The Mycobacterium Tuberculosis Dormancy Program

描述（由申请人提供）：世界上三分之一的人口感染结核分枝杆菌（Mtb），其中大多数感染是潜伏性的。结核杆菌可以在肺部病变中保持不活动状态，几十年后才出现，引发新的结核病爆发。此外，结核病是最难治疗的细菌感染之一，并且仍然比任何其他细菌感染造成更多的死亡。芽孢杆菌以复制和非复制状态存在于一系列氧气浓度和营养物质可用性不同的微环境中。在潜伏感染期间存活的杆菌可能以非复制状态存在，并且对活跃生长的细菌有效的抗菌剂通常对非复制细菌无效。很少有人知道结核分枝杆菌的代谢机制，以生存潜伏感染或恶劣的微环境中的坏死干酪样结节病变，氧气是有限的，营养来源次优。结核分枝杆菌不能生长，但在没有有氧呼吸的情况下生存。因此，非复制厌氧状态被认为是体内持久性杆菌的主要模型。在有氧呼吸的情况下，结核分枝杆菌需要一个功能性的电子传递系统来驱动ATP的合成。然而，杆菌维持氧化还原平衡的核心代谢机制尚不清楚。因此，我们的中心研究问题是"当有氧呼吸被抑制时，结核分枝杆菌采用什么代谢机制？至少有三个因素限制了结核分枝杆菌的有氧呼吸：巨噬细胞产生的一氧化氮和一氧化碳的抑制作用，以及成熟肉芽肿的结构。所有这三种条件都强烈诱导DosR调节子，这是厌氧生存所必需的调节子。然而，调节子不编码完全可识别的中间代谢途径。我们的表达分析和生化数据强烈表明，结核分枝杆菌-专性需氧菌-保持一个独特的多方面的中间代谢途径，在有氧呼吸的情况下。因此，在结核分枝杆菌作为一种坦率的人类病原体的整个进化过程中，它一直保持着广泛的酶阵列，这些酶似乎专门用于无氧代谢功能。该途径预测Mtb具有厌氧代谢脂质和所有其他主要碳源的潜力。迫切需要设计用于杀死非复制型厌氧杆菌的抗菌剂。我们的研究直接支持这一目标。新的抗分枝杆菌药物和药物组合常规测试对缺氧/厌氧杆菌，但问题的适当协议和我们有限的了解相关的中间代谢途径限制了合理的方法来药物设计。我们的初步数据表明，我们正处于对结核分枝杆菌厌氧代谢的基本了解的边缘。我们的工作假设是：结核分枝杆菌采用一种新的厌氧代谢循环与DosR调节子相结合，以赋予在TB病变内的非呼吸条件下的存活。为了验证这一假设，我们将研究所提出的厌氧代谢途径的关键方面。 公共卫生相关性：世界上三分之一的人口潜伏感染结核分枝杆菌。结核病是最难治疗的细菌感染之一，并且仍然比任何其他细菌感染造成更多的死亡。在潜伏感染和抗菌治疗期间持续存在的细菌可能处于非复制状态，具有低水平的代谢活性。我们的研究旨在证明M.结核病在非复制状态下存活，以便提供可以被新型抗菌剂靶向的机制。

DESCRIPTION (provided by applicant): A third of the world's population is infected with Mycobacterium tuberculosis (Mtb), and most of these infections are latent. Tubercle bacilli can remain inactive in lung lesions only to emerge decades later to seed new outbreaks of tuberculosis. In addition, tuberculosis is one of the most difficult bacterial infections to treat and continues to cause more deaths than any other bacterial infection. Bacilli exist in replicating and non-replicating states in a range of microenvironments that vary in oxygen concentration and nutrient availability. The bacilli that survive during latent infection likely exist in a non-replicating state and antimicrobials, effective against actively growing bacteria, are often not effective against non-replicating bacteria. Little is known about the metabolic mechanisms employed by Mtb to survive latent infection or the hostile microenvironment of necrotic caseous tubercle lesions where oxygen is limited and nutrient sources suboptimal. Mtb cannot grow but endures in the absence of aerobic respiration. Therefore, the non-replicating anaerobic state is considered a prime model for persistent bacilli in vivo. In the absence of aerobic respiration Mtb requires a functional electron transport system to drive ATP synthesis. However, the core metabolic mechanisms by which the bacilli maintain redox balance are unknown. Therefore, our central research question is "What metabolic mechanisms are employed by Mtb when aerobic respiration is inhibited?" At least three factors limit Mtb aerobic respiration: the inhibitory effect of macrophage-produced nitric oxide and carbon monoxide, and the structure of mature granulomas. All three of these conditions strongly induce the DosR regulon, a regulon essential for anaerobic survival. However, the regulon does not encode a complete recognizable intermediary metabolic pathway. Our expression analysis and biochemical data strongly indicate that Mtb - an obligate aerobe - maintains a unique multifaceted intermediary pathway for metabolism in the absence of aerobic respiration. Thus, throughout the evolution of Mtb as a frank human pathogen, it has maintained an extensive array of enzymes which appear to be geared specifically for anaerobic metabolic functions. The pathway predicts that Mtb has the potential to metabolize lipids and all other major carbon sources anaerobically. Antimicrobials designed to kill non-replicating anaerobic bacilli are sorely needed. Our research directly supports this goal. New antimycobacterial drugs and drug combinations are routinely tested against hypoxic/anaerobic bacilli, but questions about the proper protocol and our limited understanding of relevant intermediary metabolic pathways limit a rational approach to drug design. Our preliminary data suggests we are at the brink of a fundamental understanding of Mtb anaerobic metabolism. Our working hypothesis is: Mtb employs a novel anaerobic metabolic cycle in conjunction with the DosR regulon to confer survival during non- respiring conditions within TB lesions. To test this hypothesis we will investigate key aspects of the proposed anaerobic metabolic pathway. PUBLIC HEALTH RELEVANCE: A third of the world's population is latently infected with Mycobacterium tuberculosis. Tuberculosis is one of the most difficult bacterial infections to treat and continues to cause more deaths than any other bacterial infection. The bacteria that persist during latent infection and antibacterial treatment are likely in non-replicating states with low levels of metabolic activity. Our research is designed to demonstrate the unique metabolic pathway used by M. tuberculosis to survive in a non-replicating state in order to provide mechanisms that can be targeted by novel antimicrobials.