Plasmodium ovale hypnozoite development and relapse: a coordinated in vivo in vitro study

卵形疟原虫休眠子的发育和复发：体内体外协调研究

基本信息

批准号：
10304203
负责人：
John H Adams
金额：
$ 17.68万
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：
2020
资助国家：
美国
起止时间：
2020-11-17 至 2024-10-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/10304203
关键词：
Accounting Address Africa Aminoquinolines Anemia Anopheles gambiae Antibodies Antimalarials Area Asia Biological Assay Biology Blood Cessation of life Child Chronic Clinical Cohort Studies Country Cryopreservation Culicidae Data Detection Development Enrollment Entomology Epidemiology Exhibits Florida Frequencies Funding Gabon Genetic Variation Genotype Health Hepatocyte Hospitalization Human Image Immunity In Vitro Incidence Individual Infection Intervention Liver Malaria Malaria Diagnostic Measures Meiosis Methods Minority Modeling Molecular North Carolina Parasites Patients Pattern Persons Pharmaceutical Preparations Phenotype Plasmodium Plasmodium falciparum Plasmodium ovale Plasmodium vivax Play Prevalence Primaquine Prospective Studies Recurrence Regimen Relapse Research Personnel Science Ships Siblings Site Sleep South America Sporozoites Tanzania Testing Time Universities Variant Vivax Malaria Work deep sequencing design drug development epidemiologic data experimental study feeding follow-up in vivo malaria transmission molecular diagnostics neglect neglected tropical diseases novel prevent recurrent infection targeted sequencing tool volunteer

项目摘要

ABSTRACT Malaria control interventions focused on P. falciparum are not adequate to address the growing burden of non- falciparum species, especially those malaria species that cause relapse. Plasmodium ovale, like P. vivax, causes recurrent infections arising from hypnozoites in the liver. Hypnozoites “sleeping” in the liver before they reactivate to cause relapse are invisible to malaria diagnostics and impervious to first-line ACT regimens. Thus they likely play a key role in the rising number of P. ovale cases across Africa, estimated to exceed 15 million cases each year. Almost nothing is known about P. ovale hypnozoites and their relapse patterns. We have only recently learned that P. ovale in fact comprises two non-recombining species - P. ovale curtisi and P. ovale wallikeri. Interestingly, these two species may exhibit distinct relapse patterns, suggesting species- specific hypnozoite biology. However, the little evidence available regarding the two species’ relapse patterns is confusing: epidemiologic data in travelers suggest that P.o. wallikeri relapses occur at shorter intervals, but the first prospective study of P. ovale in Africa only found relapses due to P.o. curtisi, not wallikeri. We aim to resolve this question by examining in vivo relapse phenotypes for both species as well as directly measuring hypnozoite commitment in vitro. We hypothesize that both P. ovale curtisi and wallikeri develop hypnozoites and relapse in a species-specific manner. To test our hypothesis, we will deploy tools built to study P. vivax. Using targeted sequencing methods designed to distinguish relapses from re-infections in endemic settings developed by investigators at the University of North Carolina, and a state-of-the-art 384-well primary human hepatocyte platform for studying Plasmodium liver stages developed at the University of South Florida, we will 1) Conduct an observational cohort study to define species-specific relapse rates of P.o. curtisi and wallikeri and 2) Establish a liver stage model for P. ovale to evaluate hypnozoite commitment in both species. We will conduct the fieldwork for this proposal within the framework of a larger R01-funded malaria transmission study in Bagamoyo, Tanzania. This will allow us to leverage the significant molecular and entomologic capacity we have developed there, where we have already successfully infected Anopheles gambiae mosquitoes with P.ovale. In partnership with the Muhimbili University of Health and Allied Sciences, we will identify 40 volunteers with qPCR-positive P. ovale infection, follow them every 2 weeks to genotype any recurrences that occur over 8-12 months, and conduct mosquito feeding assays to generate 15-20 P. ovale sporozoite isolates using blood-fed mosquitoes from the same volunteers. Cryopreserved infectious sporozoites will be shipped to the USF, where liver-stage experiments will be performed to measure hypnozoite commitment (the ratio of developing schizonts to small-form hypnozoites) and to test anti- hypnozoite drugs. This study will establish the first liver-stage model of P. ovale. Findings will crucially inform the development of drugs and strategies to achieve the elimination of all malaria, not just P. falciparum.

抽象的以恶性疟为重点的疟疾控制干预措施不足以解决非疟疾日益严重的负担恶性疟原虫，特别是那些导致复发的疟原虫，如间日疟原虫，引起由肝脏中的休眠子引起的反复感染。重新激活导致复发对于疟疾诊断来说是不可见的，并且对于一线 ACT 治疗方案也无影响。它们可能在非洲卵形疟原虫病例数量不断增加的过程中发挥了关键作用，估计超过 1500 万例我们对卵形潜孢子及其复发模式几乎一无所知。直到最近才得知，P. ovale 实际上包含两个非重组物种 - P. ovale curtisi 和 P. ovale curtisi。卵形wallikeri暗示，这两个物种可能表现出不同的复发模式，表明物种- 然而，关于这两个物种的复发模式的证据很少。令人困惑的是：旅行者的流行病学数据表明，P.o. 复发的时间间隔较短。非洲第一项针对 P. ovale 的前瞻性研究仅发现 P.o curtisi 引起的复发，而不是 wallikeri。通过检查两个物种的体内复发表型以及直接测量来解决这个问题我们勇敢地发现 P. ovale curtisi 和 wallikeri 都会发育。为了检验我们的假设，我们将部署专门构建的工具。研究间日疟原虫使用旨在区分复发和再次感染的靶向测序方法。由北卡罗来纳大学研究人员开发的流行环境和最先进的 384 孔南方大学开发的用于研究疟原虫肝脏阶段的主要人类肝细胞平台佛罗里达州，我们将 1) 进行一项观察性队列研究，以确定 P.o. curtisi 的物种特异性复发率。和 wallikeri 以及 2) 建立 P. ovale 的肝脏阶段模型，以评估两者的催眠作用我们将在 R01 资助的更大的疟疾框架内开展本提案的实地调查。在坦桑尼亚巴加莫约进行的传播研究这将使我们能够利用重要的分子和我们在那里开发了昆虫学能力，我们已经成功感染了按蚊冈比亚蚊子与 P.ovale 与 Muhimbili 健康与相关科学大学合作，我们将鉴定 40 名 qPCR 阳性 P. ovale 感染志愿者，每 2 周对他们进行一次跟踪，以对任何人进行基因分型 8-12 个月内发生的复发，并进行蚊子喂养试验以产生 15-20 P. ovale 使用来自同一志愿者的血液喂养的蚊子分离出子孢子。子孢子将被运送到南佛罗里达大学，在那里将进行肝脏阶段实验来测量催眠体承诺（发育中的裂殖体与小型催眠体的比率）并测试抗这项研究将建立第一个 P. ovale 肝脏阶段模型。为药物开发和战略提供信息，以实现消除所有疟疾，而不仅仅是恶性疟原虫。