Abstract
Premature infants, especially those with bronchopulmonary dysplasia (BPD), develop recurrent severe respiratory viral illnesses. We have shown that hyperoxic exposure of immature mice, a model of BPD, increases lung IL-12-producing Clec9a+ CD103+ dendritic cells (DCs), pro-inflammatory responses, and airway hyperreactivity following rhinovirus (RV) infection. However, the requirement for CD103+ DCs and Clec9a, a DAMP receptor that binds necrotic cell cytoskeletal filamentous actin (F-actin), for RV-induced inflammatory responses has not been demonstrated. To test this, 2-day-old C57BL/6J, CD103+ DC-deficient Batf3-/- or Clec9agfp-/- mice were exposed to normoxia or hyperoxia for 14 days. Also, selected mice were treated with neutralizing antibody against CD103. Immediately after hyperoxia, the mice were inoculated with RV intranasally. We found that compared with wild-type mice, hyperoxia-exposed Batf3-/- mice showed reduced levels of IL-12p40, IFN-γ, and TNF-α, fewer IFN-γ-producing CD4+ T cells, and decreased airway responsiveness following RV infection. Similar effects were observed in anti-CD103-treated and Clec9agfp-/- mice. Furthermore, hyperoxia increased airway dead cell number and extracellular F-actin levels. Finally, studies in preterm infants with respiratory distress syndrome showed that tracheal aspirate CLEC9A expression positively correlated with IL12B expression, consistent with the notion that CLEC9A+ cells are responsible for IL-12 production in humans as well as mice. We conclude that CD103+ DCs and Clec9a are required for hyperoxia-induced pro-inflammatory responses to RV infection. In premature infants, Clec9a-mediated activation of CD103+ DCs may promote pro-inflammatory responses to viral infection, thereby driving respiratory morbidity.