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通过同源重组将编码异源抗原的DNA整合到减毒的鼠伤寒沙门氏菌的染色体上，获得了表达霍乱毒素B亚单位（CTB）的双价活疫苗候选株。该系统包括两个步骤：首先将GisOG缺失突变的DNA片段整合进鼠伤寒沙门氏菌疫苗候选株SL3261的染色体上，得到His营养缺陷型。然后，用带有CTB抗原基因的完整HisOGDNA片段置换HisOG缺失的DNA片段，获得表达CTB的His回复的SL3261菌株（命名为TT201）。Southern杂交证明，TT201菌株的染色体带有CTB抗原基因。Westernblot分析表明，TT201菌株能表达CTB，且具有很好的稳定性。用重组菌株口服免疫接种小鼠，能够激发抗CTB抗体的产生。TT201菌株是一种潜在的双价疫苗候选株。
A bivalent live vaccine candidate expressing cholera toxin B subunit (CTB) was obtained by integrating DNA encoding a heterologous antigen into the attenuated Salmonella typhimurium chromosome by homologous recombination. The system consists of two steps: First, the GisOG deletion mutant DNA fragment is integrated into the chromosome of the Salmonella typhimurium vaccine candidate strain SL3261 to obtain His auxotrophy. Then, the HisOG-deleted DNA fragment was replaced with the entire HisOGDNA fragment carrying the CTB antigen gene to obtain a His-recovered SL3261 strain (designated TT201) expressing CTB. Southern hybridization proved that the chromosome of TT201 strain carries the CTB antigen gene. Western blot analysis showed that TT201 strain can express CTB with good stability. Oral vaccination of mice with recombinant strains stimulated the production of anti-CTB antibodies. The TT201 strain is a potential bivalent vaccine candidate.