Mechanisms and regulation of Mycobacterium tuberculosis iron acquisition

描述(申请人提供)：结核病(TB)，由结核分枝杆菌(Mtb)引起，是已知的最古老的人类疾病之一。然而，这种疾病仍然是死亡的主要原因之一，因为每年有近200万人死于这种疾病。尽管广泛使用了减毒活疫苗和几种抗生素，但结核病比以往任何时候都多，需要新的疫苗、药物和更具体、更快速的诊断。结核分枝杆菌是一种兼性的细胞内病原体，在巨噬细胞内复制，在肺腔内细胞外复制。在感染期间，结核分枝杆菌暴露在不同的环境和压力条件下，它必须适应这些条件才能生存和繁殖。缺铁就是其中一种情况。就像大多数活着的生物体一样，结核分枝杆菌需要铁作为酶的辅助因子，这些酶参与了基本功能，包括呼吸、DNA复制和防御有毒的氧化应激。因此，如果能找到干扰结核分枝杆菌获得铁的能力的方法，这些信息可能对设计新的抗结核疗法有用。该提案的具体目的是首先了解利用铁载体获取Mtb铁的主要途径是如何发挥作用的。这包括了解与铁载体络合的铁是如何输入到结核分枝杆菌中的，以及如何以细胞可以利用的形式释放铁来发挥其基本功能。因为铁的获取是必不可少的，病原体通常不会依靠单一的方法来获得这种营养。我们发现Mtb可以利用血红素和血红蛋白作为铁源，而不依赖于铁载体。我们将探索从血红素中获取铁的机制，以及血红素利用在结核分枝杆菌毒力中的可能作用。第二个目标试图通过体外和体内相结合的方法来理解为什么铁摄取和储存的主要调节因子IDER是必不可少的。第三个目标将利用在前两个目标和早期工作中获得的信息来开发新的活的、安全的减毒疫苗株，这些疫苗株可用于在普通人群以及免疫受损的个人中预防结核病。

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, as almost 2 million people die each year from this disease. Despite the widespread use of an attenuated live vaccine and several antibiotics, there is more TB than ever before, requiring new vaccines, drugs and more specific and rapid diagnostics. Mtb is a facultative intracellular pathogen that replicates in macrophages and extracellularly in lung cavities. During infection, Mtb is exposed to diferent environments and stres conditions to which it must adapt in order to survive and multiply. Iron deficiency is one of those conditions. As is the case for most living organisms, Mtb requires iron as cofactor for enzymes that are involved in essential functions, including respiration, DNA replication and defense against toxic oxidative stress. Thus, if ways can be found to interfere with Mtb's ability to acquire iron, this information could be useful in designing new anti-tubercular therapies. The specific aims of the proposal are first, to understand how the major pathway of Mtb iron acquisition, using siderophores, functions. This includes learning how iron complexed to siderophores is imported into Mtb and how iron is then released in a form that can be used by the cell for its essential functions. Because iron acquisition is essential, pathogens do not usually rely in a single method to get this nutrient. We found that Mtb can use heme and hemoglobin as iron source independently of siderophores. We will explore the mechanisms for iron acquisition from heme and the possible role of heme utilization in Mtb's virulence. The 2nd aim seeks to understand why IdeR, the major regulator of iron uptake and storage is essential, using a combination of in vitro and in vivo approaches. The 3rd aim wil use the information obtained in the first two aims and earlier work to develop new live attenuated, safe vaccine strains that could be used to prevent TB in the general population, as well as immunocompromised individuals.