Transcriptomics of murine ex vivo isolated alveolar type 2 epithelial cells from Influenza A respiratory infection

Background: Influenza A virus (IAV) infections periodically cause substantial morbidity and mortality in the human population. In the lung, the primary targets for IAV replication are type II alveolar epithelial cells (AECII), which are increasingly recognized for their immunological potential. However, our knowledge of the role of AECII in anti-IAV immunity is incomplete and their in vivo response to infection has not been evaluated. To increase our understanding of their role in host-response to IAV-infection, we analyzed transcriptional regulation in primary AECII isolated from infected mice. Results: Microarray analyses of AECII isolated on the first three days following IAV-infection revealed extensive transcriptional regulation. A multitude of differentially expressed transcripts was identified and in comparison to whole-lung tissue revealed a strong contribution of AECII to respiratory anti-IAV responses. Type I interferon played a major role in the detected gene expression profile and functional pathway analyses showed AECII to be highly active in pathogen recognition, cell recruitment and antigen-presentation. Analysis of Toll-like receptor 7 (TLR7) deficient mice indicated AECII to rely on the hosts expression of this innate IAV-sensor to elicit their full response. Importantly, the AECII transcriptional profiles correlated to cell recruitment and type I interferon levels detected in the lungs of infected animals. Conclusions: Ex vivo analysis of primary murine AECII proved as a powerful tool to increase our understanding of AECII biology in infection. Our analysis revealed an exceptionally strong contribution of AECII to local host defenses by integrating signals provided by surrounding cells and direct pathogen recognition.

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Stegemann-Koniszewski S, Jeron A, Gereke M, Geffers R, Kröger A, Gunzer M, Bruder D