Antigen export in M. tuberculosis evasion of CD4 T cells

结核分枝杆菌逃避 CD4 T 细胞的抗原输出

• 批准号: 9318402
• 负责人: Joel D. Ernst
• 金额: $ 72.01万
• 依托单位: NEW YORK UNIVERSITY SCHOOL OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-07-20 至 2020-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9318402
• 关键词: Animal Model; Antigen Presentation; Antigen Presentation Pathway; Antigen Targeting; Antigens; Antimycobacterial Agents; Attenuated; Autophagocytosis; Bacteria; Bacterial Antigens; Bypass; CD4 Positive T Lymphocytes; Cell membrane; Cells; Clinical Trials; Data; Dendritic Cells; Development; Disease Progression; Dynamin; Effectiveness; Extracellular Space; Generations; Genus Mycobacterium; Goals; Histocompatibility Antigens Class II; Immune system; Immunodominant Antigens; Impairment; Infection; Infection Control; Kinesin; Lung; Manuscripts; Measures; Mediator of activation protein; Membrane; Microbe; Microtubules; Molecular; Molecular Motors; Mycobacterium tuberculosis; Pathway interactions; Phagosomes; Pharmaceutical Preparations; Pharmacology; Phase; Problem Solving; Proteins; Publications; Reporting; Role; Secondary to; Shunt Device; Site; T cell response; T-Lymphocyte; Testing; Time; Tuberculosis; Tuberculosis Vaccines; Vaccination; Vaccine Design; Vaccines; Vesicle; Vesicle Transport Pathway; Work; adaptive immunity; improved; in vivo; lymph nodes; macrophage; novel; pathogen; prevent; response; vaccine development

A major obstacle to developing an efficacious TB vaccine is illustrated by the results of a recent clinical trial in which the vaccine induced polyfunctional T cell responses, yet it did not prevent TB. This obstacle is also illustrated in animal models, as existing TB vaccines induce T cell responses, but have only modest effects on bacterial burdens. These results suggest that antigen-specific T cells are generated by infection or vaccination and they can be activated by ex vivo restimulation, but they are not activated effectively at the site of infection. The long term objective of this project is to guide development of efficacious TB vaccines by: 1) characterizing a major mechanism that limits the ability of antigen-specific CD4 T cells to recognize M. tuberculosis-infected cells and become activated at the site of infection; and 2) developing solutions that overcome or bypass that mechanism. We have discovered that M. tuberculosis-infected cells activate CD4 T cells poorly because multiple secreted bacterial antigens are shunted away from the MHC class II antigen processing and presentation pathway and are exported from the infected cells. This novel mechanism, which we term antigen export, involves intracellular vesicular transport, and requires the microtubule-directed molecular motor, kinesin-2. When we deplete M. tuberculosis-infected cells of kinesin 2 and thus block antigen export, we find increased MHC class II antigen presentation and CD4 T cell activation by infected cells, resulting in improved control of intracellular M. tuberculosis. This indicates that CD4 T cells have the potential to exert effective antimycobacterial activity, but their activation is limited by poor antigen presentation by infected cells, and poor antigen presentation is secondary to antigen export. This project will extend these findings and characterize the other cellular mechanisms required for antigen export, including budding of antigen export vesicles (AEV) from phagosomes, intracellular targeting of AEV, and fusion of AEV membranes with the plasma membrane for release of antigens to the extracellular space. Our goal is to identify host molecules that can be targeted with drugs to block antigen export and make antigen-specific CD4 T cells more effective in TB. To inform TB vaccine design, we hypothesize that nonsecreted (and nonexported) antigens are more desirable than secreted antigens in TB vaccines, since secreted antigens are exported from infected cells, making the infected cells poor targets for recognition by CD4 T cells specific for those antigens. To test the hypothesis that CD4 T cells directed against a nonsecreted antigen are more efficacious than those directed against a secreted antigen, we have modified an immunodominant secreted M. tuberculosis antigen (Ag85B) so that it is not secreted, and we will determine whether bacteria that express nonsecreted-nonexported Ag85B are better controlled by CD4 T cells in vivo. Together, our proposed studies will guide efforts to make naturally-occurring and vaccine-induced CD4 T cells more effective in TB, and contribute to solving the problem of global tuberculosis.

最近的一项临床试验的结果说明了开发有效结核病疫苗的主要障碍 疫苗会诱导多功能T细胞反应，但并不能阻止结核病。这个障碍也是 在动物模型中说明，因为现有的结核病疫苗会引起T细胞反应，但对 细菌负担。这些结果表明，抗原特异性T细胞是通过感染或疫苗接种产生的。 它们可以通过体内重新刺激来激活它们，但在感染部位没有有效地激活它们。 该项目的长期目标是指导有效的结核病疫苗的开发：1）表征 限制抗原特异性CD4 T细胞识别结核分枝杆菌感染的能力的主要机制 细胞并在感染部位激活； 2）开发克服或绕过该解决方案 机制。我们发现，结核分枝杆菌感染的细胞激活CD4 T细胞，因为 多种分泌细菌抗原从MHC II类抗原加工和 演示途径并从受感染的细胞中导出。这种新型机制，我们称其为抗原 导出，涉及细胞内囊泡转运，需要微管指导的分子运动， 动力蛋白-2。当我们耗尽驱动蛋白2的结核病感染细胞并因此阻断抗原输出时，我们发现 增加了感染细胞的MHC II类抗原表现和CD4 T细胞激活，从而改善 控制细胞内结核分枝杆菌。这表明CD4 T细胞有可能发挥有效 抗菌活性，但它们的激活受感染细胞表现不佳的限制，并且不良 抗原表现是抗原出口的继发的。该项目将扩展这些发现并表征 抗原出口所需的其他细胞机制，包括抗原输出囊泡的萌芽（AEV） 来自吞噬体，AEV的细胞内靶向以及AEV膜与质膜的融合 将抗原释放到细胞外空间。我们的目标是确定可以针对的宿主分子 药物阻止抗原出口并使抗原特异性CD4 T细胞在结核病中更有效。通知结核病 疫苗设计，我们假设未分泌（和非运动）抗原比 TB疫苗中的分泌抗原，因为分泌的抗原是从感染细胞中导出的，使得 受感染的细胞对特异性抗原特异性CD4 T细胞识别的较差靶标。检验以下假设 针对非分泌抗原的CD4 T细胞比针对A 分泌的抗原，我们已经修改了一种免疫主导分泌的结核分枝杆菌抗原（AG85B），以便它是 不是分泌的，我们将确定表达非分泌非固定的AG85B的细菌是否更好 由CD4 T细胞在体内控制。我们拟议的研究一起指导努力使自然疾病 疫苗诱导的CD4 T细胞在结核病方面更有效，并有助于解决全局的问题 结核。