MOLECULAR AND CELL BIOLOGY OF PATHOGENIC MYCOBACTERIA

溃疡分枝杆菌和海洋分枝杆菌是致病性分枝杆菌，可引起人类持续皮肤病变。与结核分枝杆菌一样，海洋分枝杆菌是一种兼性细胞内病原体，可引起人类肉芽肿性皮肤病和免疫功能低下患者危及生命的全身性感染。与结核分枝杆菌一样，海洋分枝杆菌在细胞内的巨噬细胞内复制，表现为成熟阻滞。我们实验室的工作旨在了解海洋分枝杆菌是如何利用巨噬细胞达到自己的目的，并避免通过溶酶体途径降解巨噬细胞的。由于海洋分枝杆菌和结核分枝杆菌之间的密切遗传关系，我们假设巨噬细胞内复制的机制即使不相同，也会相似。利用与绿色荧光蛋白的融合，我们从巨噬细胞中分离出几种表达差异的海洋分枝杆菌基因，并表明结核分枝杆菌中存在密切的同源物。一旦这些基因在发病机制中的作用被确定，我们将对结核分枝杆菌同源物进行突变。这项工作的总体目标是了解细胞内分枝杆菌如何能够在吞噬细胞内生存和复制。溃疡引起严重的坏死性皮肤病变（布鲁里溃疡），在存在广泛组织损伤的情况下没有急性炎症反应。我们已经从溃疡分枝杆菌中分离出一种毒素，并通过生化和遗传证据表明，这种分子在布鲁里溃疡的发病机制中起着重要作用。这种毒素分子，霉菌内酯，是一种12元环大环内酯，以picg量使真核细胞处于细胞周期阻滞（G1），随后通过凋亡死亡。我们目前正在研究霉菌内酯诱导细胞损伤和免疫抑制的确切机制。此外，我们正在探索是否一种毒素减突变体，可能是一种有效的疫苗。虽然大环内酯是亲脂性的，因此本身不具有抗原性，但我们正在探索使这种分子具有抗原性的可能性，并确定一种抗毒素是否有可能作为布鲁里溃疡的治疗剂。最后，某些肿瘤细胞系的微妙和不同的敏感性表明该分子可能具有抗肿瘤药物的价值。我们正在探索这种可能性。-大环内酯类，分枝杆菌多酮类，细胞内存活，避免溶酶体融合，L929细胞，J774巨噬细胞

Mycobacterium ulcerans and Mycobacterium marinum are pathogenic mycobacteria which cause persistent cutaneous lesions in humans. M. marinum, like M. tuberculosis is a facultative intracellular pathogen which causes a granulomatous skin disease in humans, and life threatening systemic infections in immunocompromised patients. Like M. tuberculosis, M. marinum replicates within macrophages in an intracellular compartment which shows arrested maturation. Work in our laboratory is directed towards understanding how M. marinum commandeers the macrophage for its own purposes and avoids degradation via the lysosomal pathway. Because of the close genetic relationship between M. marinum and M. tuberculosis, we hypothesize that the mechanisms involved in intramacrophage relication will be similar if not identical. Using fusions to Green Fluorescent Protein, we have isolated several genes from M. marinum expressed differentially in macrophages and have shown that close homologues are present in M. tuberculosis. Once the role of these genes in pathogenesis is established, we will make mutations in the M. tuberculosis homologues. The overall goal of this work is to understand how intracellular mycobacteria are able to survive and replicate within phagocytic cells.M. ulcerans causes a severe necrotic skin lesion (Buruli ulcer) remarkable for the absence of an acute inflammatory response in the presence of extensive tissue damage. We have isolated a toxin from M. ulcerans, amd shown with both biochemical and genetic evidence that this molecule plays a major role in the pathogenesis of Buruli ulcer. The toxin molecule, mycolactone, is a 12-membered ring macrolide which at picogram quantities places eucaryotic cells in cell cycle arrest (G1) followed by death via apoptosis. We are currently investigating the precise mechansm by which mycolactone induces cell damage and immunosuppression. In addition we are expoloring whether a toxin minus mutant, might be an effective vaccine. Although macrolides are lipophilic, and thus not antigenic by themselves, we are exploring the possibility of making this molecule antigenic and determining whether an anti-toxin might be valuable as a therapeutic agent for Buruli ulcer. Finally, the exquisite and differential sensitivity of some tumor cell lines suggests this molecule may have value as an anti-neoplastic agent. We are exploring this possibility. - macrolides, mycobacterial polyketides, intracellular survival, avoidance of lysosomal fusion, L929 cells, J774 macrophages