Outer membrane proteins of Borrelia burgdorferi

描述(申请人提供)：莱姆病是世界范围内的一个主要公共卫生问题，也是美国最常见的节肢动物传播的感染。伯氏疏螺旋体是北美莱姆病的病原，是一种细胞外病原体，具有逃避宿主免疫反应的独特能力，可感染个体数年至数十年。为了更好地了解这种微生物如何在受感染的哺乳动物体内存活，许多实验室，包括我们自己的实验室，都专注于鉴定和表征伯氏杆菌的外表面蛋白。由于伯氏杆菌与其哺乳动物宿主之间的界面是其外表面，因此定位在外膜上的蛋白质在传播、毒力、组织趋向性以及最终的免疫逃避中发挥着重要作用。在过去的资助期间，我们已经鉴定并专注于伯氏杆菌的几种外表面脂蛋白(OSPs)。我们已经确定了许多表面脂蛋白在发病机制中的作用，并检查了它们作为疫苗候选的潜力。虽然我们继续在表征能够结合H因子以帮助帮助螺旋体的表面脂蛋白方面非常有成效 为了在感染的急性期逃避血清介导的杀伤，我们还没有确定一种特定的脂蛋白，可以作为莱姆病的潜在候选疫苗。在过去的一段时间里，我们对各种脂蛋白缺乏良好的疫苗效力，这促使我们开始寻找完整的、跨膜的外膜蛋白(OMP)，这些蛋白可能被用作更可行的莱姆病潜在疫苗候选。这些最新的研究也引导我们发现了OMP在伯氏杆菌外膜上的伴侣和组装所需的蛋白质机制。虽然螺旋体的外膜生物发生机制尚不清楚，但我们最近的研究表明，为了将OMPS正确地组装到片状OM中，需要一个异源低聚OM蛋白β-桶组装机器(BAM)复合体。伯氏杆菌BAM复合体由完整的外膜蛋白BAMA和位于外膜内叶的另外两个周质脂蛋白BB0324和BB0028组成。我们已经证明，将OMPS插入到硼的外膜中需要硼的BAM络合物。我们在这份修订后的更新申请中提出的研究将使我们能够表征BAM复合体，并详细研究它在OMPS输出和转运到这种螺旋体病原体表面的作用。更好地理解BAM复合体伴侣并将OMP输出到伯氏杆菌表面的基本机制也将使我们第一次开始阐明完整的外表面 伯氏假单胞菌OMP积分含量。此外，由于BAM系统是所有革兰氏阴性菌中OMP输出和定位的保守途径，因此本文概述的研究可能导致新型抗菌化合物的开发，这些化合物不仅对致病螺旋体如伯氏杆菌和梅毒螺旋体有影响，而且可能广泛适用于其他重要的人类病原体，如大肠杆菌、沙门氏菌、弧菌、假单胞菌、奈瑟氏菌、螺杆菌等。

DESCRIPTION (provided by applicant): Lyme disease is a major public health problem worldwide and is the most common arthropod- borne infection in the United States. Borrelia burgdorferi, which is the cause of Lyme disease in North America, is an extracellular pathogen that has the unique ability to evade the host immune response and infect individuals for years to decades. To gain a better understanding of how this organism persists in the infected mammal, many laboratories, including our own, have focused on identifying and characterizing outer surface proteins of B. burgdorferi. Since the interface between B. burgdorferi and its mammalian host is its outer surface, proteins localized in the outer membrane must play an important role in dissemination, virulence, tissue tropism, and, ultimately, immune evasion. Over the last funding period, we have identified and focused on several outer surface lipoproteins (Osps) from B. burgdorferi. We have determined the role of numerous surface lipoproteins in pathogenesis and examined their potential as vaccine candidates. While we continue to be very productive in characterizing surface lipoproteins that are capable of binding factor H to help aid the spirochete in evading serum-mediated killing during the acute stage of infection, we have yet to identify a specific lipoprotein that could work as a potential vaccine candidate for Lyme disease. The lack of good vaccine efficacy for the various lipoproteins we have been characterizing over the last funding period prompted us to start identifying integral, membrane spanning, outer membrane proteins (OMPs) that could be used as more viable potential vaccine candidates for Lyme disease. These more recent studies also led us to discover the protein machinery required for chaperoning and assembling OMPs into the B. burgdorferi outer membrane. Although the mechanism of outer membrane biogenesis is poorly understood in spirochetes, our recent studies have indicated that a heterooligomeric OM protein beta-barrel assembly machine (BAM) complex is required for proper assembly of OMPs into the borrelial OM. The B. burgdorferi BAM complex is made up of the integral outer membrane protein BamA, and two additional periplasmic lipoproteins located in the inner leaflet of the outer membrane, BB0324 and BB0028. We have shown that the borrelial BAM complex is required for inserting OMPs into the borrelial outer membrane. The studies we propose in this revised, renewal application will allow us to characterize the BAM complex and examine in detail its role in export and translocation of OMPs to the surface of this spirochetal pathogen. A better understanding of the basic mechanisms by which the BAM complex chaperones and exports OMPs to the surface of B. burgdorferi will also allow us, for the first time, to begin elucidating the complete outer surface integral OMP content of B. burgdorferi. Additionally, since the BAM system is a conserved pathway for OMP export and localization among all Gram-negative bacteria, the studies outlined here could lead to the development of novel antibacterial compounds that could have an impact not only against pathogenic spirochetes such as B. burgdorferi and Treponema pallidum, but could potentially be widely applicable against other important human pathogens, such as E. coli, Salmonella, Vibrio, Pseudomonas, Neisseria, Helicobacter and others.