Despite a significant increase in IFN-γ protein amounts in the lung at day 3 post-infection of FI-RSV-vaccinated mice (Fig. 1D), FI-RSV-immunized IFN-γ-deficient mice displayed no alteration in either airway obstruction or weight loss (Fig. 6A) as compared to WT controls. This evidence concerns the gene IFNG and Airway obstruction.