Surfactant protein D enhances clearance of influenza A virus from the lungin vivo

Mice lacking surfactant protein surfactant protein. D (SP-D-/-) and wild-ty pe mice (SR-D+/+) were infected with influenza A virus (IAV) by intranasal instillation.. IAV infection increased the endogenous SP-D concentration in wild-type mice. SP-D-deficient mice showed decreased viral clearance of th e Phil/82 strain of IAV and increased production of inflammatory cytokines in response to viral challenge. However, the less glycosylated strain of UV , Mem/71, which is relatively resistant to SP-D in vitro, was cleared effic iently from the lungs of SP-D-/- mice. Viral clearance of the Phil/82 strai n of IAV and the cytokine response were both normalized by the coadministra tion of recombinant SP-D. Since the airway is the usual portal of entry for influenza A virus and other respiratory pathogens, SP-D is likely to play an important role in innate defense responses to IAV.