Mechanistic Studies Of The Mode Of Action Of The Staphylococcus aureus LukAB Cyto

描述（由申请人提供）：金黄色葡萄球菌是在医院和社区环境中引起感染的最重要的人类病原体之一。由于高度的抗生素耐药性和缺乏有效的疫苗，对抗金黄色葡萄球菌感染的治疗选择有限。因此，有一个重要的需要开发有效的治疗这种有机体。金黄色葡萄球菌致病成功的关键是

DESCRIPTION (provided by applicant): Staphylococcus aureus is one of the most important human pathogens responsible for infections in both hospital and community settings. Therapeutic options to combat S. aureus infections are limited due to the high level of antibiotic resistance and lack of an effective vaccine. Thus, there is a significant need for the development of effective therapeutics against this organism. Critical to the pathogenic success of S. aureus is the ability of this bacterium to avoid clearance by the host via targeted killing of neutrophils; innate immune cells integral to the control of Staphylococcal infections. Thus, the long-term goal of this research program is to understand the mechanism employed by S. aureus to deplete these critical phagocytes. Recently, we have described the leukotoxin A/B (LukAB) as a virulence factor that plays an integral role in protecting S. aureus from neutrophil-mediated killing by targeting and eliminating these cells. In addition, we have demonstrated that LukAB contributes to the pathogenesis of community-associated, methicillin-resistant Staphylococcus aureus (CA-MRSA) in a murine model of systemic dissemination. We have found that: LukAB is conserved in S. aureus, contributes to the cytotoxicity of a variety of strains including methicilln-sensitive and methicillin- resistant S. aureus, is responsible for the killing of not only neutrophls, but also monocytes, macrophages and dendritic cells, is the most divergent member of the bi-component pore-forming family of toxins found in S. aureus, and it exhibits unique properties that have not been observed by the other leukotoxins. Based on our findings, we propose a model whereby LukAB selectively binds to phagocytes resulting in toxin oligomerization and pore-formation, which ultimately leads to membrane damage and killing of the target cell. The primary goal of this application is to test this model. To this end, we propose three Specific Aims. In Aim 1 we plan to elucidate the contribution of candidate cellular factors for LukAB tropism towards phagocytes. In Aim 2 we seek to define functional regions involved in LukAB-mediated toxicity. Lastly, in Aim 3 we propose to determine the mechanism by which LukAB contributes to S. aureus pathogenesis in vivo. To accomplish these Aims, we propose to employ a multidisciplinary approach that combines molecular biology, genetics, immunology, and biochemistry, together with ex vivo and in vivo infection models. Understanding the molecular details of how LukAB mediates targeting and killing of phagocytes is crucial for the development of novel therapeutic modalities to inhibit this toxin as a new approach to combat S. aureus infections.