Role of surface exposed proteins of M. paratuberculosis in the pathogenesis of Johne's disease in ruminants

鸟分枝杆菌副结核病（MAP）是约内氏病（JD）的病原体，约内氏病是反刍动物的一种使人衰弱的慢性胃肠炎。JD对奶牛有很大的经济影响，因为过早淘汰，降低了胴体价值和牛奶产量。人们也越来越关注Map与克罗恩病的关系。由于JD没有可用的治愈方法和受阻碍的控制程序，迫切需要通过鉴定和表征参与发病机制和宿主免疫应答的细菌组分来改进诊断工具。我们已经确定了两个蛋白质家族的地图，PE和PPE蛋白，这是有前途的候选人在这方面。这些科是分枝杆菌所特有的，并且在该属的致病成员中高度扩展。In M.在结核病（Mtb）中，它们涉及毒力因子，并且已知在感染期间是免疫刺激性的。一些Mtb PE/PPE蛋白在细胞表面上表达，并被认为提供可能导致免疫逃避的抗原变异。在Map中有10个PE和37个PPE基因，占基因组的1%，但它们在JD中的潜在作用从未被研究过。所提出的研究的假设是，Map的一些PPE蛋白通过与细胞壁结合而暴露于表面，在细胞壁处它们与宿主细胞相互作用以促进感染。我们最近发现四个PPE蛋白的地图是表面暴露在细胞壁在体外。我们将进一步研究PPE蛋白在Map中的亚细胞定位，因为这暗示了它们的功能。我们将通过分析PPE蛋白在巨噬细胞摄取Map细胞和侵入上皮细胞后的表达来更好地了解它们在感染中的作用。我们将研究PE和PPE蛋白质之间的假定复合物形成，并确定PPE蛋白质与宿主蛋白质，细胞和组织的其他蛋白质-蛋白质相互作用。最后，我们将研究PPE蛋白与细胞壁的特异性相互作用。我们预计，发现的功能（S）和相互作用的PE和PPE蛋白的地图将有很大的影响，对JD的发病机制的理解。

Mycobacterium avium subsp. paratuberculosis (Map) is the causative agent of Johne's disease (JD), a debilitating chronic gastroenteritis in ruminants. JD has a great economic impact in dairy cattle due to premature culling, reduced carcass value and decreased milk production. There is also a growing concern about the association of Map with Crohn's disease. With no available cure for JD and hampered control programs, there is an urgent need to improve diagnostic tools by the identification and characterization of the bacterial components involved in the pathogenesis and the host immune response. We have identified two protein families in Map, the PE and PPE proteins, which are promising candidates in this respect. Those families are unique to Mycobacteria and are highly expanded in the pathogenic members of this genus. In M. tuberculosis (Mtb), they are implicated as virulence factors and known to be immunostimulatory during infection. Some of the Mtb PE/PPE proteins are expressed on the cell surface and are suggested to provide the antigenic variation that could lead to immune evasion. There are 10 PE and 37 PPE genes in Map, comprising 1% of the genome, but their potential role in JD has never been studied. The hypothesis of the proposed studies is that some PPE proteins of Map are surface exposed by binding to the cell wall where they interact with host cells to promote infection. We have recently discovered four PPE proteins of Map to be surface exposed on the cell wall in vitro. We will further study the subcellular localization of the PPE proteins in Map since this is suggestive of their function. We will gain a better understanding of their role in infection by analyzing the expression of the PPE proteins after ingestion of Map cells by macrophages and invasion in epithelial cells. We will study the putative complex formation between PE and PPE proteins and identify other protein-protein interactions of the PPE proteins with host proteins, cells and tissues. Finally, we will investigate the specific interactions of the PPE proteins with the cell wall. We anticipate that the discovery of the function(s) and interactions of the PE and PPE proteins of Map will have a great impact on the understanding of the pathogenesis of JD.