Molecular evolution of antigen polymoiphism of modem malaria parasite populations

1.感染复数的地理变异比较了不同地理区域恶性疟原虫种群的感染复数（MOI）。通过基于PCR的mspl- 5'单体型分型测量的MOI在非洲是高的，而在非洲的MOI和疟疾传播强度之间没有可辨别的关联。结果提示，疟疾株特异性保护性免疫的获得不仅与疟疾传播强度有关，还与当地流行的基因型数量和MOI有关.间日疟原虫mspl多态性的起源和自然选择为了研究间日疟原虫mspl多态性的进化历史，构建了间日疟原虫及其相关猴疟原虫mspl基因的系统发育树。所有间日疟原虫mspl等位基因都聚集在间日疟原虫谱系中，并且不分布于其他物种中。类似地，所有食蟹猴P mspl等位基因聚集在食蟹猴P谱系中。这表明间日疟原虫mspl多态性的起源相对较近。我们在间日疟原虫谱系中观察到阳性选择，而在食蟹猴中没有。本研究表明，不同寄生品系间mspl的进化历史存在很大差异.疟原虫属的胞质SSURRNA的系统发育。为了推断疟原虫属的SSURRNA系统发育，获得了8种猴疟原虫的细胞SSURRNA，A型样和S型样基因的旁系同源拷贝的基因编码序列。这些序列的最大似然分析，连同数据库中目前可用的所有细胞-SSURNA序列，清楚地证明了无根疟原虫树中的四个独立的进化枝：猿猴疟原虫+间日疟原虫进化枝，啮齿类疟原虫进化枝（伯氏疟原虫/约氏疟原虫），包括三日疟原虫、恶性疟原虫、赖氏疟原虫以及鸟类和爬行动物疟原虫物种的大进化枝，以及卵形疟原虫进化枝。

1. Geographic variation in multiplicity of infectionMultiplicity of infection (MOI) was compared among P falciparum populations from diverse geographic areas. MOI as measured by PCR-based mspl- 5' haplotyping was high in Africa, whereas there was no discernible association between MOI and the intensity of malaria transmission in Melanesia. Results suggest that the acquisition of strain specific protective immunity against malaria is associated with not only the intensity of malaria transmission but also the number of genotypes prevalent in local areas and MOI.2. Origin of and natural selection in mspl polymorphism of P. vivaxTo investigate the evolutionary history of mspl polymorphism in P vivax, phylogenetic trees of mspl from P. vivax and related monkey malaria parasite species was constructed. All P vivax mspl alleles cluster in the P vivax lineage and are not distributed among other species. Similarly, all P cynomolgi mspl alleles cluster in the P cynomolgi lineage. This suggests that the origin of P. vivax mspl polymorphism is relatively recent. We observed positive selection_in the P vivax lineage but not in P cynomolgi. This study shows that the evolutionary history of mspl differs greatly among parasite lineages.3. Phylogeny of the cytosolic SSUrRNA of Plasmodium spp.To infer the SSUrRNA phylogeny of the genus Plasmodium, sequences of genes encoding paralogous copies of the cyto-SSUrRNA, A-type-like and S-type-like genes, from eight simian Plasmodium species were obtained. The maximum likelihood analyses of these sequences, together with all cyto-SSUrRNA sequences currently available in the database, clearly demonstrated four independent clades in the unrooted Plasmodium tree: a simian Plasmodium + P vivax clade, a rodent Plasmodium clade (P. berghei/P. yoelii), a large clade including P malariae, P. falciparum, P reichnowi, and avian and reptilian Plasmodium species, and a P ovale clade.