Dynamic Innate Immune Responses of Human Bronchial Epithelial Cells against SARS-CoV and DOHV infection

Severe acute respiratory syndrome-associated coronavirus (SARS-CoV) infection causes an immune-mediated disease. We have recently shown that SARS-CoV-induced epithelial Calu-3 cytokines could exacerbate and dampen host inflammatory and T cell responses, respectively, through modulating the functions of macrophages and dendritic cells, thereby suggesting that not only are lung epithelial cells the primary cells of SARS-CoV infection, but they also involve in initiating and orchestrating the host innate and adaptive immunity. Comprehensive evaluation of the complex epithelial signaling to SARS-CoV is, thus, crucial for paving the way to better understand SARS pathogenesis and develop the innovative therapeutics against SARS. Here, based on the microarray-based functional genomics, we reported that 2B4 cells, a clonal derivative of Calu-3 cells, elicited a temporal and spatial activation of nuclear factor (NF)kappaB, activator protein (AP)-1 (ATF2/c-Jun), and interferon regulatory factor (IRF)-3/-7 at 12-, 24-, and 48-hrs post infection (p.i.), respectively, resulting in the activation of many antiviral genes, including interferon (IFN)-, -s, SARS-related inflammatory mediators, and various IFN-stimulated genes (ISGs). While elevated responses of IFN- and IFN-s were not detected until 48-hrs p.i., as a consequence of a delayed IRF-3/-7 activation, we showed, for the first time, that both types of IFNs exerted previously under-described non-redundant, complementary, and/or synergistic effects on the epithelial defense against SARS-CoV. Collectively, our results highlight the molecular mechanisms of the sequential activation of virus- and IFN-dependent signaling of lung epithelial cells against SARS-CoV and identify novel cellular targets for future studies, aiming at advancing strategies against SARS.

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Yoshikawa T, Hill TE, Yoshikawa N, Popov VL, Galindo CL, Garner HR, Peters CJ, Tseng CT