The objective of this study was to obtain better antigen specific cytotoxic T cell responses in vivo. We examined the augmented induction of antigen-specific cytotoxic T cell responses to co-administration of oligonucleotides (CpG-ODN), dimethyl dioctadecyl ammonium bromide (DDA), and Lipofectamine™ 2000 with a DNA vaccine (pVAX1-CpG-Loop) and boosting with pVAX1-CpG-Loop in BALB/c mice. The results show that Loop protein-specific T cell proliferation, cytotoxic T cell activity, and the production of CD8+ T cells and IFN-γ were enhanced after co-immunization of mice with adjuvants and pVAX1-CpG-Loop. We demonstrated that significant T cell-mediated immune responses were induced in the mice with the help of DDA, CpG-ODN and Lipofectamine™ 2000.