Figure 2.

MHC class II-targeted NA-bivalent heterodimers efficiently induce antibody responses after a single DNA vaccination

(A) BALB/c mice were vaccinated once i.m. with 5 μg of each A and B plasmids (10 μg DNA in total) encoding the indicated heterodimeric vaccine proteins (box), followed immediately by EP. Blood was sampled at the indicated time points. (B) NA-specific (top) and HA-specific (bottom) IgG (left), IgG1 (center), and IgG2a (right) titers were measured by ELISA at the indicated time points after immunization. Statistical analysis compared targeted vs. non-targeted and antigen-bivalent vs. monovalent groups. (C) BALB/c mice were immunized once i.m./EP with different amounts of the indicated DNA vaccines. Serum was analyzed for NA-specific IgG responses 4 weeks post vaccination. (D) IgG responses specific for inactivated H1N1 PR8 virus (left), rec. NA protein (center), or rec. HA protein (right) in sera harvested 6 weeks post vaccination from mice immunized once with 5 μg/plasmid (10 μg total) were analyzed in ELISA. Mean ± SEM of n = 8 mice/group. ND, not detected; ns, not significant. ∗p ≤ 0.05, ∗∗p ≤ 0.01, ∗∗∗p ≤ 0.001; two-way ANOVA (B), two-tailed Mann-Whitney test (C), or Kruskal-Wallis multiple-comparisons test with Dunn’s correction (D). (E) A standard dilution of pooled sera from 5 mice/group vaccinated 4 weeks earlier (10 μg total DNA) were incubated with serial dilutions of inactivated influenza H1N1 PR8 virus. NA- or HA-specific IgG was measured in ELISA. Mean ± SD of technical triplicates.