An Epithelial Integrin Regulates the Amplitude of Protective Lung Interferon Responses against Multiple Respiratory Pathogens

Meliopoulos, Victoria A.; Van de Velde, Lee-Ann; Van de Velde, Nicholas C.; Karlsson, Erik A.; Neale, Geoff; Vogel, Peter; Guy, Cliff; Sharma, Shalini; Duan, Susu; Surman, Sherri L.; Jones, Bart G.; Johnson, Michael D. L.; Bosio, Catharine; Jolly, Lisa; Jenkins, R. Gisli; Hurwitz, Julia L.; Rosch, Jason W.; Sheppard, Dean; Thomas, Paul G.; Murray, Peter J.; Schultz-Cherry, Stacey

The most likely mechanism of protection in influenza infected β6 KO mice was decreased viral titers. However, tissue culture infectious dose 50 (TCID 50 ) and quantitative real-time PCR showed no significant differences in viral titers, although RT-PCR suggested a trend towards lower titers in β6 KO mice (Fig 3A and 3B ). We therefore spatially monitored viral spread in the lungs by immunohistochemistry for viral nucleoprotein (NP) and use of a reporter virus [34, 35] . Viral spread into the alveolar spaces was reduced in β6 KO mice in comparison to WT mice, which had extensive NP staining of type II pneumocytes and macrophages in the alveolar spaces by 5 dpi. In contrast, NP staining in β6 KO mice was largely restricted to the terminal bronchiolar epithelium and adjacent alveoli (Fig 3C) . This is even more evident using our NLuc CA/09 reporter virus, which clearly demonstrates decreased virus in β6 KO ( [34, 35] , S1 Fig) . Finally, WT lungs had a higher percentage of sites of active infection at 5 and 7 dpi as well as more viral antigen detected in the alveolar spaces (Fig 3D and 3E) . Collectively, viral spread in KO lungs was limited compared to WT mice, with less extensive involvement of alveolar epithelial cells possibly explaining the improved lung function relative to controls. These findings are consistent with studies suggesting that increased survival during influenza infection can be independent of changes in viral titers [36] [37] [38] [39] [40] .