Morbidity, survival, and lung viral titers after influenza virus challenge of young and middle-aged mice.

<p>Groups of 14 BALB/cAnNCr mice of age 2 months (A, C, and E) or 11 months (B, D, and F) were immunized as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0153195#pone.0153195.g001" target="_blank">Fig 1</a>. In addition, 6 mice per age group were left unvaccinated (naïve, Fig 4E and 4F). One month after rAd, animals were challenged with 10⁴ TCID₅₀ A/FM-ma. Panels A and B show the mean % starting body weight + SD of 8 mice per group. Panels C and D show survival until weight loss endpoint; *p≤0.001 by the log-rank (Mantel-Cox) for all groups compared to B/NP control. Lung virus titers (E and F) were determined by TCID₅₀ assay on the lungs of 3 animals per group harvested on day 3 (open bars) and day 5 (solid bars) after challenge, along with lungs from naïve mice of the same age infected at the same time. Shown are the mean ± SEM of 3 mice per group with the limit of detection indicated by a horizontal line. ** p≤0.01 was determined by ANOVA vs. the B/NP and naïve control groups. The difference was statistically significant (**p<0.01) on day 5 for two-month-old animals. The 2- and 11-month-old groups were not performed simultaneously, so we cannot conclude that there was superior control of viral replication in one age group.