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Phase variation of virulence factors in Clostridium difficile

艰难梭菌毒力因子的相位变化

基本信息

批准号：
10463619
负责人：
RITA TAMAYO
金额：
$ 41.55万
依托单位：
UNIV OF NORTH CAROLINA CHAPEL HILL
依托单位国家：
美国
项目类别：
财政年份：
2013
资助国家：
美国
起止时间：
2013-05-20 至 2024-08-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/10463619
关键词：
5&apos Untranslated Regions Adherence Affect Anabolism Animal Disease Models Animal Model Antibiotics Area Attenuated Bacteria Binding Sites Biochemistry Cells Centers for Disease Control and Prevention (U.S.)Cessation of life Clostridium difficile Code Cytotoxin DNA DNA Sequence Data Development Diarrhea Disease Down-Regulation Epithelial Cells Flagella Gene Expression Gene Expression Regulation Genes Genetic Recombination Genetic Transcription Goals Health Care Costs Human Immune In Vitro Infection Inflammatory Response Intestines Investigation Knowledge Laboratories Link Mediating Messenger RNA Mission Modeling Molecular Molecular Biology Operon Pathogenesis Pathogenicity Phase Physiological Physiological Processes Physiology Preventive Production Pseudomembranous Colitis Public Health Publishing Regulation Regulatory Element Reporting Research Resources Rho Factor Role Sigma Factor Site Swimming Symptoms Testing Therapeutic Toxin Transcript Transcription Initiation United States National Institutes of Health Variant Virulence Virulence Factors bacterial genetics base cell motility combat gene product gut colonization host colonization in vivo innovation intestinal epithelium mutant pathogen pathogenic bacteria premature recombinase rho transcription termination

项目摘要

PROJECT SUMMARY Clostridium difficile is a major public health threat, causing disease ranging from mild diarrhea to pseudomembranous colitis. C. difficile disease symptoms are largely mediated by the secreted cytotoxins, TcdA and TcdB. Many aspects of the pathogenicity of this bacterium remains poorly understood, including how C. difficile regulates the production of the toxins and other virulence factors. Toxin gene expression is linked to expression of flagellar genes via the flagellar sigma factor sigma-D, which is encoded in the flgB operon. Thus, factors that regulate the expression of the flgB operon will impact toxin production in addition to flagellar motility. Our long-term goal is to determine how C. difficile coordinately regulates flagellum and toxin gene expression, as these mechanisms are likely fundamental to pathogenesis. We recently showed that flagellar gene expression is subject to phase variation through site-specific DNA recombination of an invertible sequence upstream of the flgB operon. Notably, inversion of the DNA sequence, which we term the “flagellar switch”, also impacts the production of toxins essential for virulence. We identified RecV as the DNA recombinase that mediates inversion of the flagellar switch, and we have begun to define the mechanism by which the orientation of the flagellar switch sequence controls gene expression. Our central hypothesis is that phase variation of flagellum and toxin production is critical to C. difficile pathogenesis, and consequently interfering with the ability of C. difficile to phase vary will attenuate one or more aspects of virulence. While flagella and/or motility may be important for some aspects of infection, downregulation of flagella is likely vital for C. difficile to evade host immune recognition. Toxin production may similarly be beneficial or detrimental to C. difficile during different stages of infection. The objective of this proposal is to define the molecular mechanisms underlying phase variation and to evaluate the impact of phase variation on host colonization and virulence. This proposal is innovative because it represents an entirely new area of investigation toward understanding C. difficile disease: phase variable expression of flagella and toxins. Completion of the proposed studies will provide much needed mechanistic information on how C. difficile controls virulence factor production during infection, and may expose potential targets for inhibition of intestinal colonization and toxin production to facilitate efforts to combat this increasingly problematic pathogen.

项目摘要艰难梭菌是一种主要的公共卫生威胁，引起从轻度腹泻到伪膜性结肠炎C.艰难梭菌疾病症状主要由分泌的细胞毒素介导， TcdA和TcdB。这种细菌致病性的许多方面仍然知之甚少，包括如何 C.艰难梭菌调节毒素和其它毒力因子的产生。毒素基因的表达与通过鞭毛σ因子σ-D表达鞭毛基因，σ-D在flgB操纵子中编码。因此，在本发明中，调节flgB操纵子表达的因子除了影响鞭毛外，能动性我们的长期目标是确定C。艰难梭菌协同调控鞭毛和毒素基因表达，因为这些机制可能是发病机制的基础。我们最近发现鞭毛基因表达通过逆转录酶的位点特异性DNA重组而经历相位变化。序列上游的flgB操纵子。值得注意的是，DNA序列的反转，我们称之为“鞭毛 “转换”也会影响毒性所必需的毒素的产生。我们确认RecV就是重组酶，介导鞭毛开关的反转，我们已经开始定义的机制，其中鞭毛开关序列的方向控制基因表达。我们的核心假设是，鞭毛的时相变化和毒素的产生是C.发病机制不明确，因此干扰C.艰难梭菌的阶段变化将减弱毒力的一个或多个方面。而鞭毛和/或运动性对于感染的某些方面可能是重要的，鞭毛的下调可能是至关重要的梭难以逃避宿主免疫识别。毒素的产生可能类似地有益于或有害于 C.在感染的不同阶段。该提案的目的是定义分子阶段变化的机制，并评估阶段变化对宿主定殖的影响，毒性。这项建议是创新的，因为它代表了一个全新的研究领域，理解C。艰难梭菌病：鞭毛和毒素的时相可变表达。完成建议研究将为C.艰难梭菌控制毒力因子在感染过程中产生，并可能暴露抑制肠道定植和毒素的潜在靶点生产，以促进努力打击这种日益成问题的病原体。