Infectious respiratory syncytial virus (RSV) effectively inhibits the proliferative T cell response to inactivated RSV in vitro.

The effect of respiratory syncytial virus (RSV) on the cellular immune response of human mononuclear cells in vitro was examined. Inhibition by RSV of the lymphocyte response to phytohemagglutinin in vitro was confirmed using cells from human umbilical cord blood. In addition, RSV significantly inhibited both the proliferative and T cell colony responses of human mononuclear cells to Epstein-Barr virus. An RSV-specific cellular immune response was induced in vitro by stimulation of mononuclear cells from RSV-seropositive donors with beta-propiolactone-inactivated RSV. This RSV-specific response was significantly inhibited by infectious RSV itself, and the inhibition was mediated by an extracellular factor produced by RSV-infected mononuclear cells. A similar inhibition in vivo of the RSV-induced cellular immune response may contribute significantly to delayed recovery from primary infection and to reduced resistance to subsequent infections.