To determine whether Bac-RSV/G has protective efficacy against RSV infection, mice were challenged with live RSV A2 virus at four weeks after booster immunization. While there was active RSV replication in the lungs of the Bac-control or PBS immune mice, immunization of Bac-RSV/G prevented any detectable RSV replication in the lungs during the peak of infection (Fig. 6) . Interestingly, immunization of Bac-control resulted in partial decrease of viral replication at the peak. This might be due to nonspecific innate immunity induced by baculovirus inoculation. It was previously reported that intranasal administration of wild-type baculovirus induces strong innate immune responses and provides protection against lethal challenge of influenza virus (16) . Fig. 3 . BAL was performed five days after RSV challenge, and BAL cells were stained with antibodies to CD45, Siglec-F, and CD11c, and eosinophils were quantitated among CD45 