PLASMIDS AND VIRULENCE IN PLAGUE

鼠疫中的质粒和毒力

• 批准号: 3132962
• 负责人: Jon D. Goguen
• 金额: $ 19.18万
• 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/3132962
• 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 假结核耶尔森菌和耶尔森菌属于同一属 小肠结肠炎，也会引起人类疾病。 这些侵入性的每一个 病原体携带大约 75 KB n 大小的质粒， 发病机制所必需的：要么丢失质粒，要么适当 质粒突变导致毒力完全丧失。 75 千碱基 所有三个物种的质粒都密切相关。 两个重要的 所有这些物种的明显特征是（1）复杂的调节 质粒毒力基因随温度和 Ca 2+ 浓度的变化以及 (2) 吞噬作用抗性的质粒依赖性发展。 据信温度和 Ca 2+ 的调节可以控制 毒力基因在三种重要环境中的作用 细菌：在哺乳动物宿主外部（低温），在宿主内部，但是 其他宿主细胞外部（高温、高 Ca 2+）和内部 这些细菌可以在其中生长的宿主细胞，例如巨噬细胞（高 温度，低Ca 2+)。 对吞噬作用的抵抗力由以下因素控制 这个监管体系。 人们认为它是在感染早期发展的， 也许是因为细菌被隐藏在巨噬细胞内，并发挥作用 保护细胞外细菌免受多形核细胞的攻击 疾病后期阶段的白细胞。 该活性是质粒- 确定的属性在逻辑上与发病机制最相关，并且很可能 解释了 75kb 质粒在毒力中的关键作用。 吞噬作用的调节和抵抗机制是 不太了解。 该项目的长期目标是确定 吞噬作用抵抗和吞噬作用的分子机制 控制它的监管体系，并确定它们在其中的作用 发病。 这将通过遗传和生化来实现 Y. 75 kb 质粒的基因和基因产物分析。 鼠疫菌，并通过分析小鼠和吞噬细胞的相互作用 含有鼠疫耶尔森氏菌菌株的细胞，带有明确的突变质粒。 鼠疫耶尔森氏菌携带除 75 KB 物种以外的质粒，这些质粒是 在其他耶尔森氏菌中未发现，并且可能至少部分地解释了 鼠疫的系统性和暴发性特征 从 9.5 公斤起 鼠疫耶尔森菌株中常见的质粒，我们最近定义并 对一个名为 pla 的基因进行了测序，该基因编码两种纤溶酶原 激活剂和凝固酶活性。 我们认为产品很可能 该基因对于鼠疫耶尔森氏菌的传播能力很重要 迅速从周围感染部位传播并具有两个重要特征 鼠疫病理学：严重弥散性血管内凝血 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突变对疾病的影响和 小鼠感染实验中产生的病理学。 这些研究将为理解 耶尔森菌毒力基因的功能和调节，并且应该 也被证明对于改进鼠疫疫苗的设计很有用。