Background
Early-life wheezing-associated respiratory infection with human rhinovirus (RV) is associated with asthma development. RV infection of 6-day-old immature mice causes mucous metaplasia and airway hyperresponsiveness which is associated with the expansion of IL-13-producing type 2 innate lymphoid cells (ILC2s) and dependent on IL-25 and IL-33. We examined regulation of this asthma-like phenotype by IL-1β.
Conclusion
Macrophage IL-1β limits type 2 inflammation and mucous metaplasia following RV infection by suppressing epithelial cell innate cytokine expression. Reduced IL-1β production in immature animals provides a mechanism permitting asthma development after early-life viral infection.
Methods
Six-day-old wild-type or NRLP3-/- mice were inoculated with sham or RV-A1B. Selected mice were treated with IL-1 receptor antagonist (IL-1RA), anti-IL-1β, or recombinant IL-1β.
Results
Rhinovirus infection induced Il25, Il33, Il4, Il5, Il13, muc5ac, and gob5 mRNA expression, ILC2 expansion, mucus metaplasia, and airway hyperresponsiveness. RV also induced lung mRNA and protein expression of pro-IL-1β and NLRP3 as well as cleavage of caspase-1 and pro-IL-1β, indicating inflammasome priming and activation. Lung macrophages were a major source of IL-1β. Inhibition of IL-1β signaling with IL-1RA, anti-IL-1β, or NLRP3 KO increased RV-induced type 2 cytokine immune responses, ILC2 number, and mucus metaplasia, while decreasing IL-17 mRNA expression. Treatment with IL-1β had the opposite effect, decreasing IL-25, IL-33, and mucous metaplasia while increasing IL-17 expression. IL-1β and IL-17 each suppressed Il25, Il33, and muc5ac mRNA expression in cultured airway epithelial cells. Finally, RV-infected 6-day-old mice showed reduced IL-1β mRNA and protein expression compared to mature mice.