不同血清型变形链球菌表面蛋白可变区(extended-V)的同源性分析

目的 分析不同血清型变形链球菌表面蛋白可变区（extended-V）的基因及蛋白质的同源性，探讨该区在防龋疫苗研制中的作用。方法 以变形链球菌血清型c、d、f、g参考株及部分c型临床株为模板，PCR扩增SrV+区片段，通过内切酶DdeⅠ进行限制性片段长度多态性分析并测序，将其测序结果在NCBI服务器上用blastn搜索软件进行同源性比较。结果 在相同条件下血清c、f型菌株均扩增出约1.13 kb左右的片段，酶切后出现5种基因型（A、B、C、D、E）。选取所占比例较多的A、B、C型代表株进行测序，经比较显示其基因型间的同源性达92%-98%。血清d、g型无扩增产物，将g型6715表面蛋白SpaA全片段基因同OMZ175的产物序列在blastn上进行比较，有3个大小不一的片段出现同源性；血清d型OMZ176的表面蛋白基因序列在GeneBank上未能查出，故无法比较，但其相应蛋白质的同源性也在77%-82%之间，显示出相当高的同源性。结论 就c、f型菌株来说，可以将该区纳入疫苗的研究范畴；d、g型虽未能扩增出相应产物，但其基因还是存在部分区域的相似性，且其蛋白质同源性很高，也可以考虑利用d、g型上同c、f型共有的某些肽段进行疫苗的研制。

Homology Analysis of the Extended-V Region of the Surface Proteins in Different Serotype Streptococcus mutans

Objective  To analysis the homology among the extended-V region of the surface proteins in different serotype Streptococcus mutans（c, f, d, g） and to find out it′s significance in anti-caries vaccine. Methods  The DNA
of the bacteria（standarded serotype c, d, f, g and partial serotype c clinicals） was extracted and the extended-V
region（SrV+, 1 384—2 514 bp） was amplified using polymerase chain reaction（PCR）. Then the products were assessed
using restriction fragment length polymorphism（RFLP） by endonuclease DdeⅠ. The genotypings were sequenced and analysised using the program of BLAST on NCBI Gene Bank database. Results  About 1.13 kb fragments were produced both in serotype c and f, the serotype d and g were failed. The RFLP results showed that five different patterns（A, B, C, D, E） among the 117 PCR products were reveled by DdeⅠ. The ration of the genotypings A and B were the most among the strains，the C was lower，the D and E respectively was 1 and 3 strains per genotype. OMZ175（serotype f） was belong to B genotype. Selected one of the A, B, C genotypings to sequenced and blasted. Then the results of the blastn showed that the identities of the gene sequence were 92%—98% between the serotype c and serotype f, part sequence of the serotype g was homology with the SrV+ of the serotype c, the protein sequence among serotype c, d, f, g were 77%—82%. Conclusion  It is reasonable to use some putative pipetides to study the anti-caries vaccine among the extended-V regions of the surface proteins in different serotype（c, d, f, g） in S. mutans.