恶性疟原虫云南株丝氨酸重复抗原部分基因的克隆和序列分析

CLONING AND SEQUENCE ANALYSIS OF THE SERINE REPEATED ANTIGEN GENE FRAGMENT OF A PLASMODIUM FALCIPARUM STRAIN FROM YUNNAN OF CHINA

用ＰＣＲ方法特异性扩增ＳＥＲＡ基因片段，并将该基因片段克隆于Ｍ１３噬菌体，用双脱氧链末端终止法进行测序，应用ＰＣＧＥＮＥ软件对该基因序列进行了分析，结果显示该基因片段长度为４５３ｂｐ，Ａ＋Ｔ／Ｇ＋Ｃ为２．６∶１，符合恶性疟原虫结构基因的特点。同源性分析显示该基因在不同虫株间高度保守，我国ＰＦＤ－３／ＹＮ虫株ＳＥＲＡ基因片段仅与Ｂ１、Ｂ２、Ｂ３（巴西）株及Ｓ１６（塞内加尔）株在第６６７位氨基酸有不同，与ＦＣＲ３（冈比亚）、ＦＣＢＲ（哥化比亚）、及Ｓ１４、Ｓ１５（塞内加尔）等其它虫株ＳＥＲＡ基因序列完全一致。抗原表位预测分析显示该多肽Ｎ端和Ｃ端可能有抗原表位存在。

The serine repeated antigen(SERA) gene fragment of a Plasmodium falciparum strain from Yunnan of China was amplified by polymerase chain reaction and cloned into M13 bacteriophage. M13 SERA single strand DNAs of three positive clones were extracted respectively. Then, the nucleotide sequence of the SERA gene fragment was determined by the dideoxy chain termination method and analyzed with PCGENE software. It was showed that the gene fragment was 453 bp and contained high A+T contents(A+T/G+C for 2.6∶1), which accorded with the structure gene composition of Plasmodium falciparum . The homology analysis indicated that there was only one amino acid difference at the SERA 667 site among Plasmodium falciparum PFD 3/YN(from China), B1, B2,B3 and S16 isooates, no difference among Plasmodium falciparum PFD 3/YN, FCR3, FCBR, S14 and S15 isolates. The result indicated that the gene fragment is highly conservative in different isolates. The prediction of the antigenic epitope exhibited that the fragment might carry antigenic epitopes at N and C terminals.