Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand; Department of Molecular Tropical Medicine and Genetics, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
Department of Biological Sciences, Eck Institute for Global Health, Galvin Life Sciences, University of Notre Dame, Notre Dame, IN, USA.
Infect Genet Evol. 2023 Sep;113:105467. doi: 10.1016/j.meegid.2023.105467. Epub 2023 Jun 15.
The local diversity and population structure of malaria parasites vary across different regions of the world, reflecting variations in transmission intensity, host immunity, and vector species. This study aimed to use amplicon sequencing to investigate the genotypic patterns and population structure of P. vivax isolates from a highly endemic province of Thailand in recent years. Amplicon deep sequencing was performed on 70 samples for the 42-kDa region of pvmsp1 and domain II of pvdbp. Unique haplotypes were identified and a network constructed to illustrate genetic relatedness in northwestern Thailand. Based on this dataset of 70 samples collected between 2015 and 2021, 16 and 40 unique haplotypes were identified in pvdbp and pvmsp1, respectively. Nucleotide diversity was higher in pvmsp1 than in pvdbp (π = 0.027 and 0.012), as was haplotype diversity (Hd = 0.962 and 0.849). pvmsp1 also showed a higher recombination rate and higher levels of genetic differentiation (F) in northwestern Thailand versus other regions (0.2761-0.4881). These data together suggested that the genetic diversity of P. vivax in northwestern Thailand at these two studied loci evolved under a balancing selection, most likely host immunity. The lower genetic diversity of pvdbp may reflect its stronger functional constrain. In addition, despite the balancing selection, a decrease in genetic diversity was observed. Hd of pvdbp decreased from 0.874 in 2015-2016 to 0.778 in 2018-2021; π of pvmsp1 decreased from 0.030 to 0.022 over the same period. Thus, the control activities must have had a strong impact on the parasite population size. The findings from this study provide an understanding of P. vivax population structure and the evolutionary force on vaccine candidates. They also established a new baseline for tracking future changes in P. vivax diversity in the most malarious area of Thailand.
本研究旨在利用扩增子测序技术，调查近年来泰国高度流行地区间疟原虫的基因型模式和种群结构。对 70 个样本的 42-kDa 区 pvmsp1 和 pvdbp 结构域 II 进行了扩增子深度测序。鉴定了独特的单倍型，并构建了一个网络来展示泰国西北部的遗传关系。基于该数据集（2015 年至 2021 年采集的 70 个样本），在 pvdbp 和 pvmsp1 中分别鉴定出 16 个和 40 个独特单倍型。pvmsp1 的核苷酸多样性高于 pvdbp（π=0.027 和 0.012），单倍型多样性（Hd）也是如此（Hd=0.962 和 0.849）。与其他地区相比，pvmsp1 在泰国西北部的重组率更高，遗传分化（F）水平也更高（0.2761-0.4881）。这些数据表明，在所研究的两个基因座中，泰国西北部间日疟原虫的遗传多样性是在平衡选择下进化的，这很可能是由宿主免疫引起的。pvdbp 的遗传多样性较低可能反映了其较强的功能约束。此外，尽管存在平衡选择，但遗传多样性仍呈下降趋势。pvdbp 的 Hd 从 2015-2016 年的 0.874 下降到 2018-2021 年的 0.778；pvmsp1 的 π 在同一时期从 0.030 下降到 0.022。因此，控制活动肯定对寄生虫种群规模产生了重大影响。本研究结果提供了对间日疟原虫种群结构和疫苗候选物进化力的认识。它们还为泰国最疟疾流行地区间日疟原虫多样性的未来变化跟踪建立了新的基线。
