Staphylococcus aureus binds factor H to moderate complement host defense

描述（由申请人提供）：金黄色葡萄球菌在美国是一种主要的健康威胁，可引起皮肤脓肿、骨骼感染、关节感染、肺炎、心脏感染、手术后感染和植入装置感染。国际关注的是由耐甲氧西林金黄色葡萄球菌（MRSA）引起的感染数量迅速增加。本提案的长期目标是阐明金黄色葡萄球菌促进逃避体液宿主防御功能的机制，作为开发预防或减轻疾病的新疗法的先决条件。本课题的实验重点是鉴定与宿主补体调节蛋白因子H结合的金黄色葡萄球菌细胞壁组分，阐明因子H对金黄色葡萄球菌表面的免疫调节作用。因子H是一种血清蛋白，通过破坏补体级联中的关键转化酶来控制补体活化。我们提出的工作将建立在我们之前发表的金黄色葡萄球菌结合因子H的发现，以及我们新的初步发现，即至少有两种金黄色葡萄球菌的细胞壁成分结合纯化的因子H。我们将利用研究者的体液免疫专业知识和EVMS George L. Wright Jr.生物医学蛋白质组学中心的蛋白质组学专业知识来实现两个具体目标：1)阐明H因子与金黄色葡萄球菌结合在补体介导的宿主防御中的作用；2)鉴定结合H因子的金黄色葡萄球菌细胞壁蛋白。在目标1中，我们将使用标准的微生物学和补体技术来测量H因子在金黄色葡萄球菌表面替代途径c3转化酶和末端补体级联c5转化酶的不稳定性中的作用。在目标2中，我们将使用标准的蛋白质纯化技术结合串联质谱法来鉴定结合因子H的金黄色葡萄球菌细胞壁成分。公共卫生相关性：拟议的项目将表征金黄色葡萄球菌细胞壁与宿主免疫调节蛋白因子H之间的相互作用。了解这种细菌如何操纵因子H将有助于确定预防和治疗金黄色葡萄球菌感染的新靶点。

DESCRIPTION (provided by applicant): Staphylococcus aureus is a major health threat in the United States causing skin abscesses, bone infections, joint infections, pneumonias, heart infections, post-operative infections, and infections of implanted devices. Of international concern is the rapidly increasing number of infections caused by methicillin-resistant S. aureus (MRSA). The long-term objective of this proposal is to elucidate S. aureus mechanisms that facilitate evasion of humoral host defense functions as a prerequisite to the development of novel therapies to prevent or attenuate disease. The experimental focus of this proposal is to identify S. aureus cell wall components that bind the host complement regulatory protein factor H and to elucidate the immunomodulatory actions of factor H on the S. aureus surface. Factor H is a serum protein that controls complement activation by destabilizing critical convertases along the complement cascade. The proposed work will build upon our previously published findings that S. aureus binds factor H as well as our new preliminary findings that at least two cell wall components of S. aureus bind purified factor H on overlay Western blot assay. We shall take advantage of the investigator's humoral immune expertise and the proteomic expertise of the George L. Wright Jr. Center for Biomedical Proteomics at EVMS to achieve two specific aims: 1) elucidate the role of factor H binding to S. aureus on complement-mediated host defenses, 2) identify S. aureus cell wall protein(s) that bind factor H. In aim 1 we will use standard microbiologic and complement techniques to measure the effect of factor H in the destabilization of the alternative pathway C3-convertase and the terminal complement cascade C5-convertases on the S. aureus surface. In aim 2 we will use standard protein purification techniques coupled with tandem mass spectrometry to identify S. aurues cell wall components that bind factor H. PUBLIC HEALTH RELEVANCE: The proposed project will characterize interactions between Staphylococcus aureus cell wall and the host immuno-regulatory protein factor H. Understanding how this bacteria manipulates factor H will help identify new targets for prevention and treatment of Staphylococcus aureus infections.