(A) BALB/c mice were immunized twice at 2-week intervals with plasmids encoding NY-ESO-1 or control vector by gene gun. These mice were inoculated with 2 × 10⁶ CMS5a-HE tumor cells (NY-ESO-1–negative), and tumor growth was analyzed 3 times per week. After 7 days, injection of 0.5–1 × 10⁶ CFU of S. typhimurium–NY-ESO-1 or of the control strain at the tumor site was performed. Some groups of mice were also injected intravenously with anti-CD4 or anti-CD8 mAb or control Ab in the form of 25-μl ascites every 5 days. Arrows indicate time points of S. typhimurium administration. Each line represents the tumor growth of an individual mouse. Tumor size was calculated as longitudinal diameter (mm) × horizontal diameter (mm). (B) CD8⁺ T cells were purified from spleens from control vector– or NY-ESO-1–preimmunized mice bearing CMS5a-HE, either untreated or treated with S. typhimurium–NY-ESO-1 or the control strain, and analyzed for the number of specific IFN-γ–producing cells by ELISPOT assay. Data are mean ± SD. Experiments were performed independently at least twice with similar results.