Role of phase-variable DNA methylase in virulence of Haemophilus influenzae

相变DNA甲基化酶在流感嗜血杆菌毒力中的作用

• 批准号: 7620544
• 负责人: Arnold Lee Smith
• 金额: $ 15.47万
• 依托单位: SEATTLE CHILDREN'S HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-09-30 至 2009-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7620544
• 关键词: Affect; Anatomic Sites; Anatomy; Animal Model; Animals; Antibodies; Bacteremia; Bacteria; Blood; Blood Circulation; Bronchitis; Child; Clinical; DNA; DNA Restriction-Modification Enzymes; DNA biosynthesis; Disease; Drug Delivery Systems; Ear; Environment; Enzymes; Future; Gene Expression Regulation; Genes; Genetic Transcription; Genome; Goals; Haemophilus influenza virulence; Haemophilus influenzae; Heat-Shock Response; Human; Individual; Infant; Infection; Influenza; Initiator Codon; Knock-out; Laboratories; Lipopolysaccharides; Lung; Membrane Proteins; Meningitis; Methylation; Methyltransferase; Microarray Analysis; Modeling; Nasopharynx; Neisseria meningitidis; Nontypable Haemophilus influenza; Numbers; Nutrient; Ohio; Organism; Otitis; Otitis Media; Parents; Pathogenesis; Pattern; Pharyngeal structure; Phase; Physiological; Physiological Adaptation; Prevention; Production; Proteins; Rattus; Regulation; Reporting; Role; Site; Structure; Surface; Switch Genes; Systemic infection; Tandem Repeat Sequences; Tetranucleotide Repeat; Universities; Upper Respiratory Infections; Vaccines; Variant; Virulent; Work; base; genome sequencing; member; middle ear; migration; mutant; novel; prevent; promoter; rapid technique; tool

DESCRIPTION (provided by applicant): Haemophilus influenzae is a member of the normal bacterial flora colonizing the human nasopharynx. It is also a cause of infections of the upper respiratory tract, such as otitis media and bronchitis, and of systemic infections, such as bacteremia and meningitis. Ideally, prevention or treatment of H. influenzae disease would affect only disease-associated bacteria without perturbing normal flora. The long-term goal of this work is to understand the transition from asymptomatic colonization to mucosal or systemic infection. We hypothesize that one of the mechanisms by which nasopharyngeal bacteria adapt to a new environment such as the middle ear or the bloodstream is phase variation of a DNA methylase gene, mod. Phase variation of surface structures such as outer membrane proteins and lipopolysaccharide has been studied in H. influenzae for several years. The mod gene contains a tandem repeat region similar to those identified in other, well-characterized phase-variable genes in H. influenzae, but a physiologic role for mod phase variation was unknown until recently. Our collaborators compared a mod deletion mutant with a mod+ parent by microarray analysis and reported that mod affects transcription of at least 15 genes (Srikhanta et al. 2005 PNAS 102:5547-51) apparently via methylation of promoters. Not all of these genes have known functions, but generally genes upregulated by mod expression are involved in nutrient acquisition, while several of those downregulated by mod expression are in the heat-shock group. It is proposed that phase variation of mod is a mechanism for random, coordinated on/off switching of several other genes. These studies used the laboratory-adapted, avirulent strain Rd KW20. Phase-variable mod genes have also been identified in clinical isolates of H. influenzae and in other mucosal organisms such as Neisseria meningitidis. This exploratory project will study this novel mechanism of gene regulation in virulent H. influenzae, (i) using microarrays to identify mod-related genes in clinical isolates and (ii) examining the effect of mod phase in experimental infections. Finding that mod regulation is common in clinical isolates and affects pathogenesis will provide the basis for future studies on the physiological adaptation of bacteria to different anatomic niches within the human host. Haemophilus influenzae is a bacterium that usually grows harmlessly in the human throat, but is also able to cause disease. If we can understand how these bacteria change as they move from the throat to sites of infection (such as the ear, lungs, or blood), we may someday be able to prevent disease.

性状（由申请方提供）：流感嗜血杆菌是定植于人鼻咽部的正常细菌植物群的成员。它也是上呼吸道感染的原因，如中耳炎和支气管炎，以及全身感染，如菌血症和脑膜炎。理想情况下，预防或治疗H。流感疾病将仅影响疾病相关的细菌而不干扰正常的植物群。这项工作的长期目标是了解从无症状定植到粘膜或全身感染的转变。我们假设鼻咽细菌适应新环境（如中耳或血流）的机制之一是DNA甲基化酶基因的相位变化。流感几年来mod基因含有一个串联重复区，与H.流感，但直到最近才知道mod相位变化的生理作用。我们的合作者通过微阵列分析比较了mod缺失突变体与mod+亲本，并报道了mod显然通过启动子的甲基化影响至少15个基因的转录（Srikhanta等人，2005 PNAS 102：5547-51）。并不是所有这些基因都有已知的功能，但一般来说，mod表达上调的基因参与营养物质的获取，而mod表达下调的基因中有几个是在热休克组中。有人提出，相位变化的国防部是一个随机的，协调的开/关开关的其他几个基因的机制。这些研究使用了实验室适应的无毒力菌株Rd KW 20。在临床分离的H.流感和其它粘膜生物如脑膜炎奈瑟氏菌。这个探索性的项目将研究这种新的基因调控机制，在有毒的H。流感， (i)使用微阵列鉴定临床分离株中的MOD相关基因， (ii)检查MOD阶段在实验感染中的作用。 发现mod调节在临床分离株中是常见的，并且影响发病机制，这将为将来研究细菌对人类宿主内不同解剖学小生境的生理适应提供基础。 流感嗜血杆菌是一种细菌，通常在人类喉咙中无害地生长，但也能够引起疾病。如果我们能够了解这些细菌从喉咙到感染部位（如耳朵，肺部或血液）的变化，我们可能有一天能够预防疾病。