Role of the saeR/S gene regulatory system in S. aureus pathogenesis

描述（由申请人提供）：金黄色葡萄球菌（S. aureus）是世界范围内人类感染的主要原因，并引起从轻微到危及生命的各种严重疾病。金黄色葡萄球菌引起疾病的能力部分是基于它破坏先天免疫系统的能力。最近的研究表明，金黄色葡萄球菌逃避人类多形核白细胞（PMNs或中性粒细胞）的杀伤。然而，关于病原体如何检测先天免疫系统的成分以在宿主内作出反应和生存，人们知之甚少。因此，本研究的长期目标是更好地了解金黄色葡萄球菌的发病机制。具体假设是saeR/S促进金黄色葡萄球菌逃避先天宿主防御，因此在发病机制中很重要。这一假设基于以下几个关键观察结果：1)saeR/S影响毒力因子的表达；2) saeR/S似乎在细胞密度信号与环境刺激信号的整合中发挥作用；3) saeR/S在5株强毒金黄色葡萄球菌与人PMNs相互作用过程中高度上调。基于这些观察结果（来自我们小组和其他人），本提案的重点是确定saeR/S在金黄色葡萄球菌发病机制中的功能。这将通过针对两个具体目标的研究来实现。第一个目标是利用金黄色葡萄球菌菌株MW2（脉冲场型USA400）中的等基因saeR/S缺失突变体，确定saeR/S在与PMNs相互作用中的作用。这一目标将通过创建saeR/S缺失突变体，并研究对saeR/S突变体和野生型菌株的PMN吞噬、ROS产生和杀菌活性来实现。此外，该目的将确定saeR/S是否在野生型金黄色葡萄球菌中被特定的PMN成分诱导。寡核苷酸微阵列也将用于全面分析saeR/S对金黄色葡萄球菌病毒的影响。第二个目的是利用金黄色葡萄球菌感染的小鼠模型来确定saeR/S是否对金黄色葡萄球菌的毒力很重要。小鼠模型将由软组织和菌血症组成，并将通过感染组织的组织病理学分析。总之，我们预计这些研究将为了解saeR/S在金黄色葡萄球菌发病机制中的作用提供有价值的见解。也许更重要的是，拟议的研究应该确定金黄色葡萄球菌启动感染的致病策略。

DESCRIPTION (provided by applicant): Staphylococcus aureus (S. aureus) is a leading cause of human infections worldwide and causes a variety of diseases ranging in severity from mild to life-threatening. The ability of S. aureus to cause disease is based in part on its ability to subvert the innate immune system. Recent studies suggest S. aureus evades killing by human polymorphonuclear leukocytes (PMNs or neutrophils). However, relatively little is known about how pathogens detect components of the innate immune system to respond and survive within the host. Therefore, the long term goal of this study is to gain a better understanding of S. aureus pathogenesis. The specific hypothesis is that saeR/S facilitates evasion of innate host defenses by S. aureus and is therefore important for pathogenesis. This hypothesis is based on a few key observations: 1) saeR/S impacts expression of virulence factors; 2) saeR/S appears to play a role in integrating cell density signaling with cues from the environmental stimuli; and 3) saeR/S was highly up-regulated during interaction with human PMNs in five virulent strains of S. aureus. Based on these observations (from our group and others), the focus of this proposal is to determine the function of saeR/S in S. aureus pathogenesis. This will be achieved by studies directed at two specific aims. The first aim will identify the role of saeR/S during interaction with PMNs using an isogenic saeR/S deletion mutant in S. aureus strain MW2 (pulse-field type USA400). This aim will be accomplished by creating a saeR/S deletion mutant and investigating PMN phagocytosis, ROS production, and bactericidal activity toward the saeR/S mutant and wild-type strains. In addition, this aim will determine if saeR/S is induced in wild-type S. aureus by specific PMN components. Oligonucleotide microarrays will also be used to gain a comprehensive analysis of the influence of saeR/S on the S. aureus virulon. The second aim will determine if saeR/S is important for S. aureus virulence using murine models of S. aureus infection. Mouse models will consist of soft-tissue and bacteremia and will be analyzed by histopathology of infected tissues. In summary, we anticipate these studies will provide valuable insight into the role of saeR/S in S. aureus pathogenesis. Perhaps more importantly, the proposed research should identify pathogenic strategies used by S. aureus to initiate infection.