肠毒素性大肠杆菌菌毛抗原CS6和霍乱毒素B亚基在人伤寒沙门菌中的共表达及其免疫学效果观察

Coexpression of CS6 of ETEC and CTB in a genetic avirulent Salmonella typhi strain and the immunologic properties

目的 :构建表达肠毒素性大肠杆菌菌毛抗原基因CS6和霍乱毒素B亚基 (CTB)基因的细菌性腹泻基因工程多价疫苗。方法 :以基因工程减毒的人伤寒沙门菌为抗原载体 ,利用基于asd基因功能互补的宿主染色体_质粒平衡致死表达系统 ,实现了在没有抗生素选择压力的条件下 ,CS6和CTB在人伤寒沙门菌中的稳定表达。结果与结论 :检测结果表明 ,CS6和CTB的表达虽对宿主菌的生长有一定影响 ,但经过一段时间的培养 ,重组菌株仍可达到高密度生长。动物免疫结果显示 ,重组菌株在家兔体内均可诱生相应抗体 ,但从诱生的抗体效价、抗体持续时间方面评价 ,单独表达CS6与CTB的重组菌株的免疫学效果均好于两者共表达的重组菌株 ,提示在以后的疫苗研究实践中 ,可以考虑将分别表达CS6与CTB的重组菌株按一定比例混合 ,组成联合疫苗 ,用于细菌性腹泻的免疫预防。本研究结果对于细菌性腹泻基因工程多价疫苗的构建有指导意义。

Objective:To construct multivalent vaccine against bacterial diarrhea,which can express coli surface antigen 6 (CS6) of enterotoxigenic Escherichia coli (ETEC) and cholera toxin B subunit (CTB).Methods:An asd gene_based host_plasmid balancing system was used to express CS6 and CTB in a genetic avirulent Salmonella typhi strain, in which CS6 and CTB can be expressed stably in the absence of antibiotic selection.Results and Conclusions:Although the expression of CS6 and CTB altered the growth rate of recombinant bacterial strain, all the recombinants can grow up to be a high_density culture, and can elicit corresponding antibodies in rabbits. Results of titration of the antibodies showed that the recombinant expressing either CS6 or CTB was better than that expressing both CS6 and CTB in the aspect of titer and duration of the antibodies. All the results indicate that it might be considered to compose multivalent vaccine candidates for bacterial diarrhea by mixing recombinant strains expressing respectively different antigens. This research may be valuable for construction of multivalent vaccine against bacterial diarrhea.