Fig 2.

Cross-protection of mice against drift variants within a viral subtype by intranasal immunization with A/Solomon Islands/3/2006 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/Solomon Islands/3/2006 SV vaccine and 100 μg of γ-PGA-NPs (SV+NP), or 1 μg of A/Solomon Islands/3/2006 WV vaccine (WV). Fourteen days after the final immunization, the mice were infected with A/Solomon Islands/3/2006 (H1N1; 10⁷ PFU) (A), A/Brisbane/59/2007 (H1N1; 10⁷ PFU) (B), A/New Caledonia/20/99 (H1N1; 10⁷ PFU) (C), or A/PR/8/34 (H1N1; 10³ PFU) (D), and the mortality was assessed. *, P < 0.05 versus the group inoculated intranasally with PBS.