Epigenetic changes and serotype-specific interferon-responses of lung epithelial cells in late post-influenza pneumococcal pneumonia

Abstract

AbstractPneumococcal infection following influenza A virus (IAV) pneumonia is a synergistic complication with high mortality. IAV modulates host antibacterial responses and invasiveness of pneumococcal serotypes and is an important pathogenic factor2. Yet, serotype-specifc immediate-early responses of the IAV-perturbed alveolar epithelium have not been adressed. We analyzed gene transcription in alveolar type II epithelial cells (AECII) from mice infected with IAV and/or one of threeS. pneumoniae(S.pn.) serotypes of varying invasiveness (4 > 7F > 19F). IAV, 14 days post infection, rendered the lung susceptible to invasiveS.pn.infection with serotype 4 and the mildly invasive 7F but not 19F. Only 7F secondary infection induced exacerbated cytokine/chemokine responses. IAV/7F infection induced superior protein expression of type I and II interferons, exceeding that in IAV/serotype 4 infection. Inference of a scale-free-like ARACNE gene co-expression network revealed interferon-response network modules. Network-mapping unfoldedS.pn.serotype-specific transcriptional network responses/usage. SecondaryS.pn.infection abrogated the IAV-induced pneumocyte proliferative configuration and IAV infection rendered the transcriptional response to 7F comparable to that of serotype 4. This related to network genes correlating with the expression of two master regulators of interferon responses:Irf7andStat1. Epigenetic ATAC-seq analysis of AECII in resolved IAV infection identified enhanced expression of ARACNE network genesHist1h2bf,Igtp,Mki67,Rasl10b,H2-Q6andH2-Q7to be associated with increased chromatin accessability at promoter regions. We show that AECII retain a sustained IAV-associated transcriptional configuration with epigenetic involvement that serotype-specifically affects proliferation and intensifies the AECII transcriptional response, mainly to interferons, inS.pn.infection.