Figure 6.

PGA/Alum enhances cross-protective efficacy of pH1N1 vaccine antigen. C57BL/6 mice (n = 5 per group) were vaccinated i.m. with 0.5 μg the pH1N1 split vaccine antigen together with 400 μg alum, 400 μg γ-PGA, or 800 μg PGA/Alum on days 0 and 14. Two week after the last immunization, the mice were i.n. challenged with 10 LD₅₀ H1N1 virus (A/Puerto Rico/8/1934) (A,B) or 10 LD₅₀ H3N2 viruses (C,D). Body weight and survival rates were monitored for 14 days. (E,F) Before viral challenge, sera and splenocytes were harvested from the immunized mice. (E) ADCC activity was determined by measuring lysis of H1N1- or H3N2-infected MDCK cells by co-culture of sera from the vaccinated mice and naïve NK cells. (F) Splenocytes were stimulated with UV-inactivated H1N1 or UV-inactivated H3N2 for 3 days, and the number of IFN-γ⁺ SFUs was determined by an ELISPOT assay. Statistically significant differences were identified by one-way ANOVA/Bonferroni or log-rank test (for survival); *P < 0.05 and **P < 0.01.