The most important findings of this study are the deficient induction of IL-15 by RV in alveolar macrophages from asthmatic subjects in vitro, deficient IL-15 levels in asthma in BAL fluid in vivo, and the relationships of these to airway hyperresponsiveness, severity of symptoms and virus load on subsequent RV infection in vivo. This evidence concerns the gene IL15 and airway hyperresponsiveness.