NEUTROPHILS AND STAPHYLOCOCCUS AUREUS

描述（改编自申请人摘要）：金黄色葡萄球菌是一种 主要的人类病原体，造成重大的发病率和死亡率，在这两个 社区和医院感染。对出现 多药耐药菌株，特别是对所有 目前可用的抗生素，重新引起了人们对了解 该病原体的毒力机制在分子水平上，并在阐明 主机防御元件，其提供保护免受或限制 感染中性粒细胞（PMN）一直被认为是提供重要的宿主细胞， 防御S。金黄色葡萄球菌感染。然而，我们对S.金黄色诱导的 腹膜炎和脓毒症表明，PMN既具有保护作用， 有害的角色。为了证明PMN有助于 致病性S.金黄色葡萄球菌感染，我们已经使用了多种方法， 限制或促进PMN迁移到感染部位。我们的数据 表明中性粒细胞数量过多和C-X-C水平升高 趋化因子MIP-2在S.金黄色葡萄球菌感染创造了一个环境 这导致病原体的细胞外复制增强， 细胞内的生存在中性粒细胞的损害主机;中性粒细胞分离 足以在未感染动物中建立感染; 感染的中性粒细胞内的一些细菌存在于核内体中， 部分或完全降解的膜;以及两个调控位点突变体， (agr-和sar-）缺乏几种毒力因子的表达， 能够在过量PMN和MIP-2存在下存活和/或避免清除。 我们假设S.金黄色葡萄球菌表现为毒力决定因子， 利用宿主的炎症反应来提高其存活率。 此外，我们假设炎症反应的外源性调节 足以改变宿主对感染的易感性。测试 这个假设，我们将追求以下具体目标：#1）确定 在两种情况下，保护和有害作用所需的PMN数量 S.金黄色葡萄球菌感染; #2）定义C-X-C趋化因子的贡献， CXCR 2受体和S.金黄色 创造一个环境， 病原体的复制和细胞内存活; #3）阐明已知的 毒力因子，其基因在体内和体外均被激活 特别是在C-X-C趋化因子和PMN的存在下;和#4）确定 摄取机制和野生型和同基因型的细胞内区域 S. C-X-C在体内和体外对金黄色葡萄球菌的摄取 趋化因子刺激的PMN。

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.