Department of Parasitology, TIDREC, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia.
Malar J. 2013 Jun 4;12:182. doi: 10.1186/1475-2875-12-182.
Plasmodium knowlesi is the fifth species identified to cause malaria in humans and is often misdiagnosed as Plasmodium malariae due to morphological similarities. The development of an inexpensive, serological detection method utilizing antibodies specific to P. knowlesi would be a valuable tool for diagnosis. However, the identification of specific antigens for these parasites remains a major challenge for generating such assays. In this study, surface protein containing an altered thrombospondin repeat domain (SPATR) was selected as a potentially specific antigen from P. knowlesi. Its multistage expression by sporozoites, asexual erythrocytic forms and gametocytes, along with its possible role in liver cell invasion, suggests that SPATR could be used as a biomarker for diagnosis of P. knowlesi.
The spatr gene from P. knowlesi was codon optimized and cloned (pkhspatr). Recombinant pkHSPATR protein was expressed, purified, and evaluated for its sensitivity and specificity in immunoblot and ELISA-based assays for detecting P. knowlesi infection.
The recombinant pkHSPATR protein allows sensitive detection of human P. knowlesi infection in serum samples by immunoblot and ELISA.
With further research, recombinant pkHSPATR protein could be exploited as a marker for detection of P. knowlesi infection in humans. Therefore, this finding should contribute to the development of immunodiagnostic assays for the species-specific detection of malaria.
疟原虫 knowlesi 是第五种被发现可导致人类疟疾的疟原虫，由于形态相似，常被误诊为疟原虫 malariae。开发一种利用针对疟原虫 knowlesi 的特异性抗体的廉价血清学检测方法将是一种有价值的诊断工具。然而，鉴定这些寄生虫的特异性抗原仍然是生成此类检测方法的主要挑战。在这项研究中，从疟原虫 knowlesi 中选择了含有改变的血栓反应蛋白重复结构域（SPATR）的表面蛋白作为潜在的特异性抗原。它在孢子体、无性红细胞期和配子体中的多阶段表达，以及其在肝细胞入侵中的可能作用，表明 SPATR 可作为诊断疟原虫 knowlesi 的生物标志物。
对疟原虫 knowlesi 的 spatr 基因进行密码子优化和克隆（pkhspatr）。表达重组 pkHSPATR 蛋白，并在免疫印迹和 ELISA 检测中评估其在检测疟原虫 knowlesi 感染中的敏感性和特异性。
重组 pkHSPATR 蛋白可通过免疫印迹和 ELISA 灵敏地检测人血清中的疟原虫 knowlesi 感染。
通过进一步研究，重组 pkHSPATR 蛋白可被开发为检测人类疟原虫感染的标志物。因此，这一发现应该有助于针对疟疾特异性检测的免疫诊断检测方法的开发。
