Combined blockade of TNF-a and IFN-I receptors in experimental RSV infection: analysis of STAT protein modulation

Abstract

Abstract Respiratory syncytial virus (RSV) is the leading cause of acute lower respiratory illness in young children. Two cytokines key to RSV pathogenesis are tumor necrosis factor (TNF)-a and type-I interferon (IFN-I). Using a dual receptor antibody blockade of IFNAR1 with either TNFR1 or TNFR2, we previously reported that IFN-I and TNF-a synergistically contribute to clinical disease while also controlling peak lung viral replication in RSV-infected Balb/c mice. The objective of the current study was to investigate the possible effect of TNF-a/IFN-I on prolonged viral shedding and to dissect canonical signaling pathways that would likely mediate the above-described activity. We found that viral titer in the lung of all treatment groups was comparable to the RSV control mice at days six and seven post-infection, indicating that lack of these cytokine receptor signaling was not involved in prolonged viral shedding. We then determined expression levels of total lung STAT1, STAT2, STAT3 and their phosphorylated forms as well as IRF1, pIRF3, IRF7, and IRF9 by western blot. Though RSV/IFNAR1, RSV/TNFR1, and RSV/TNFR2 demonstrated variations in protein expression for several of these signaling molecules, none of these proteins were uniquely modulated by the dual receptor blockade. These findings collectively demonstrate that while TNF-a/IFN-I receptor signaling controls peak viral replication in the lung, they have no effect on extended viral shedding and that STAT1, STAT2, and STAT3 signaling appears to be dispensable for the enhanced viral replication observed in the dual receptor blockade treated mice. Supported by grants from AI062885, AI25434, Clinical and Translational Science Award [(NRSA (TL1) Training Core TL1TR001440)],Supported by UTMB McLaughlin Fellowship