An animal experiment was performed to test the immunogenicity of the target peptides in vivo. DNA corresponding to the target peptides was cloned into the HHD gene to produce a DNA vaccine candidate containing the peptide-b 2 -microglobulin-MHC class-I heavy chain complex that could be expressed on the cell surface and trigger the immune system. Mice received a total of three administrations and were sacrificed 1 week after the last injection. Splenocytes were collected for the cytotoxicity and ELISPOT assays. Cytotoxicity was measured by the amount of TDA released from the target cells. The target cells (T2 cells) were loaded with the target peptides. Therefore, the peptide-loaded T2 cells would be killed if the corresponding peptides were immunogenic to the mice. The results from the cytotoxicity assay showed that the highest percentage of cytotoxic response was triggered in mice immunized with plasmids encoding NP373 and NP458, and the effect was similar to that produced by the positive control (N220). During an 1 h incubation period, NP373 exhibited a 14% and 10% killing efficiency with the effector cell-to-target cell ratios of 50:1 and 10:1, respectively, and NP458 exhibited a 13% and 9% killing efficiency with the effector cell-to-target cell ratios of 50:1 and 10:1, respectively. However, the killing efficiency of T cells triggered by the NP189 was comparatively low (7%) with the effector cellto-target cell ratios of 50:1. The result produced by NP158 was significantly lower, with only a 3.7% killing efficiency at an effector cell-totarget cell ratio of 50:1 (Fig. 3 ).