Using the MHC class I cytoplasmic tail to control tumor Ag presentation by DCs

描述(由申请人提供)：利用细胞毒性T淋巴细胞(CTL)的免疫疗法已被证明在消除动物模型和人类癌症患者的巨大肿瘤负担方面有效。由于树突状细胞(DC)是最有效的抗原提呈细胞，可激发初始CD8 T细胞成为激活的CTL，以MHC I类限制性方式有效地杀伤靶细胞，因此人们对开发用于癌症治疗的DC疫苗产生了广泛的兴趣。该项目的具体目标是通过利用控制MHC-I运输和DC表面表达的自然机制来产生一种改进的DC疫苗，以改善肿瘤抗原呈递给CD8T细胞的质量和持续时间。我们的中心假设是，MHC-I细胞质尾部中的保守基序不仅控制MHC-I/肽复合体在细胞表面呈递的持续时间，还控制MHC-I通过特殊的内吞交叉呈递间隔运输。我们提出这一假设是基于我们的初步结果，即确定了两个功能不同的MHC-I尾部基序，它们直接控制小鼠MHC-I分子的DC内吞转运和交叉递送功能，并在体内产生抗病毒CTL反应中发挥关键作用(Lizee等，自然免疫学)。这一建议的基本原理是，利用我们对这些保守基序在DC中如何运作的知识，将能够提高肿瘤抗原负载量，并延长基于DC的人类肿瘤疫苗的抗原呈递持续时间，从而改善CTL启动结果。我们计划测试我们的中心假设，并通过专注于以下三个具体目标来实现我们改进基于DC的癌症疫苗的总体目标：(1)确定MHC-I细胞质尾部的修改如何影响抗原特异性CTL的启动，并改变DC抗原呈递的动力学。(2)利用已建立的小鼠模型，评价MHC-I尾部修饰的DC疫苗在激发抗原特异性CTL和诱导抗肿瘤反应方面的效果。(3)分析炎症介质和肿瘤衍生因子对DC MHC-I尾部磷酸化、细胞内转运和抗原提呈的影响。这项拟议的工作具有创新性，因为它将揭示DC启动最佳有效抗肿瘤CTL反应的分子机制。它还将填补目前关于在Toll样受体(TLR)配体或先天免疫信号激活DC过程中发生的MHC-I运输和抗原递呈的动态变化的知识库的空白。这些结果将产生重要的积极影响，因为它们将为下一代改进的DC疫苗铺平道路。它们将使能够修改MHC-I尾巴的新疗法的设计成为可能，从而潜在地允许在MHC-I抗原呈递的水平上操纵免疫反应。这些研究的成功完成可能会对人类疾病治疗的其他领域产生影响，包括自身免疫、移植免疫学和病原体感染。 与公共卫生相关：癌症疫苗通过在癌症患者的血液中激发特定的细胞毒性(‘杀手’)T淋巴细胞(CTL)发挥作用，而CTL反过来又摧毁肿瘤。基于树突状细胞(DC)的疫苗在临床上显示出很大的前景，但我们对DC生物学缺乏基本的了解，限制了这些疫苗的发展。这笔赠款建议利用我们对MHC I类生物学的基本知识来提高基于DC的癌症疫苗的效力，最终目标是改善患者对基于CTL的免疫疗法的反应。

DESCRIPTION (provided by applicant): Immunotherapies that utilize cytotoxic T lymphocytes (CTLs) have proven effective at eradicating large tumor burdens in both animal models and human cancer patients. Since dendritic cells (DCs) are the most potent antigen-presenting cells for priming naive CD8+ T-cells to become activated CTLs that efficiently kill target cells in an MHC class I-restricted fashion, there has been widespread interest in developing DC-based vaccines for use in cancer therapy. The specific objective of this project is to generate an improved DC vaccine by exploiting the natural mechanisms that control MHC-I trafficking and DC surface expression to improve the quality and duration of tumor antigen presentation to CD8+ T cells. It is our central hypothesis that conserved motifs within the MHC-I cytoplasmic tail control not only the duration of presentation of MHC-I/peptide complexes at the cell surface, but also MHC-I trafficking through specialized, endocytic cross-presentation compartments. We have formulated this hypothesis on the basis of our Preliminary Results identifying two functionally distinct MHC-I tail motifs that directly control DC endocytic trafficking and cross-presentation function of murine MHC-I molecules, and which play a crucial role in the generation of antiviral CTL responses in vivo (Lizee et al, Nature Immunology). The rationale for this proposal is that utilizing our knowledge of how these conserved motifs operate in DCs will allow for the ability to improve tumor antigen loading and extend duration of antigen presentation in human DC-based cancer vaccines, thus improving CTL priming outcomes. We plan to test our central hypothesis and accomplish our overall objective of improving DC-based cancer vaccines by focusing on the following three specific aims: (1) Determine how modifications to the MHC-I cytoplasmic tail impact the priming of antigen-specific CTLs and alter the dynamics of DC antigen presentation. (2) Using established murine models, assess the efficacy of MHC-I tail-modified DC vaccines in priming antigen-specific CTLs and in the induction of antitumor responses. (3) Analyze how inflammatory mediators and tumor-derived factors affect MHC-I tail phosphorylation, intracellular trafficking, and antigen presentation in DCs. The proposed work is innovative, because it will uncover the molecular mechanisms utilized by DCs to prime optimally effective antitumor CTL responses. It will also fill in gaps in the current knowledge base with regard to the dynamic changes in MHC-I trafficking and antigen presentation that occur during DC activation by toll-like receptor (TLR)-ligands or innate immune signals. Such results will have an important positive impact, because they will pave the way towards the next generation of improved, DC-based vaccines. They will enable the design of novel therapeutics capable of modifying the MHC-I tail, thus potentially allowing for manipulation of immune responses at the level of MHC-I antigen presentation. Successful completion of these studies is likely to have an impact in other areas of human disease treatment, including autoimmunity, transplant immunology, and pathogen infections. PUBLIC HEALTH RELEVANCE: Cancer vaccines work by eliciting specific cytotoxic ('killer') T lymphocytes (CTL) in the blood of cancer patients, which in turn destroy the tumor. Dendritic cell (DC)-based vaccines have shown much promise clinically, but our lack of basic understanding of DC biology has limited the development of these vaccines. This grant proposes to utilize our basic knowledge of MHC class I biology to improve the potency of DC-based based cancer vaccines, with the ultimate goal of improving patient responses to CTL-based immunotherapy.