Discovery of chemically validated malaria liver stage targets

描述(申请人提供)：由于血液期感染会导致疟疾的大多数临床表现，药物开发主要集中在针对恶性疟原虫的分裂药物的开发，恶性疟原虫是人类最严重形式的疟疾的病原体。资金的增加和人们对寄生虫耐药性问题的日益认识，帮助推动了一些新的精神分裂症药物进入开发流程，甚至是临床试验。另一方面，这些候选药物中几乎没有几个对红外期疟疾有效，更没有几个可能提供根治间日疟的药物。随着根除疟疾成为世界卫生界的更高优先事项，对可作为伯喹替代品的药物的需求更加迫切。为了刺激针对肝期的药物开发活动，需要更多的工作来了解肝期生物学，并发现其活性对肝脏和血期发育至关重要的靶点。我将使用化学遗传学方法来研究对血液和肝脏寄生虫发育至关重要的途径，然后描述通过这种方法揭示的靶标(S)的特征。具体地说，我将在亚致死浓度的小分子下培养寄生虫，这些小分子对血液和肝脏阶段的寄生虫具有活性，直到寄生虫对小分子获得低水平的抵抗力。我将使用基因组扫描来确定可能的目标(S)。突变将被改造成敏感的寄生虫菌株，以证明它们会引起抗药性。可能的靶点将使用免疫和电子显微镜以及定位研究以及干扰研究来进一步表征。这项工作可能有助于更好地理解如何治疗组织期疟疾，提供新的抗生素耐药基因，并提供有关真核病原体如何对药物产生抗药性的信息。 与公共卫生相关：许多抗疟疾药物可以缓解症状，但不一定能完全治愈，因为一些疟疾寄生虫能够在肝脏中无症状地存活数月或数年。无法消除隐蔽的肝脏形式给根除疟疾造成了障碍。我们建议寻找对肝脏分期和血液分期至关重要的新靶点，长期目标是设计更好的药物。

DESCRIPTION (provided by applicant): Because blood stage infections produce most clinical manifestations of malaria, drug development has primarily focused on the development of schizonticides targeting Plasmodium falciparum, the causative agent of the most severe form of human malaria. Increased funding and a growing awareness of the problem of parasite resistance have helped to push a number of new schizonticides into the developmental pipeline and even clinical trials. On the other hand, few of these drug candidates are effective against malaria exoerythrocytic stages, and even fewer are likely to provide a radical cure for P. vivax malaria. The need for drugs which can act as a replacement for primaquine is even more urgent as malaria eradication becomes a higher priority for the world health community. In order to stimulate drug development activity against hepatic stages, more work is needed to understand hepatic stage biology and to discover targets whose activity is essential for both hepatic and blood stage development. I will use a chemical genetic approach to investigate pathways that are critically essential to both blood and hepatic parasite development and then characterize the target(s) revealed by this approach. Specifically, I will grow parasites under sub-lethal concentrations of small molecules with activity against blood and hepatic stage parasites until the parasites acquire low level resistance to the small molecules. I will use genome-scanning to determine the likely target(s). Mutations will be engineered into sensitive parasite strains to prove that they cause resistance. Likely targets will be further characterized using immuno and electron microscopy and localization studies, as well as disruption studies. The work may lead to a better understanding of how to treat tissue stage malaria, provide new antibiotic resistance genes, and provide information about how eukaryotic pathogens become resistant to drugs. PUBLIC HEALTH RELEVANCE: Many antimalarial drugs alleviate symptoms but do not necessarily result in a complete cure because some malaria parasites are able to persist asymptomatically in the liver for months or years. The inability to eliminate cryptic liver forms creates a barrier to malaria eradication. We propose to find new targets that are critical to the liver stages as well as the blood stages with the long term aim of designing better drugs.