FIGURE 4.

Viral replication, cytokine profile, and immune cell composition. (A–D) Mice (n = 4 per group) were vaccinated with 10⁶ PFU of X-31ca and challenged with 10⁶ PFU of RSV A2 2 days later (–2d Vac). Non-vaccinated mice were infected with 10⁶ PFU of RSV A2 only (No Vac). After RSV challenge, lungs and BAL fluids were obtained daily for 4 days, and the lung viral titer was determined by plaque assay (A). In BAL fluids, the levels of IFN-α and IFN-β were determined by ELISA, and the mean concentration of IFN-γ, IL-6, and TNF-α was measured by Luminex (B). The dotted line represents the limit of detection; IFN-α: 5, IFN-β: 0.5, IFN-γ: 3.49, TNF-α: 1.14, IL-6: 2.23 pg/mL, respectively. To investigate the immune cell subsets, flow cytometry analysis of cells obtained from BAL was performed as in Figures 3B,C (C,D) (^∗P < 0.05, ^∗∗P < 0.01 compared with the No Vac control group).