Figure 2. HA-specific antibody responses induced by differently designed H7-HA DNA vaccines (H7-HA-wt, H7-HA-tPA, and H7-HA-dTM) in rabbits. (A) Temporal serum anti-HA IgG responses is measured by ELISA at 1:1000 serum dilution against H7-HA-dTM as the coating antigen. The arrows indicate the time points of DNA immunizations by electroporation. Each curve represents the mean OD values with standard deviations of each group of 3 rabbits. (B) End titration titers of serum anti-H7-HA-dTM IgG responses at 2 wk after the fourth DNA immunization.