Analysis of MHC Class Ib-Restricted Polyoma Virus-Specific CD8 T Cells

描述(申请人提供)：对细胞内病原体的免疫监控主要由传统的TCR12 CD8 T淋巴细胞介导，这些T淋巴细胞识别高度多态的“经典”或MHC Ia类分子所呈现的病原体来源的寡肽。然而，越来越多的人意识到，这些寡晶型的“非经典”或MHC Ib类分子也可能呈现病原体来源的抗原。然而，到目前为止的证据表明，MHC-Ib限制的CD8 T细胞介导的免疫被降级为宿主防御细胞内细菌感染。利用小鼠多瘤病毒(PYV)模型，我们最近发现，缺乏MHC Ia类分子但保留MHC Ib类分子的小鼠(即KB-/-DB-/-小鼠)与其野生型小鼠一样对该病毒的致癌潜力具有抵抗力，有效地控制了感染的急性和持续性阶段，并以CD8ab T细胞依赖的方式做到这一点。我们鉴定了病毒多肽及其MHC Ib类限制性分子，构建了MHC-I四聚体试剂，并跟踪了这些新的非常规CD8 T细胞在PYV感染过程中的进化、功能完整性和维持。重要的是，我们确定这些抗病毒CD8 T细胞对PYV感染具有保护作用，并且构成了以前未被认识的抗病毒CD8 T细胞的组成部分。因此，我们的新数据为明确的MHC Ib类限制性抗病毒CD8 T细胞反应提供了第一个证据，有助于宿主防御。这项应用的总体目标是使用小鼠PYV感染系统来全面定义诱导这些非传统CD8 T细胞的要求，并应用这些研究的见解来评估促进抗病毒CD8 T细胞跨越MHC Ia类同种异体屏障招募的候选干预措施。他们提出了三个具体目标：(1)确定选择和维持PYV特异的MHC Ib类限制性CD8T细胞的要求；(2)研究PYV感染的机制(S)，以解释大多数这些T细胞在功能上受到损害的发现；以及(3)确定CD4T细胞的贡献和选择在产生和维持功能性抗PYV MHC Ib类限制性CD8T细胞中的共刺激途径，以便促进对MHC-Ia异基因株小鼠中PYV感染的控制。这些研究应该会推动在其他病毒感染中发现MHC Ib类限制性CD8 T细胞反应的努力，并鉴于MHC Ib类分子的有限多态性，为开发具有广泛覆盖MHC单倍型的多肽病毒疫苗提供平台。公共卫生相关性：CD8 T细胞在保护宿主免受病毒感染方面发挥着核心作用。到目前为止，这些抗病毒T细胞被认为只能识别由MHC复合体的经典分子呈递的病毒抗原。我们最近发现，负载到非经典MHC分子上的多肽也可以被CD8T细胞识别，并且这些新的细胞可以产生抗病毒免疫。这项应用调查了有效地产生这些非传统病毒特异性CD8T细胞的要求，这些细胞识别由经典MHC血型不合的个体提出的共同抗原决定簇。

DESCRIPTION (provided by applicant): Immunosurveillance for intracellular pathogens is primarily mediated by conventional TCR12 CD8 T lymphocytes that recognize pathogen-derived oligopeptides presented by the highly polymorphic "classical" or MHC class Ia molecules. Yet, there is growing appreciation that these oligomorphic "nonclassical" or MHC class Ib molecules may also present pathogen-derived antigens. Evidence to date, however, has suggested that MHC-Ib-restricted CD8 T cell-mediated immunity is relegated to host defense against intracellular bacterial infections. Using the mouse polyoma virus (PyV) model, we recently discovered that mice lacking MHC class Ia molecules but retaining MHC class Ib molecules (i.e., Kb-/-Db-/- mice) are as resistant as their wild type counterparts to the oncogeneic potential of this virus, efficiently control acute and persistent phases of infection, and do so in a CD8ab T cell-dependent manner. We identified the viral peptide and its MHC class Ib-restricting molecule, constructed MHC-I tetrameric reagents, and tracked the evolution, functional integrity, and maintenance of these novel unconventional CD8 T cells throughout the course of PyV infection. Importantly, we determined that these antiviral CD8 T cells confer protection against PyV infection, and constitute a previously unappreciated component of the antiviral CD8 T cell repertoire. Our new data thus provides the first evidence for a defined MHC class Ib-restricted antiviral CD8 T cell response that contributes to host defense. The overall goal of this application is to use the mouse PyV infection system to comprehensively define the requirements for eliciting these unconventional CD8 T cells, and to apply insights from these studies to evaluate candidate interventions to promote recruitment of antiviral CD8 T cells across MHC class Ia allogeneic barriers. Three Specific Aims are proposed: (1) to define the requirements for selection and maintenance of PyV-specific, MHC class Ib-restricted CD8 T cells; (2) to investigate mechanism(s) to explain the finding that the majority of these T cells are functionally compromised; and (3) to define the contributions of CD4 T cells and select costimulatory pathways in generating and maintaining functional anti-PyV MHC class Ib-restricted CD8 T cells in order to promote control of PyV infection in mice of MHC-Ia allogeneic strains. These studies should motivate efforts to uncover MHC class Ib-restricted CD8 T cell responses in other viral infections, and, given the limited polymorphism of MHC class Ib molecules, provide a platform for developing peptide-based viral vaccines having broad coverage across MHC haplotypes. PUBLIC HEALTH RELEVANCE: CD8 T cells play a central role in protecting the host against viral infections. To date, these antiviral T cells have been thought only to be able to recognize viral antigens presented by the classical molecules of the MHC complex. We recently discovered that peptides loaded onto nonclassical MHC molecules can also be recognized by CD8 T cells, and that these novel cells can confer antiviral immunity. This application investigates the requirements for efficiently generating these unconventional virus-specific CD8 T cells, which recognize a common antigenic determinant presented by classical MHC-incompatible individuals.