Variation in Resistance and Fitness to Artemisinins in African Malaria

非洲疟疾对青蒿素的耐药性和适应性的变化

基本信息

批准号：
9010406
负责人：
Jonathan J Juliano
金额：
$ 67.54万
依托单位：
UNIV OF NORTH CAROLINA CHAPEL HILL
依托单位国家：
美国
项目类别：
财政年份：
2015
资助国家：
美国
起止时间：
2015-12-01 至 2020-11-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/9010406
关键词：
Affect Africa African Antimalarials Area Artemisinins Asia Biological Assay CRISPR/Cas technology Characteristics Child Clinical Coculture Techniques Combined Modality Therapy Containment Data Disasters Drug resistance Early Diagnosis Ensure Evolution Failure Falciparum Malaria Frequencies Gene Combinations Generations Genes Genetic Genetic Polymorphism Growth In Vitro Individual Infection Investigation Kenya Laboratories Light Linear Models Malaria Masks Measures Membrane Metabolic Clearance Rate Methods Modeling Molecular Monitor Mutation Parasite resistance Parasites Patients Pharmacotherapy Phenotype Plasmodium falciparum Play Population Dynamics Predisposition Protocols documentation Public Health Resistance Role Sampling Site Staging Tanzania Techniques Testing Time Treatment Efficacy Variant Weight Work artemisinine chemotherapy cost deep sequencing drug efficacy efficacy testing feeding fitness global health in vivo insight killings malaria infection mathematical model meetings molecular marker novel novel strategies population survey public health relevance reproductive fitness research study reverse genetics tool transmission process

项目摘要

DESCRIPTION (provided by applicant) The emergence of drug resistant malaria parasites has been a major hurdle in the control of Plasmodium falciparum, which has evolved resistance to nearly every antimalarial drug in use. A major concern is the apparent emergence of resistance to the current front-line artemisinin derivatives, which could spark a global health crisis. In order to ensure the continued efficacy of these drugs, early detection of resistance, good surveillance, and containment are required. The current clinical tool for phenotyping parasites in the field and monitoring therapeutic efficacy of artemisinins is the parasite clearance curve. Parasites that have longer slower clearance times (longer half-lives) are considered more "resistant". Parasite clearance curves are less informative in regions with relatively high complexity of infection. This is because the parasite clearance curve is a whole-infection level measure that represents a weighted average of the clearance phenotypes of different parasites within that sample. In Africa, the majority of falciparum malaria infections are polyclonal meaning that resistant parasites are likely to share their host with sensitive parasites, particularly early during the spread of resistance. In these areas, the effects of resistant clones on infection-level estimates of resistance may therefore be obscured by the sheer number of sensitive parasites in an infection. In order to overcome this limitation, we previously proposed a novel approach that capitalizes on second generation sequencing in order to reveal phenotypic signatures of resistance among individual parasite clones that rise in relative abundance over the course of drug treatment in polyclonal infections. Using these new deep sequencing protocols, we confirmed this hypothesis, finding clones with clearance half-lives similar to artemisinin resistant parasites from Asia among Tanzanian isolates. Thus, emerging artemisinin resistance in Africa might go undetected using the standard clinical definition. None of the resistant clones identified in Tanzania contained polymorphisms in the kelch (K13) gene recently associated with high-level artemisinin resistance in Asia. Accordingly, these resistant clones would even go undetected by molecular surveillance. These findings suggest that clones with low-level resistance to artemisinins exist in Africa and will go undetected until they become dominant in a polyclonal infection. In this proposal, we seek to better characterize these African resistant clones. Our deep sequencing approach provides a novel framework for studying antimalarial resistance at this early stage and potentially the long-term evolution of artemisinin resistance in Africa. We will use it to confirm that slow clearance by these parasite clones is due to resistance rather than other clinical factors. With further investigation of these low frequency slow clearing clones and the functional significance of newly described novel African K13 mutations that may impact resistance, we have the chance to detect resistance prior to significant clinical failures in Africa and understan the ecological factors that may enhance or retard that spread.

描述（由申请人提供）抗药性疟疾寄生虫的出现一直是控制恶性疟原虫的重大障碍，疟原虫几乎进化出对使用的每种抗疟药的耐药性。一个主要的问题是，明显对当前一线青蒿素衍生物的抵抗力明显紧急，这可能引发全球健康危机。为了确保持续的效率需要这些药物，耐药性，良好的监测和遏制。当前用于现场表型寄生虫的临床工具，并监测青蒿素是寄生虫清除曲线。清除时间较长的寄生虫（更长的半衰期）被认为更“抗性”。在感染复杂性相对较高的地区，寄生虫清除曲线的信息较低。这是因为寄生虫清除曲线是整个感染水平度量，代表该样品中不同寄生虫的清除表型的加权平均值。在非洲，大多数恶性疟疾感染是多克隆的，这意味着抗性寄生虫可能与敏感的寄生虫共享宿主，尤其是在耐药性传播期间。因此，在这些地区，抗性克隆对感染水平抗性估计的影响可能会因感染中敏感的寄生虫数量而掩盖。为了克服这一局限性，我们先前提出了一种新的方法，该方法利用了第二代测序，以揭示单个寄生虫克隆之间抗药性的表型特征，这些克隆在多克隆感染中的药物治疗过程中相对抽象增加。使用这些新的深层测序方案，我们证实了这一假设，发现了具有清除半衰期类似于坦桑尼亚分离株中亚洲苯厄莫动蛋白抗性寄生虫的克隆。这是非洲新兴的青蒿素耐药性可能不会使用标准临床定义进行。坦桑尼亚鉴定出的抗性克隆都没有在最近与亚洲高级青蒿素耐药性相关的Kelch（K13）基因中包含多态性。彼此之间，这些抗药性克隆甚至不会通过分子监视而无法发现。这些发现表明，在非洲，直到它们在多克隆感染中占主导地位为止。在此提案中，我们寻求更好地描述这些非洲抗药性克隆。我们的深层测序方法为在这个早期阶段研究抗疟疾的抗药性提供了一种新颖的框架，并可能是阿昔逝抗药性在非洲的长期演变。我们将使用它来确认这些寄生虫克隆的缓慢间隙是由于抵抗而不是其他临床因素所致。通过进一步研究这些低频缓慢的清除克隆，以及新描述的新型非洲K13突变的功能意义，我们有机会在非洲发生重大临床失败之前检测抗药性，并了解可能增强或延伸的生态因素。