Molecular Biology of Malaria and Opportunistic Parasites Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
Medical Sciences Program, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
Sci Rep. 2023 Mar 9;13(1):3951. doi: 10.1038/s41598-023-30975-4.
Glutamic acid-rich protein of Plasmodium falciparum (PfGARP) binds to erythrocyte band 3 and may enhance cytoadherence of infected erythrocytes. Naturally acquired anti-PfGARP antibodies could confer protection against high parasitemia and severe symptoms. While whole genome sequencing analysis has suggested high conservation in this locus, little is known about repeat polymorphism in this vaccine candidate antigen. Direct sequencing was performed from the PCR-amplified complete PfGARP gene of 80 clinical isolates from four malaria endemic provinces in Thailand and an isolate from a Guinean patient. Publicly available complete coding sequences of this locus were included for comparative analysis. Six complex repeat (RI-RVI) and two homopolymeric glutamic acid repeat (E1 and E2) domains were identified in PfGARP. The erythrocyte band 3-binding ligand in domain RIV and the epitope for mAB7899 antibody eliciting in vitro parasite killing property were perfectly conserved across isolates. Repeat lengths in domains RIII and E1-RVI-E2 seemed to be correlated with parasite density of the patients. Sequence variation in PfGARP exhibited genetic differentiation across most endemic areas of Thailand. Phylogenetic tree inferred from this locus has shown that most Thai isolates formed closely related lineages, suggesting local expansion/contractions of repeat-encoding regions. Positive selection was observed in non-repeat region preceding domain RII which corresponded to a helper T cell epitope predicted to be recognized by a common HLA class II among Thai population. Predicted linear B cell epitopes were identified in both repeat and non-repeat domains. Besides length variation in some repeat domains, sequence conservation in non-repeat regions and almost all predicted immunogenic epitopes have suggested that PfGARP-derived vaccine may largely elicit strain-transcending immunity.
恶性疟原虫谷氨酸丰富蛋白（PfGARP）与红细胞带 3 结合，可能增强感染红细胞的细胞黏附性。天然获得的抗 PfGARP 抗体可以提供针对高寄生虫血症和严重症状的保护。虽然全基因组测序分析表明该基因座高度保守，但对该疫苗候选抗原的重复多态性知之甚少。直接从来自泰国四个疟疾流行省份的 80 个临床分离株和来自几内亚患者的分离株的 PCR 扩增的完整 PfGARP 基因进行测序。还包括该基因座的公开可用的完整编码序列进行比较分析。在 PfGARP 中鉴定了六个复杂重复（RI-RVI）和两个同质谷氨酸重复（E1 和 E2）结构域。在结构域 RIV 中的红细胞带 3 结合配体和 mAB7899 抗体诱导体外寄生虫杀伤特性的表位在分离株中完全保守。结构域 RIII 和 E1-RVI-E2 中的重复长度似乎与患者的寄生虫密度相关。PfGARP 中的序列变异在泰国的大多数流行地区表现出遗传分化。从该基因座推断的系统发育树表明，大多数泰国分离株形成密切相关的谱系，表明重复编码区域的局部扩张/收缩。在对应于泰国人群中常见 HLA 类 II 识别的辅助 T 细胞表位的预测前结构域 RII 之前观察到非重复区的正选择。在重复和非重复结构域中均鉴定到预测的线性 B 细胞表位。除了一些重复结构域的长度变化外，非重复区的序列保守性和几乎所有预测的免疫原性表位表明 PfGARP 衍生的疫苗可能会引起广泛的菌株跨越免疫。
