Fig. 5

PGA/Alum-adjuvanted pH1N1 vaccine-immunized aged mice drastically protect against pH1N1 virus infection. A–D Aged mice (n = 5 per group) were i.m. administered the pH1N1 split vaccine alone (0.25, 0.5, or 1 µg) or mixed with PGA/Alum (A and B) or 0.5 μg the vaccine antigen alone or mixed with γ-PGA, alum, or PGA/Alum (C and D) on days 0 and 14. Two weeks after the final administration, the mice were i.n. infected with 50 LD₅₀ pH1N1 viruses. Survival rates (A and C) and body weight changes (B and D) were monitored daily for 14 days post-challenge. E Viral titers were measured using lung homogenates (n = 3 per group) on days 3, 5, and 7 after the viral challenge and are expressed as log₁₀TCID₅₀/mL. F Five and 7 days post-infection, the left lung was sectioned and stained with anti-influenza nucleoprotein (NP) Ab followed by incubation with Alexa Fluor 488-conjugated anti-mouse IgG. The nuclei were stained with DAPI. Statistical significance was analyzed by log-rank test (A and C) or by one-way ANOVA/Bonferroni (E); *P < 0.05, **P < 0.01, and ***P < 0.001. NS, not-significant