Fig. 1.

Influenza-specific antibody response following DNA vaccination. Pigs were vaccinated twice (arrows) i.d. with needle-free delivery with 200 μg (n = 6), 800 μg (n = 6) or 1972 μg (n = 5) DNA, or not DNA vaccinated at all (n = 5). Levels of IgG in the sera were measured by ELISA. Recombinant influenza proteins that were (a-d) homologous to the vaccine or (e-h) heterologous to the vaccine were used as the coating antigens. All serum samples were tested using a fixed 1:100 or 1:125 serum dilution. Error bars indicate the mean ± SEM, and significant differences from the no-vaccine control group are indicated by: ****: p < 0.0001; ***: p < 0.001; **: p < 0.01; *: p < 0.05.