Antimalarial Drug Resistance in P. falciparum

多重耐药（MDR）恶性疟原虫是全球疟疾卷土重来的部分原因。随着许多抗疟药物的失败，大多数疟疾流行国家已改用基于青蒿素的联合疗法（ACT）。尽管 ACT 非常有效，但最近在东南亚几个地区检测到恶性疟原虫对青蒿素的敏感性降低，引起了人们的极大关注。尽管早期耐药性检测对于阻止和遏制耐药性至关重要，但目前青蒿素耐药性的检测完全依赖于临床观察和体外药物测定。由于缺乏对青蒿素确切作用方式和耐药机制的了解，使得青蒿素部署地区的耐药性监测非常困难。为了解决这一紧迫问题，我们选择了泰国、中国云南和缅甸作为研究青蒿素耐药性的战略地点。东南亚一直是耐药疟疾寄生虫的中心。耐多药寄生虫的流行、青蒿素通常作为单一疗法的广泛使用以及寄生虫群体对青蒿素敏感性降低的检测表明，该地区可能会出现青蒿素耐药性。在这项研究中，我们建议：1）系统地对恶性疟原虫临床分离株进行取样，并准确确定其对包括青蒿素在内的一组抗疟药物的体外敏感性； 2）利用候选基因和全基因组关联研究（GWAS）方法确定青蒿素耐药性与基因组多态性的相关性； 3）通过等位基因交换实验验证候选基因内有希望的突变； 4) 开发分子方法来检测导致青蒿素耐药的突变并对耐药标记进行现场监测。 全面的采样方案、准确的体外药物测定和 GWAS 的整合将为阐明青蒿素耐药机制、了解青蒿素耐药性如何演变以及促进分子方法的设计以密切监测 ACT 部署领域的耐药性发展提供重要信息。

Multidrug-resistant (MDR) Plasmodium falciparum is partially responsible for the global resurgence of malaria. With the failing of many antimalarial drugs, most malaria-endemic countries have changed to artemisinin-based combination therapies (ACTs). Although ACT is highly effective, recent detection of reduced sensitivity in P. falciparum to artemisinins in several regions of Southeast Asia has raised great concerns. Although early resistance detection is essential for deterring and containing resistance, current detection of artemisinin resistance relies exclusively on clinical observations and in vitro drug assays. The lack of understanding of the exact mode of action and the mechanism of resistance for artemisinins makes resistance surveillance in areas of artemisinin deployment very difficult. To address this urgent problem, we have selected Thailand, China's Yunnan and Myanmar as our strategic sites to investigate artemisinin resistance. Southeast Asia has been the epicenter of drug resistant malaria parasites. The prevalence of MDR parasites, extensive deployment of artemisinins often as monotherapy, and the detection of reduced susceptibility to artemisinins among parasite populations suggest that artemisinin resistance is likely to arise in this region. In this study, we propose to 1) systematically sample P. falciparum clinical isolates and accurately determine their in vitro sensitivity to a panel of antimalarial drugs including artemisinins; 2) determine the correlations of artemisinin-resistance with polymorphisms in the genome using both candidate gene and genome-wide association study (GWAS) approaches; 3) validate promising mutations within candidate genes through allelic exchange experiments; and 4) develop molecular methods for detecting the mutation(s) responsible for artemisinin resistance and perform field surveillance of the resistance marker(s). The integration of a comprehensive sampling scheme, accurate in vitro drug assays and GWAS will provide essential information for elucidating the mechanism of artemisinin resistance, understanding how artemisinin resistance evolves, and facilitating the design of molecular methods to closely monitor resistance development in areas of ACT deployment.