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-α 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.
Ann Marie LeVine, Jodie Gwozdz, James Stark, Michael Bruno, Jeffrey Whitsett, Thomas Korfhagen