Prophage contribution to the virulence of Staphylococcus aureus

描述（由申请人提供）：金黄色葡萄球菌是一种重要的革兰氏阳性人类病原体，在医院和社区环境中引起多种人类疾病。这种细菌与前噬菌体密切相关，因此很少发现没有前噬菌体的金黄色葡萄球菌分离株。在葡萄球菌噬菌体中，β -溶血素（hlb）转化噬菌体是最成功的噬菌体；在90%以上的金黄色葡萄球菌临床分离株中发现。噬菌体编码多种毒力因子，如外毒素和免疫调节分子，可抑制人的先天免疫反应。然而，一些证据表明，葡萄球菌的原噬菌体除了提供毒力因子外，还通过其他机制增加细菌的毒力：1)在原噬菌体调节基因中插入转座子，而不是在毒力因子基因中插入转座子，减少了金黄色葡萄球菌对秀丽隐杆线虫的杀伤；2)尽管hlb转化噬菌体编码的单个毒力基因缺失？在小鼠模型中，NM3对葡萄球菌毒力无影响。NM3降低葡萄球菌毒力；3)删除？NM3不仅破坏了染色体编码的重要毒力因子α -毒素的产生，而且改变了细胞外蛋白谱。在本研究计划中，我们验证了噬菌体不仅通过提供毒力因子，而且通过改变细菌基因表达来增加葡萄球菌毒力的假设。为了验证这一假设，我们将进行以下具体目标：1)确定？NM3对细菌基因表达；2)确定与？nm3介导的毒力增强和α -毒素表达激活。这些研究结果有可能改变我们目前对噬菌体在细菌发病机制中的作用的看法，促进我们对葡萄球菌发病机制的理解，并开发针对这一重要人类病原体的治疗剂。公共卫生相关性：该提案将决定β -溶血素转化噬菌体如何？NM3增加了金黄色葡萄球菌的致病潜力。这些研究结果将引导我们了解噬菌体在金黄色葡萄球菌引起的疾病中的作用，以及如何通过阻断噬菌体的贡献机制使金黄色葡萄球菌更容易受到免疫反应的影响。

DESCRIPTION (provided by applicant): Staphylococcus aureus is an important gram-positive human pathogen causing a variety of human diseases in both hospital and community settings. This bacterium is so closely associated with prophages that it is rare to find S. aureus isolates without prophages. Of the staphylococcal phages, the beta-hemolysin (hlb)-converting phage is the most successful phage; it is found in more than 90% of clinical isolates of S. aureus. The phage encodes multiple virulence factors such as exotoxins and immune modulatory molecules, which can inhibit human innate immune responses. Several lines of evidence, however, suggest that staphylococcal prophages increase bacterial virulence by additional mechanisms other than providing virulence factors:1) Transposon insertion in prophage regulatory genes, but not in the genes for virulence factors, reduces S. aureus killing of Caenorhabditis elegans; 2) Although deletion of individual virulence genes encoded by the hlb-converting phage ?NM3 had no effect on the staphylococcal virulence in murine model, deletion of the entire ?NM3 reduced the staphylococcal virulence; 3) The deletion of ?NM3 not only abolished the production of alpha-toxin, an important virulence factor encoded by the chromosome, but also altered the extracellular protein profile. In this research proposal, we test the hypothesis that prophages can increase staphylococcal virulence not only by providing virulence factors but also by altering bacterial gene expression. To test the hypothesis, we will conduct the following specific aims: 1) Determine the global effects of ?NM3 on bacterial gene expression; and 2) Identify genetic determinants involved in the ?NM3-mediated virulence increase and activation of alpha-toxin expression. The results from these studies have the potential to change our current view on the role of phages in bacterial pathogenesis and facilitate our understanding of staphylococcal pathogenesis and the development of therapeutic agents against the important human pathogen. PUBLIC HEALTH RELEVANCE: This proposal will determine how the beta-hemolysin converting phage ?NM3 increases the pathogenic potential of Staphylococcus aureus. The results from these studies will lead us to understand the role of prophages in diseases caused by S. aureus, and how we can make S. aureus more susceptible to immune responses by blocking the phage contribution mechanism.