Influenza virus infection modulates expression of the anti-inflammatory mucin 1 in both epithelial and immune cells

Cell-associated mucin 1(MUC1/Muc1) is a component of the mucus barrier in the respiratory tract that acts as a physical barrier and signaling molecule. Our prior work shows that MUC1 expression is increased during influenza virus (IAV) infection in human airway epithelial (HAE) cultures in vitro. Here we further detail MUC1 expression patterns and report that IAV-induced cytokines, including type I interferons (IFNs), trigger the expression of a low-molecular-weight form of MUC1 which localizes to the cytoplasm and nucleus, and is expressed in different epithelial cell types. Further, IFN-driven changes in the cellular composition of HAE toward a more secretory phenotype require MUC1, suggesting that MUC1 plays an important role in shaping the epithelial response during viral infection. Using a mouse model of IAV infection, we confirmed the upregulation of Muc1 throughout the epithelium in vivoand observed altered Muc1 levels in lung immune cells. Specifically, Muc1 was upregulated in interstitial macrophages but downregulated in antigen-presenting cells (APCs) including alveolar macrophages and dendritic cells as early as 2 days post-infection (dpi). By 5 dpi, Muc1 was significantly upregulated in various T cell subsets and their effector counterparts including CD4 +, CD8 +, and double-negative effector T cells. We also found a negative correlation between Muc1 levels in APCs and the expansion of effector T cell populations, supporting the putative immunoregulatory roles of MUC1/Muc1. Our ongoing work further explores the impact of Muc1 expression in specific cellular subsets on the immune response and IAV pathogenesis. This work was supported by the National Heart, Lung, and Blood Institute (R01HL151840, to MAS)