Effector and regulatory T cell responses and protection from clinical malaria

描述（由申请人提供）：迫切需要有效的疟疾疫苗，但由于我们对疟疾免疫机制的了解有限以及缺乏可靠的体外保护相关物，阻碍了这一目标的进展。最近的研究表明，通过在抗疟药物的“掩护”下用活的子孢子进行实验性感染，可以实现对疟疾的保护性免疫，这种药物可以消灭血液期寄生虫，但允许红细胞前期寄生虫发育。该方案诱导产生IL-2、TNFα和IFNγ的CD 4 T细胞，并导致对同源攻击的无菌保护，持续至少2年。在上一个融资期，我们测试了假设 在乌干达对幼儿进行每月一次的双氢青蒿素-哌喹（DP）化学预防的随机试验，在高度流行的环境中，化学预防加上自然接触疟疾可以产生类似的保护作用。我们发现，在干预结束后的一年随访期间，高度遵守每月DP的儿童表现出对自然发生的疟疾毒株的持续保护。随机分配至DP组的儿童出现了更高频率的疟疾特异性CD 4 T细胞共产生IL-2/TNFα，这与前瞻性保护相关，以及更低频率的CD 4细胞共产生IL 10/IFNγ，这与风险增加相关。这些数据表明，CD 4 T细胞应答的功能质量受到化学预防的影响，并且是保护性免疫的关键决定因素。在更新期，我们希望通过利用目前正在进行的一项新试验的样本和数据，更全面地描述与保护相关的T细胞反应的功能、表型和转录差异，在该试验中，孕妇及其婴儿被随机接受每月一次DP化学预防在怀孕期间和生命的前2年。我们将评估慢性疟疾抗原暴露如何影响CD 4 T细胞和Vδ2+ γδ T细胞，Vδ2 + γδ T细胞是一种对疟疾抗原具有内在反应性的半先天淋巴细胞群体。在第一个目标中，我们将描述与每月接受DP化学预防的儿童中疟疾保护相关的CD 4 T细胞应答，并确定疟疾特异性CD 4细胞的表型，功能和转录程序如何受到慢性疟疾抗原暴露的影响。在第二个目标中，我们将确定疟疾暴露如何影响Vγ 9VS 2 T细胞群体，包括它们的频率、分化状态、克隆型组成以及活化和抑制性NK受体（NKRs）的表达。我们还将研究NKR表达对疟疾抗原功能反应的影响。在第三个目标中，我们将测量疟疾特异性T细胞应答（CD 4和Vγ9Vδ2）与免受恶性疟原虫寄生虫血症和症状性疟疾的保护之间的关联。这些研究将解决我们对疟疾保护性免疫背后的细胞和分子机制的理解的根本差距，并可以为在怀孕期间或婴儿早期实施疟疾化学预防提供强有力的公共卫生理由。

DESCRIPTION (provided by applicant): An effective malaria vaccine is urgently needed, but progress toward this goal has been hindered by our limited understanding of the mechanisms underlying immunity to malaria and a lack of reliable in vitro correlates of protection. It has recently been shown that protective immunity to malaria can be achieved by experimental infection with viable sporozoites under "cover" of antimalarial drugs that eradicate blood-stage parasites but allow the pre-erythrocytic parasite stages to develop. This regimen induces CD4 T cells that produce IL-2, TNFα, and IFNγ and results in sterile protection from homologous challenge that persists for at least 2 years. In the prior funding period, we tested the hypothesis that chemoprevention coupled with natural exposure to malaria could yield similar protection when given to children in a high endemnicity setting, leveraging a randomized trial of monthly dihydroartemisinin-piperaquine (DP) chemoprevention given to young children in Uganda. We found that children highly adherent to monthly DP exhibited sustained protection against naturally occurring malaria strains during one year of follow-up after the intervention ended. Children randomized to DP developed higher frequencies of malaria-specific CD4 T cells co-producing IL-2/TNFα, which were associated with prospective protection, and lower frequencies of CD4 cells co-producing IL10/IFNγ, which were associated with increased risk. These data suggest that the functional quality of the CD4 T cell response is influenced by chemoprevention and is a critical determinant of protective immunity. In the renewal period, we wish to more fully characterize the functional, phenotypic, and transcriptional differences in T cell responses associated with protection by leveraging samples and data from a new trial, currently underway, in which pregnant women and their infants are randomized to receive monthly DP chemoprevention during pregnancy and the first 2 years of life. We will assess how chronic malaria antigen exposure impacts both CD4 T cells and Vδ2+ γδ T cells, a semi-innate lymphocyte population with intrinsic reactivity to malaria antigens. In the first aim, we will characterize CD4 T cell responses associated with protection from malaria in children receiving monthly DP chemoprevention, and determine how the phenotype, function, and transcriptional program of malaria-specific CD4 cells is impacted by chronic malaria antigen exposure. In the second aim, we will determine how malaria exposure impacts the Vγ9Vδ2 T cell population, including their frequency, differentiation status, clonotype composition, and expression of activating and inhibitory NK receptors (NKRs). We will also examine the impact of NKR expression on functional responsiveness to malaria antigens. In the third aim, we will measure associations between malaria-specific T cell responses (CD4 and Vγ9Vδ2) and protection from P. falciparum parasitemia and symptomatic malaria. These studies will address fundamental gaps in our understanding of the cellular and molecular mechanisms underlying protective immunity to malaria, and could provide a strong public health rationale for implementing malaria chemoprevention during pregnancy or early infancy.