Mechanisms of Mycoplasmal Disease Pathogenesis

支原体疾病发病机制

基本信息

批准号：
8512647
负责人：
KEVIN F DYBVIG
金额：
$ 34.57万
依托单位：
UNIVERSITY OF ALABAMA AT BIRMINGHAM
依托单位国家：
美国
项目类别：
财政年份：
2005
资助国家：
美国
起止时间：
2005-03-01 至 2015-07-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8512647
关键词：
ATP-Binding Cassette Transporters Acetylglucosamine Address Adherence Animal Model Animals Antibiotic Therapy Arthritis Bacteria Binding Biological Assay Cell Wall Cells Chronic Chronic Disease Code Complement Complex Cytolysis Data Development Disaccharides Disease Domestic Fowls Electron Microscopy Electrons Enzymes Extracellular Matrix Galactans Galactose Genes Genital system Glass Glucose Glycolipids Glycosyltransferase Gene Goals Hand Host Defense Human Industry Infection Infection Control Joints Knowledge Lead Measures Mechanics Membrane Microbial Biofilms Mus Mycoplasma Mycoplasma arthritidis Mycoplasma gallisepticum Mycoplasma hyopneumoniae Mycoplasma mycoides Mycoplasma penetrans Mycoplasma pneumoniae Mycoplasma pulmonis Operon Organism Outcome Pathogenesis Pathway interactions Phagocytosis Plastics Polysaccharides Predisposition Production Proteins Reporting Research Research Personnel Role Solid Structure Surface Surface Antigens System Thinking Tissues Trachea Vaccines Virulence antimicrobial peptide base capsule epimerase evidence base gene cloning genome sequencing glycosyltransferase killings macrophage man mutant novel novel strategies pathogen respiratory sugar sugar nucleotide

项目摘要

DESCRIPTION (provided by applicant): The surface of virtually all bacterial pathogens is coated with polysaccharides (exopolysaccharides, EPS) that can protect bacteria from host defenses and modulate the ability of the bacteria to adhere to various surfaces including host cells and tissue and other bacteria. The field of mycoplasmology has largely ignored polysaccharides although electron micrographs suggest that many species produce a capsule and some species form biofilms that should contain EPS in the extracellular matrix. Mycoplasmas cause chronic respiratory, genital and arthritic diseases in many animals including man. The lack of a cell wall might seem to make mycoplasmas highly susceptible to killing by host defenses, but these organisms are often difficult to eradicate from the host even with the help of antibiotic therapy. Polysaccharides may be a contributing factor to the chronicity of mycoplasmal infections. Our long-range goals are to unravel the pathogenic mechanisms of mycoplasmas, with the murine pathogen Mycoplasma pulmonis serving as a model organism. One factor that contributes to the avoidance of host defenses is the mycoplasma's Vsa (variable surface antigen) proteins that protect the cells from lysis by complement and modulate adherence to solid surfaces and thus biofilm formation. Our studies on biofilms led to the recent realization that polysaccharides are produced despite the fact that the complete genome sequence of M. pulmonis has few genes annotated as having a potential role in EPS synthesis. Nevertheless, M. pulmonis produces at least two EPS molecules (EPS-I and EPS-II). Aim 1 of this proposal is to determine the structure of EPS-I and II. Knowledge of the structures will be instrumental in understanding the mechanism of their synthesis and the mechanics of how they interact with mycoplasmal proteins and host molecules. Aim 2 is to study the pathway of EPS synthesis through the isolation and study of mutants that do not produce EPS-I or II. There are several reasons for suspecting that the mechanism for synthesis may be fundamentally novel. Some data suggest that nucleotide sugars are not needed as substrates for EPS synthesis in this system. Several of the genes that are required for synthesis of EPS-I or EPS-II have already been identified. These genes code for proteins that are annotated as ABC transporters. However, EPS-I is synthesized when an operon containing two of these genes are cloned into other species of mycoplasma. Thus, these genes may code for novel glycosyltransferases that are transporters only in the sense that they export the growing polysaccharide chain during synthesis. The synthesis machinery in this system will likely be important and found in other mycoplasmas and possibly walled bacteria. Aim 3 is to examine the role of each EPS in pathogenesis. Mutants that do not produce EPS-I or EPS-II will be compared to wild-type mycoplasmas for the ability to avoid killing by complement, cytadhere, avoid phagocytosis, and cause disease in mice. These studies will lead to the development of new approaches for the control of mycoplasmal infections, such as the targeting of the polysaccharides or the machinery for their synthesis.

描述（由申请人提供）：几乎所有细菌病原体的表面都涂有多糖（胞外多糖，EPS），可以保护细菌免受宿主防御并调节细菌粘附到各种表面（包括宿主细胞和组织以及其他细菌）的能力。支原体学领域在很大程度上忽略了多糖，尽管电子显微照片表明许多物种产生荚膜，一些物种形成生物膜，在细胞外基质中应含有 EPS。支原体在包括人类在内的许多动物中引起慢性呼吸道、生殖器和关节炎疾病。缺乏细胞壁似乎使支原体非常容易被宿主防御杀死，但即使在抗生素治疗的帮助下，这些生物体通常也很难从宿主中根除。多糖可能是支原体感染慢性化的一个因素。我们的长期目标是以鼠病原体肺支原体作为模式生物，揭示支原体的致病机制。有助于避免宿主防御的因素之一是支原体的 Vsa（可变表面抗原）蛋白，它通过补体保护细胞免遭裂解，并调节对固体表面的粘附，从而形成生物膜。我们对生物膜的研究使我们最近认识到，尽管肺支原体的完整基因组序列中很少有基因被注释为在 EPS 合成中具有潜在作用，但多糖仍然会产生。然而，肺支原体至少产生两种 EPS 分子（EPS-I 和 EPS-II）。该提案的目标 1 是确定 EPS-I 和 EPS-II 的结构。了解这些结构将有助于理解它们的合成机制以及它们如何与支原体蛋白和宿主分子相互作用的机制。目标2是通过分离和研究不产生EPS-I或II的突变体来研究EPS合成途径。有几个理由怀疑合成机制可能是根本新颖的。一些数据表明，在该系统中不需要核苷酸糖作为 EPS 合成的底物。合成 EPS-I 或 EPS-II 所需的几个基因已被鉴定。这些基因编码的蛋白质被注释为 ABC 转运蛋白。然而，当含有两个这些基因的操纵子被克隆到其他支原体物种中时，EPS-I就被合成了。因此，这些基因可能编码新型糖基转移酶，这些糖基转移酶仅在合成过程中输出不断增长的多糖链的意义上才是转运蛋白。该系统中的合成机制可能很重要，并且在其他支原体和可能的有壁细菌中也有发现。目标 3 是检查每种 EPS 在发病机制中的作用。将不产生 EPS-I 或 EPS-II 的突变体与野生型支原体进行比较，以确定其避免被补体杀死、细胞粘附、避免吞噬作用和引起小鼠疾病的能力。这些研究将导致控制支原体感染的新方法的开发，例如多糖的靶向或其合成机制。