A. Schema of the experiment. Briefly, 5~8 weeks old female C57BL/6 mice (3 mice/group) were vaccinated with 50 μg/mouse of pcDNA3-HPV18-E6 or empty pcDNA3 vector DNA through IM injection followed by electroporation. The mice were boosted twice with the same regimen with 4-day intervals. 7 days after the last vaccination, splenocytes were harvested from the mice, stimulated with HPV18 E6aa67-75 peptide (1 μg/ml) at the presence of GolgiPlug (1 μl/ml) overnight at 37°C. The cells were then harvested, washed with PBS+0.5% BSA, surface stained with PE-conjugated anti-mouse CD8a antibody. After wash, the cells were then permeabilized, fixed and intracellularly stained with FITC-conjugated anti-mouse IFN-γ antibody. The cells were acquired with FACSCalibur flow cytometer and analyzed with CellQuest software. B. Representative flow cytometry data. C. Bar graph summary of the flow cytometry data. Data are represented as mean ± SD. p-values were calculated by 2-tailed Student’s t test. * = p<0.05.