Lung surfactant protein A provides a route of entry for respiratory syncytial virus into host cells

Lung surfactant protein A (SP-A) has a central role in host defense mediate d by the interaction of surface carbohydrates of inhaled pathogens with the lectin domains of SP-A, Respiratory syncytial virus (RSV), the most import ant viral pathogen of neonates and infants, encodes a highly glycosylated a ttachment protein, G, Binding studies were performed with G-protein from RS V (human, A2 strain) and human SP-A, The effect of SP-A on the interaction between RSV and host cells was determined by two methods: an infectivity st udy with monolayers of Hep-2C cells and by interleukin-8 (IL-8) release fro m buffy coat (BC) cells. SP-A binds to RSV G-protein in a concentration-dep endent manner that is inhibitable by both ethylenediamine tetraacetic acid (EDTA) and mannan, indicating that binding is through the carbohydrate reco gnition domain of the SP-A and a carbohydrate moiety of the G-protein, The level of RSV infection of Hep-2C cells increases with increasing concentrat ions of SP-A, The amount of IL-8 released by BC cells in the presence of RS V is increased with SP-A concentrations of 2.9 mu g/mL or greater. Our resu lts show that SP-A enhances the attachment of RSV and subsequent entry into host cells. The effect of SP-A on viral uptake by epithelial cells and mac rophage may determine both innate and adaptive immune responses to RSV.