SCT PROBES FOR PATHOGEN IMMUNITY

描述（由申请人提供）：MHC I类分子向CD8 T细胞呈递抗原是获得性免疫系统检测和消除病毒感染细胞的主要途径。所有有核细胞都表达MHC I类分子，因此在感染时可能直接向CD8 T细胞呈递抗原。然而，最近的一些（但不是全部）研究表明，主要是dc（或dc的特定子集）是体内CD8 T细胞对病毒的启动所必需的。由于病原体可能不会直接感染这些必需的dc，交叉呈递途径被提出；本质上，受感染的细胞可能不是原代抗原呈递细胞。此外，对于许多节肢动物传播的病毒，病毒特异性抗原可能需要从皮肤中的迁移dc转移到淋巴结驻留dc以有效地启动CD8 T细胞。然而，病原体特异性抗原从感染细胞转移到DC或DC亚群之间的机制尚不清楚。毫不奇怪，这些直接呈递与交叉呈递的问题同样适用于CD8 T细胞对肿瘤的反应或DNA疫苗接种后的反应。作为引发病原体免疫的新策略，我们设计了预处理和预加载的MHC I类分子作为单链肽，β -2微球蛋白和I类重链。我们称这些复合物为单链三聚体或sct。sct在细胞表面非常稳定地表达，我们和其他人已经证明sct引发了强大的CD8 T细胞反应。在这项资助中，我们将测试SCT是否赋予对病毒和细菌的保护性免疫，并探索SCT疫苗接种后CD8 T细胞体内启动的细胞和分子基础。我们的假设是SCT疫苗的效力是由CD81 dc通过一种涉及细胞膜交换的新机制交叉表达而产生的。

DESCRIPTION (provided by applicant): Antigen presentation by MHC class I molecules to CD8 T cells is a major pathway by which the acquired immune system detects and eliminates virus infected cells. All nucleated cells express MHC class I molecules and are thus potentially capable of direct antigen presentation to CD8 T cells upon infection. However, several, but not all, recent studies suggest that predominantly DCs (or a specific subset of DCs) are uniquely required for in vivo priming of CD8 T cells to virus. Because pathogens may not directly infect these requisite DCs, cross presentation pathways have been proposed; in essence, the infected cell may not be the primary antigen presenting cell. Additionally, for many arthropod-transmitted viruses, virus-specific antigens may require transfer from migratory DCs in the skin to lymph node resident DCs to efficiently prime CD8 T cells. However, the mechanism by which pathogen-specific antigens are shuttled from the infected cells to DCs or between DC subsets is unknown. Not surprisingly, these same issues of direct presentation vs. cross-presentation also apply to CD8 T cell responses to tumors or following DNA vaccination. As a novel strategy to elicit pathogen immunity, we have engineered preprocessed and preloaded MHC class I molecules as single chains of peptide, beta-2 microglobulin and class I heavy chain. We have termed these complexes single chain trimers or SCTs. SCTs are very stably expressed at the cell surface and we and others have demonstrated that SCTs elicit a robust CD8 T cell response. In this grant we will test whether SCTs confer protective immunity against viruses and bacteria, and probe the cellular and molecular basis of vivo priming of CD8 T cells following SCT vaccination. Our hypothesis is that SCT vaccine efficacy results from crosspresentation by CD81 DCs using a novel mechanism involving intercellular membrane exchange. PUBLIC HEALTH RELEVANCE: Protective immunity to several pathogens requires that MHCI molecules bind antigenic peptides for presentation to CD8 T cells. However, to bind MHCI molecules, pathogen-derived peptides must compete with an extensive pool of endogenous peptides of the host. We have engineered MHCI molecules so that they can be pre-loaded with pathogen-derived peptides. In this grant, we will test the efficacy and mechanism of using these pre-loaded MHCI as vaccines.