Virulence of the Opportunistic Pathogen Rhodococcis Equi

机会性病原体马红球菌的毒力

• 批准号: 7343180
• 负责人: MARY HONDALUS
• 金额: $ 31.55万
• 依托单位: UNIVERSITY OF GEORGIA
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-02-01 至 2011-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7343180
• 关键词: Actinobacteria class; Actinomyces; Address; Affect; Attenuated; Bacteria; Binding; Binding Sites; Biological Assay; Biology; Breathing; Cellular biology; Clinical; Complex; Data; Defect; Development; Disease; Disruption; Epidemic; Event; Gene Family; Genes; Genetic; Goals; Granulomatous; Growth; HIV; High temperature of physical object; Homologous Gene; Host Defense; Immunity; In Vitro; Individual; Infection; Inflammation; Investigation; Ions; Knowledge; Life; Light; Lipoproteins; Location; Lysosomes; Macrophage Cell Biology; Malignant Neoplasms; Methods; Molecular; Molecular Mechanisms of Action; Monitor; Mus; Mutagenesis; Mycobacterium tuberculosis; Nature; Obstruction; Oxidative Stress; Pathogenesis; Pathway interactions; Persons; Phagocytosis; Phagosomes; Phenotype; Physiology; Plasmids; Pneumonia; Positioning Attribute; Process; Production; Proteins; Recombinants; Regulation; Regulatory Pathway; Regulon; Reporter; Research; Research Personnel; Resources; Rhodococcus equi; Role; Signal Transduction; Soil; Stimulus; Sum; Surface; System; Temperature; Testing; Time; Virulence; Work; attenuation; base; chemotherapy; expectation; genetic analysis; genetic manipulation; in vivo; innovation; insight; intracellular parasitism; killings; macrophage; member; mortality; mouse model; mutant; novel; pathogen; programs; promoter; resistance factors; response; tool; trafficking

With the arrival of the HIV epidemic and the increase in individuals undergoing chemotherapy for various cancers, the understudied zoonotic opportunistic pathogen Rhodococcus equi has emerged as cause of life- threatening pneumonia in persons of compromised immunity. Rhodococcal pneumonia is characterized by pyogranulomatous inflammation with cavitation, which can be misdiagnosed as Mycobacterium tuberculosis infection. R. equi is a common soil-borne facultative actinomycete which, when inhaled, resists innate killing mechanisms and readily multiplies in macrophages of susceptible hosts, likely by perturbation of endosomal trafficking. Little is known about the molecular basis for R. equi pathogenesis, and prior to our recent work, few tools existed to allow a thorough genetic analysis of this bacterium. Recently, we have developed the genetic methods to construct defined mutants of R. equi and have also created an efficient transposon mutagenesis system. Using these new tools, we demonstrated that vapA (virulence associated p/otein A), a gene present on the virulence plasmid of R. equi, is required for intracellular growth and full virulence. Deletion of vapA attenuates the bacterium, rendering it incapable of growth in vivo and unable to replicate in macrophages cultured in vitro. Our long-term goal is to completely dissect the genetic basis for R. equi virulence. We propose to do so by first expanding our understanding of vapA, which is to date the only known R. equi virulence determinant. The first AIM of this work is to identify the mechanism of action of vapA. To do so, we will define the intracellular events post phagocytosis of both wild type R. equi and the vapA deletion mutant. Specifically we will characterize the process of phagosomal maturation in wild type R. equi infected macrophages and test the influence of VapA on phagosome acidification and fusion with lysosomes. We will identify interacting host protein partners of VapA. The second AIM is to characterize the R. equi virulence regulon through the examination of regulators of vapA expression, VirR (yjrulence regulator) and VarA (yap regulator). We will identify the specific signals transduced by these regulators and identify additional genes controlled by them. We will establish the effects of deletion mutants of virR and varA on R. equi virulence. Finally, we will identify the binding sites of the regulators to the vapA promoter. These studies addressing the molecular mechanisms of R. equi pathogenesis will further our understanding of macrophage cell biology and will yield insight into the biology of actinomycete host-pathogen relationships in general.

随着HIV流行的到来以及接受化学疗法的个体的增加 癌症，研究的人畜共患病原体病原体等级已成为生命的原因 - 威胁免疫力受损的人威胁性肺炎。犀牛肺炎的特征是 秋水枝炎和气炎，可以误诊为结核分枝杆菌 感染。 R. Equi是一种常见的土壤传播的辅导性放线菌，当吸入时，它抵抗先天杀人 易感宿主的巨噬细胞中的机制和易于乘以，可能是由于内体扰动 贩运。关于Equi发病机理的分子基础，在我们最近的工作之前，知之甚少 很少有工具可以允许对该细菌进行彻底的遗传分析。最近，我们开发了 构建R. equi的定义突变体的遗传方法，并创建了有效的转座子 诱变系统。使用这些新工具，我们证明了VAPA（毒力相关的P/otein a），a 存在于R. equi的毒力质粒上的基因是细胞内生长和充分毒力所必需的。 删除VAPA会减弱细菌，使其无法体内生长，无法复制 巨噬细胞在体外培养。我们的长期目标是彻底剖析R.Equi的遗传基础 毒力。我们建议通过首先扩展对VAPA的理解来做到这一点，这是迄今为止的唯一 已知的R. Equi毒力决定因素。这项工作的第一个目的是确定行动机理 vapa。为此，我们将定义野生型吞噬作用后的细胞内事件。 VAPA缺失突变体。具体而言，我们将表征野生型R中的吞噬体成熟过程。 Equi感染了巨噬细胞，并测试VAPA对吞噬体酸化和融合的影响 溶酶体。我们将确定VAPA的相互作用的宿主蛋白伴侣。第二个目的是表征 R. Equi毒力调节，通过检查VAPA表达的调节剂ViRR（yjrulence） 调节器）和VARA（YAP调节器）。我们将确定这些监管机构传输的特定信号，并 确定由它们控制的其他基因。我们将建立VIRR缺失突变体的影响和 R. equi毒力上的瓦拉。最后，我们将确定调节器与VAPA启动子的结合位点。 这些针对R. equi发病机理的分子机制的研究将进一步了解我们的理解 巨噬细胞生物学的生物学，并将深入了解放线菌的生物学 一般来说。