Department of Histology and Embryology, Shantou University Medical College, Shantou, Guangdong, People's Republic of China.
School of Food Engineering and Biotechnology, Hanshan Normal University, Chaozhou, Guangdong, People's Republic of China.
Malar J. 2019 Sep 18;18(1):317. doi: 10.1186/s12936-019-2948-y.
Plasmodium falciparum apical membrane antigen-1 (PfAMA-1) is a promising candidate antigen for a blood-stage malaria vaccine. However, antigenic variation and diversity of PfAMA-1 are still major problems to design a universal malaria vaccine based on this antigen, especially against domain I (DI). Detail understanding of the PfAMA-1 gene polymorphism can provide useful information on this potential vaccine component. Here, general characteristics of genetic structure and the effect of natural selection of DIs among Bioko P. falciparum isolates were analysed.
214 blood samples were collected from Bioko Island patients with P. falciparum malaria between 2011 and 2017. A fragment spanning DI of PfAMA-1 was amplified by nested polymerase chain reaction and sequenced. Polymorphic characteristics and the effect of natural selection were analysed using MEGA 5.0, DnaSP 6.0 and Popart programs. Genetic diversity in 576 global PfAMA-1 DIs were also analysed. Protein function prediction of new amino acid mutation sites was performed using PolyPhen-2 program.
131 different haplotypes of PfAMA-1 were identified in 214 Bioko Island P. falciparum isolates. Most amino acid changes identified on Bioko Island were found in C1L. 32 amino acid changes identified in PfAMA-1 sequences from Bioko Island were found in predicted RBC-binding sites, B cell epitopes or IUR regions. Overall patterns of amino acid changes of Bioko PfAMA-1 DIs were similar to those in global PfAMA-1 isolates. Differential amino acid substitution frequencies were observed for samples from different geographical regions. Eight new amino acid changes of Bioko island isolates were also identified and their three-dimensional protein structural consequences were predicted. Evidence for natural selection and recombination event were observed in global isolates.
Patterns of nucleotide diversity and amino acid polymorphisms of Bioko Island isolates were similar to those of global PfAMA-1 DIs. Balancing natural selection across DIs might play a major role in generating genetic diversity in global isolates. Most amino acid changes in DIs occurred in predicted B-cell epitopes. Novel sites mapped on a three dimensional structure of PfAMA-1 showed that these regions were located at the corner. These results may provide significant value in the design of a malaria vaccine based on this antigen.
恶性疟原虫顶膜蛋白 1（PfAMA-1）是一种有前途的血阶段疟疾疫苗候选抗原。然而，PfAMA-1 的抗原变异和多样性仍然是基于该抗原设计通用疟疾疫苗的主要问题，尤其是针对结构域 I（DI）。详细了解 PfAMA-1 基因多态性可以为这一潜在疫苗成分提供有用信息。在这里，分析了比科岛恶性疟原虫分离株 PfAMA-1 的 DI 中遗传结构的一般特征和自然选择的影响。
2011 年至 2017 年间，从比科岛恶性疟原虫患者中采集了 214 份血样。通过巢式聚合酶链反应扩增 PfAMA-1 的 DI 片段，并进行测序。使用 MEGA 5.0、DnaSP 6.0 和 Popart 程序分析多态性特征和自然选择的影响。还分析了全球 576 个 PfAMA-1 DI 中的遗传多样性。使用 PolyPhen-2 程序对新氨基酸突变位点的蛋白质功能进行预测。
在 214 个比科岛恶性疟原虫分离株中鉴定出 131 种不同的 PfAMA-1 单倍型。在比科岛上发现的大多数氨基酸变化发生在 C1L。在比科岛 PfAMA-1 序列中发现的 32 个氨基酸变化发生在 RBC 结合位点、B 细胞表位或 IUR 区域。比科岛 PfAMA-1 DI 的氨基酸变化总体模式与全球 PfAMA-1 分离株相似。来自不同地理区域的样本观察到不同的氨基酸取代频率。还鉴定了比科岛分离株的 8 个新氨基酸变化，并预测了它们的三维蛋白质结构后果。在全球分离株中观察到自然选择和重组事件的证据。
比科岛分离株的核苷酸多样性和氨基酸多态性模式与全球 PfAMA-1 DI 相似。在 DI 中平衡自然选择可能在全球分离株的遗传多样性中起主要作用。DI 中的大多数氨基酸变化发生在预测的 B 细胞表位中。映射在 PfAMA-1 三维结构上的新位点表明这些区域位于角落。这些结果可能为基于该抗原设计疟疾疫苗提供重要价值。
