Antimalarial Drug Resistance in P. falciparum

多重耐药（MDR）恶性疟原虫是全球疟疾死灰复燃的部分原因。由于许多抗疟药物失效，大多数疟疾流行国家已改用青蒿素类复方疗法。虽然青蒿素综合疗法非常有效，但最近在东南亚几个地区发现恶性疟原虫对青蒿素的敏感性降低，引起了极大的关注。虽然早期耐药性检测对于阻止和遏制耐药性至关重要，但目前对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。由于对青蒿素的确切作用方式和耐药性机制缺乏了解，在青蒿素部署地区进行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我们调查青蒿素耐药性的战略地点。东南亚一直是抗药性疟疾寄生虫的中心。多药耐药寄生虫的流行，青蒿素的广泛部署往往作为单一疗法，并检测到寄生虫种群对青蒿素的敏感性降低，表明青蒿素耐药性很可能在这一地区出现。在本研究中，我们提出1）系统地采集恶性疟原虫临床分离株并准确测定其对包括青蒿素在内的一组抗疟药物的体外敏感性; 2）使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;以及4）开发用于检测导致青蒿素抗性的突变的分子方法，并对抗性标记进行实地监测。 综合全面的采样计划、准确的体外药物分析和全球WAS将为阐明青蒿素耐药性机制、了解青蒿素耐药性如何演变以及促进设计分子方法以密切监测青蒿素综合疗法部署地区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.