New Zealand White (NZW) rabbits were used in the current study to produce large quantities of sera for both binding antibody and functional antibody analyses. Animals were immunized with one of the three H5-HK HA DNA vaccines (individually) via gene gun. Positive antibody responses were elicited in immunized rabbit sera against the HK HA antigen and levels of such responses increased with repeated immunizations while the negative control rabbit group that received empty DNA vector did not have HAspecific antibody responses (Fig. 2B ). As measured by both temporal and peak-level antibody responses, there was no difference in the ability of the three forms of H5-HK HA DNA vaccines to elicit H5 HA-specific antibody responses ( Fig. 2B and 2C) .