Disparate selection of mutations in the dihydrofolate reductase gene (dhfr) of Plasmodium ovale curtisi and P. o. wallikeri in Africa.
Disparate selection of mutations in the dihydrofolate reductase gene (dhfr) of Plasmodium ovale curtisi and P. o. wallikeri in Africa.
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卵圆囊柯蒂西和P. o的二氢叶酸还原酶基因（DHFR）中突变的不同选择。非洲的Wallikeri。
DOI：
10.1371/journal.pntd.0010977
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发表时间：
2022-12
影响因子：
3.8
通讯作者：
中科院分区：
文献类型：
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作者：
卵圆库氏疟原虫和卵圆瓦利克氏疟原虫都是撒哈拉以南非洲、中东和东南亚的地方病。目前，卵形疟原虫耐药分子监测资料有限。我们分析了从非洲返回中国的旅行者收集的147个样本中卵形疟原虫podhfr、pocrt和pocytb基因的多态性。在卵形圆鼻虫中检测到S58R和S113N/T两个podhfr突变，高/中频率分别为52.17%和17.39%。在卵形圆叶豆中发现了podhfr阳性选择的证据（dN/dS = 2.41），突变等位基因两侧微卫星标记的多样性（He）下降表明两者都发生了选择性扫描。在卵圆圆斑蛙的pote中发现了E34G（1.50%）和L43V（1.50%）突变，在卵圆圆斑蛙的wallikeri中发现了E34G（3.70%）、I102M（1.80%）和V111F（1.80%）突变。卵圆圆蛙和卵圆蛙均存在R66K（6.20%）、R75K（11.63%）和R95K（3.88%）突变。这些结果表明，非洲卵形疟原虫的podhfr基因可能受到药物选择的影响，值得进一步关注。我们观察到两个卵形种之间podhfr突变的流行和分布存在显著差异，表明它们之间存在根本的生物学差异。迄今为止被忽视的疟疾寄生虫卵形curcuri疟原虫、卵形walllikeri疟原虫和疟疾疟原虫的重要性现在变得越来越明显。很明显，这些物种在非洲的流行率比以前认为的要高得多，而且它们造成了大量与疟疾有关的发病率。尽管这些寄生虫很重要，但目前对它们的流行病学知之甚少。特别重要的是了解这些寄生虫是否以与恶性疟原虫和间日疟原虫相似的方式进行耐药性选择。关于这些寄生虫的分子流行病学所知甚少的事实是，由于在现场难以识别它们，它们在血液中通常以低寄生虫密度存在，经常被恶性疟原虫的共同感染所掩盖，并且没有可用于它们的体外培养系统。我们能够利用一种独特而无价的资源。卵形疟原虫样本，主要是来自非洲无免疫力的中国旅行者的单感染，对已知与其他疟疾寄生虫物种耐药性有关的几个基因的同源物进行测序。这一资源使我们能够从一个广泛的地理区域取样一些寄生虫；这在以前是不可能的。通过对已知与其他疟原虫耐药相关的几个基因的同源物测序，在非洲卵形疟原虫分离株的podhfr中观察到高频率的S58R和S113N/T突变。此外，通过使用微卫星标记调查这些位点周围的遗传多样性，我们能够表明，非洲卵形瓢虫的podhfr基因经历了特定突变的选择，可能是由于药物压力，这值得进一步关注。
Plasmodium ovale curtisi and P. ovale wallikeri are both endemic in sub-Saharan Africa, the Middle East and Southeast Asia. Molecular surveillance data for drug resistance in P. ovale spp. is limited at present. We analysed polymorphisms in the podhfr, pocrt and pocytb genes of P. ovale spp. in 147 samples collected from travelers returning to China from Africa. Two podhfr mutations, S58R and S113N/T were detected in P. ovale curtisi with high/moderate frequencies of 52.17% and 17.39%, respectively. Evidence of positive selection (dN/dS = 2.41) was found for podhfr in P. ovale curtisi and decreased diversity (He) of microsatellite markers flanking the mutant alleles suggests that selective sweeps have occurred for both. Mutations E34G (1.50%) and L43V (1.50%) in pocrt of P. ovale curtisi, and E34G (3.70%), I102M (1.80%) and V111F (1.80%) of P. ovale wallikeri were found at low frequencies. Mutations R66K (6.20%), R75K (11.63%) and R95K (3.88%) of pocytb were found in both P. ovale curtisi and P. ovale wallikeri. These results suggest that the podhfr gene of P. ovale curtisi may be subject to drug selection in Africa, warranting further attention. We observed significant differences in the prevalence and distribution of podhfr mutations between the two P. ovale species, suggestive of fundamental biological differences between them. The importance of the hitherto neglected malaria parasites Plasmodium ovale curtisi, Plasmodium ovale wallikeri and Plasmodium malariae is now becoming apparent. It is clear that these species are prevalent in Africa at much higher rates than previously thought, and that they are responsible for a significant amount of malaria-related morbidity. There is very little currently known about the epidemiology of these parasites, despite their importance. Of particular importance is understanding whether these parasites undergo selection for drug resistance in similar ways as Plasmodium falciparum and Plasmodium vivax. The fact that little is known regarding the molecular epidemiology of these parasites is due to difficulties in identifying them in the field, the fact that they are often present at low parasite densities in the blood, are often masked by co-infection with P. falciparum, and that there is no in vitro culture system available for them. We were able to utilise a unique and priceless resource–P. ovale spp. samples, mostly in mono-infections, from non-immune Chinese travellers to Africa–to sequence orthologues of several genes known to be linked to drug resistance in other malaria parasite species. This resource enabled us to sample a number of parasites from a widespread geographical area; something that has never before been possible. Through sequencing of the orthologues of several genes known to be linked to drug resistance in other malaria parasite species, high frequencies of S58R and S113N/T mutations were observed in podhfr in P. ovale curtisi isolates from Africa. Furthermore, by surveying the genetic diversity around these loci using microsatellite markers, we were able to show that the podhfr gene of African P. ovale curtisi has undergone selection for particular mutations, probably due to drug pressure, and this warrants further attention.