FIG 4.
Protection induced by chimeric HA/B HA vaccination is mediated by antibodies, likely via Fc-mediated effector functions. (A and B) Weight loss (A) and survival (B) of mice that received passive transfer of serum from cHA/Bcys, SOC (animals received two vaccinations with a human seasonal inactivated vaccine containing the B/Malaysia/2506/04 influenza B virus component), or naive animals and were subsequently challenged with B/Malaysia/2506/04 (Victoria lineage). Differences in survival between the cHA/Bcys and naive groups were statistically significant (P = 0.0023 [**]). (C) Neutralizing activity of sera from cHA/Bcys, SOC, and naive animals tested in a microneutralization assay with B/Malaysia/2506/04 virus. (D) Activity of the same sera in an ADCC reporter assay. (E) Day 3 and day 6 lung virus titers in animals directly vaccinated with cHA/Bcys and in animals in the prime-only (prime-onlycys), SOC, and naive groups after challenge with B/Malaysia/2506/04. Statistical significance is indicated where tested (**, P ≤ 0.01).