FIG. 4.
Serum HI antibody responses following one or two doses of dk/Sing vaccine. Mice were vaccinated i.m. with alum alone (A), 10 μg of dk/Sing vaccine alone (B), or vaccine with alum (C). Sera from 17 to 20 mice per group were collected 3 weeks after the first and second vaccinations and tested individually for HI antibody against HK/156 virus. HI titers are expressed as a log2 value of the reciprocal of the highest dilution of serum inhibiting agglutination of 0.5% of turkey erythrocytes at 4 HA units of virus. Antibody responses shown in panel C were significantly greater than the corresponding responses shown in panel B (P < 0.001). A log2 value of ≥5.3 represents an HI titer of ≥40. Solid bars represent the GMT.