钩端螺旋体（简称钩体）病是全球性人兽共患病。动物感染后尿液排菌形成疫水、人接触疫水感染后从血流扩散至内脏分别是钩体病流行和病情恶化关键。近年发现细菌利用细胞内吞循环系统／囊泡运输系统（ERS/VTS）跨细胞扩散及泡内繁殖。我们前期研究发现钩体通过跨细胞途径穿越血管内皮细胞且吞噬泡不与溶酶体融合，也能穿越肾小管上皮和成纤维细胞且胞内钩体数量增加，但机制不明。本项目拟从分子／细胞和动物不同层次并采用先进可靠技术，先确定ITG-FAK或CAV1-PI3K通路介导血管内皮、肾小管上皮和成纤维细胞内吞钩体分子机制，再确定钩体吞噬泡经Rab5-Rab4-Rab11或CAV1-EEA1-Rab11囊泡转运途径形成出胞及膜融合复合体、激活钙通道并经FAK或PI3K通路介导Ca2+及微丝或微管依赖细胞骨架重排实现胞外钩体跨细胞转运以及肾细胞吞噬泡内钩体繁殖与出胞分子机制，对钩体病防控及治疗均具有重要意义。

Leptospirosis is a globally-spreading zoonotic disease. Animals after infection with Leptospira will discharge leptospires from their urine to contaminate natural water, while humans will be infected by contact with the Leptospira-containing water and the invaded leptospires in patient’s bloodstream diffuse into internal organs to cause the aggravation of patient’s condition. The recent literatures reported that bacteria can utilize cellular endocytic recycling system / vesicular transport system (ERS/VTS) to diffuse in vivo through transcytosis and propagate in vesicles. Our previous study found that leptospires pass through the vascular endothelial cell monolayers by transcytosis and their phagocytotic vesicles did not fuse with lysosomes, while leptospires could also pass through the renal tubule epithelial cells and fibroblasts and the leptospiral number was increased, but their molecular machanims are unknown. In this project, we will study from molecular, cellular and animal levels and use advanced and reliable techniques to determine the mechanism of vascular endothelial cells, renal tubule epithelial cells and fibroblasts phagocytosing the leptospires through ITG-FAK- or CAV1-PI3K-mediated pathway. Subsequently, we will determine the mechanisms of extracellular leptospiral transcytosis through Rab5-Rab4-Rab11 or CAV1-EEA1-Rab11 vesicle transport route, formation of exocyst complex and membrane fusion complex, activation of calcium channels, and FAK or PI3K signaling pathway-mediated Ca2+ / microfilament or microtubule-dependent cytoskeleton rearragment as well as the the mechanisms of leptospiral propagation in phagocytotic vesicles of renal cells and exocytosis of the propagated leptospires. The results of this project have important significance in control and treatment of leptospirosis.