Mechanisms of Mycobacterial Antigen Processing

描述（由申请人提供）：结核病是一种对人类影响巨大的全球性疾病。每年死于肺结核的人比死于其他疾病的人多。现有的卡介苗对儿童有部分保护作用，对成人疾病无效。我们已经确定，导致卡介苗效力降低的一个主要因素是其阻止巨噬细胞中有效抗原加工的能力。我们还发现结核分枝杆菌(？fbpA)对小鼠的保护效果优于BCG。因此，这项研究将使用这种候选疫苗，并验证一种假设，即改进树突状细胞中的“肽抗原加工”将为开发更有效的结核病疫苗铺平道路。由于吞噬体成熟阻滞，卡介苗的结构抗原被隔离在吞噬体内，而其分泌的抗原则被最低限度地加工成MHC-II和MHC-I肽表位。相比之下，？fbpA新疫苗吞噬体成熟受限，MHC-II途径的肽呈递增强，我们假设它也通过MHC-I机制呈递肽。与目前使用的卡介苗不同，？fbpA具有完整的ESAT-6和CFP-10蛋白，我们将通过选择性删除基因和过表达ESAT-6、Ag85B和CFP-10抗原来修饰病原体成分，从而增强抗原性。因此，我们将确定引发与疫苗设计相关的保护性免疫反应的病原体成分，并通过基因工程制备具有更高免疫原性和安全性的新型疫苗结构。本提案的主要目标是开发一种吞噬体成熟胜任衍生物？与以前的疫苗相比，树突状细胞有望更有效地加工产生更多免疫原性肽的双酚a疫苗。目的是：1)研究提高免疫原性的细胞内策略。通过增强MHC-II肽的呈现，以及II)表征MHC-I肽增加？fbpA候选疫苗。公共卫生相关性：结核病是细菌感染导致死亡的主要原因，通过疫苗预防这种疾病将对公共卫生和人类的未来产生影响。艾滋病和结核病是撒哈拉以南非洲和亚洲的致命组合，还需要努力开发多价疫苗。这个提案也解决了这个问题。这是一项研究资助提案，旨在利用野生型结核分枝杆菌的遗传操作开发一种新的结核病疫苗。缺乏Ag85A的初始候选疫苗(？由于其吞噬体成熟有限的性质导致抗原呈递增强，已经生产出了有希望的疫苗效力。这种高免疫原性疫苗可以作为一种多价载体疫苗，以一种更安全的形式用于人类疾病的多种疾病。该项目是一项合作提案，涉及休斯顿健康科学中心大学（Jagannath博士和Hunter博士）、圣安东尼奥健康科学中心大学（Dhandayuthapani博士）和俄克拉何马大学（William Hildebrand博士）的研究人员。小组将以高度协同的方式进行疫苗评估、基因重建和表位发现，并提高我们对抗结核疫苗的现有知识。

DESCRIPTION (provided by applicant): Tuberculosis is a global disease of immense impact on mankind. More people die of tuberculosis each year than due to other diseases. The available BCG vaccine is partially protective against children and is not effective against adult disease. We have determined that one major factor that contributes to the reduced efficacy of BCG vaccine is its ability to prevent effective antigen processing in macrophages. We also discovered that a mutant vaccine from Mycobacterium tuberculosis (?fbpA) protects mice better than BCG. This investigation will therefore use this candidate vaccine and test the hypothesis that improved 'peptide antigen processing' in dendritic cells will pave the way for development of a more effective vaccine against tuberculosis. Due to phagosome maturation arrest, structural antigens of BCG vaccine remain sequestered within phagosomes while its secreted antigens are minimally processed for MHC-II and MHC-I peptide epitopes. In contrast, ?fbpA novel vaccine undergoes limited phagosome maturation, with enhanced peptide presentation for MHC-II pathway and we hypothesize that it also presents peptides through MHC-I mechanism. Unlike the currently used BCG vaccine, ?fbpA has intact ESAT-6 and CFP-10 proteins and we will enhance antigenicity by modification of pathogen components through selective deletion of genes as well as over expression of ESAT-6, Ag85B and CFP-10 antigens. We will therefore identify pathogen components that elicit protective immune responses relevant to vaccine design and prepare novel vaccine constructs through genetic engineering with increased immunogenicity and safety. The major goal of this proposal is to develop a phagosome maturation competent derivative of ?fbpA vaccine that is expected to be more efficiently processed by dendritic cells to present more immunogenic peptides than previous vaccines. The aims are to- I) Investigate the intracellular strategies that increase the immunogenicity of ?fbpA candidate vaccine by enhancing the presentation of MHC-II peptides, and II) Characterize the MHC-I peptides that increase the immunogenicity of ?fbpA candidate vaccine. PUBLIC HEALTH RELEVANCE: Tuberculosis is the leading cause of death due to bacterial infections and prevention of this disease through a vaccine will have an impact on the public health and future of mankind. AIDS and tuberculosis is a deadly combination in sub saharan Africa and Asia and efforts are also needed to develop polyvalent vaccines. This proposal addresses this issue as well. This is a research grant proposal that seeks to develop a new vaccine for tuberculosis using genetic manipulations of the wild type Mycobacterium tuberculosis. An initial candidate vaccine that lacks Ag85A (?fbpA) has already been produced that shows promising vaccine efficacy due to its nature of limited phagosome maturation leading to enhanced antigen presentation. The highly immunogenic vaccine can be potentially used as a polyvalent carrier vaccine and in a safer form for multiple diseases of the human disease. The project is a collaborative proposal which involves investigators at the University of Heath Sciences Center Houston (Dr. Jagannath and Dr. Hunter) University of Heath Sciences Center-San Antonio (Dr. Dhandayuthapani) and University of Oklahoma (Dr. William Hildebrand). The teams will perform vaccine evaluation, genetic re-construction and epitope discovery in a highly synergistic manner and boost our existing knowledge on anti-tuberculosis vaccines.