Essential Role of B7-H1 in Double-Stranded RNA–Induced Augmentation of an Asthma Phenotype in Mice

Clinical and epidemiological studies have shown the contribution of viral infection to the development of allergic asthma. Many RNA viruses, pathogenic for the respiratory tract, generate double-stranded (ds)RNA during their replication. Typical innate immune responses triggered by dsRNA involve the endosomal and cytoplasmic pathways. The former is mediated by Toll/IL-1R domain–containing adaptor inducing IFN-β (TRIF), and the latter by IFN-β promoter stimulator 1 (IPS-1). We explored the effect of polyinocinic polycytidilic acid, a synthetic dsRNA, on the development of an asthma phenotype in mice. Administration of dsRNA during ovalbumin sensitization augmented airway eosinophilia and airway hyperresponsiveness after an antigen challenge, which was associated with enhanced induction of IL-13–producing CD8+ T cells. The augmentation was induced in IPS-1–deficient mice but not in TRIF-deficient mice. The interactions between dendritic cells (DCs) and T cells are regulated by B7-family costimulatory molecu...