Remodeling of the M. tuberculosis cell wall by the host microenvironment

描述（由申请人提供）：当结核分枝杆菌（M.tb）通过空气传播感染时，杆菌沉积在肺的肺泡间隙中。在肺泡内及其近端存在许多先天免疫机制，这些机制对维持肺内稳态至关重要。结核分枝杆菌是一种高度适应宿主的巨噬细胞内病原体，可能在感染过程中利用这些机制发挥其优势。Torrelles博士目前在施莱辛格博士的实验室的研究重点是了解结核分枝杆菌如何利用其甘露糖基化表面来识别和适应宿主。他正在研究表面甘露糖基化脂聚糖在c型凝集素对人巨噬细胞的识别中的作用，以及M.tb甘露糖覆盖的脂阿拉伯糖甘露聚糖在这些细胞中的代谢。对于结核分枝杆菌在巨噬细胞外的肺泡微环境中如何受到免疫压力的影响，我们所知甚少。除肺泡巨噬细胞外，肺泡间隙肺防御的主要成分是I型和II型上皮细胞、单核细胞和中性粒细胞，以及它们分泌到肺泡腔的产物（即表面活性剂）。每个肺泡隔室细胞都有自己独特的水解酶阵列，这些酶被释放到肺泡环境中，并被表面活性剂隔离。当结核分枝杆菌最初沉积在末端细支气管和肺泡中，以及从裂解的巨噬细胞中释放出来时，杆菌与这些水解酶密切接触。在K99/R00 NIH独立途径奖期间，Torrelles博士将研究人类肺泡环境对结核分枝杆菌细胞包膜的影响以及这些影响如何决定宿主内结核分枝杆菌的命运。利用放射性标记的毒力结核分枝杆菌H37Rv，以及生物化学、分子和细胞生物学方法，我们提出：1)表征来自肺泡室细胞和肺表面活性剂的特异性水解酶对结核分枝杆菌H37Rv细胞包膜的影响。为了确保研究的重点，我们将优先考虑候选水解酶，并将实验限制在总共3-5个水解酶的研究中；2)表征我们选择的人肺水解酶对毒力M.tb H37Rv细胞包膜完整性的影响；3)研究水解酶修饰结核分枝杆菌H37Rv细胞膜对肺泡腔细胞内芽孢杆菌存活的影响。鉴定影响宿主内结核分枝杆菌命运的肺泡水解酶将有助于开发更具预测性的体外模型，并鉴定新的药物靶点。

DESCRIPTION (provided by applicant): When Mycobacterium tuberculosis (M.tb) infection occurs by airborne transmission, bacilli are deposited in the alveolar spaces of the lungs. Within the alveolar space and proximal to it exist a number of innate immune mechanisms that are critical in maintaining pulmonary homeostasis. M.tb, a highly host-adapted intracellular pathogen of macrophages, may use these mechanisms to its advantage during infection. Dr. Torrelles' current research in Dr. Schlesinger's laboratory is focused on understanding how M.tb uses its mannosylated surface in host recognition and adaptation. He is studying the role of surface mannosylated lipoglycans in recognition by C-type lectins on human macrophages and the metabolism of M.tb mannose-capped lipoarabinomannan within these cells. Little is known about how M.tb is affected by the immune pressure that it encounters in the alveolar microenvironment outside of the macrophage. In addition to alveolar macrophages, major constituents of lung defense in the alveolar space are type I and II epithelial cells, monocytes, and neutrophils, and their secreted products to the alveolar lumen (i.e., surfactant). Each of these alveolar compartment cells contains its own unique array of hydrolases that are released to the alveolar environment and sequestered in surfactant. When M.tb is initially deposited in the terminal bronchioles and alveoli, as well as following release from lysed macrophages, the bacilli are in close contact with these hydrolases. During the K99/R00 NIH Pathway to Independence Award, Dr. Torrelles will examine the effects of the human alveolar environment on the cell envelope of M.tb and how these effects dictate the fate of M.tb within the host. Using radiolabeled virulent M.tb H37Rv, and biochemical, molecular and cell biology approaches, we propose: 1) To characterize specific hydrolases derived from alveolar compartment cells and pulmonary surfactant that affect the cell envelope of M.tb H37Rv. To ensure that the studies remain focused, we will prioritize candidate hydrolases and restrict our experiments to the study of the 3-5 hydrolases in total; 2) To characterize the effects of our selected human lung hydrolases on the integrity of the virulent M.tb H37Rv cell envelope; and 3) To determine how hydrolase-derived modifications on the cell envelope of M.tb H37Rv affect the bacillus survival within alveolar compartment cells. The identification of alveolar hydrolases that affect M.tb fate within the host will enable more predictive in vitro models to be developed and novel drug targets to be identified.