytomegalovirus (CMV) infection in transplant patients is associated with an increased incidence of gram-negative pneumonia; the mechanism for this is unknown. Human alveolar macrophages (HAM) are an important part of the response of the lung to gram-negative bacteria. They interact with lipopolysaccharide (LPS) via the surface receptor CD14. The effect of CMV on CD14 expression by HAM was examined. HAM were obtained from normal volunteers by bronchoalveolar lavage, and some were exposed to CMV. CD14 expression was assessed by immunofluorescent microscopy and flow cytometry. CMV inhibited the surface expression of CD14 on HAM. Release of soluble CD14 was also reduced from infected cells, and Northern blot analysis revealed that CD14 mRNA was reduced in CMV-exposed cells. These findings were specific for CD14 expression. These results demonstrate that CMV inhibits the ability of HAM to express CD14.