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都会导致各种人类疾病。这种细菌与前驱噬菌体关系如此密切，以至于很少发现没有前驱噬菌体的金黄色葡萄球菌分离株。在葡萄球菌噬菌体中，转化β-溶血素的噬菌体是最成功的噬菌体，90%以上的金黄色葡萄球菌临床分离株都含有该噬菌体。该噬菌体编码多种毒力因子，如外毒素和免疫调节分子，可抑制人类的先天免疫反应。然而，几条证据表明，葡萄球菌噬菌体通过除了提供毒力因子外，通过另外的机制增加细菌的毒力：1)转座子插入到前噬菌体调控基因中，但不在毒力因子的基因中，减少了金黄色葡萄球菌对秀丽线虫的杀灭；2)虽然删除了HLB型噬菌体编码的单个毒力基因？Nm3在小鼠模型中对葡萄球菌的毒力没有影响，但整个？Nm3的缺失降低了葡萄球菌的毒力；3)？Nm3的缺失不仅取消了由染色体编码的一种重要的毒力因子-α-毒素的产生，而且还改变了细胞外的轮廓。在这个研究方案中，我们验证了这样的假设，即前驱体不仅可以通过提供毒力因子，而且可以通过改变细菌基因表达来增加葡萄球菌的毒力。为了验证这一假说，我们将进行以下具体目标：1)确定NM3对细菌基因表达的整体影响；2)确定与NM3介导的毒力增加和α-毒素表达激活有关的遗传决定因素。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，并有助于我们理解葡萄球菌的发病机制和开发针对这种重要人类病原体的治疗药物。公共卫生相关性：这项提案将确定β-溶血素转化噬菌体？NM3如何增加金黄色葡萄球菌的致病潜力。这些研究结果将引导我们理解前驱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.