Pyomelanin and Legionella pneumophila Infection

黑色素和嗜肺军团菌感染

• 批准号: 7940261
• 负责人: NICHOLAS P CIANCIOTTO
• 金额: $ 22.88万
• 依托单位: NORTHWESTERN UNIVERSITY AT CHICAGO
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-06-01 至 2012-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7940261
• 关键词: Aerosols; Alveolar Macrophages; Animal Disease Models; Area; Assimilations; Biochemical Genetics; Cells; Data; Development; Disease; Epithelial Cells; Epithelium; Genes; Growth; Habitats; Homogentisic Acid; Human; Infection; Inflammation; Invaded; Iron; Label; Laboratories; Lead; Leadership; Legionella; Legionella pneumophila; Legionnaires' Disease; Light; Lung; Lung Inflammation; Mediating; Melanins; Microbe; Microbial Biofilms; Mus; Parasites; Pathogenesis; Pigments; Prevention; Production; Protozoa; Public Health; Research Project Grants; Resistance; Risk; Role; Screening procedure; Siderophores; Staging; System; Testing; Tissues; United States National Institutes of Health; Virulence Factors; Water; Work; disease diagnosis; extracellular; iron (III) reductase; mouse model; mutant; pathogen; programs; public health relevance; uptake

DESCRIPTION (provided by applicant): Legionella neumophila (Lp) is the agent of Legionnaires' disease. It is ubiquitous in natural and man-made water systems, infecting humans after aerosol inoculation. In aquatic habitats, Lp survives in biofilms and as an intracellular parasite of protozoa, and in the lung, it flourishes as an intracellular parasite of alveolar macrophages and epithelia. Iron is vital to Lp growth in extra- and intracellular niches and its ability to cause disease. For twenty years, my laboratory has been involved in deciphering mechanisms by which Lp causes disease and, for fifteen of those years, has served a leadership role in the study of Lp iron acquisition. Previously, we documented that Lp expresses both siderophore (legiobactin)-mediated ferric iron uptake and FeoB-mediated ferrous iron assimilation and that each of these is required for optimal infection of the lung. In the course of screening for genes involved in legiobactin production, we determined that the secreted brown pigment of Lp, a pyomelanin derived from homogentisic acid (i.e., HGA-melanin), confers ferric reductase activity. In light of these data, we hypothesize i) that secreted HGA-melanin promotes Lp iron acquisition by providing ferrous iron for import into the bacterial cell and ii) that this pyomelanin is required for Lp growth within the infected lung. The pursuit of this hypothesis would be the first test of whether HGA-melanin mediated iron reduction is a (general) mechanism for bacterial iron uptake as well as the first direct assessment of the importance of a bacterial melanin, Lp or otherwise, in an animal model of disease. In this R21 , we will utilize purified HGA-melanin and Lp mutants specifically lacking HGA-melanin to i) determine whether or not secreted pyomelanin can mediate iron acquisition and promote bacterial growth under low-iron conditions, ii) determine the importance of pyomelanin for bacterial growth, inflammation, and tissue damage within Lp-infected mouse lungs. The impact of the proposed studies is significant for multiple reasons. First, it will increase our understanding of Lp, which is an important public health concern throughout the world. Second, since many other important pathogens as well as other important environmental microbes secrete HGA-melanin, it will elucidate new paradigms for both iron assimilation and bacterial pathogenesis. Third, it will potentially provide a new type of target for disease diagnosis, treatment, and/or prevention.

描述（由申请人提供）：嗜肺军团菌（Lp）是军团病的病原体。它在天然和人造水系统中普遍存在，通过气溶胶接种后感染人类。在水生栖息地中，Lp 在生物膜中生存并作为原生动物的细胞内寄生虫，而在肺部，它作为肺泡巨噬细胞和上皮细胞的细胞内寄生虫蓬勃发展。铁对于 Lp 在细胞外和细胞内生态位的生长及其引起疾病的能力至关重要。二十年来，我的实验室一直致力于破译 Lp 引起疾病的机制，其中十五年，在 Lp 铁获取的研究中发挥了领导作用。之前，我们记录了 Lp 表达铁载体（军团菌素）介导的三价铁摄取和 FeoB 介导的二价铁同化，并且这些都是最佳肺部感染所必需的。在筛选参与军团菌素生产的基因的过程中，我们确定 Lp 分泌的棕色素（一种源自尿黑酸的脓黑素（即 HGA-黑色素））赋予铁还原酶活性。根据这些数据，我们假设 i) 分泌的 HGA-黑色素通过提供亚铁进入细菌细胞来促进 Lp 铁的获取，ii) 这种脓黑素是受感染肺内 Lp 生长所必需的。对这一假设的追求将是第一次测试 HGA-黑色素介导的铁还原是否是细菌铁吸收的（一般）机制，以及第一次直接评估细菌黑色素、Lp 或其他在动物中的重要性。疾病模型。在本 R21 中，我们将利用纯化的 HGA-黑色素和特别缺乏 HGA-黑色素的 Lp 突变体来 i) 确定分泌的黑色素是否可以在低铁条件下介导铁获取并促进细菌生长，ii) 确定黑色素对Lp 感染小鼠肺部的细菌生长、炎症和组织损伤。由于多种原因，拟议研究的影响是重大的。首先，它将增加我们对 Lp 的了解，Lp 是全世界重要的公共卫生问题。其次，由于许多其他重要的病原体以及其他重要的环境微生物都会分泌 HGA-黑色素，因此它将阐明铁同化和细菌发病机制的新范例。第三，它有可能为疾病诊断、治疗和/或预防提供一种新型靶标。