Genetics and Molecular Biology Laboratory, National Institute of Malaria Research, Sector-8, Dwarka, New Delhi 110077, India.
Malar J. 2011 May 2;10:111. doi: 10.1186/1475-2875-10-111.
Genetic polymorphism is an inevitable component of a multistage infectious organism, such as the malaria parasite. By means of genetic polymorphism, parasite opts particular polymorph and reveals survival advantage. Pvs25 and pvs28 are sexual stage antigen genes, expressed at the ookinete stage inside the mosquito gut, and considered as potential transmission-blocking vaccine candidates. This study presents sequence variations in two important transmission blocking antigen genes pvs25 and pvs28 in the field isolates of P. vivax from the Indian subcontinent.
One hundred microscopically diagnosed P. vivax isolates were collected from five geographical regions of India. Pvs25 and pvs28 genes were PCR amplified and sequenced to assess sequence variation among field isolates.
A total of 26 amino acid substitutions were observed in Pvs25 (10) and Pvs28 (16) among field isolates of P. vivax. Tandem repeat polymorphism observed in pvs28 shows 3-6 tandem repeats in the field isolates. Seven and eight novel amino acid substitutions were observed in Pvs25 and Pvs28, respectively in Indian isolates. Comparison of amino acid substitutions suggests that majority of substitutions observed in global isolates were also present in Indian subcontinent. A single haplotype was observed to be major haplotype among isolates of Delhi, Nadiad, Chennai and Panna except in isolates of Kamrup. Further, population comparison analyses suggest that P. vivax isolates inhabiting in north-eastern region (Kamrup) were distantly related with the isolates from remaining parts of the country. Majority of the amino acid substitutions observed in Indian isolates were more identical to the substitutions reported from isolates of Thailand and Bangladesh.
Study uncovered many new amino acid substitutions as well as a predominance of single haplotype in Indian subcontinent except in north-eastern region of the country. The amino acid substitutions data generated in this study from different geographical regions of the Indian subcontinent could be helpful in designing a more effective anti-malarial transmission-blocking vaccine.
遗传多态性是疟疾寄生虫等多阶段感染生物不可避免的组成部分。通过遗传多态性，寄生虫选择特定的多态性并表现出生存优势。Pvs25 和 pvs28 是性阶段抗原基因，在蚊子肠道内的配子体阶段表达，被认为是潜在的传播阻断疫苗候选物。本研究介绍了来自印度次大陆的间日疟原虫现场分离株中两个重要的传播阻断抗原基因 pvs25 和 pvs28 的序列变异。
从印度五个地理区域收集了 100 个显微镜诊断的间日疟原虫分离株。对 Pvs25 和 pvs28 基因进行 PCR 扩增和测序，以评估现场分离株之间的序列变异。
在间日疟原虫现场分离株中观察到 Pvs25（10）和 Pvs28（16）共 26 个氨基酸取代。在 pvs28 中观察到串联重复多态性，在现场分离株中显示 3-6 个串联重复。在印度分离株中分别观察到 Pvs25 和 Pvs28 的 7 个和 8 个新氨基酸取代。氨基酸取代的比较表明，在全球分离株中观察到的大多数取代也存在于印度次大陆。在德里、纳迪亚德、钦奈和潘纳的分离株中观察到单一单倍型为主，除了在卡姆鲁普的分离株中。此外，种群比较分析表明，栖息在东北部地区（卡姆鲁普）的间日疟原虫分离株与该国其余地区的分离株关系较远。在印度分离株中观察到的大多数氨基酸取代与来自泰国和孟加拉国分离株的取代更为相似。
除了该国东北部地区外，本研究在印度次大陆发现了许多新的氨基酸取代和单一单倍型的优势。本研究从印度次大陆不同地理区域获得的氨基酸取代数据有助于设计更有效的抗疟传播阻断疫苗。
