Antimalarial Drug Resistance in P. falciparum

耐多药(MDR)恶性疟原虫是全球疟疾死灰复燃的部分原因。随着许多抗疟疾药物的失败，大多数疟疾流行国家已经转向基于青蒿素的联合疗法(ACTS)。虽然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敏感性降低的情况引起了极大的关注。虽然早期耐药性检测对于阻止和遏制耐药性是必不可少的，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检测。对青蒿素的确切作用模式和耐药机制缺乏了解，使青蒿素部署地区的耐药性监测非常困难。为了解决这个紧迫的问题，我们选择了泰国、中国的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。耐多药寄生虫的流行，青蒿素的广泛使用，通常作为单一疗法，以及在寄生虫种群中检测到对青蒿素的敏感性降低，表明该地区可能出现青蒿素耐药性。在这项研究中，我们建议1)系统地采集恶性疟原虫临床分离株的样本，并准确地确定它们对包括青蒿素在内的一系列抗疟疾药物的体外敏感性；2)使用候选基因和全基因组关联研究方法来确定青蒿素耐药性与基因组多态的相关性；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)建立检测导致青蒿素耐药性的突变的分子方法(S)，并进行耐药标记S的现场监测。 全面的抽样方案、准确的体外药物分析和GWAS的整合将为阐明青蒿素耐药性的机制、了解青蒿素耐药性的演变以及促进设计分子方法以密切监测ACT部署地区的耐药性发展提供必要的信息。

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.