Manganese acquisition and Mycobacterium tuberculosis virulence

 描述（由申请人提供）：结核病（TB）由结核分枝杆菌（Mtb）引起，是已知最古老的人类疾病之一。然而，这种疾病仍然是全世界死亡的主要原因之一，每年造成150万人死亡。尽管广泛使用减毒活疫苗和几种抗生素，但目前结核病的发病率比以往任何时候都高。这种可怕的情况由于抗生素抗性Mtb的日益流行而变得更加复杂，抗生素抗性Mtb的出现是由抗生素治疗的漫长过程和Mtb通过抵消宿主免疫防御机制而在宿主中持续存在的能力所促进的。因此，需要新的疫苗和药物来实现从人类宿主中快速消除Mtb。结核分枝杆菌是一种兼性细胞内病原体，在巨噬细胞内和肺腔细胞外复制。在感染过程中，M.结核病必须适应宿主施加的必需微量营养素限制，这是称为“营养免疫”的抗微生物战略的一部分。特别地，宿主清除必需的金属离子，包括铁（Fe）、锰（Mn）和锌（Zn），以防止它们被微生物获得。为了克服这一限制，结核分枝杆菌拥有复杂的分子系统，用于检测和获取必需金属。锰螯合最近出现作为一个重要的机制，在一些细菌和真菌感染的宿主抗性。此外，Mn稳态机制的失活已被证明会损害许多细菌物种在多个宿主中成功定殖和引起疾病的能力。然而，锰与结核分枝杆菌发病机制的相关性尚未研究，因为结核分枝杆菌锰代谢的分子机制的知识非常有限。我们最近在Mtb中鉴定了两种Mn转运蛋白，MntH和MntABCD，它们是在人类巨噬细胞中Mn限制和复制中生存所必需的。我们推测，这些转运蛋白通过抵消人类锰螯合系统，Nramp 1锰转运蛋白和锰结合蛋白钙卫蛋白的活性来促进结核分枝杆菌的毒力。该建议将通过在巨噬细胞水平和TB小鼠模型中分析宿主和病原体Mn转运系统之间的功能相互作用来验证这一假设。使用缺乏锰转运蛋白和巨噬细胞的细菌突变体和Nramp 1和钙卫蛋白缺乏的小鼠，我们将表征锰进口对结核分枝杆菌发病机制的贡献。这项研究有可能指导新型病原体和/或宿主定向疗法的开发，旨在利用锰饥饿的宿主防御机制。

 DESCRIPTION (provided by applicant): Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is one of the oldest known human maladies. Yet this disease is still one of the major causes of mortality worldwide, killing 1.5 million people each year. Despite the widespread use of an attenuated live vaccine and several antibiotics, there is currently more TB than ever before. This dire situation is compounded by increasing prevalence of antibiotic-resistant Mtb whose emergence is facilitated by the lengthy course of antibiotic treatment and the ability of Mtb to persist in the host by counteracting the host immune defense mechanisms. Thus, new vaccines and drugs are required to achieve rapid elimination of Mtb from the human host. Mtb is a facultative intracellular pathogen that replicates within macrophages and extracellularly in lung cavities. During infection, M. tuberculosis must adapt to essential micronutrient limitation imposed by the host as part of an antimicrobial strategy known as "nutritional immunity". In particular, the host scavenges essential metal ions, including iron (Fe) manganese (Mn) and zinc (Zn), to prevent their acquisition by the microbe. To counteract this limitation, Mtb possesses sophisticated molecular systems for sensing and acquisition of essential metals. Mn sequestration has recently emerged as an important mechanism of host resistance in several bacterial and fungal infections. Furthermore, inactivation of Mn homeostatic mechanisms has been shown to compromise the ability of many bacterial species to successfully colonize and cause disease within multiple hosts. However, the relevance of Mn to Mtb pathogenesis has not been investigated because the knowledge of the molecular mechanisms involved in Mtb Mn metabolism has been very limited. We recently identified two Mn transporters in Mtb, MntH and MntABCD, which are required to survive Mn limitation and replicate in human macrophages. We hypothesize that these transporters promote Mtb virulence by counteracting the activity of human Mn sequestration systems, the Nramp1 Mn transporter and Mn-binding protein calprotectin. This proposal will test this hypothesis by analyzing the functional interactions between host and pathogen Mn transport systems at the macrophage level and in the mouse model of TB. Using bacterial mutants lacking Mn transporters and macrophages and mice deficient in Nramp1 and calprotectin, we will characterize the contribution of Mn import to Mtb pathogenesis. This study has the potential to guide the development of novel pathogen and/or host directed therapies designed to harness the host defense mechanism of Mn starvation.