Iron dependent membrane vesicle production in M. tuberculosis

由结核分枝杆菌（Mtb）引起的结核病（TB）是已知的最古老的人类疾病之一 也是世界范围内死亡的主要原因，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，目前结核病比以往任何时候都多， 世界上感染结核病的人口。这种可怕的情况因日益普遍的 耐药结核分枝杆菌，其出现是由漫长的抗生素治疗过程和 Mtb在宿主中持续存在的能力。在感染过程中，宿主清除必需的金属离子，特别是铁， 作为一种被称为“营养免疫”的抗菌策略的一部分。为了应对铁的限制，病原体， 包括结核分枝杆菌，不仅合成高亲和力的铁螯合分子， 以及其他因素使病原体能够抵抗免疫攻击。越来越多的证据表明， 病原菌将毒力因子浓缩并包装到小的膜囊泡（MV）中， 释放到细胞外环境中，并具有影响病原体-宿主相互作用的能力。特别是 最近的研究表明，结核分枝杆菌还产生和释放MV，其中含有免疫活性 分子。因此，MV可能是Mtb用来克服宿主防御的工具，因此， 治疗干扰的目标。此外，用分离的MV免疫可产生保护性免疫， 对小鼠结核病的反应。尽管这些发现表明MV在宿主中起着重要作用， 病原体的相互作用，很少有人知道的生物起源，调节和功能的结核分枝杆菌MV。我们 研究结果表明，在响应铁限制Mtb显着提高生产的MV和修改 他们的内容。为了鉴定参与结核分枝杆菌MV生物发生的因素，我们设计了一种基于 对铁限制下产生的MV的性质进行研究，以鉴定具有改变的MV产生的突变体。在 除了鉴定正常MV形成所需的基因外，这些突变体的可用性将有助于 有效的努力来阐明MV生产与Mtb发病机制的相关性。以互补 方法，我们将测试假设，即在铁限制的条件下，MV生产是由 机制，调节铁稳态结核病。具体来说，我们将测试主转录是否 铁的吸收，铁转运蛋白和铁载体的调节剂是需要正常的MV生物合成期间铁 限制.这些研究的结果将有助于阐明结核分枝杆菌使用的一种仍然知之甚少的机制， 与宿主相互作用，并确定新的干预点，以开发新的治疗或预防药物， 治疗

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is one of the oldest known human maladies and a major cause 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, with one third of the world population infected with Mtb. 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. During infection, the host scavenges essential metal ions, particularly iron, as part of an antimicrobial strategy known as “nutritional immunity”. In response to iron limitation, pathogens, including Mtb, synthesize not only high affinity iron sequestering molecules, but also virulence determinants and other factors that allow the pathogen to withstand the immune attack. Accumulating evidence shows that pathogenic bacteria concentrate and pack virulence factors into small membrane vesicles (MVs) that are released into the extracellular milieu and have the capacity to influence pathogen-host interplay. In particular, it was shown recently that Mtb also produces and releases MVs, which contain immunologically active molecules. Thus, MVs might be a tool used by Mtb to overcome host defenses and, as such, are potential targets of therapeutic interference. Furthermore, immunization with isolated MVs elicits a protective immune response against TB in mice. Although these findings indicate that MVs play an important role in host- pathogen interactions, very little is known regarding the biogenesis, regulation and functions of Mtb MVs. Our findings indicate that in response to iron limitation Mtb significantly enhances production of MVs and modifies their content. To identify factors involved in MV biogenesis in Mtb, we have designed a genetic screen based on the properties of MVs produced under iron limitation to identify mutants with altered MVs production. In addition to identifying genes required for normal MV formation, the availability of these mutants will facilitate effective efforts to elucidate the relevance of MV production for Mtb pathogenesis. In a complementary approach, we will test the hypothesis that under conditions of iron limitation, MV production is controlled by the machinery that regulates iron homeostasis in Mtb. Specifically, we will test whether the master transcriptional regulator of iron uptake, iron transporters, and siderophores are required for normal MV biogenesis during iron limitation. The results of these studies will help elucidate a still poorly understood mechanism used by Mtb to interact with the host and identify new points of intervention for development of new therapeutic or preventive therapies.