Since the RSV G contains I-E d -restricted CD4 T-cell epitope, we examined whether Bac-RSV/G immunization induces specific CD4 T cells or not. To this end, Bac-RSV/G, Bac-control, or PBS immune mice were challenged with RSV. CD4 T cell responses were evaluated at 5 days after challenge by measuring the production of IFN-γ in lung lymphocytes that had been stimulated with I-E d -restricted G (183-195) epitope peptide ex vivo. As shown in Fig. 3 , G-specific CD4＋IFN-γ＋ cells were detected in the lungs of Bac-RSV/G-immunized group (∼2.5% of gated CD4 T cells on average), while few specific cells (＜0.2% of CD4 T cells) were observed in the lungs of Bac-control or PBS-immunized group. We next investigated whether immunization of Bac-RSV/G induces other CD4＋ T cell subset such as Th2 and Th17. Bac-RSV/G-vaccinated mice showed increased frequency of G-specific IL-17-producing CD4 T cells in the lungs after RSV challenge (∼3.7% of gated CD4 T cells on average; Fig. 4 ). However, the levels of Th2-type cytokines such as IL-4, IL-5, IL-10, and IL-13 measured by multiplex antibody-based bead assays were not significantly different in the lungs from all groups of mice (Fig. 5) . Together, these results indicated that mixed G-specific Th1/Th17-cell responses were induced by Bac-RSV/G vaccination.