STAT2 Signaling Regulates Macrophage Phenotype during Influenza and Bacterial Super-infection

Influenza is the common respiratory problem that infects between 5-20% of the US population and results in 30,000 deaths annually. A primary cause of the influenza-associated death is due to secondary bacterial pneumonia. In this study, we investigated the role of STAT2 signaling during influenza and influenza-bacterial super-infection in mice. Herein, we demonstrate that STAT2 signaling is required for viral control, regulation of inflammation, and limiting mortality during influenza single infection. Surprisingly, despite this deficiency in anti-viral immunity, we found increased bacterial control and survival in STAT2 deficient mice during influenza-MRSA super-infection compared to controls. This protection in the absence of STAT2 was associated with accumulation of dual phenotype M1/M2 macrophages, which were required for control of bacterial infection. Together, these results suggest that the STAT2 signaling is involved in suppressing macrophage activation and bacterial control during influenza-bacterial super-infection. We analyzed whole lung RNA from WT and STAT2-/- mice infected with influenza A/PR/8/34 for 6 days followed by MRSA USA300 for one additional day.