Mechanisms of Mycobacterial Antigen Processing

描述(申请人提供)：结核病是一种对人类影响巨大的全球性疾病。每年死于结核病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它阻止巨噬细胞有效的抗原处理的能力。我们还发现，结核分枝杆菌突变疫苗(？fbpA)比卡介苗对小鼠的保护作用更好。因此，这项研究将使用这种候选疫苗，并验证这样一种假设，即改进树突状细胞的“肽抗原处理”将为开发更有效的结核病疫苗铺平道路。由于吞噬小体成熟停滞，卡介苗的结构抗原仍然滞留在吞噬小体内，而其分泌的抗原被最小限度地加工为MHC-II和MHC-I多肽表位。相反，fbpA新型疫苗经历了有限的吞噬小体成熟，增强了MHC-II途径的多肽呈递，我们假设它也通过MHC-I机制呈递多肽。与目前使用的卡介苗不同，FbpA具有完整的ESAT-6和CFP-10蛋白，我们将通过选择性缺失基因和过度表达ESAT-6、Ag85B和CFP-10抗原来修饰病原体成分，以增强抗原性。因此，我们将通过基因工程识别与疫苗设计相关的保护性免疫反应的病原体成分，并制备具有更高免疫原性和安全性的新型疫苗结构。这项建议的主要目标是开发一种吞噬小体成熟的？fbpA疫苗的衍生物，有望被树突状细胞更有效地处理，比以前的疫苗提供更多的免疫原肽。其目的是：1)研究通过增加MHC-II多肽的呈递来提高FbpA候选疫苗免疫原性的细胞内策略；2)鉴定提高FbpA候选疫苗免疫原性的MHC-I多肽。公共卫生相关性：结核病是细菌感染导致的主要死亡原因，通过疫苗预防这一疾病将对公共健康和人类的未来产生影响。在撒哈拉以南的非洲和亚洲，艾滋病和结核病是致命的组合，还需要努力开发多价疫苗。这项提议也解决了这个问题。这是一项研究拨款提案，旨在利用野生型结核分枝杆菌的基因操作开发一种新的结核病疫苗。一种缺乏Ag85A(？fbpA)的初步候选疫苗已经被生产出来，由于其有限的吞噬小体成熟导致抗原提呈增强，因此显示出良好的疫苗效果。这种高度免疫原性的疫苗可能被用作多价载体疫苗，并以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，涉及休斯顿卫生科学大学中心(Jagannath博士和Hunter博士)、圣安东尼奥大学卫生科学中心(Dhandayuthapani博士)和俄克拉荷马大学(William Hildebrand博士)的研究人员。这些团队将以高度协同的方式进行疫苗评估、基因重建和表位发现，并增强我们现有的抗结核病疫苗知识。

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.