胃癌MG7-Ag模拟表位口服DNA疫苗的研制

目的　利用减毒鼠伤寒沙门氏菌研制胃癌MG7 Ag模拟表位的口服DNA疫苗 ,并观察其对小鼠的免疫效能及保护作用。方法　构建MG7 Ag模拟表位和通用性辅助性T细胞表位融合基因的真核表达载体。将真核表达载体转入减毒鼠伤寒沙门氏菌得到模拟表位的口服DNA疫苗。以 1× 10 8cfu疫苗菌口服免疫C5 7BL/6J小鼠 ,以携带空载体的沙门氏菌和PBS口服作为对照。以ELISA法检测小鼠血清中抗MG7 Ag抗体的滴度 ,以H TDR掺入法检测小鼠脾淋巴细胞对人工合成的MG7 Ag抗原肽刺激的增殖能力。同时 ,用表达MG7 Ag的小鼠艾氏腹水瘤细胞进行肿瘤攻击 ,观察疫苗对小鼠的保护作用。结果　口服疫苗可诱导小鼠产生MG7抗体 ,但各组小鼠脾淋巴细胞体外刺激增殖实验差异无显著性。肿瘤攻击 2周后 ,疫苗免疫组 7只小鼠中有 2只未见肿瘤形成 ,而对照组 4只小鼠则全部成瘤。结论　胃癌MG7 Ag模拟表位的口服DNA疫苗具有免疫原性 ,可以诱导小鼠产生抗肿瘤免疫 ,并具有一定保护作用

Development of oral DNA vaccine based on MG(7)-Ag mimotope of gastric cancer

OBJECTIVE: To develop an oral DNA vaccine based on MG(7)-Ag mimotope of gastric cancer using attenuated Salmonella typhimurium and evaluate its efficacy and protective effect. METHODS: The eukaryotic expression vector including the MG(7)-Ag mimotope and a Th epitope was constructed, and then transduced into an attenuated Salmonella typhimurium to get the oral DNA vaccine. C57BL/6 J mice were orally immunized with 1 x 10(8) cfu Salmonella transfectants, with Salmonella harboring empty plasmid, with phophate buffered saline (PBS) as control. At the 6th week, serum titer of MG(7) antibody was detected by ELISA. In the 8th week, a (3)H]-thymidine incorporation assay was performed to test the proliferation of murine spleen cells to the stimulant of MG(7)-Ag mimicry peptide. At the same time, Ehrlich ascites carcinoma cells expressing MG(7)-Ag were used in tumor challenge assay to evaluate the protective effect of the immunization. RESULTS: The oral DNA vaccine induced MG(7) antibody in mice, while in vivo unprimed proliferation assay of the spleenocytes showed no difference among the three groups. Two weeks after tumor challenge, 2 in 7 immunized mice were tumor free, while none in the control group was protected. CONCLUSION: Oral DNA vaccine based on the MG(7)-Ag momitope is immunogenic. It is able to induce specific immunity response against tumor in mice, and the vaccine is partially protective.