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。金黄色葡萄球菌是一个重大的临床和公共卫生问题，导致 一些与医院和社区有关的最严重的疾病，影响到大约50万人 在美国每年都有个人。在发达国家，金黄色葡萄球菌是IE的主要原因， 在美国，每年约有4万人受到影响，20%-66%的患者死亡。金黄色葡萄球菌IE也是 最具侵袭性、组织破坏性和致命性的IE。金黄色葡萄球菌IE的治疗是具有挑战性的，需要 长时间的抗生素治疗或手术切除感染的瓣膜。耐甲氧西林金黄色葡萄球菌感染 是频繁的，复杂的治疗，并增加死亡率。人们对金黄色葡萄球菌的毒力因子知之甚少 对IE的发展和导致这种侵袭性疾病的机制至关重要。这个 机械地理解IE是非常重要的，因为它的发生率、严重性和致命性 在过去的50年里没有减少过。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(TSST1)和肠毒素基因簇(EGC)在 金黄色葡萄球菌引起IE的病原学研究肠毒素缺失/互补研究证明 兔源金黄色葡萄球菌IE模型中SEC、TSST1和EGC毒素的需求 阀门IE。葡萄球菌肠毒素以其强大的超抗原性而闻名，可导致CD4+ T细胞依赖性细胞因子风暴导致炎症综合征、中毒性休克综合征或感染性休克。 虽然适应性免疫系统激活是葡萄球菌肠毒素的特征，但这并不是它们唯一的 生物功能。肠毒素还通过一种途径与内皮细胞、上皮细胞和脂肪细胞直接相互作用。 独立于超抗原活性的机制。在上皮细胞中，激活依赖于一种 十二肽位于分子的中心a-螺旋的底部。在目标1中，我们将使用菌株 表达的肠毒素与T细胞受体、MHC-II受体或内皮细胞相互作用的能力被灭活 细胞和兔IE模型，以确定IE是由于超抗原活性还是由于十二肽- 中介效应，或者两者兼而有之。IE是一种主动脉内皮细胞感染。人的感染和炎症 血管内皮细胞是公认的血管病理介质，如动脉粥样硬化。因此， 目的2确定肠毒素影响血管内皮细胞促进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 人主动脉内皮细胞株在体内、体外和体外的作用机制。我们期待我们的 拟议的研究将产生数据，这些数据将显著促进我们对金黄色葡萄球菌IE的了解，并提供 洞察预后和治疗价值，以降低IE的严重程度和死亡率。

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.