Cell cycle arrest by transforming growth factor beta1 enhances replication of respiratory syncytial virus in lung epithelial cells.

Respiratory syncytial virus (RSV) is a common respiratory viral infection in children which is associated with immune dysregulation and subsequent induction and exacerbations of asthma. We recently reported that treatment of primary human epithelial cells (PHBE cells) with transforming growth factor beta (TGF-beta) enhanced RSV replication. Here, we report that the enhancement of RSV replication is mediated by induction of cell cycle arrest. These data were confirmed by using pharmacologic inhibitors of cell cycle progression, which significantly enhanced RSV replication. Our data also showed that RSV infection alone resulted in cell cycle arrest in A549 and PHBE cells. Interestingly, our data showed that RSV infection induced the expression of TGF-beta in epithelial cells. Blocking of TGF-beta with anti-TGF-beta antibody or use of a specific TGF-beta receptor signaling inhibitor resulted in rescue of the RSV-induced cell cycle arrest, suggesting an autocrine mechanism. Collectively, our data demonstrate that RSV regulates the cell cycle through TGF-beta in order to enhance its replication. These findings identify a novel pathway for upregulation of virus replication and suggest a plausible mechanism for association of RSV with immune dysregulation and asthma.