Plasmodium falciparum erythrocyte binding antigen-175 (PfEBA-175) is a candidate antigen for a blood-stage malaria vaccine, while various polymorphisms and dimorphism have prevented to development of effective vaccines based on this gene. This study aimed to investigate the dimorphism of PfEBA-175 on both the Bioko Island and continent of Equatorial Guinea, as well as the genetic polymorphism and natural selection of global PfEBA-175. The allelic dimorphism of PfEBA-175 region II of 297 bloods samples from Equatorial Guinea in 2018 and 2019 were investigated by nested polymerase chain reaction and sequencing. Polymorphic characteristics and the effect of natural selection were analyzed using MEGA 7.0, DnaSP 6.0 and PopART programs. Protein function prediction of new amino acid mutation sites was performed using PolyPhen-2 and Foldx program. Both Bioko Island and Bata district populations, the frequency of the F-fragment was higher than that of the C-fragment of PfEBA-175 gene. The PfEBA-175 of Bioko Island and Bata district isolates showed a high degree of genetic variability and heterogeneity, with π values of 0.00407 & 0.00411 and Hd values of 0.958 & 0.976 for nucleotide diversity, respectively. The values of Tajima's D of PfEBA-175 on Bata district and Bioko Island were 0.56395 and − 0.27018, respectively. Globally, PfEBA-175 isolates from Asia were more diverse than those from Africa and South America, and genetic differentiation quantified by the fixation index between Asian and South American countries populations was significant (FST > 0.15, P < 0.05). A total of 310 global isolates clustered in 92 haplotypes, and only one cluster contained isolates from three continents. The mutations A34T, K109E, D278Y, K301N, L305V and D329N were predicted as probably damaging. This study demonstrated that the dimorphism of F-fragment PfEBA-175 was remarkably predominant in the study area. The distribution patterns and genetic diversity of PfEBA-175 in Equatorial Guinea isolates were similar another region isolates. And the levels of recombination events suggested that natural selection and intragenic recombination might be the main drivers of genetic diversity in global PfEBA-175. These results have important reference value for the development of blood-stage malaria vaccine based on this antigen.

中文翻译：

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赤道几内亚恶性疟原虫红细胞结合抗原175（EBA-175）基因的群体遗传分析

恶性疟原虫红细胞结合抗原 175 (PfEBA-175) 是血液阶段疟疾疫苗的候选抗原，而各种多态性和二态性阻碍了基于该基因的有效疫苗的开发。本研究旨在研究PfEBA-175在比奥科岛和赤道几内亚大陆上的二态性，以及全球PfEBA-175的遗传多态性和自然选择。通过巢式聚合酶链反应和测序研究了2018年和2019年赤道几内亚297份血液样本的PfEBA-175 II区等位基因二态性。使用MEGA 7.0、DnaSP 6.0和PopART程序分析了多态性特征和自然选择的影响。使用PolyPhen-2和Foldx程序进行新氨基酸突变位点的蛋白质功能预测。Bioko Island和Bata区人群中，PfEBA-175基因的F片段频率高于C片段。比奥科岛和巴塔区分离株的 PfEBA-175 显示出高度的遗传变异性和异质性，核苷酸多样性的 π 值分别为 0.00407 和 0.00411，Hd 值分别为 0.958 和 0.976。Bata区和Bioko岛PfEBA-175的Tajima's D值分别为0.56395和-0.27018。在全球范围内，来自亚洲的 PfEBA-175 分离株比来自非洲和南美洲的分离株更加多样化，并且通过亚洲和南美国家人口之间的固定指数量化的遗传分化显着（FST > 0.15，P < 0.05）。总共 310 个全球分离株聚集在 92 个单倍型中，并且只有一个集群包含来自三大洲的分离株。预测突变 A34T、K109E、D278Y、K301N、L305V 和 D329N 可能具有破坏性。该研究表明，F 片段 PfEBA-175 的二态性在研究区域中显着占优势。PfEBA-175在赤道几内亚分离株中的分布模式和遗传多样性与其他地区的分离株相似。重组事件的水平表明，自然选择和基因内重组可能是全球 PfEBA-175 遗传多样性的主要驱动因素。这些结果对于开发基于该抗原的血期疟疾疫苗具有重要的参考价值。该研究表明，F 片段 PfEBA-175 的二态性在研究区域中显着占优势。PfEBA-175在赤道几内亚分离株中的分布模式和遗传多样性与其他地区的分离株相似。重组事件的水平表明，自然选择和基因内重组可能是全球 PfEBA-175 遗传多样性的主要驱动因素。这些结果对于开发基于该抗原的血期疟疾疫苗具有重要的参考价值。该研究表明，F 片段 PfEBA-175 的二态性在研究区域中显着占优势。PfEBA-175在赤道几内亚分离株中的分布模式和遗传多样性与其他地区的分离株相似。重组事件的水平表明，自然选择和基因内重组可能是全球 PfEBA-175 遗传多样性的主要驱动因素。这些结果对于开发基于该抗原的血期疟疾疫苗具有重要的参考价值。重组事件的水平表明，自然选择和基因内重组可能是全球 PfEBA-175 遗传多样性的主要驱动因素。这些结果对于开发基于该抗原的血期疟疾疫苗具有重要的参考价值。重组事件的水平表明，自然选择和基因内重组可能是全球 PfEBA-175 遗传多样性的主要驱动因素。这些结果对于开发基于该抗原的血期疟疾疫苗具有重要的参考价值。