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目的以减毒鼠伤寒沙门菌为疫苗载体,构建基于胃癌MG7-Ag模拟表位的口服活菌疫苗,观察Balb/c小鼠口服免疫后诱导的体液和细胞免疫反应。方法构建MG7-Ag模拟表位和HBcAg融合基因的原核表达载体,将其转入减毒鼠伤寒沙门菌得到模拟表位的口服活菌疫苗。用构建的口服鼠伤寒沙门菌疫苗免疫Balb/c小鼠,以PBS和携带pYA3341空载体的减毒鼠伤寒沙门菌作为对照。初次口服接种6周后应用ELISA法检测小鼠血清中抗MG7-Ag抗体的滴度。初次免疫后8周时,取免疫鼠脾细胞,以51Cr释放法检测小鼠脾淋巴细胞对靶细胞的杀伤效果,用表达MG7-Ag的小鼠艾氏腹水瘤细胞进行肿瘤攻击实验,观察疫苗对小鼠的保护作用。结果口服疫苗免疫小鼠后疫苗免疫组小鼠血清抗MG7-Ag抗体较PBS和空载体对照组显著增高,三组分别为0.954±0.040,0.653±0.018和0.692±0.012(P<0.01)。各组小鼠脾淋巴细胞体外杀伤实验未见显著差异,三组分别为234.7±27.7,183.4±26.0和195.7±8.0(P>0.05)。小鼠艾氏腹水瘤的攻击实验显示:疫苗免疫组中5只小鼠有1只未见肿瘤形成,而对照组小鼠则全部成瘤,且免疫组的成瘤重量为(0.05±0.01)g,明显小于两对照组的(0.10±0.04)和(0.09±0.04)g(P<0.01)。结论以胃癌MG7-Ag模拟表位为基础的口服减毒鼠伤寒沙门菌疫苗具有免疫原性,可诱导小鼠产生抗肿瘤免疫,并具有一定的保护作用。
OBJECTIVE To construct attenuated Salmonella typhimurium vaccine vector and construct an oral live vaccine based on gastric cancer MG7-Ag mimotope, and to observe the humoral and cellular immune responses induced by oral immunization of Balb / c mice. Methods The prokaryotic expression vector of MG7-Ag mimotope and HBcAg fusion gene was constructed and transferred into attenuated Salmonella typhimurium to obtain the mimotope oral live vaccine. Balb / c mice were immunized with the constructed oral Salmonella typhimurium vaccine, with PBS and attenuated Salmonella typhimurium harboring pYA3341 empty vector as controls. Six weeks after the first oral inoculation, the titer of anti-MG7-Ag antibody in serum of mice was detected by ELISA. At 8 weeks after the first immunization, splenocytes of immunized mice were taken and the killing effect of splenic lymphocytes on target cells was detected by 51Cr release assay. The mice were challenged with Ehrlich ascites tumor cells expressing MG7-Ag, Protective effect on mice. Results Serum anti-MG7-Ag antibody in the immunized mice immunized with oral vaccine was significantly higher than that in PBS and empty vector control groups (0.954 ± 0.040,0.653 ± 0.018 and 0.692 ± 0.012, P <0.01). The in vitro cytotoxicity of splenic lymphocytes in all groups showed no significant difference (234.7 ± 27.7, 183.4 ± 26.0 and 195.7 ± 8.0, respectively) (P> 0.05). The mice Ehrlich ascites tumor attack experiments showed that: one vaccine-immunized group of 5 mice did not see the tumor formation, while the control group mice were all tumor formation, and the tumor weight of the immune group was (0.05 ± 0.01) g, significantly less than (0.10 ± 0.04) and (0.09 ± 0.04) g (P <0.01) of the two control groups. Conclusion The oral attenuated Salmonella typhimurium vaccine based on gastric cancer MG7-Ag mimotopes is immunogenic and can induce anti-tumor immunity in mice and has some protective effects.