GENETIC REQUIREMENTS OF HELICOBACTER PYLORI INFECTION

描述（由申请人提供）：幽门螺杆菌慢性感染全球50%人口的胃。10%至30%的受感染者会出现严重的疾病，包括消化性溃疡和胃癌15。H.幽门相关疾病不能仅仅归因于特定细菌毒素的表达。相反，我们的总体工作假设是H。幽门螺杆菌病是建立和维持感染所必需的细菌因子与所产生的宿主防御之间相互作用的副产物。这种相互作用是动态的，细菌和宿主在几十年的感染中不断变化。为了研究这一复杂的过程，我们利用小鼠感染模型，并研究来自人类临床人群的分离株之间的遗传变异。我们的体内筛选H。在前一个资助期，我们对幽门螺杆菌定植基因的研究表明，29%的测试基因具有定植缺陷，60%的定植基因显示菌株特异性表型16。这项对超过一半基因组的分析证实了先前涉及的途径，但也确定了意想不到的和研究较少的基因类别，包括参与DNA摄取和修饰的基因以及大量假设的蛋白质（81）。在我们的更新中，我们专注于完成对胃定植基因的全球分析，并探索参与DNA转化和基于重组的DNA修复的自然能力的基因促进感染的机制。H.幽门螺杆菌的天然感受态允许超感染菌株之间的重组，以在感染期间产生新的基因型，并传播菌株群体内产生的新等位基因。我们将探索DNA交换和基于重组的修复在单个菌株感染期间可能发挥的作用，包括1。修复感染过程中遇到的DNA损伤2.）适应性遗传变异的产生;催化影响促进（或限制）定殖的基因表达的遗传转换事件。我们努力全面绘制有助于毒力的基因，将确定持续感染的介质，临床人群中遗传变异的研究将显示这些介质如何适应与感染相关的慢性炎症并导致严重疾病（溃疡，癌症）。我们对H.幽门螺杆菌促进了基因交流和多样化，也应该增加对抗菌素耐药性传播的理解，这是治疗幽门螺杆菌的一个日益严重的临床问题。幽门。这符合NIAID了解和治疗传染病的使命。公共卫生相关性：幽门螺杆菌感染了世界上50%人口的胃，在那里它可以引起轻度炎症，溃疡疾病甚至胃癌，部分取决于感染菌株的遗传多样性。在这个项目中，我们询问哪些基因是持续定植所必需的，并测试通过与其他细菌的遗传交换和重组使基因组多样化的能力是否实际上是成功定植所必需的。我们的工作将确定开发抗微生物疗法的目标，并通过研究遗传交换，带来关于抗生素耐药性通过细菌种群传播的机制的新知识。

DESCRIPTION (provided by applicant): Helicobacter pylori chronically infect the human stomach of 50% of the population worldwide. Ten to 30% of those infected will present with severe disease including peptic ulcers and gastric cancers15. H. pylori associated diseases cannot be attributed solely to expression of particular bacterial toxins. Instead, our overall working hypothesis is that H. pylori disease is a by-product of the interaction between bacterial factors necessary for establishing and maintaining infection and the resultant host defenses. This interaction is dynamic with both the bacteria and host changing over decades of infection. To study this complex process, we utilize a mouse model of infection and study genetic variation among isolates from human clinical populations. Our in vivo screen for H. pylori colonization genes in the previous funding period showed 29% of genes tested had a colonization defect and 60% of our colonization genes showed strain specific phenotypes16. This analysis, of over half of the genome, confirmed pathways previously implicated, but also identified unexpected and less well studied classes of genes, including genes involved in DNA uptake and modification plus a large number of hypothetical proteins (81). In our renewal we focus on completing our global analysis of genes contributing to stomach colonization and explore the mechanisms by which genes involved in natural competence for DNA transformation and recombination-based DNA repair promote infection. H. pylori's natural competence allows recombination between super-infecting strains to generate new genotypes during infection and spread of new alleles generated within a strain population. We will explore the roles DNA exchange and recombination-based repair may play during infection of a single strain including 1.) repair of DNA damage encountered during infection 2.) generation of adaptive genetic variation and 3). catalysis of genetic switching events affecting the expression of genes promoting (or limiting) colonization. Our efforts to fully map the genes contributing to virulence will identify the mediators of persistent infection and studies of genetic variation in the clinical population will show how these mediators adapt during chronic inflammation that is associated with infection and leads to severe disease (ulcer, cancer). Our study of the mechanisms by which H. pylori promotes genetic exchange and diversification should also increase understanding of the spread of antimicrobial resistance, an increasing clinical problem in the treatment of H. pylori. This fits the mission of NIAID to understand and treat infectious diseases. PUBLIC HEALTH RELEVANCE: Helicobacter pylori infect the human stomach of 50% of the world's population where it can cause mild inflammation, ulcer disease and even gastric cancer, depending in part on the genetic diversity of the infecting strain. In this project we ask which genes are necessary for persistent colonization and test whether the ability to diversify the genome through genetic exchange and recombination with other bacteria is in fact required for successful colonization. Our work will identify targets for developing antimicrobial therapies and, through the study of genetic exchange, bring new knowledge on the mechanisms by which antimicrobial resistance is spread through bacterial populations.