FIG. 3.

Neutralization activity. Neutralizing antibodies against A/PR8 (A) or A/WSN (B). Viral neutralizing antibody activities were determined using plaque assays for sera collected 4 weeks after the final immunization from mice immunized with 40 μg or 10 μg VLPs (12 mice per group analyzed). Serial dilutions of sera from individual mice were incubated with approximately 100 PFU of PR8 virus for 1 h at 37°C, and a standard plaque reduction assay was performed using MDCK cells. 40 μg VLP, 40 μg influenza VLPs containing HA and M1 at weeks 0 and 3; 10 μg VLP, 10 μg influenza VLPs containing HA and M1 at weeks 0, 3, and 6.