Surfactant protein-A enhances respiratory syncytial virus clearance in vivo

To determine the role of surfactant protein-A(SP-A) in antiviral host defense, mice lacking SP-A (SP-A(-/-)) were produced by targeted gene inactivation. SP-A(-/-) and control mice (SP-A(+/+)) were infected with respiratory syncytial virus (RSV) by intratracheal instillation. Pulmonary infiltration after infection was more severe in SP-A(-/-) than in SP-A(+/+) mice and was associated with increased RSV plaque-forming units in lung homogenates. Pulmonary infiltration with polymorphonuclear leukocytes was greater in the SP-A(-/-) mice. Levels of proinflammatory cytokines tumor necrosis factor-alpha and interleukin-6 were enhanced in lungs of SP-A(-/-) mice. After RSV infection, superoxide and hydrogen peroxide generation was deficient in macrophages from SP-A(-/-) mice, demonstrating a critical role of SP-A in oxidant production associated with RSV infection. Coadministration of RSV with exogenous SP-A reduced viral titers and inflammatory cells in the lung of SP-A(-/-) mice. These findings demonstrate that SP-A plays an important host defense role against RSV in vivo.