Host Immune Responses to Antigens of Malaria Parasites

宿主对疟疾寄生虫抗原的免疫反应

基本信息

批准号：
7732670
负责人：
Carole Long
金额：
$ 59.95万
依托单位：
NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES
依托单位国家：
美国
项目类别：
财政年份：
资助国家：
美国
起止时间：
至
项目状态：
未结题

项目摘要

During the past fiscal year the Long laboratory has continued to integrate into the Laboratory of Malaria and Vector Research (LMVR) and to expand our investigations into the interface between the malaria parasite and the host innate and adaptive immune systems. To accomplish this we have employed both clinical research studies in Mali and several different rodent models of malaria infection. In this context we have continued our ongoing analyses of animal and human sera directed to malaria parasite antigens using a standardized parasite growth inhibition assay (GIA) that we have developed. Results from preclinical and clinical trials using this assay have contributed significantly to decisions about clinical development of various blood-stage antigens. In addition, we have explored the interaction of anti-merozoite antibodies of different specificities. We had previously shown that naive US volunteers vaccinated with AMA1 produce antibodies which inhibit merozoite invasion. However, when the same formulation was taken to Mali for a similar clinical trial in adults, antibodies were elicited by the vaccine but no increase in the GIA was seen. In collaboration with Dr. Kazutoyo Miura of MVDB, we tested two hypotheses: 1) that the antibodies produced by malaria-experienced Africans were qualitatively different so that they were not effective in GIA, or 2) that other antibodies in the sera of malaria experienced Africans interfered with the biological activity of the anti-AMA1 antibodies. We affinity purified AMA1 specific antibodies from US and Malian sera and, while there were small differences, we showed that in general anti-AMA1 antibodies elicited by vaccination or by infection with parasites had comparable biological activity. We then addressed the second hypothesis and showed that non-AMA1 IgGs from Malians could interfere with the GIA activity of anti-AMA1 antibodies of Malians or US volunteers. These results likely explain the failure to see increased GIA in immunized Africans and also have implications for laboratory evaluation of blood stage malaria vaccine trials. We also propose that this interference by other anti-malaria antibodies is a mechanism by which the parasite maintains a balance within the vertebrate host. Finally,we have begun to apply the GIA assay as a research tool to identify novel erythrocytic-stage vaccine candidates. On the cellular level we have established techniques for analysis of human and mouse CD4+ T cell responses to malaria antigens including identification of T memory cells, T cells with a regulatory phenotype, and Th17 cells. For the rodent studies, we have collaborated with Drs. James Burns and Robert Seder in identifying and characterizing multifunctional CD4+ T lymphocytes specific for P. yoelii MSP8. We are now determining the fate of these cells, which produce more than one cytokine, after parasite infection. We are also extending these studies to other parasite antigens and to other rodent models of malaria infection. In regard to CD4+ T cells in humans, we have continued to refine the analysis of different cell subtypes including T memory cells and multifunctional T cells. We have completed a study of kinetics of CD4+ T cell responses to AMA1 in a clinical trial and we are currently completing analysis of another clinical trial employing Alhydrogel with CPG. To extend these studies to malaria endemic areas, we have collaborated with Dr. Rick Fairhurst of LMVR and Dr.Mahamadou Diakite to initiate a longitudinal study of 1260 children of various ages in 3 villages in Mali. A subset of these children is being followed for in depth T cell responses, as well as development of humoral immune responses. In addition, we have initiated studies on innate immune responses in these children.

在过去的会计年度中，长实验室继续纳入疟疾和媒介研究实验室（LMVR），并扩大我们对疟原虫寄生虫与宿主先天和适应性免疫系统之间界面的研究。为了实现这一目标，我们已经在马里进行了临床研究和疟疾感染的几种不同啮齿动物模型。在这种情况下，我们继续使用我们开发的标准化寄生虫生长抑制测定法（GIA）对动物和人类血清进行的动物和人类血清进行了持续的分析。使用该测定法的临床前和临床试验的结果对各种血液阶段抗原的临床发展做出了重大贡献。此外，我们还探索了不同特异性的抗杂化抗体的相互作用。我们先前曾表明，幼稚的美国志愿者接种了AMA1的疫苗会产生抑制梅罗洛罗兹入侵的抗体。但是，当将相同的配方带到马里进行成人类似的临床试验时，疫苗会引起抗体，但观察到GIA的增加。通过与MVDB的Kazutoyo Miura博士合作，我们检验了两个假设：1），疟疾经验丰富的非洲人产生的抗体在质量上有所不同，因此它们在GIA中没有有效，或者2）其他抗体在马拉里亚的Sera of Malaria经验丰富的非洲人对Antibib的生物学Antibib的生物学活动。我们从美国和马里血清中纯化了AMA1特异性抗体，虽然存在很小的差异，但我们表明，通常，通过疫苗接种或通过寄生虫感染引起的一般抗MAMA1抗体具有相当的生物学活性。然后，我们解决了第二个假设，并表明来自马里人的非MAMA1 IgG可以干扰马里人或美国志愿者的抗MAMA1抗体的GIA活性。这些结果可能解释了免疫非洲人中GIA的增加，并且对血液期疟疾疫苗试验的实验室评估有影响。我们还建议，其他抗马拉里亚抗体的这种干扰是一种机制，寄生虫在脊椎动物宿主中保持平衡。最后，我们开始将GIA分析作为研究工具，以识别新型的红细胞疫苗候选物。在细胞水平上，我们建立了用于分析人和小鼠CD4+ T细胞对疟疾抗原的反应的技术，包括鉴定T记忆细胞，具有调节表型的T细胞和TH17细胞。对于啮齿动物的研究，我们与Drs合作。詹姆斯·伯恩斯（James Burns）和罗伯特·塞德（Robert Seder）在识别和表征对P. yoelii MSP8的多功能CD4+ T淋巴细胞的表征。现在，我们正在确定寄生虫感染后产生多种细胞因子的这些细胞的命运。我们还将这些研究扩展到其他寄生虫抗原和其他疟疾感染的啮齿动物模型。关于人类的CD4+ T细胞，我们继续完善对包括T记忆细胞和多功能T细胞在内的不同细胞亚型的分析。我们已经完成了一项在临床试验中对CD4+ T细胞对AMA1反应的动力学的研究，目前我们正在完成对使用CPG Alhydrogel的另一项临床试验的分析。为了将这些研究扩展到疟疾流行区域，我们与LMVR的Rick Fairhurst博士和Mahamadou Diakite博士合作，开始了对马里3个村庄的1260名不同年龄段的1260名儿童进行纵向研究。在深度T细胞反应以及体液免疫反应的发展中遵循这些儿童的一部分。此外，我们还开始了这些儿童先天免疫反应的研究。