The Innate Cytokines IL-25, IL-33, and TSLP Cooperate in the Induction of Type 2 Innate Lymphoid Cell Expansion and Mucous Metaplasia in Rhinovirus-Infected Immature Mice

Early-life respiratory viral infection is a risk factor for asthma development. Rhinovirus (RV) infection of 6-d-old mice, but not mature mice, causes mucous metaplasia and airway hyperresponsiveness that are associated with the expansion of lung type 2 innate lymphoid cells (ILC2s) and are dependent on IL-13 and the innate cytokine IL-25. However, contributions of the other innate cytokines, IL-33 and thymic stromal lymphopoietin (TSLP), to the observed asthma-like phenotype have not been examined. We reasoned that IL-33 and TSLP expression are also induced by RV infection in immature mice and are required for maximum ILC2 expansion and mucous metaplasia. We inoculated 6-d-old BALB/c (wild-type) and TSLP receptor-knockout mice with sham HeLa cell lysate or RV. Selected mice were treated with neutralizing Abs to IL-33 or recombinant IL-33, IL-25, or TSLP. ILC2s were isolated from RV-infected immature mice and treated with innate cytokines ex vivo. RV infection of 6-d-old mice increased IL-33 and TSLP protein abundance. TSLP expression was localized to the airway epithelium, whereas IL-33 was expressed in epithelial and subepithelial cells. RV-induced mucous metaplasia, ILC2 expansion, airway hyperresponsiveness, and epithelial cell IL-25 expression were attenuated by anti-IL-33 treatment and in TSLP receptor-knockout mice. Administration of intranasal IL-33 and TSLP was sufficient for mucous metaplasia. Finally, TSLP was required for maximal ILC2 gene expression in response to IL-25 and IL-33. The generation of mucous metaplasia in immature RV-infected mice involves a complex interplay among the innate cytokines IL-25, IL-33, and TSLP.