Fig. 5.

Passive serum transfer protects mice influenza virus challenge. Mice were vaccinated intramuscularly with 100 ng A/canine/Illinois/11613/2015 HA trimers admixed with CoPoP/PHAD or alum, and the serum from these mice was pooled and administered to naive mice immediately prior to challenge with 2.5 × LD₅₀ of influenza A/Hong Kong/1/1968 (H3N2) to assess antibody-mediated protection based on (A) body weight, (B) clinical score, and (C) mortality. Pooled serum (200 μL) was transferred to each recipient mouse. Data show mean ± SEM for groups of n = 8 mice. Statistical analysis in A and B was performed with one-way ANOVA with Dunnett’s comparison against control and C with log-rank test. *P < 0.05, **P < 0.01.