V-specific IgG (Panel A), IgG1 (Panel B), or IgG2a (Panel C) concentrations measured at 12 weeks after the boost immunization in mice receiving various V vaccine regimens: codon optimized V DNA vaccine alone (V-DNA), V DNA vaccine prime followed by V protein boost formulated with IFA (V-DNA + Prot/IFA), V protein formulated with IFA (V-Prot/IFA), V protein alone (V-Prot), or empty DNA vaccine vector alone (Vector). Antibody titers were measured by ELISA against V protein. Each bar represents the mean IgG concentration in each group of 5 mice with standard error. Statistically significant differences (p < 0.05) are indicated as “*”, “#” or “^” when comparing V-DNA, V-DNA + Prot/IFA, and V-Prot/IFA groups.