Figure 5.

MHC class II-targeted NA DNA vaccine induces superior NA-specific antibody responses compared with conventional inactivated virus after one vaccination

(A, B) BALB/c mice were immunized once i.m. with 0.2, 1, or 5 μg of formalin-inactivated H1N1 PR8 virus or with 5 μg/plasmid (10 μg total) of the indicated DNA vaccines, followed by EP (box). (A) NA-specific (left) and HA-specific (right) titers were measured by ELISA at the indicated time points after immunization. Mean ± SEM is shown. (B) Mice were challenged with 5× LD₅₀ H1N1 PR8 virus 11 week post vaccination. Weight (left, mean ± SEM) and survival (right) were monitored up to 12 days post challenge. Dead mice were assigned a weight of 75%; n = 8 mice/group. Statistical analysis compared the different doses of inactivated virus with DNA vaccination with MHC class II-targeted NA and/or HA. ∗∗p ≤ 0.01, ∗∗∗p ≤ 0.001; two-way ANOVA (IgG titers, weight curve) or Mantel-Cox test (survival).