PLASMIDS AND VIRULENCE IN PLAGUE

鼠疫中的质粒和毒力

• 批准号: 3132966
• 负责人: Jon D. Goguen
• 金额: $ 17.19万
• 依托单位: UNIV OF MASSACHUSETTS MED SCH WORCESTER
• 依托单位国家: 美国
• 财政年份: 1986
• 资助国家: 美国
• 起止时间: 1986-12-01 至 1992-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3132966
• 关键词: Yersinia pestis; Yersinia pestis disease; bacterial antigens; bacterial cytopathogenic effect; bacterial genetics; bacterial proteins; calcium; gene expression; genetic manipulation; genetic mapping; genetic regulation; laboratory mouse; laboratory rabbit; molecular cloning; mutant; nucleic acid sequence; phagocytes; plasmids; plasminogen activator; temperature; tissue /cell culture; virulence

Yersinia pestis is the causative agent of plague, a natural disease of mice, rats, and other rodents which also affects man. two other species in the same genus, Yersinia pseudotuberculosis and Yersinia enterocolitica, also cause human disease. Each of these invasive pathogens carries a plasmid approximately 75 kilobases n size which is essential to pathogenesis: either loss of the plasmid or appropriate plasmid mutations results in complete loss of virulence. The 75 kilobase plasmids of all three species are closely related. Two important features apparent in all of these species are (1) complex regulation of plasmid virulence genes by temperature and Ca 2+ concentration and (2) plasmid-dependent development of resistance to phagocytosis. Regulation by temperature and Ca 2+ is believed to control expression of virulence genes in three important environments encountered by the bacteria: outside a mammalian host (low temperature), inside a host, but outside other the hosts cells (high temperature, high Ca 2+) and within host cells, such as machrophages, in which these bacteria can grow (high temperature, low Ca 2+). Resistance to phagocytosis is controlled by this regulatory system. It is thought to develop early in infection, perhaps as the bacteria are sheltered within macrophages, and act to protect extracellular bacteria from attack by polymorphonuclear leukocytes during later stages of disease. this activity is the plasmid- determined property most logically related to pathogenesis and may well account for the critical role of he 75kb plasmids in virulence. The mechanisms of both regulation and resistance to phagocytosis are poorly understood. The long-term goals of this project are to determine the molecular mechanisms of both resistance to phagocytosis and the regulatory system which controls it, and determine their role in pathogenesis. This will be accomplished through genetic and biochemical analysis of the genes and gene products of the 75 kb plasmid of Y. pestis, and by analysis of the interaction of both mice and phagocytic cells with Y. pestis strains bearing well-defined mutant plasmids. Y. pestis carries plasmids other than the 75 kilobase species which are not found in the other Yersinia and may account, at least in part, for the systemic and fulminant character of plague. From the 9.5 kilobase plasmid commonly found in Y. pestis strains, we have recently defined and sequenced a gene, designated pla, which encodes both plasminogen activator and coagulase activities. We think it likely that products of this gene are important in the ability of Y. pestis to disseminate rapidly from a periferral site of infection and in two important features of plague pathology: severe disseminated intravascular coagulation and hemorrhaging. As part of this project we will test these hypotheses by analyzing the effect of pla mutations on the coarse of disease and the resulting pathology in mouse infection experiments. These studies will provide information fundamental to understanding the function and regulation of virulence genes in the yersiniae, and should also prove useful int he design of improved plague vaccines.

鼠疫耶尔森氏菌是鼠疫的病原体， 老鼠，大鼠和其他啮齿动物，也影响人类。另外两个物种 假结核耶尔森氏菌和耶尔森氏菌属 小肠结肠炎也会引起人类疾病。 每一种侵入性 病原体携带大小约为75个内切酶的质粒， 致病所必需的：质粒的丢失或适当的 质粒突变导致毒力完全丧失。 第75章 所有三个物种的质粒都密切相关。 两个重要 所有这些物种的明显特征是（1）复杂的调节， 温度和Ca 2+浓度对质粒毒力基因的影响; 对吞噬作用的抗性的质粒依赖性发展。 温度和Ca 2+的调节被认为控制了 毒力基因在三个重要的环境中遇到的 细菌：哺乳动物宿主外（低温），宿主内，但 在其他宿主细胞外（高温、高Ca 2+）和细胞内 宿主细胞，例如这些细菌可以生长的宿主细胞（高 温度、低Ca 2+）。 对吞噬作用的抵抗力由 这个监管体系。 人们认为它会在感染早期发展， 也许是因为细菌被巨噬细胞所保护， 保护细胞外细菌免受多形核菌的攻击 白细胞在疾病后期。 这个活性就是质粒 确定的属性最逻辑相关的发病机制， 解释了75 kb质粒在毒力中的关键作用。 调节和抵抗吞噬作用的机制是 不太了解。 该项目的长期目标是确定 抗吞噬作用的分子机制和 监管系统，控制它，并确定他们的作用， 发病机制 这将通过遗传和生物化学 对Y. 鼠疫，并通过分析小鼠和吞噬细胞的相互作用， Y.携带明确的突变质粒的鼠疫菌株。 Y.鼠疫携带质粒，而不是75种酶， 在其他耶尔森氏菌中没有发现，至少部分原因是 鼠疫的系统性和暴发性。 从9.5倍酶 质粒在Y.鼠疫菌株，我们最近定义， 对一个命名为pla的基因进行测序，该基因编码纤溶酶原和 激活剂和凝固酶活性。 我们认为， 这个基因对Y染色体的能力很重要。传播鼠疫 从感染的外周部位迅速地，并且在两个重要特征中 鼠疫病理学：严重的弥散性血管内凝血和 - - 作为本项目的一部分，我们将测试这些假设， 分析了pla突变对疾病的影响， 导致小鼠感染实验中的病理学。 这些研究将提供基本的信息，以了解 耶尔森氏菌毒力基因的功能和调控，并应 在改进鼠疫疫苗的设计中也证明是有用的。