AIM:To develop an oral DNA vaccine against gastric cancerand evaluate its efficacy in mice.METHODS:The genes of the MG7-Ag mimotope and auniversal Th epitope (Pan-DR epitope,PADRE) wereincluded in the PCR primers.By PCR,the fusion gene ofthe two epitopes was amplified.The fusion gene wasconfirmed by sequencing and was then cloned into pcDNA3.1(+) plasmid.The pcDNA3.1 (+)-MG7/PADRE was usedto transfect an attenuated Salmonella typhimurium.C57BL/6 mice were orally immunized with 1×10~8 cfuSalmonella transfectants.Salmonella harboring the emptypcDNA3.1(+) plasmid and phosphate buffer saline (PBS)were used as negative controls.At the 6th week,serumtiter of MG7-Ag specific antibody was detected by ELISA.At the 8th week cellular immunity was detected by anunprimed proliferation test of the spleenocytes by usinga [~3H]-thymidine incorporation assay.Ehrlich ascitescarcinoma cells expressing MG7-Ag were used as a modelin tumor challenge assay to evaluate the protective effectof the vaccine.RESULTS:Serum titer of antibody against MG7-Ag wassignificantly higher in mice immunized with the vaccine thanthat in control groups (0.841 vs 0.347,P<0.01;0.841 vs0.298,P<0.01),while in vitro unprimed proliferation assayof the spleenocytes showed no statistical differencebetween those three groups.Two weeks after tumorchallenge,2 in 7 immunized mice were tumor free,whileall the mice in the control groups showed tumor formation.CONCLUSION= Oral DNA vaccine against the MG7-Agmomitope of gastric cancer is immunogenic.It can inducesignificant humoral immunity against tumor in mice,andthe vaccine has partially protective effects. AIM: To develop an oral DNA vaccine against gastric cancerand evaluate its efficacy in mice. METHODS: The genes of the MG7-Ag mimotope and a universal Th epitope (Pan-DR epitope, PADRE) wereincluded in the PCR primers.By PCR, the fusion gene of the two epitopes was amplified. The fusion gene wasconfirmed by sequencing and was then cloned into pcDNA3.1 (+) plasmid.The pcDNA3.1 (+) - MG7 / PADRE was usedto transfect an attenuated Salmonella typhimurium. C57BL / 6 mice were orally immunized with 1 × 10-8 cfu Salmonella transfectants. Salmonella harboring the emptyp cDNA3.1 (+) plasmid and phosphate buffer saline (PBS) were used as negative controls. At the 6th week, serumtiter of MG7-Ag specific antibody was detected by ELISA . At the 8th week cellular immunity was detected by an unprimed proliferation test of the spleenocytes by using [~ 3H] -thymidine incorporation assay. Ehrlich ascitescarcinoma cells expressing MG7-Ag were used as a model in tumor challenge assay to evaluate the protective effect of the vaccine. RES ULTS: Serum titer of antibody against MG7-Ag wassignificantly higher in mice immunized with the vaccine thanthat in control groups (0.841 vs 0.347, P <0.01; 0.841 vs 0.298, P <0.01), while in vitro unprimed proliferation assay of the spleen cells showed no statistical difference between those three groups. Two weeks after tumor challenge, 2 in 7 immunized mice were tumor free, while the mice were in control of tumor groups. CONCLUSION = Oral DNA vaccine against the MG7-Agmomitope of gastric cancer is immunogenic. inducesignificant humoral immunity against tumor in mice, and the vaccine has partially protective effects.