Figure 5.

In vivo efficacy of HA stem-fragment immunogens against lethal homologous virus challenge. Mice (n = 10/group) were vaccinated with the test immunogens on days 0 (prime) and 28 (boost). The immunized mice were challenged 3 weeks after boost with 2LD₉₀ of mouse-adapted HK68 virus. (A) Survival and (B) average weight changes (of surviving mice) were monitored for 14 days post virus challenge. Naïve mice were used as controls. The oligomeric derivatives of H3HA10 conferred partial protection (40–50%). However, all the surviving mice showed significant weight recovery by end of the study period after initial weight loss. The efficacy of test immunogens was evaluated by analyzing the Kaplan–Meier survival curves with log rank significance test (p-values: *** ≤0.005, ** ≤0.05, and n.s. ≥ 0.05). The difference(s) in fractional body weight(s) after recovery (at day 14) and maximal loss (day 9) were analyzed by Student’s t-test (p-value: ** ≤0.05).