Pathways of Antigen Presentation to CD8 T Cells In Vivo

描述(申请人提供)：CD8+T细胞是抗病毒免疫反应的重要组成部分。原始CD8+T细胞只有在识别抗原提呈细胞(APC)表面的多肽-MHC-I类复合体后才能分化为效应细胞。被认为是多肽-MHC复合体一部分的多肽可以由两个空间上不同的来源产生。直接提呈的多肽是由病毒感染的pAPC内表达的蛋白质抗原产生的。或者，未被感染的pAPC可以呈现多肽，这一过程被称为交叉引发。交叉启动需要将来自病毒感染细胞的抗原转移到pAPC，然后再呈递给初始的CD8+T细胞。在体内，直接启动或交叉启动在多大程度上有助于初始CD8+T细胞的激活尚不清楚。该项目的总体目标是描述在体内初始CD8+T细胞启动过程中产生MHC-I类多肽复合体的机制。我们的基本假设是，蛋白质表达或定位的变化可以并且确实定义了体内直接或交叉启动途径的使用。为了研究这一问题，我们将使用重组病毒表达多种蛋白质抗原，并分析在体外和体内对初治和效应CD8+T细胞的抗原提呈。在目标1中，我们将探索导致一种新的免疫逃避模式的机制，在这种模式中，晚期痘苗病毒抗原被阻止进入交叉递呈途径。在目标2中，我们将研究病毒清除后MHC I类限制性抗原呈递时间延长的机制，这是CD8+T细胞在反应的记忆阶段最佳进入的先决条件。我们将研究直接和交叉提呈途径对抗原提呈持续性的贡献，并研究短暂的抗原提呈细胞群体如何在较长时间内提呈抗原。在目标3中，我们将使用一种独特的系统来检查不同细胞类型以及不同成熟阶段的细胞类型直接呈现的效率。此外，我们将明确概述直接和交叉呈现在启动CD8+T细胞反应中的作用。阐明体内不同抗原提呈途径的作用机制对于合理设计疫苗和免疫治疗策略以诱导具有保护性的CD8+T细胞至关重要。与公共卫生相关：一种被称为CD8T细胞的免疫细胞亚群可以通过杀死感染病毒的细胞来提供对许多病毒感染的保护。显然，诱导这些CD8T细胞是任何疫苗接种策略所希望的结果。然而，目前还没有疫苗策略有效地针对CD8 T细胞的诱导，可能是因为缺乏关于触发这些细胞所需事件的信息。我们的建议将调查CD8T细胞触发的早期事件，以期获得对设计有效的抗病毒疫苗至关重要的知识。

DESCRIPTION (provided by applicant): CD8+ T cells are critical components of the anti-viral immune response to viruses. Naive CD8+ T cells differentiate into effectors cells only after recognition of peptide-MHC Class I complexes on the surface of antigen presenting cells (APC). The peptides recognized as part of the peptide-MHC complex can be generated from two spatially distinct sources. Directly presented peptides are generated from protein antigens expressed within a virus-infected pAPC. Alternatively, pAPC that are not infected can present peptides, a process termed cross-priming. Cross-priming requires the transfer of antigen derived from virus-infected cells to pAPC prior to presentation to naive CD8+ T cells. The extent to which direct-priming or cross-priming contribute to activation of naive CD8+ T cells in vivo is not known. The overall objective of this project is to delineate the mechanisms used to generate MHC Class I-peptide complexes during priming of naive CD8+ T cells in vivo. Our underlying hypothesis is that alteration in protein expression or localization can, and does, define the usage of the direct or cross-priming pathways in vivo. To examine this issue we will use recombinant viruses to express multiple protein antigens and will analyze antigen presentation to naive and effector CD8+ T cells both in vitro and in vivo. In Aim 1 we will explore the mechanisms responsible for a novel mode of immune evasion in which late vaccinia virus antigens are prevented from entering the cross presentation pathway. In Aim 2 we will examine the mechanisms responsible for prolonged MHC Class I-restricted antigen presentation following clearance of virus, a prerequisite for optimal entry of CD8+ T cells in the memory phase of the response. We will examine the contribution of the direct and cross presentation pathways to the persistence of antigen presentation, and examine how a short-lived population of antigen presenting cells can present antigen for extended periods of time. In Aim 3 we will use a unique system to examine the efficiency of direct presentation by different cell types, and by cell types at various stages of maturation. In addition, we will definitely outline the role of direct and cross presentation in initiation of CD8+ T cell responses. Delineation of the mechanisms governing the use of different antigen presentation pathways in vivo is essential to provide a basis for the rational design of vaccines and immunotherapeutic strategies aimed at induction of protective CD8+ T cells. PUBLIC HEALTH RELEVANCE: A subset of immune cells known as CD8 T cells can provide protection against many virus infections by killing virus-infected cells. Clearly, induction of these CD8 T cells is a desirable outcome of any vaccination strategy. However, currently no vaccine strategies effectively target induction of CD8 T cells, probably because information about the events required to trigger these cells is lacking. Our proposal will investigate the early events in the triggering of CD8 T cells, with a view to gaining knowledge vital for the design of effective antiviral vaccines.