IDENTIFICATION OF THE RESPIRATORY SYNCYTIAL VIRUS-INDUCED IMMUNOSUPPRESSIVE FACTOR PRODUCED BY HUMAN PERIPHERAL-BLOOD MONONUCLEAR-CELLS IN-VITRO AS INTERFERON-ALPHA

Respiratory syncytial virus (RSV) can inhibit the proliferative respon se of human peripheral blood mononuclear cells (PBMC) in vitro. This i nhibition is mediated by an extracellular RSV-induced factor. In the p resent study, the factor was clearly identified as interferon (IFN)-al pha. The RSV-induced IFN-alpha bound strongly to PBMC and inhibited th e anti-RSV proliferative response only when added within the first few days of stimulation. There was, however, no concomitant decrease in t he production of interleukin (IL)-2 nor in the cell surface expression of CD25, CD71, and HLA-DR. Inhibition by RSV-induced IFN-alpha was un related to the levels of IL-1, -2, and -6 or of IFN-gamma induced by R SV in vitro or to the presence of IL-1 inhibitor, tumor necrosis facto r-alpha, prostaglandin, or IL-10. Immunosuppression by IFN-alpha may s ignificantly affect the outcome of infection and reinfection with RSV.