FIG 4.

DB1-QUAD attenuation and efficacy in BALB/c mice. (A) To measure viral attenuation, groups of 5 mice were inoculated intranasally with 10⁶ FFU of mKate2-labeled A2-line19F, DB1, or DB1-QUAD, and lung viral loads were measured by FFU assay on days 2, 4, 6, and 8 postinfection. (B) To measure vaccine efficacy, groups of 5 mice were similarly inoculated with virus or mock infected. On day 96 p.i., the mice were challenged with 10⁶ PFU of RSV 12-35, and lung viral loads were measured by standard plaque assays 4 days later. Two experimental replicates of 5 mice per group were performed. Each point represents a single animal, and the horizontal lines represent means. ****, P < 0.00005 by two-way ANOVA with Tukey's multiple-comparison test.