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视主要由常规TCR 12 CD 8 T淋巴细胞介导，该T淋巴细胞识别由高度多态性“经典”或MHC Ia类分子呈递的病原体衍生寡肽。然而，人们越来越认识到这些寡聚“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-Ib限制性CD 8 T细胞介导的免疫力被降级为针对细胞内细菌感染的宿主防御。使用小鼠多瘤病毒（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）与它们的野生型对应物一样对该病毒的致癌潜力具有抗性，有效地控制感染的急性和持续阶段，并且以CD 8ab T细胞依赖性方式这样做。我们鉴定了病毒肽及其MHC Ib类限制性分子，构建了MHC-I四聚体试剂，并在PyV感染的整个过程中跟踪了这些新型非常规CD 8 T细胞的进化、功能完整性和维持。重要的是，我们确定这些抗病毒CD 8 T细胞赋予针对PyV感染的保护，并且构成抗病毒CD 8 T细胞库的先前未被认识的组分。因此，我们的新数据为确定的MHC Ib类限制性抗病毒CD 8 T细胞应答提供了第一个证据，该应答有助于宿主防御。本申请的总体目标是使用小鼠PyV感染系统来全面定义引发这些非常规CD 8 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CD 8 T细胞跨越MHC Ia类同种异体屏障的募集。提出了三个具体目的：（1）确定选择和维持PyV特异性、MHC Ib类限制性CD 8 T细胞的要求;（2）研究机制以解释大多数这些T细胞功能受损的发现;以及（3）确定CD 4 T细胞的贡献并选择共刺激途径以产生和维持功能性抗PyV MHC Ib类。限制性CD 8 T细胞，以促进对MHC-Ia同种异体株小鼠中PyV感染的控制。这些研究应该激励努力揭示其他病毒感染中的MHC Ib类限制性CD 8 T细胞应答，并且鉴于MHC Ib类分子的有限多态性，为开发具有广泛覆盖MHC单倍型的基于肽的病毒疫苗提供平台。公共卫生相关性：CD 8 T细胞在保护宿主免受病毒感染方面发挥着核心作用。迄今为止，这些抗病毒T细胞被认为只能识别由MHC复合物的经典分子呈递的病毒抗原。我们最近发现，装载到非经典MHC分子上的肽也可以被CD 8 T细胞识别，并且这些新的细胞可以赋予抗病毒免疫力。本申请研究了有效产生这些非常规病毒特异性CD 8 T细胞的要求，这些细胞识别由经典MHC不相容个体呈递的共同抗原决定簇。

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.