Chua Chuen Yang, Lee Ping Chin, Lau Tiek Ying
Biotechnology Research Institute, Universiti Malaysia Sabah, 88400 Kota Kinabalu, Sabah, Malaysia.
J Genet. 2017 Sep;96(4):653-663. doi: 10.1007/s12041-017-0817-4.
The apical membrane antigen-1 (AMA-1) of Plasmodium spp. is a merozoite surface antigen that is essential for the recognition and invasion of erythrocytes. Polymorphisms occurring in this surface antigen will cause major obstacles in developing effective malaria vaccines based on AMA-1. The objective of this study was to characterize ama1 gene in Plasmodium knowlesi isolates from Sabah. DNA was extracted from blood samples collected from Keningau, Kota Kinabalu and Kudat. The Pkama1 gene was amplified using nested PCR and subjected to bidirectional sequencing. Analysis of DNA sequence revealed that most of the nucleotide polymorphisms were synonymous and concentrated in domain I of PkAMA-1. Forteen haplotypes were identified based on amino acid variations and haplotype K5 was the most common haplotype. d/d ratios implied that purifying selection was prevalent in Pkama1 gene. Fu and Li's D and F values further provided evidence of negative selection acting on domain II of Pkama1. Lownucleotide diversitywas also detected for the Pkama1 sequences,which is similar to reports on Pkama1 from Peninsular Malaysia and Sarawak. The presence of purifying selection and low nucleotide diversity indicated that domain II of Pkama1 can be used as a target for vaccine development.
疟原虫属的顶端膜抗原1（AMA-1）是一种裂殖子表面抗原，对红细胞的识别和入侵至关重要。该表面抗原中出现的多态性将给基于AMA-1开发有效的疟疾疫苗带来重大障碍。本研究的目的是对来自沙巴州的诺氏疟原虫分离株中的ama1基因进行特征分析。从斗湖、哥打基纳巴卢和古达采集的血样中提取DNA。使用巢式PCR扩增Pkama1基因并进行双向测序。DNA序列分析表明，大多数核苷酸多态性是同义的，且集中在PkAMA-1的结构域I中。基于氨基酸变异鉴定出14种单倍型，单倍型K5是最常见的单倍型。d/d比值表明纯化选择在Pkama1基因中普遍存在。傅和李的D和F值进一步提供了对Pkama1结构域II进行负选择的证据。还检测到Pkama1序列的核苷酸多样性较低，这与马来西亚半岛和砂拉越关于Pkama1的报道相似。纯化选择的存在和低核苷酸多样性表明，Pkama1的结构域II可作为疫苗开发的靶点。
