CD209d/e promotes inflammation and lung injury during influenza virus infection

Influenza virus infects millions each year, contributing greatly to human morbidity and mortality. Upon viral infection, pathogen-associated molecular patterns activate pattern recognition receptors on host cells, triggering an immune response. The CD209 protein family, homologs of DC-SIGN (dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin), is thought to modulate immune responses to viruses. The effects of the mouse functional DC-SIGN homolog CD209d/e on the lung immune responses during influenza viral infection are not known. Therefore, we generated mice that lack both CD209d and e isoforms to determine the role in influenza viral infection. We infected wild-type and CD209d/e gene-deficient (CD209d/e-/-) mice with influenza virus and measured the cellular response in bronchoalveolar lavage, the expression of proinflammatory cytokines, antiviral genes, toll-like receptors (TLRs) in the lung, and lung pathology. We found CD209d/e-/- mice had decreased viral burden, TLR3 and TLR9 expression, interferon response, macrophages in bronchoalveolar lavage, and parenchymal lung inflammation compared with control mice. We also found less influenza viral uptake in alveolar macrophages and bone marrow-derived macrophages isolated from CD209d/e-/- mice when compared with control mice. We further investigated the role CD209d/e by treating bone marrow-derived macrophages from control and CD209d/e-/- mice with TLR agonists. We found that lacking CD209d/e decreased the expression of TLR3, TLR9, RIG1, STAT1, and STAT2 compared with controls. Collectively these results show that CD209d/e plays an important role in viral sensing/uptake and inflammatory immune responses during influenza viral infection.