SCT PROBES FOR PATHOGEN IMMUNITY

描述（由申请方提供）：MHC I类分子向CD 8 T细胞的抗原呈递是获得性免疫系统检测和清除病毒感染细胞的主要途径。所有有核细胞表达MHC I类分子，因此在感染时潜在地能够将抗原呈递给CD 8 T细胞。然而，最近的几项但不是全部的研究表明，主要是DC（或DC的特定亚群）是体内引发CD 8 T细胞对病毒的独特需要。由于病原体可能不会直接感染这些必需的DC，因此提出了交叉呈递途径;本质上，受感染的细胞可能不是主要的抗原呈递细胞。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性DC转移到淋巴结驻留DC以有效地引发CD 8 T细胞。然而，病原体特异性抗原从感染细胞穿梭到DC或DC亚群之间的机制尚不清楚。毫不奇怪，直接呈递与交叉呈递的这些相同问题也适用于对肿瘤或DNA疫苗接种后的CD 8 T细胞应答。作为引发病原体免疫的新策略，我们已经将预处理和预装载的MHC I类分子设计为单链肽、β-2微球蛋白和I类重链。我们将这些复合物称为单链三聚体或SCT。SCT在细胞表面非常稳定地表达，并且我们和其他人已经证明SCT引起稳健的CD 8 T细胞应答。在这项资助中，我们将测试SCT是否赋予针对病毒和细菌的保护性免疫，并探索SCT疫苗接种后CD 8 T细胞体内引发的细胞和分子基础。我们的假设是，SCT疫苗的效力是由CD 81 DC使用涉及细胞间膜交换的新机制交叉表达的结果。 公共卫生相关性：对几种病原体的保护性免疫需要MHCI分子结合抗原肽以呈递给CD 8 T细胞。然而，为了结合MHCI分子，病原体衍生的肽必须与宿主的大量内源性肽竞争。我们已经改造了MHCI分子，使它们可以预先装载病原体衍生的肽。在这项拨款中，我们将测试使用这些预载MHCI作为疫苗的功效和机制。

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.