Deficient inflammasome activation permits an exaggerated asthma phenotype in rhinovirus C-infected immature mice

Compared to other RV species, RV-C has been associated with more severe respiratory illness and is more likely to occur in children with a history of asthma or who develop asthma. We therefore inoculated 6-day-old mice with sham, RV-A1B, or RV-C15. Inflammasome priming and activation were assessed, and selected mice treated with recombinant IL-1β. Compared to RV-A1B infection, RV-C15 infection induced an exaggerated asthma phenotype, with increased mRNA expression of Il5 , Il13 , Il25 , Il33 , Muc5ac , Muc5b , and Clca1 ; increased lung lineage-negative CD25+CD127+ST2+ ILC2s; increased mucous metaplasia; and increased airway responsiveness. Lung vRNA, induction of pro-inflammatory type 1 cytokines, and inflammasome priming (pro-IL-1β and NLRP3) were not different between the two viruses. However, inflammasome activation (mature IL-1β and caspase-1 p12) was reduced in RV-C15-infected mice compared to RV-A1B-infected mice. A similar deficiency was found in cultured macrophages. Finally, IL-1β treatment decreased RV-C-induced type 2 cytokine and mucus-related gene expression, ILC2s, mucous metaplasia, and airway responsiveness but not lung vRNA level. We conclude that RV-C induces an enhanced asthma phenotype in immature mice. Compared to RV-A, RV-C-induced macrophage inflammasome activation and IL-1β are deficient, permitting exaggerated type 2 inflammation and mucous metaplasia.