Alveolar Type II Epithelial Cells Contribute to the Anti-Influenza A Virus Response in the Lung by Integrating Pathogen- and Microenvironment-Derived Signals

Abstract

Influenza A virus (IAV) periodically causes substantial morbidity and mortality in the human population. In the lower lung, the primary targets for IAV replication are type II alveolar epithelial cells (AECII), which are increasingly recognized for their immunological potential. So far, little is known about their reaction to IAV and their contribution to respiratory antiviral immunity in vivo. Therefore, we characterized the AECII response during early IAV infection by analyzing transcriptional regulation in cells sorted from the lungs of infected mice. We detected rapid and extensive regulation of gene expression in AECII following in vivo IAV infection. The comparison to transcriptional regulation in lung tissue revealed a strong contribution of AECII to the respiratory response. IAV infection triggered the expression of a plethora of antiviral factors and immune mediators in AECII with a high prevalence for interferon-stimulated genes. Functional pathway analyses revealed high activity in pathogen recognition, immune cell recruitment, and antigen presentation. Ultimately, our analyses of transcriptional regulation in AECII and lung tissue as well as interferon I/III levels and cell recruitment indicated AECII to integrate signals provided by direct pathogen recognition and surrounding cells. Ex vivo analysis of AECII proved a powerful tool to increase our understanding of their role in respiratory immune responses, and our results clearly show that AECII need to be considered a part of the surveillance and effector system of the lower respiratory tract.

Lung epithelial cells have virus-specific and shared gene expression responses to infection by diverse respiratory viruses

“…These genes included cytokines and chemokines (Cxcl9, Ccl5, IL12b, Ccl8) , IFN response genes (Ifitm6, Ifi27l2a, Ifna2, Ifit2, Ifitm5, Ifra11 ), and genes involved in processing MHC class I antigens (Psmb10, Tap2, H2-Q2, H2-K1, Psmd9, Psme2, Psme1). The significant up-regulation of host defense genes in response to PR8 in the LA4 cell line corresponds with the expression profile of murine type II alveolar epithelial cells in response to PR8 infection in mice [37]. Furthermore, strong up-regulation of immune response-related genes upon PR8 infection of mice correlates with disease severity [11].…”

“…Alveolar epithelial cells have a key role in alerting the immune system to infection by respiratory viruses and shaping immune responses [37, 56, 57]. As viruses from several different families all target respiratory epithelial cells, it is important to understand the similarities and differences in how these cells respond to a diverse set of viruses.…”

Visualizing the Selectivity and Dynamics of Interferon Signaling In Vivo

“…These cells can be identified in enzyme-digested lung tissue using flow cytometry. We defined AT-I as CD45 À , T1a + MHC-I + , AT-II as CD45 À , T1a À , EpCAM + MHC-II high , and cilia cells as CD45 À , T1a À , EpCAM + MHC-II int as previously described (Stegemann-Koniszewski et al, 2016;Cardani et al, 2017;Hasegawa et al, 2017) ( Figure 3A). Although two recent transcriptomic studies identified an IFN gene signature in AT-II (Stegemann-Koniszewski et al, 2016;Steuerman et al, 2018), to the best of our knowledge, the IFN-response in this and other pulmonary epithelial cells has yet to be compared.…”

Antigen and G-Protein Coupled Receptor signaling differentially control CD8 T cell motility immediately before and after virus clearance in a primary infection

“…Chemokines and chemokine receptors are critical in directing T cells to sites of infection. CXCL9 and CXCL10 from epithelial cells are strongly induced by influenza infection [14, 17]. The receptor for these chemokines, CXCR3, is expressed on activated CD8 T cells and is required for efficient infiltration of the infected respiratory tract [18].…”