Project description:Influenza A virus (IAV) infection is a global respiratory disease, which annually leads to 3-5 million cases of severe illness, resulting in 290,000-650,000 deaths. Additionally, during the past century, four global IAV pandemics have claimed millions of human lives. The epithelial lining of the trachea plays a vital role during IAV infection, both as point of viral entry and replication as well as in the antiviral immune response. Tracheal tissue is generally inaccessible from human patients, which makes animal models crucial for the study of the tracheal host immune response. In this study, pigs were inoculated with swine- or human-adapted H1N1 IAV to gain insight into how host adaptation of IAV shapes the innate immune response during infection. In-depth multi-omics analysis (global proteomics and RNA sequencing) of the host response in upper and lower tracheal tissue was conducted, and results were validated by microfluidic qPCR. Additionally, a subset of samples was selected for histopathological examination. A classical innate antiviral immune response was induced in both upper and lower trachea after infection with either swine- or human-adapted IAV with upregulation of genes and higher abundance of proteins associated with viral infection and recognition, accompanied by a significant induction of interferon stimulated genes with corresponding higher proteins concentrations. Infection with the swine-adapted virus induced a much stronger immune response compared to infection with a human-adapted IAV strain in the lower trachea, which could be a consequence of a higher viral load and a higher degree of inflammation. Central components of the JAK-STAT pathway, apoptosis, pyrimidine metabolism, and the cytoskeleton were significantly altered depending on infection with swine- or human-adapted virus and might be relevant mechanisms in relation to antiviral immunity against putative zoonotic IAV. Based on our findings, we hypothesize that during host adaptation, IAV evolve to modulate important host cell elements to favor viral infectivity and replication.

Project description:Infection with a single influenza A virus (IAV) is only rarely sufficient to initiate productive infection. Here, we exploit both single cell approaches and whole-animal systems to show that the extent of IAV reliance on multiple infection varies with virus strain and host species. Influenza A/guinea fowl/HK/WF10/99 (H9N2) [GFHK99] virus exhibits strong dependence on collective interactions in mammalian systems. This reliance focuses viral progeny production within coinfected cells and therefore results in frequent genetic exchange through reassortment. In contrast, GFHK99 virus has greatly reduced dependence on multiple infection in avian systems, indicating a role for host factors in viral collective interactions. Genetic mapping implicated the viral polymerase as a major driver of multiple infection dependence. Mechanistically, quantification of incomplete viral genomes showed that their complementation only partly accounts for the observed reliance on coinfection. Indeed, even when all polymerase components are detected in single cell mRNA sequencing, robust polymerase activity of GFHK99 virus in mammalian cells is reliant on multiple infection. In sum, IAV collective interactions not only augment reassortment, but can also overcome species-specific barriers to infection. These findings underscore the importance of virus-virus interactions in IAV infection, evolution and emergence. We used a single-cell sequencing platform (10x Genomics) to elucidate the differential infection rate of an avian influenza A virus on an avian cell line (DF1) and a mammalian (MDCK) cell line. Our work on IAV reassortment has raised new questions about the fundamental strategies that drive influenza virus evolution. Our data indicate that a large majority of influenza virus genomesare incomplete within cells, comprising less than the eight complete segments normally found in a replication competent infectious viral particle. This led us to ask: what underlying mechanisms give rise to incomplete genomes? What constitute an infectious unit? What are the implications for viral diversification, evolution and spread. By addressing these questions, we will advance he field by deepening our understanding how viral infections are initiated and propagated.

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O-GlcNAc transferase senses influenza viral RNA and restricts viral infection by integrating innate immunity and lipid metabolism

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