Ketley J M, Michalski J, Galen J, Levine M M, Kaper J B
Center for Vaccine Development, University of Maryland School of Medicine, Baltimore.
FEMS Microbiol Lett. 1993 Jul 15;111(1):15-21. doi: 10.1111/j.1574-6968.1993.tb06355.x.
Attenuated Vibrio cholerae O1 vaccine strains lacking the gene encoding the A subunit of cholera toxin have proven efficacious in preventing experimental cholera. As these strains move from closed, contained testing environments to large-scale field trials, a readily assayable phenotypic trait to distinguish a vaccine strain from wild-type V. cholerae O1 is desirable. We have constructed three derivatives of the attenuated V. cholerae strain CVD 103 which carry a mercury resistance or urease marker in the hlyA gene. CVD 103-HgR was constructed using a protracted marker-exchange procedure; this strain was found to have somewhat lowered colonisation efficiency in infant mice in comparison to its parent strain, CVD 103. The insertion of the resistance marker was repeated using a suicide vector system; CVD 103-HgR2 was found to colonise infant mice as efficiently as CVD 103. Strain CVD 103-UR, in which sequences encoding urease were inserted using a suicide vector, also colonised infant mice as well as CVD 103. The genetically marked strains CVD 103-HgR, CVD 103-HgR2 and CVD 103-UR form the basis for a generation of defined oral vaccines that may give single-dose, long-lasting protection to populations at risk from cholera.
缺乏霍乱毒素A亚基编码基因的减毒霍乱弧菌O1疫苗株已被证明在预防实验性霍乱方面有效。随着这些菌株从封闭的实验环境进入大规模现场试验，需要一种易于检测的表型特征来区分疫苗株和野生型霍乱弧菌O1。我们构建了减毒霍乱弧菌菌株CVD 103的三个衍生物，它们在hlyA基因中携带汞抗性或脲酶标记。CVD 103-HgR是通过一种延长的标记交换程序构建的；与亲代菌株CVD 103相比，该菌株在幼鼠中的定殖效率有所降低。使用自杀载体系统重复插入抗性标记；发现CVD 103-HgR2在幼鼠中的定殖效率与CVD 103相同。菌株CVD 103-UR通过自杀载体插入了编码脲酶的序列，其在幼鼠中的定殖情况也与CVD 103一样。基因标记菌株CVD 103-HgR、CVD 103-HgR2和CVD 103-UR构成了新一代口服疫苗的基础，这些疫苗可能为有霍乱风险的人群提供单剂量、持久的保护。
