RESUMO
Respiratory syncytial virus (RSV) is the major pathogen causing severe lung disease in children. RSV initially replicates efficiently in the respiratory tract but becomes undetectable by 7 to 21 d after infection in normal children, suggesting that intrinsic cellular mechanisms, as yet undefined, may restrict virus replication. To provide an in vitro model to examine mechanisms that restrict RSV replication, three human lung epithelial cell lines were exposed to RSV in vitro and virus replication proceeded in a dose- and time-dependent manner, although less efficiently than the highly permissive CV-1 cell line (monkey kidney epithelial cell). Tumor necrosis factor alpha (TNF alpha) and/or interferon beta (IFN beta) markedly inhibited RSV replication in a dose- and time-dependent manner. TNF alpha combined with IFN beta essentially aborted RSV replication in A549 epithelial cells. TNF alpha and/or IFN beta did not induce cell membrane damage, cause cell lysis, or inhibit cellular protein synthesis. RSV-infected human alveolar macrophages, which produce TNF alpha, failed to productively infect lung epithelial cells in co-culture. Together these studies suggest that endogenous TNF alpha coupled with exogenous IFN beta could restrict RSV replication in lung epithelium.