Immune evasion by the Adenovirus E3-19K protein

描述(申请人提供)：人类免疫系统的主要功能之一是通过控制入侵病原体的传播和毒力来引起预防感染的反应。维持免疫的核心是通过主要组织相容性复合体(MHC)类分子将抗原肽呈递给CD8+细胞毒性T淋巴细胞。现在公认的是，病毒已经进化出选择性机制，以破坏宿主的抗病毒细胞免疫防御系统，并建立持续感染。在大多数情况下，这些机制是通过病毒蛋白的作用来运作的，能够抑制细胞表面I类MHC分子的表达。这项建议的重点是研究腺病毒(ADS)中的一种这样的病毒蛋白的免疫调节功能。 Ad基因组包括许多编码免疫调节蛋白的基因，其中来自E3(E3-19K)的19 kDa蛋白是最具特征的。E3-19K是一种I型膜蛋白，与腺病毒感染细胞内质网(ER)中的I类MHC分子结合，阻止其转运到细胞表面。E3-19K的两个结构特征被认为是导致这些观察的原因：它的管腔结构域与I类MHC分子的管腔结构域结合，而它的C末端胞浆尾巴通过ER检索基序将I类MHC分子保留在内质网中。这一过程的几个分子和机制方面还知之甚少。这项研究计划有两个具体目标：生产重组的、可溶的E3-19K并表征其生化和生物物理性质；以及在体外重建其与两种不同形式的重组、可溶的I类MHC分子的相互作用。这些研究将提供对E3-19K区域与I类MHC分子结合的见解，以及表明E3-19K如何与I类组装途径中的一系列事件相关的功能的直接证据。这些知识将增加我们对Ad发病机制和宿主细胞生物学的了解。这是我们预防、治疗和治愈与呼吸道、胃肠道、眼部和尿路疾病相关的Ad诱导的免疫功能障碍的能力的基础。这些研究在免疫和基因治疗方面也很重要，因为有可能将AdS用作基因传递的载体。

DESCRIPTION (provided by applicant): One of the primary functions of the human immune system is to elicit responses that protect against infections by controlling the spread and virulence of invading pathogens. Central to maintaining immunity is the cell-surface presentation of antigenic peptides to CD8+ cytotoxic T-lymphocytes by class I major histocompatibility complex (MHC) molecules. It is now well-established that viruses have evolved selective mechanisms to subvert the host antiviral cellular immune defenses and establish persistent infections. In most cases, these mechanisms operate by the action of viral proteins able to suppress the expression of class I MHC molecules at the cell-surface. This proposal is focused on investigating the immunomodulatory function of one such viral protein from Adenoviruses (Ads). The Ad genome includes a number of genes that code for immunomodulatory proteins, of which the 19 kDa protein from E3 (E3-19K) is the best characterized. E3-19K is a type I membrane protein that has been shown to associate with class I MHC molecules in the endoplasmic reticulum (ER) of Ad-infected cells, and prevent their transport to the cell-surface. Two structural features of E3-19K are thought to be responsible for these observations: its lumenal domain associates with the lumenal domain of class I MHC molecules, whereas its C-terminal cytosolic tail functions to retain class I MHC molecules in the ER by virtue of an ER-retrieval motif. Several molecular and mechanistic aspects of this process are poorly understood. This Research Plan has two specific goals; to produce recombinant, soluble E3-19K and characterize its biochemical and biophysical properties; and to reconstitute in vitro its interactions with two distinct forms, peptide-filled and "empty", of recombinant, soluble class I MHC molecules. These studies will provide insights in the region of E3-19K that binds to class I MHC molecules, as well as direct evidence to suggest how E3-19K may function in relation to the sequential series of events in the class I assembly pathway. This knowledge will increase our understanding of Ad pathogenesis and host cell biology. This is fundamental to our ability to prevent, treat, and cure, Ad-induced immune dysfunctions associated with respiratory, gastrointestinal, ocular, and urinary tract diseases. These studies are also important in relation to immunization and gene therapy given the potential to use Ads as vectors for the delivery of genes.