Identification of Mycobacterium tuberculosis genes that mediate inhibition of the host cell IFN-beta signaling

摘要 据估计，世界上约有三分之一的人口潜伏感染结核分枝杆菌 （Mtb）.每年新增1 000万例结核病病例，造成约100万人死亡，这进一步突出表明， 这种病原体对全球公共卫生的影响。结核病已经发展出多种途径来逃避宿主 免疫反应在大多数情况下，这些宿主病原体相互作用的分子机制仅仅是 开始被理解。目前建议的前提是由一系列新颖和 未发表的结果表明Mtb抑制IFN-α/β受体（IFNAR）介导的细胞信号传导， 导致细菌的细胞内生长得到改善。因此，这些发现描述了一种新的免疫逃避 Mtb参与的途径。这项应用的核心假设是，基因筛选将能够识别 Mtb中对抑制IFNAR介导的细胞信号传导重要的基因。在目标1.1中，我们建议执行 使用M.用Mtb-DNA粘粒文库转染的耻垢病克隆。这 PI实验室已成功对另外两个屏幕执行了该方法。接下来，在目标1.2中，我们描述 如何鉴定一个分离的结核分枝杆菌中大约40个基因中的相关Mtb基因。 总的来说，我们预计当前项目的成功完成将产生至少一个Mtb删除 IFNAR介导的细胞信号传导抑制缺陷的突变体，并且可能对几种其他Mtb的知识缺乏 包含额外基因的区域。这些发现将成为竞争性R01应用的基础， 本研究拟完成以下工作：1）完成所有参与IFN-β介导的细胞毒作用抑制的结核分枝杆菌基因的鉴定 信号传导，2）使用突变体详细分析抑制的分子机制，和3） 表征抑制IFNAR介导的细胞信号传导对于Mtb体内毒力的重要性。

Abstract It is estimated that about one third of the world’s population is latently infected with Mycobacterium tuberculosis (Mtb). The 10 million annual new cases of tuberculosis resulting in about one million deaths further underline the global public health impact of this pathogen. Mtb has developed a multitude of pathways to evade the host immune response. For the most part, the molecular mechanisms of these host pathogen interactions are only beginning to be understood. The premise of the current proposal is supported by a series of novel and unpublished results which demonstrate that Mtb inhibits IFN-a/b-receptor (IFNAR)-mediated cell signaling which results in improved intracellular growth of the bacteria. These findings thus describe a novel immunoevasion pathway engaged by Mtb. The central hypothesis of this application is that genetic screens will be able to identify the genes in Mtb important for inhibition of the IFNAR-mediated cell signaling. In Aim 1.1 we propose to execute a “gain-of-function” genetic screen using M. smegmatis clones transfected with a Mtb-DNA cosmid library. This approach has been successfully executed for two other screens by the PI’s lab. Next, in Aim 1.2 we describe how the relevant Mtb gene out of the approximately 40 genes in one of the isolated cosmids will be identified. Overall, we anticipate that the successful completion of the current project will generate at least one Mtb deletion mutant deficient in inhibition of IFNAR-mediated cell signaling and potentially the knowledge of several other Mtb regions that contain additional genes. These findings will be the basis for a competitive R01 application which will propose to: 1) complete the identification of all of the Mtb genes involved in inhibition of IFN-β-mediated cell signaling, 2) to use the mutants for detailed analysis of the molecular mechanisms of the inhibition and 3) to characterize the importance of inhibiting IFNAR-mediated cell signaling for in vivo virulence of Mtb.