Fig 1.

Cross-protection of mice against the homotype or subtype influenza virus strains by intranasal immunization with A/PR/8/34 vaccines. Groups of mice (5 per group) were inoculated twice intranasally with PBS, 100 μg of γ-PGA-NPs (NP), a mixture of 1 μg of A/PR/8/34 SV vaccine and 100 μg of γ-PGA-NPs (SV+NP), or 1 μg of A/PR/8/34 WV vaccine (WV). Fourteen days after the final immunization, the mice were infected with A/PR/8/34 (H1N1; 10³ PFU) (A), A/Hiroshima/53/2005 (H3N2; 10⁷ PFU) (B), or B/Malaysia/2506/2004 (10⁶ PFU) (C), and the mortality was assessed. *, P < 0.05 versus the group inoculated intranasally with PBS.