Cross-Protective Immunity to African Trypanosomes

对非洲锥虫的交叉保护性免疫

• 批准号: 8033918
• 负责人: John M. Mansfield
• 金额: $ 21.89万
• 依托单位: UNIVERSITY OF WISCONSIN-MADISON
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-01-15 至 2012-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8033918
• 关键词: Achievement; Africa; Africa South of the Sahara; African; African Trypanosomiasis; Amino Acid Sequence; Animals; Antigenic Variation; Antigens; B-Lymphocytes; Blood; Blood Vessels; C-terminal; Clinical; Coupled; DNA; Diagnosis; Disease; Elements; Genes; Genetic Transcription; Host resistance; Human; Immune; Immune response; Immunity; Immunization; Immunotherapeutic agent; Individual; Infection; Interferons; Laboratories; Link; Macrophage Activation; Mediating; Membrane Glycoproteins; Monitor; Mus; N-terminal; Organism; Parasite Control; Parasites; Patients; Peptide Sequence Determination; Preventive; Production; Recombinants; Relative (related person); Research Infrastructure; Resistance; Resolution; Site; Specificity; T cell response; T-Lymphocyte; Testing; Th1 Cells; Therapeutic; Therapeutic Intervention; Time; Tissues; Trypanosoma; Variant; Work; disorder control; glycoprotein structure; immune clearance; innovation; microbial; novel; novel strategies; pathogen; prevent; research study; response; tool

DESCRIPTION (provided by applicant): All successful microbial pathogens evade or alter host immune responses. Arguably the most well-known example of immune evasion by parasites is antigenic variation of the variant surface glycoprotein (VSG) coat by the African trypanosomes, which prevents immune elimination of the organisms from vascular and- extra vascular tissue sites of infection. VSG-specific B cell responses are associated with, and largely limited to, control of Parasites in the blood, but are VSG-specific Th1 cell responses that are functionally and genetically linked to relative resistance against trypanosomes. This resistance is mediated by IFN-? activation of macrophages for production of the trypanocidal factors RNI, ROS and TNFa In the extra vascular tissues. Thus, IFN-? production is critical for host survival but is largely dependent on Th1 cell recognition of VSG-specific epitomes. Ultimately, however, antigenic variation of the VSG coat leads to immune escape and trypanosome infections are invariably fatal for their hosts. Two recent achievements in our laboratory have opened a window of opportunity for immunological control or cure of African trypanosomiasis. The first is a discovery that temporally protective VSG-specific T cell responses are directed exclusively at highly variable N-terminal micro domains within the VSG molecule, and are not directed at residues within the highly conserved -terminal domain. Thus, VSG specific T cell responses are variant specific and do not cross-react with other VSGs that express homologous C-terminal domain sequences. This information provides a unique opportunity to artificially direct Th1 cell responses to conserved VSG sequences and to promote control or cure of infection. The second discovery is that by expressing an exogenous eGFP gene from a stable transcription site in trypanosome DNA, we are able for the first time to visualize viable trypanosomes within the extra vascular tissues and to monitor the efficacy of immunotherapeutic treatments for host resistance. These novel elements form the infrastructure for this proposal. The central hypothesis to be tested is that activation of T cell responses to conserved C-terminal residues of the trypanosome variant surface glycoprotein (VSG) molecule will promote variant cross- protective immunity to infection, leading to control or cure of disease. Aim 1 encompasses experiments in which natural, altered natural, recombinant and synthetic conserved C-terminal VSG subsequences will be used to provoke variant cross-specific Th1 cell responses in na¿ve mice. Immunized animals subsequently will be infected with different trypanosome variants expressing the conserved VSG residues. This aim will provide "proof of principle" for the central hypothesis. Aim 2 extends the work plan to experiments that have clinical translational potential. Treatment of mice already infected with African trypanosomes will be accomplished by immunization with invariant VSG cross- protective protein sequences identified in Aim 1. Animals will be monitored for resolution of infection coupled with activation of appropriate T cells with specificity for variant cross-protective sequences. This aim provides a hypothetical "real world test" for the central hypothesis, in which patients diagnosed with the disease could be rescued by intervention therapy. The ability to induce cross-variant specific T cell responses and parasite elimination in individuals already infected would have tremendous impact on clinical disease in Africa. Thus, the experiments proposed here provide, for the first time, a novel approach to the control or cure of a Third World disease that has proven intractable to every form of preventive or clinical therapy to date. PUBLIC HEALTH RELEVANCE: African trypanosomiasis (Human Sleeping Sickness) is a devastating Third World disease that is endemic throughout Sub-Saharan Africa. There is no natural cure for infection, primarily due to extensive antigenic variation of the parasite variant surface glycoprotein (VSG) coat. Further, all preventive and therapeutic strategies aimed at controlling the disease have been unsuccessful to date. Therefore the present proposal tests a novel approach and uses innovative new tools aimed at the induction and monitoring of variant cross-protective immunity to African trypanosomiasis, and findings relative to VSG structure/function will be applicable to other microbial infections in which infected hosts preferentially respond to variant rather than invariant residues of protective antigens.

