The impact of CMV on the respiratory burst of macrophages in response to Pneumocystis carinii

Infection of human monocyte-derived macrophages with CMV decreased the resp iratory burst when cells were stimulated with opsonized zymosan or Pneumocy stis carinii (P. carinii). Such an effect, though smaller, was also seen wi th heat-inactivated CMV, but only when triggered by zymosan. The effect was most pronounced in cells obtained from CMV antibody-negative donors. Dexam ethasone further reduced the respiratory burst, both in uninfected and CMV- infected cells. Interferon-gamma increased the response in uninfected cells and, to a lesser extend, in cells treated with heat-inactivated CMV, where as no effect was seen with infective CMV. No overt productive infection or cytopathology could be detected, however, the monocytes incubated with infe ctive but also heat-inactivated CMV formed clusters, a phenomenon that was equally pronounced in cultures from CMV antibody positive and negative-dono rs. These results might help explain the worse prognosis of P. carinii pneu monia in patients coinfected with CMV and receiving dexamethasone.