FIG 7.

DB1-QUAD attenuation and efficacy in cotton rats. (A and B) To measure viral attenuation, groups of 3 cotton rats were inoculated i.n. with 10⁶ FFU of mKate2-labeled A2, DB1, or DB1-QUAD, and viral loads in nasal (A) and lung (B) homogenates were measured by standard plaque assays. (C and D) To measure vaccine efficacy, groups of 5 cotton rats were similarly inoculated with either MEM (mock infection) or mKate2-labeled A2-line19F, DB1, or DB1-QUAD. The animals were challenged with A2-line19F on day 42 p.i., and viral loads in nasal (C) and lung (D) homogenates were quantified by plaque assays 4 days later. Each point represents a single animal, and the horizontal lines represent means. *, P < 0.05; ***, P < 0.0005 by two-way ANOVA with Tukey's multiple-comparison test.