Induction of Type I Interferon Signaling byPseudomonas aeruginosaIs Diminished in Cystic Fibrosis Epithelial Cells

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The clinical manifestations of infection in cystic fibrosis (CF) are restricted to the lung, and involve a limited number of pathogens, suggesting a specific defect in mucosal immunity. We postulated that cystic fibrosis transmembrane conductance regulator (CTFR) mutations could affect the activation of type I interferon signaling in airway epithelial cells, which function in immune surveillance and initiate the recruitment and activation of immune cells. In response to infection withPseudomonas aeruginosa,Ifnbwas induced more than 100-fold in the murine lung, and the phosphorylation of STAT1 was similarly induced by the expected TLR4/TRIF/MD2/TBK1 cascade. The stimulation byP. aeruginosaof CF (IB3) cells and control (C-38) human cell lines similarly resulted in the induction of IFN-β, but to a significantly lower extent in CF airway cells. The potential consequences of diminished type I IFN signaling were demonstrated in a murine model ofP. aeruginosapneumonia, pretreatment with polyinosinic:polycytidylic acid significantly enhanced bacterial clearance and correlated with increased numbers of mature CD11c+/CD86+ dendritic cells (DCs) in the lung. Using culture supernatants from CF or control cell lines stimulated withP. aeruginosa, we similarly demonstrated the diminished activation of human monocyte-derived DCs by incubation with CF compared with normal epithelial cell culture supernatants, which was dependent on IFN-β. These observations suggest that dysfunction of the CFTR in airway epithelial cells may contribute to impaired immune surveillance in the CF airway and resultant colonization byP. aeruginosa.

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