HLA Fine Mapping to Elucidate S. aureus Susceptibility

该应用程序使用大型人类前瞻性队列来识别宿主遗传决定因素 对金黄色葡萄球菌菌血症（SAB）的易感性，这是一种常见且可能致命的感染。的 本研究要测试的首要假设是人类白细胞抗原的特定变异 (HLA) II 类区域是人类对 SAB 易感性的重要决定因素，并且这些区域 可以通过研究大量、特征明确的患者群体来确定决定因素。这个假设是 基于我们的两项独立研究，1) 确定了 HLA 变异的全基因组显着关联 II 级，欧洲血统个体感染金黄色葡萄球菌的风险增加； 2) 确定了 非洲裔美国患者中欧洲来源的 HLA II 类变异和 SAB 的全基因组关联。在 在拟议的研究中，我们将进一步细化 HLA II 类区域中 SAB 的遗传风险因素。我们创造了 金黄色葡萄球菌菌血症群 (SABG)，世界上最大的配对人类 DNA 集合之一 SAB 患者的血液细菌。我们组建了一支经验丰富的多学科团队，将 独特的 SABG 队列资源、最先进的基因分型技术和创新的体内模型系统， 突破领域的界限。我们提出三个具体目标。在目标 1 中，我们将识别遗传风险 HLA II 类因素用于开发 SAB，使用高密度基因分型和插补来饱和 HLA 该地区的 2300 名 SAB 个体和 2300 名未受影响的对照者参加了纵向、前瞻性研究 SABG 队列。在目标 2 中，我们将检查 HLA II 类等位基因和单倍型与 2300 名 SA1 基因型 SAB 患者中存在复杂的 SAB，并考虑细菌的影响 通过对从所有金黄色葡萄球菌中分离出来的血流进行基因分型，对复杂性 SAB 的风险进行基因分型 2300 名 SAB 患者。这样，我们将测试复杂的SAB是否与HLA II类关联 等位基因和单倍型由血流金黄色葡萄球菌的特定遗传谱系修改。在目标 3 中，我们 将评估目标 1、目标 2 以及我们之前的研究中确定的 HLA 等位基因的功能后果 通过体内和体外实验进行研究。我们将评估特定的 HLA II 类等位基因是否显着 使用 1) 表达转基因小鼠的金黄色葡萄球菌脓毒症模型来改变宿主 T 细胞对金黄色葡萄球菌的反应 人类 HLA II 类等位基因； 2) 使用金黄色葡萄球菌感染的抗原刺激 SAB 患者的 T 细胞 呈递表达不同HLA等位基因的细胞。该项目的长期目标是 1） 描述具有 SAB 的个体和未受影响的对照的多种族样本中的 HLA 变异特征； 2) 到 为本项目中确定的 HLA II 类变异的临床相关性提供生物学证据。采取 总之，该提案的影响是增加我们对宿主遗传变异如何影响的理解 金黄色葡萄球菌感染的起始和严重程度。阐明金黄色葡萄球菌易感性的遗传基础 感染将提高我们对这场未得到解决的紧迫医疗危机的理解、治疗和预防。

This application uses a large human prospective cohort to identify the host genetic determinants of susceptibility to Staphylococcus aureus bacteremia (SAB), a common and potentially lethal infection. The overarching hypothesis to be tested in this study is that specific variants in the Human Leukocyte Antigen (HLA) class II region are important determinants of susceptibility to SAB in humans, and that these determinants can be identified by studying large, well-characterized cohorts of patients. This hypothesis is based upon our two separate studies that 1) identified genome-wide significant associations of variants in HLA class II with an increased risk for S. aureus infections in individuals of European descent; and 2) identified a genome-wide association of European-derived HLA Class II variants and SAB in African-American patients. In the proposed study, we will further refine the genetic risk factors for SAB in the HLA class II region. We created the S. aureus Bacteremia Group (SABG), one of the world’s largest collections of paired human DNA and bloodstream bacteria from patients with SAB. We assembled an experienced multidisciplinary team to link the unique SABG cohort resources to state-of-the-art genotyping technology and innovative in vivo model systems, pushing the boundaries of the field. We propose three Specific Aims. In Aim 1, we will identify the genetic risk factors in HLA class II for developing SAB, using high-density genotyping and imputation to saturate the HLA region in 2300 individuals with SAB and 2300 unaffected controls enrolled in the longitudinal, prospective SABG cohort. In Aim 2, we will examine the association of HLA class II alleles and haplotypes with complicated SAB in the 2300 patients with SAB genotyped in SA1, and consider the impact of bacterial genotype on the risk for complicated SAB by genotyping the bloodstream S. aureus isolates from all of the 2300 SAB patients. In this way, we will test whether the association of complicated SAB with HLA class II alleles and haplotypes is modified by the specific genetic lineage of the bloodstream S. aureus. In Aim 3, we will evaluate the functional consequences of the HLA alleles identified in Aim 1, Aim 2, and in our previous studies with in vivo and in vitro experiments. We will evaluate whether specific HLA class II alleles significantly alter host T cell responses to S. aureus using 1) a S. aureus sepsis model in transgenic mice expressing human HLA class II alleles; and 2) stimulation of T cells from SAB patients using S. aureus infected antigen presenting cells expressing different HLA alleles. The long-term objectives of this project are 1) to fully characterize HLA variation in a multi-ethnic sample of individuals with SAB and unaffected controls; and 2) to provide biological evidence for the clinical relevance of the HLA class II variants identified in this project. Taken together, the impact of this proposal is to increase our understanding of how host genetic variation influences the initiation and severity of S. aureus infections. Elucidating the genetic basis of susceptibility to S. aureus infection will improve our understanding, treatment, and prevention of this urgent unmet medical crisis.