Surfactant protein a binds to the fusion glycoprotein of respiratory syncytial virus and neutralizes virion infectivity

Collectins are a family of calcium-dependent collagenous lectins that appea r to be important in innate host defense. We investigated the ability of th ree human collectins, namely, lung surfactant proteins A (SP-A) and D (SP-D ) and the serum mannose-binding protein (MBP), to bind to the surface glyco proteins of respiratory syncytial virus (RSV), SP-A was shown to bind to th e F (fusion) glycoprotein but not to the viral G (attachment) glycoprotein, and binding was completely abrogated in the presence of EDTA, Neither SP-D nor MBP bound to either glycoprotein, SP-A also neutralized RSV in a calci um dependent fashion. These results support a role for SP-A in the defense of infants against infection with RSV and indicate a possible mechanism for its protective activity.