BACKGROUND: Early-life human rhinovirus infection has been linked to asthma development in high-risk infants and children. Nevertheless, the role of rhinovirus infection in the initiation of asthma remains unclear. OBJECTIVE: We hypothesized that, in contrast to infection of mature BALB/c mice, neonatal infection with rhinovirus promotes an IL-25-driven type 2 response, which causes persistent mucous metaplasia and airways hyperresponsiveness. METHODS: Six-day-old and 8-week-old BALB/c mice were inoculated with sham HeLa cell lysate or rhinovirus. Airway responses from 1 to 28 days after infection were assessed by using quantitative PCR, ELISA, histology, immunofluorescence microscopy, flow cytometry, and methacholine responsiveness. Selected mice were treated with a neutralizing antibody to IL-25. RESULTS: Compared with mature mice, rhinovirus infection in neonatal mice increased lung IL-13 and IL-25 production, whereas IFN-gamma, IL-12p40, and TNF-alpha expression was suppressed. In addition, the population of IL-13-secreting type 2 innate lymphoid cells (ILC2s) was expanded with rhinovirus infection in neonatal but not mature mice. ILC2s were the major cell type secreting IL-13 in neonates. Finally, anti-IL-25 neutralizing antibody attenuated ILC2 expansion, mucous hypersecretion, and airways responsiveness. CONCLUSIONS: These findings suggest that early-life viral infection could contribute to asthma development by provoking age-dependent, IL-25-driven type 2 immune responses.