稳定、无抗药的痢疾福氏2a和宋内双价菌苗候选株的构建

通过体内外基因重组,将大肠杆菌粘附因子cs3基因定位整合到痢疾杆菌福氏2a疫苗株T32菌染色体的asd基因内,使asd基因灭活;将来内O抗原基因克隆至无抗药性表达载体pXL378,获得重组质粒pXL390,将其转化asd-的T32受体菌,构建成福氏2a和宋内双价苗苗株FS01。实验表明:重组质粒pXL390在不带任何抗菌素基因的情况下,在asd-的T32受体菌内是稳定的。FS01株遗传稳定,能表达两种痢疾菌的PLS-O抗原,无明显毒性作用。动物试验表明,以FS01株皮下免疫的小鼠对福氏2a和宋内有毒株的腹腔攻击有100％的保护。

Construction of Stable and Non-resistant Bivalent Vaccine Candidate Strain Against Shigella flexneri 2a and Shigella sonnei

The E. coli cs3 gene coding for CFA/11 antigen was site-specifically integrated into the asd gene locus of S. flexneri 2a vaccine strain T32, resulting in the asd gene inactivated. Meanwhile, the S. sonnei O antigen gene was cloned into a non-resistant expression vector pXL378 to construct the plasmid pXL390. By transforming the asd minus T32 strain with pXL390, the bivalent vaccine candidate strain FS01 against S. flexneri 2a and S. sonnei was finally obtained. Experiments showed that the recombinant plasmid pXL390 was very stable in the asd minus T32 strain without the use of any antibiotics; FS01 strain was genetically stable and expressed two kinds of Shigella LPS-O antigens with no enhancement of its toxicity. Animal test demonstrated that FS01 strain, when administered subcutaneously in mice,could confer 100% protection against the intraperi-toneal challenges of virulent S. flexneri 2a and S. sonnei.