DNA minigene vaccine pHI-Db protects mice from tumor challenges. (A) Groups of C57BL/6 mice (n = 8) were immunized 3 times at 1-week intervals with attenuated S typhimurium harboring the vectors indicated. Empty diamonds indicate the pCMV control group; shaded squares show the pHI control group; red triangles depict the pHI-Db group; and green circles stand for the pHI-Kb groups. Mice were challenged intravenously 2 weeks after the last immunization with 1 × 105 D121 lung carcinoma cells and monitored for survival until 75 days after tumor challenge. *P < .02 compared to pCMV control group. (B) Vaccinated mice were challenged intravenously 2 weeks after the last immunization with 1 × 105 RM9 prostate carcinoma cells. Mice were killed 28 days after tumor cell challenge and lung weights assessed. The top panel depicts representative lungs and the bottom panel shows average lung weights. Normal lung weight is about 0.2 g. *P < .001 and .001 compared to pCMV and pHI, respectively. Experiments were repeated twice with similar results. (C) In vivo depletion was performed as described in “Materials and methods.” Mice were challenged intravenously with 2.5 × 105 tumor cells and killed 23 days thereafter. Error bars indicate standard deviation (SD).
