Molecular epidemiological analysis of the antigen diversity of Plasmodium vivax and P.falciparum

对泰国和越南流行区间日疟原虫和恶性疟原虫的遗传水平分离株进行了表面抗原多样性研究。对300多株菌株进行PCR和DNA测序分析，结果如下：间日疟原虫merozoite surface antigen （MSP1）基因多态性：15株泰国分离株在ICB5 ~ ICB6区有35个排列，其中大部分为二态取代。1型和2型序列在多态区存在2种重组类型。这些结果表明，恶性疟原虫MSP1基因可能通过重组产生等位基因多样性。恶性疟原虫merozoite surface antigen （MSP1）基因多态性：利用等位基因型序列特异性引物，建立了一套PCR系统，该系统可鉴定出每个分离物多达24种不同的MSP1基因型。在越南和泰国分别鉴定出17 ~ 21种不同的MSP1基因型。MSP1基因型的频率分布在两个地区之间存在显著差异。第一次分析表明，泰国和越南分离株之间除2区外，MSP1的可变区存在显著差异。基因中频繁重组（block 4）和不频繁重组（block 3和5）以及不重组（block 6-16）的可变块之间的连锁分析。此外，泰国菌株在MSP1.3的C端19 kD区发现了2个新的多态性残基。对20个泰国分离株恶性疟原虫血栓反应蛋白相关匿名蛋白（TRAP）基因的测序显示泰国分离株特有的变异，并提示该基因存在重组。

The diversity of surface antigens of Plasmodium vivax and P.falciparum was studied at the genetic on level field isolates from endemic areas of Thailand and Vietnam. Analysis of more than 300 isolates by PCR and DNA sequencing revealed the followings.1.Polymorphism of the merozoite surface antigen (MSP1) gene of P.vivax : 15 Thai isolates possessed 35 permutations in the regions from ICB5 to ICB6, most of which were dimorphic substitutions. Two types of recombination bwtween type 1 and type 2 sequences were found in a polymorphic region. These results suggest that allelic diversity may be generated by recombination as found for the P.falciparum MSP1 gene.2.Polymorphism of the merozoite surface antigen (MSP1) gene of P.falciparum : A PCR system, which identifies up to 24 different MSP1 gene types per isolate, was developed by using primers specific for allelic type sequences. In total, 17 to 21 different MSP1 gene types were identified in Vietnam and Thailand, respectively. Frequency distribution of MSP1 gene type differed significantly between the two areas. The F st analysis indicated significant divergence in variable blocks of MSP1 except block 2 between Thai and Vietnam isolates. Linkage analysis between variable blocks localized regions in the gene for frequent recombination (block 4) and less frequent recombination (blocks 3 and 5) as well as no recombination (blocks 6-16). Furthermore, Thai isolates showed 2 new polymorphic residues in the C terminus, 19 kD region of MSP1.3.Sequencing of the thrombospondin-related anonymous protein (TRAP) gene of P.falciparum of 20 Thai isolates showed variations specific for Thai isolates and also suggested recombination in the gene.