Enterotoxin-Mediated Development of Staphylococcus aureus Infective Endocarditis

这项提案的目的是剖析肠毒素引起葡萄球菌的潜在机制 金黄色葡萄球菌感染性心内膜炎（IE）。S.金黄色葡萄球菌是一个重要的临床和公共卫生问题， 一些最严重的医院和社区相关疾病，影响约50万人 每年在美国。S.金黄色葡萄球菌是发达国家IE的主要原因， 在美国，每年影响约40，000人，并导致20 - 66%的患者死亡。S. aureus IE也是 最具侵略性、组织破坏性和致命性的IE形式。治疗S.金黄色葡萄球菌IE具有挑战性，需要 延长抗生素治疗或手术切除受感染的瓣膜。耐甲氧西林沙门氏菌感染。金黄色 是频繁的、复杂的治疗，并且增加死亡率。对S的了解很少。金黄色葡萄球菌毒力因子 这对IE的发展和导致这种侵袭性疾病的机制至关重要。的 鉴于IE的发病率、严重程度和致死率已经 在过去的50年里没有减少。目前的证据表明，葡萄球菌肠毒素C（SEC）， 中毒性休克综合征毒素（TSST 1）和肠毒素基因簇（egc）在 沙门氏菌引起IE的病因。金黄色。肠毒素缺失/互补研究表明， SEC、TSST 1和选择的egc毒素在S.金黄色葡萄球菌IE在兔模型中的天然 阀门IE。已知葡萄球菌肠毒素具有强效的超抗原特性，导致CD4 + T细胞亚群。 T细胞依赖性细胞因子风暴导致炎性综合征、中毒性休克综合征或败血性休克。 虽然适应性免疫系统激活是葡萄球菌肠毒素的特征， 生物功能。肠毒素还通过一种酶直接与内皮细胞、上皮细胞和脂肪细胞相互作用。 与超抗原活性无关的机制。在上皮细胞中，激活依赖于 位于分子中心α-螺旋底部的十二肽。在目标1中，我们将使用菌株 表达与T细胞受体、MHC-II受体或内皮细胞相互作用能力失活的肠毒素， 细胞和IE的兔模型，以确定IE是由于超抗原活性还是十二肽- 介导的效果，或两者。IE是主动脉内皮的感染。感染和炎症 血管内皮是血管病变如动脉粥样硬化的公认介质。因此，我们认为， 目的2探讨肠毒素影响内皮细胞促进IE发生的机制。 为此，我们将使用兔IE模型、兔主动脉外植体培养模型和新开发的 人主动脉内皮细胞系以阐明体内、离体和体外机制。我们期望我们 提出的研究，以产生数据，将显着推进我们的理解S。aureus IE并提供 对降低IE严重程度和死亡率预后和治疗价值的认识。

The goal of this proposal is to dissect the underlying mechanism by which enterotoxins cause Staphylococcus aureus infective endocarditis (IE). S. aureus present a significant clinical and public health problem, causing some of the most severe hospital- and community-associated illnesses and affecting approximately 500,000 individuals each year in the United States. S. aureus is the leading cause of IE in the developed world, affecting about 40,000 individuals per year in the U.S. and killing 20-66% of patients. S. aureus IE is also the most aggressive, tissue destructive, and lethal form of IE. Treatment of S. aureus IE is challenging, requiring prolonged antibiotic therapy or surgery to remove infected valves. Infections with methicillin-resistant S. aureus are frequent, complicate treatment, and increase mortality. Little is known about the S. aureus virulence factors critical for IE development and the mechanisms that lead to such an aggressive form of disease. The mechanistic understanding of IE is of utmost importance, given that its incidence, severity, and lethality have not been reduced in the last 50 years. Current evidence suggests that staphylococcal enterotoxin C (SEC), toxic shock syndrome toxin (TSST1), and the enterotoxin gene cluster (egc) play a novel and essential role in the etiology of IE caused by S. aureus. Enterotoxin deletion/complementation studies demonstrated the requirement of SEC, TSST1, and select egc toxins in development of S. aureus IE in a rabbit model of native valve IE. Staphylococcal enterotoxins are known for their potent superantigenic properties resulting in a CD4+ T cell dependent cytokine storm leading to inflammatory syndromes, toxic shock syndrome, or septic shock. While adaptive immune system activation is characteristic of staphylococcal enterotoxins, this is not their only biological function. Enterotoxins also directly interact with endothelial cells, epithelial cells, and adipocytes by a mechanism independent of superantigenic activity. In epithelial cells, activation is dependent on a dodecapeptide located at the base of the central a-helix of the molecule. In Aim 1, we will use strains expressing enterotoxins inactivated in ability to interact with the T cell receptor, MHC-II receptor, or endothelial cells and the rabbit model of IE to determine whether IE is due to superantigenic activity or dodecapeptide- mediated effects, or both. IE is an infection of the aortic endothelium. Infection and inflammation of the vascular endothelium are well-recognized mediators of vascular pathologies, such as atherosclerosis. Hence, Aim 2 will determine the mechanisms by which enterotoxins affect the endothelium to promote IE development. For this, we will use the rabbit model of IE, the rabbit aortic explant culture model, and the newly developed human aortic endothelial cell line to elucidate mechanisms in vivo, ex vivo, and in vitro. We expect our proposed studies to generate data that will significantly advance our understanding of S. aureus IE and provide insight of prognostic and therapeutic value to reduce IE severity and mortality.