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

描述（由申请人提供）：细胞内病原体的免疫监测主要由传统的TCR12 CD8 T淋巴细胞介导，该淋巴细胞识别由高度多态性的“经典”或MHC Ia类分子呈现的病原体来源的寡肽。然而，越来越多的人认识到，这些寡形的“非经典”或MHC Ib类分子也可能呈现病原体来源的抗原。然而，迄今为止的证据表明，mhc - b限制性CD8 T细胞介导的免疫被降级为宿主对细胞内细菌感染的防御。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）对该病毒的致癌潜力具有与野生型小鼠一样的抗性，有效地控制急性和持续感染阶段，并且以CD8ab T细胞依赖的方式进行。我们鉴定了病毒肽及其MHC类b限制分子，构建了MHC- i四聚体试剂，并在整个PyV感染过程中跟踪了这些新型非常规CD8 T细胞的进化，功能完整性和维持。重要的是，我们确定了这些抗病毒CD8 T细胞对PyV感染具有保护作用，并且构成了抗病毒CD8 T细胞库中以前未被认识的组成部分。因此，我们的新数据为MHC类b限制性抗病毒CD8 T细胞反应的定义提供了第一个证据，该反应有助于宿主防御。本应用程序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常规CD8 T细胞的要求，并应用这些研究的见解来评估候选干预措施，以促进抗病毒CD8 T细胞跨越MHC Ia类异体屏障的招募。本文提出了三个具体目标：(1)明确pyv特异性、MHC类ib限制性CD8 T细胞的选择和维持要求；(2)研究解释大多数T细胞功能受损的机制；(3)明确CD4 T细胞在产生和维持功能性抗PyV MHC类b限制性CD8 T细胞中的作用，并选择共刺激途径，以促进对MHC- ia异体菌株小鼠PyV感染的控制。这些研究将激励人们努力揭示MHC类Ib限制性CD8 T细胞在其他病毒感染中的反应，并且，鉴于MHC类Ib分子的有限多态性，为开发具有广泛覆盖MHC单倍型的基于肽的病毒疫苗提供了一个平台。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核心作用。迄今为止，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现的病毒抗原。我们最近发现装载在非经典MHC分子上的肽也可以被CD8 T细胞识别，并且这些新细胞可以赋予抗病毒免疫。该应用程序研究了有效生成这些非常规病毒特异性CD8 T细胞的要求，这些细胞识别由经典mhc不相容个体呈现的共同抗原决定因子。

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.