NEUTROPHILS AND STAPHYLOCOCCUS AUREUS

简介(摘自申请者摘要)：金黄色葡萄球菌是一种 在这两种疾病中导致显著发病率和死亡率的主要人类病原体 社区和医院获得性感染。对出现的问题的担忧 耐多药菌株，特别是对所有药物缺乏敏感性的菌株 目前可用的抗生素，重新引起了人们对了解 该病原菌在分子水平上的毒力机制及其在阐明中的作用 主机防御元素，提供防御或限制 感染。长期以来，中性粒细胞(PMN)被认为提供了重要的宿主 预防金黄色葡萄球菌感染。然而，我们对金黄色葡萄球菌诱导的研究 小鼠的腹膜炎和脓毒症表明PMN既有保护作用 也是一个有害的角色。为了证明PMN对 金黄色葡萄球菌感染的发病机制，我们已经使用了多种方法 限制或促进PMN向感染部位的迁移。我们的数据 表明PMN数量过多和C-X-C水平升高 金黄色葡萄球菌感染部位的趋化因子MIP-2创造了一个环境 这导致了病原体和它的细胞外复制的增强 PMN中的细胞内存活对宿主有害；PMN分离 来自这种环境的细菌足以在幼小的动物中建立感染； 这些受感染的PMN内的一些细菌存在于内体中 部分或完全降解的膜；以及两个调节基因座突变 (agr-和sar-)缺乏几种毒力因子的表达较少 能够在过量PMN和MIP-2存在的情况下存活和/或避免清除。 我们假设金黄色葡萄球菌表现为一种毒力决定因素 利用宿主的炎症反应来提高其存活率。 此外，我们假设外源性调节炎症反应 足以改变宿主对感染的易感性。为了测试 在这个假设中，我们将追求以下具体目标：#1)确定 保护所需的PMN数量及其有害作用在两个 金黄色葡萄球菌感染的模型；#2)定义C-X-C趋化因子的作用， 金黄色葡萄球菌表达的CXCR2受体和特异性毒力因子 创造的环境既能增强细胞外的活力 病原体的复制和细胞内存活；#3)阐明已知 体内和体外基因均被激活的毒力因子 特别是在C-X-C趋化因子和PMN存在的情况下；以及#4)确定 野生型和等基因的摄取机制及胞内定位 C-X-C在体内和体外对金黄色葡萄球菌突变体的摄取 趋化因子刺激的中性粒细胞。

Description (Adapted from applicant's abstract): Staphylococcus aureus is a major human pathogen causing significant morbidity and mortality in both community- and hospital-acquired infections. Concern over the emergence of multidrug resistant strains, particularly strains which lack sensitivity to all currently available antibiotics, has renewed interest in understanding the virulence mechanisms of this pathogen at the molecular level and in elucidating host defense elements which either provide protection from or which limit infection. Neutrophils (PMN) have long been thought to provide significant host defense against S. aureus infection. However, our studies of S. aureus-induced peritonitis and sepsis in mice have suggested that PMN have both a protective and a deleterious role. In order to demonstrate that PMN contribute to the pathogenesis of S. aureus infection, we have used multiple approaches which either limit or promote PMN migration into the infectious site. Our data indicate that excessive numbers of PMN and elevated levels of a C-X-C chemokine, MIP-2, at the site of a S. aureus infection create an environment which leads to enhanced extracellular replication of the pathogen and its intracellular survival in PMN to the detriment of the host; that PMN isolated from this environment are sufficient to establish infection in naive animals; that some of the bacteria inside these infected PMN are in endosomes with partially or fully degraded membranes; and that two regulatory loci mutants (agr- and sar-) which lack the expression of several virulence factors are less able to survive and/or avoid clearance in the presence of excess PMN and MIP-2. We hypothesize that S. aureus manifests as a virulence determinant the ability to exploit the host's inflammatory response in order to enhance its survival. Moreover, we hypothesize that exogenous modulation of the inflammatory response is sufficient to alter the susceptibility of the host to infection. To test this hypothesis, we will pursue the following specific aims: #1) determine the number of PMN necessary for protection and for their deleterious role in two models of S. aureus infection; #2) define the contribution of C-X-C chemokines, the CXCR2 receptor, and specific virulence factors expressed by S. aureus to the creation of the environment which leads to both enhanced extracellular replication and intracellular survival of the pathogen; #3) elucidate known virulence factors whose genes are activated both in vivo and in vitro specifically in the presence of C-X-C chemokines and PMN; and #4) determine the mechanism of uptake and the intracellular locale of wild-type and isogenic mutants of S. aureus taken up both in vivo and in vitro by C-X-C chemokine-stimulated PMN.