The Role of Cell Wall Lipids in Pathogenesis of Rifampin-Resistant TB

描述（由申请人提供）：耐多药结核病（MDR-TB），定义为对两种一线药物异烟肼和利福平耐药的结核分枝杆菌（Mtb），已成为全球结核病控制的主要威胁。中国是27个耐多药结核病高负担国家之一，这种情况在中国尤为严重。在>95%的临床耐多药结核病分离株中，利福平耐药性是由rpoB基因相对较短片段的突变介导的，该基因编码利福平的分子靶点。尽管实验室衍生的具有多种不同rpoB基因突变的突变体在营养丰富的条件下显示出较慢的生长，但是从在治疗期间产生利福平耐药性的TB个体分离的Mtb临床菌株与其利福平敏感的对应物相比显示出正常的生长，尽管具有与一些实验室衍生的菌株相同的突变。最近，我们发现了一种已知的脂质毒力因子，phthiocerol dimycerosate（PDIM），在利福平耐药结核菌的细胞壁中积累的证据。使用实验室产生的双突变株的研究表明，PDIM是利福平耐药株在活化的小鼠巨噬细胞中正常存活所必需的。该建议的中心假设是，诱导参与细胞壁相关脂质毒力因子的生物合成和转运的途径是一种代偿性代谢适应，其用于增强感染宿主中利福平耐药临床分离株的毒力。该提案代表了中国上海交通大学医学院和美国巴尔的摩约翰霍普金斯大学医学院的研究人员之间的独特合作。使用多学科方法，包括使用新型小鼠模型，该模型与转录，脂质组学，遗传和成像技术相结合，我们将研究在宿主感染期间PDIM积累是否补偿与Mtb rpoB突变相关的适应度代价。我们的数据有望产生新的药物靶点，最终目标是缩短中国和全球耐多药结核病治疗的持续时间。

DESCRIPTION (provided by applicant): Multidrug-resistant tuberculosis (MDR-TB), defined as Mycobacterium tuberculosis (Mtb) resistant to the two first-line drugs isoniazid and rifampin, has emerged as a major threat to global TB control. The situation is particularly acute in China, which is one of 27 high-burden MDR-TB countries. In >95% of clinical MDR-TB isolates, rifampin resistance is mediated by mutations in a relatively short segment of the rpoB gene, which encodes the molecular target of rifampin. Although laboratory-derived mutants with a variety of different rpoB gene mutations show slower growth under nutrient-rich conditions, Mtb clinical strains isolated from individuals with TB who developed rifampin resistance during treatment show normal growth compared to their rifampin-susceptible counterparts, despite harboring the same mutation as some of the laboratory-derived strains. Recently, we have found evidence that a known lipid virulence factor, phthiocerol dimycocerosate (PDIM), accumulates in the cell wall of rifampin-resistant TB organisms. Studies using laboratory-generated double mutant strains revealed that PDIM is required for the normal survival of rifampin-resistant strains in activated mouse macrophages. The central hypothesis of this proposal is that the induction of pathways involved in biosynthesis and transport of cell wall-associated lipid virulence factors is a compensatory metabolic adaptation, which serves to enhance the virulence of rifampin-resistant clinical isolates in the infected host. This proposal represents a unique collaboration between investigators at Jiao Tong University School of Medicine in Shanghai, China and Johns Hopkins University School of Medicine in Baltimore, U.S.A. Using a multidisciplinary approach, including the use of a novel mouse model, which develops TB lung lesions resembling their human counterparts, in combination with transcriptional, lipidomic, genetic, and imaging techniques, we will investigate whether PDIM accumulation compensates for the fitness cost associated with Mtb rpoB mutation during host infection. Our data are expected to yield novel drug targets, with the ultimate goal of shortening the duration of MDR-TB treatment in China and worldwide.