口服福氏2a志贺氏菌T32菌苗株减毒基础分析

ANALYSIS OF BASIS OF ATTENUATION OF ORAL LIVING VACCINE SH FLEXNERI 2a T32 STRAIN

福氏2a志贺氏菌(下简称F2a)T32菌苗株,其质粒DNA经琼脂糖凝胶电泳表明,具有志贺氏菌属共有的约120～140Mdal大小的质粒.DNA探针杂交试验证明,T32株与志贺氏菌属侵入有关的17kb或4.1kbDNA探针没有同源性.免疫印迹技术显示,T32株不表达侵袭性4种外膜蛋白(a,b,c和d).当将宋内氏志贺氏菌毒株I相大质粒诱动转移到T32株时,它又回复了侵入上皮细胞并引起豚鼠眼角膜结膜炎的能力.上述事实揭示,T32株的减毒基础在于140Mdal大质粒上与侵入有关的某些基因片段的缺失突变,而与毒力有关的染色体上的基因片段并未发生改变.

Sh flexneri 2a T32 strain contains a 140 Mdal plasmid.The hybridization test of DNA probes with T32 strain demonstrated that the large plasmid of T32 strain does not hybridize with 17kb or 4.1kb probes.Immunoblot assays showed that T32 strain does not express four out-membrane proteins (a,b,c and d) as reported by Hale et al.When Sh sonnei I form plasmid was transferred into T32 strain by mobilizing-transferation,T32 strain regained its virulence to cause positive Sereny's reaction in guinea pig.These facts suggested that the attenuation basis of T32 strain was attributed to deletion of certain invasive gene fragments of 140 Mdal plasmid,the chromosomal gene fragments associated with virulence presumbly remained intact.