Double-Stranded RNA-Activated Protein Kinase Regulates early innate immune responses during RSV Infection

Respiratory Syncytial virus (RSV) is the most common cause of childhood viral bronchiolitis and lung injury. Inflammatory responses significantly contribute to lung pathologies during RSV infections and bronchiolitis but the exact mechanisms have not been completely defined. The double-stranded RNA-activated protein kinase (PKR) functions to inhibit viral replication and participates in several signaling pathways associated with innate inflammatory immune responses. Using a functionally defective PKR (PKR-/-) mouse model, we investigated the role of this kinase in early events of RSV-induced inflammation. Our data showed that bronchoalveolar lavage (BAL) fluid of infected PKR-/- mice had significantly lower levels of several innate inflammatory cytokines and chemokines. Histological examinations revealed that there was less lung injury in infected PKR-/- mice as compared to the wild type. A genome-wide analysis showed that several early anti viral and immune regulatory genes were affected by PKR activation. These data suggest that PKR is a signaling molecule for immune responses during RSV infections. 6-10 week old male WT (B6.129PF1/J) (The Jackson Labs, Bar Harbor, ME) and PKR-/- mice were used in all experiments. Mice were housed and maintained in specific pathogen-free conditions and used in accordance with the regulations of the National Institutes of Health. The human long strain of RSV-A2 (originally from Dr. B.S. Graham, NIH) was propagated in HEp-2 cells (American Type Culture Collection). Viral stocks were prepared by harvesting HEp-2 cells in fresh medium and three quick freeze thaw cycles followed by high speed centrifugation (10,000 X g) to remove cellular debris.