Unravelling disease tolerance and host resistance in afebrile P. falciparum infections: a prospective study in Mozambican adults

摘要 无症状恶性疟原虫（Pf）感染削弱了受影响人口的健康， 这是一个隐藏的寄生虫传播源，可能会损害消除工作。缺乏 关于处理这种无症状水库的最佳策略的共识部分是由于知识不足 这些亚临床感染的生物学机制。莫桑比克的初步结果 表明通过快速诊断测试检测到Pf感染的无发热成年人可以发展为发热（10%）， 清除感染（20%）并稳定在低密度（50%）或高密度（20%）寄生虫血症。我们 假设这四个主要轨迹是由针对Pf变体抗原的抗体驱动的， 通过var基因家族，并在感染的红细胞表面表达，这将清除 感染，除非寄生虫发展免疫逃避机制，并通过耐受因素， 寄生虫引起的病理和维持宿主的稳态。总体目标是确定关键的 维持无发热疟疾感染的生物因素，本项目将建立一个无发热疟疾感染的队列。 对莫桑比克成年人进行为期一个月的随访，以确定能够减少病原体负荷的受试者， 最终清除感染，那些维持高密度和无发热水平的感染者（耐受）， 以及那些未能建立疾病耐受性并发展为发烧的人。我们将量化循环和 总体寄生虫生物量，并使用下一代测序在随访期间识别新感染。 来自低和高寄生虫密度个体的临床样本将用于测试 无热性Pf感染的寄生虫学轨迹与宿主抗红细胞抗体免疫相关 Pf var基因的转录参与细胞粘附和免疫逃避（Aim 1）。将对来自无发热患者的临床样本进行飞行时间细胞计数和全局质谱分析。 具有高寄生虫密度的个体（耐受性）和那些进展到发烧的个体（非耐受性），以确定 白细胞群和代谢途径参与炎症、组织损伤的调节 以及在无发热水平上支持宿主-寄生虫关系的normophosphate（目标2）。我们将验证这些 结果使用了一组独立的样本，这些样本来自乌干达的儿童和成人队列， 疟疾发病率和寄生虫流行率的纵向计量。该项目将有助于 发展Manhiça健康研究中心的科学能力，并为未来建立一个样本库 调查无热疟疾感染期间宿主和寄生虫的相互作用（目标3）。预期 该项目的结果是确定了无热性Pf感染的关键分子驱动因素， 了解这些感染在不同传播环境中的相关性， 特定环境的控制方法，以及开发新的工具，以实现消毒 提高免疫力和抗病能力。

ABSTRACT Asymptomatic Plasmodium falciparum (Pf) infections debilitate the health of affected population while representing a hidden source of parasite transmission that can compromise elimination efforts. The lack of consensus on the best strategy to deal with this asymptomatic reservoir is partly due to the poor knowledge on the biological mechanisms underlying these subclinical infections. Preliminary results in Mozambique show that afebrile adults with a Pf infection detected by rapid diagnostic tests can progress to fever (10%), clear the infection (20%) and stabilize at low-density (50%) or high-density (20%) parasitemias. We hypothesize that these four main trajectories are driven by antibodies against Pf variant antigens, codified by the var gene family and expressed on the surface of infected erythrocytes, which would clear the infection unless the parasites develop immune evasion mechanisms, and by tolerance factors that minimize parasite-induced pathology and sustains host homeostasis.With the overarching goal of identifying key biological factors sustaining afebrile malaria infections, this project will establish a cohort of afebrile Mozambican adults followed during one month to identify subjects who can reduce pathogen load and eventually clear the infection, those who maintain infections at high-density and afebrile levels (tolerant), and those who fail to establish disease tolerance and progress to fever. We will quantify circulating and overall parasite biomass, and identify new infections during follow-up using next-generation sequencing. Clinical samples from individuals with low and high parasite densities will be used to test whether parasitological trajectories of afebrile Pf infections correlate with host antibody immunity against erythrocyte surface antigens and the transcription of Pf var genes involved in cytoadhesion and immune evasion (Aim 1). Cytometry by time of flight and global mass spectrometry will be applied on clinical samples from afebrile individuals with high parasite densities (tolerant) and those progressing to fever (non-tolerant) to identify leukocyte populations and metabolic pathways involved in the regulation of inflammation, tissue damage and normoglycemia that support host-parasite relationships at afebrile levels (Aim 2). We will validate these results using an independent set of samples obtained from a Ugandan cohort of children and adults with longitudinal measurement of malaria incidence and parasite prevalence. This project will contribute to develop scientific capacity at the Manhiça Health Research Center and create a sample repository for future investigations on host and parasite interactions during afebrile malaria infections (Aim 3). The expected outcome of this project is the identification of key molecular drivers of afebrile Pf infections for a better understanding of the relevance of these infections in different transmission setting which may require context-specific control approaches, as well as for the development of new tools to achieve sterilizing immunity and enhance disease tolerance.