Female BALB/c mice were purchased from Charles River Laboratories Inc. (Yokohama, Japan). Mice kept under specific-pathogen-free conditions. For immunization, 6-to 8-weekold mice were inoculated with baculoviruses via the intranasal (i.n.) route. For i.n. immunizations, mice were lightly anesthetized by ether/chloroform inhalation, and 2×10 8 PFU of Bac-RSV/G or Bac-control in a volume of 70μl was applied to the left nostril. Three to four weeks after second immunization, the mice were challenged i.n. with 1×10 6 PFU of live RSV A2 strain. All animal studies were performed according to the guidelines of our Institutional Animal Care and Use Committee (Approval No. 2010-9-4).