PLASMIDS AND VIRULENCE IN PLAGUE

鼠疫中的质粒和毒力

• 批准号: 3132967
• 负责人: Jon D. Goguen
• 金额: $ 17.88万
• 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 1993-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3132967
• 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，鼠疫是一种自然疾病。 老鼠和其他啮齿动物也会影响人类。另外两个物种 在同一属中，假结核耶尔森氏菌和耶尔森氏菌 小肠结肠炎，也会引起人类疾病。这些入侵中的每一个 病原体携带一个大小约为75千碱基n的质粒 致病的关键因素：要么是质粒的丢失，要么是适当的 质粒突变会导致毒力完全丧失。75千碱基 这三个物种的质粒都有密切的亲缘关系。两个重要的因素 所有这些物种的明显特征是(1)复杂的调控 温度和钙离子浓度对质粒毒力基因的影响及(2) 对吞噬作用的抵抗力依赖于质粒。 温度和钙离子的调节被认为控制了细胞的表达 病毒在三个重要环境中的毒力基因 细菌：哺乳动物宿主外(低温)，宿主内，但 其他寄主细胞外(高温、高钙)和内 寄主细胞，如大噬菌体，这些细菌可以在其中生长(高密度 温度、低钙)。对吞噬的抵抗力由 这个监管体系。它被认为是在感染早期发展起来的， 也许是因为细菌躲在巨噬细胞内，并作用于 保护胞外细菌免受中性粒细胞的攻击 疾病后期的白细胞。这个活动就是质粒- 确定的属性与发病机制逻辑上最相关，很可能 解释了75kb的质粒在毒力中的关键作用。 调节和抵抗吞噬作用的机制是 人们对此知之甚少。该项目的长期目标是确定 巨噬细胞吞噬抵抗和细菌感染的分子机制 控制它的监管系统，并确定它们在其中的作用 发病机制。这将通过遗传和生物化学来实现。 Y.75kb质粒的基因和基因产物分析。 通过对小鼠和吞噬细胞相互作用的分析 含有鼠疫耶尔森氏菌菌株的细胞携带明确的突变质粒。 鼠疫耶尔森氏菌携带的质粒不是75千碱基的物种，而是 在另一个耶尔西尼亚没有发现，并可能至少部分解释了 瘟疫的系统性和暴发性。从9.5千个基数 在鼠疫耶尔森氏菌菌株中常见的质粒，我们最近定义了 测序了一个基因，命名为pla，它编码这两种纤溶酶原 激活剂和凝固酶活性。我们认为很可能是 该基因对鼠疫耶尔森氏菌的传播能力很重要 迅速从周围感染部位和两个重要特征 鼠疫病理学：严重弥漫性血管内凝血和 大出血。作为该项目的一部分，我们将通过以下方式测试这些假设 分析PLA基因突变对疾病严重程度和预后的影响 从而在小鼠感染实验中进行病理学检查。 这些研究将提供基本信息，以了解 耶尔森氏菌毒力基因的功能和调控，并应 在改进的鼠疫疫苗的设计中也被证明是有用的。