Antibody response in the sera of C57BL/6 mice immunized with different recombinant DNA vaccines. C57BL/6 mice were primed twice with pcDNA3.1/HTNV-IL-2, pcDNA3.1/HTNV-G2, pcDNA3.1/HTNV-IL-2-G2 and pcDNA3.1 (+) and PBS plasmids respectively. The second immunizations were given at intervals of approximately 2 weeks using the same amount of DNA. A) ELISA results of average titers of immunized mice sera. B) Analysis of the stimulation index of splenocytes of immunized mice to HTNV G2 and IL-2. All data were obtained from three independent experiments. Error bars represent means ± SEM. Significantly different from the corresponding control and vector. (**P < 0.01, vs pcDNA3.1(+). ##P < 0.01, vs PBS group).