描述（由申请人提供）：所有成功的微生物病原体都会逃避或改变宿主免疫反应。可以说，寄生虫免疫逃避的最著名的例子是非洲锥虫的变异表面糖蛋白（VSG）外壳的抗原变异，它阻止了生物体从血管和血管外组织感染部位的免疫消除。 VSG 特异性 B 细胞反应与血液中寄生虫的控制相关，并且在很大程度上仅限于控制血液中的寄生虫，但 VSG 特异性 Th1 细胞反应在功能和遗传上与对锥虫的相对抵抗力相关。这种抵抗是由 IFN-α 介导的。激活巨噬细胞，在维管外组织中产生杀锥虫因子 RNI、ROS 和 TNFa。因此，IFN-α生产对于宿主的生存至关重要，但很大程度上取决于 Th1 细胞对 VSG 特异性表位的识别。然而，最终，VSG 外壳的抗原变异会导致免疫逃逸，而锥虫感染对于宿主来说总是致命的。我们实验室最近取得的两项成果为免疫控制或治愈非洲锥虫病打开了机会之窗。第一个发现是，暂时保护性 VSG 特异性 T 细胞反应专门针对 VSG 分子内高度可变的 N 端微结构域，而不是针对高度保守的 N 端结构域内的残基。 因此，VSG 特异性 T 细胞反应是变体特异性的，并且不会与表达同源 C 端结构域序列的其他 VSG 发生交叉反应。该信息提供了一个独特的机会，可以人工引导 Th1 细胞对保守的 VSG 序列做出反应，并促进感染的控制或治愈。第二个发现是，通过从锥虫 DNA 中的稳定转录位点表达外源 eGFP 基因，我们首次能够可视化血管外组织内的活锥虫，并监测宿主抵抗免疫治疗的效果。这些新颖的元素构成了该提案的基础设施。待测试的中心假设是，激活 T 细胞对锥虫变异表面糖蛋白 (VSG) 分子保守 C 端残基的反应将促进针对感染的变异交叉保护性免疫，从而控制或治愈疾病。目标 1 包括使用天然的、改变的天然的、重组的和合成的保守 C 端 VSG 子序列在首次接触小鼠中激发变异的交叉特异性 Th1 细胞反应的实验。随后，免疫动物将被表达保守 VSG 残基的不同锥虫变体感染。这一目标将为中心假设提供“原理证明”。目标 2 将工作计划扩展到具有临床转化潜力的实验。对已经感染非洲锥虫的小鼠的治疗将通过使用目标 1 中确定的不变 VSG 交叉保护蛋白序列进行免疫来完成。将监测动物的感染消退以及对变异交叉保护序列具有特异性的适当 T 细胞的激活。这一目标为中心假设提供了一个假设的“现实世界测试”，其中诊断出患有该疾病的患者可以通过干预治疗来挽救。在已感染的个体中诱导跨变体特异性 T 细胞反应和消除寄生虫的能力将对非洲的临床疾病产生巨大影响。因此，这里提出的实验首次提供了一种控制或治愈第三世界疾病的新方法，迄今为止，这种疾病已被证明对每种形式的预防或临床治疗都难以解决。 公共卫生相关性：非洲锥虫病（人类昏睡病）是一种毁灭性的第三世界疾病，在整个撒哈拉以南非洲地区流行。感染没有自然治愈方法，主要是由于寄生虫变异表面糖蛋白 (VSG) 外壳的广泛抗原变异。此外，迄今为止，所有旨在控制该疾病的预防和治疗策略均未成功。因此，本提案测试了一种新颖的方法，并使用创新的新工具，旨在诱导和监测对非洲锥虫病的变异交叉保护性免疫，并且与 VSG 结构/功能相关的发现将适用于其他微生物感染，其中受感染的宿主优先对保护性抗原的变异残基而不是不变残基作出反应。