Global and temporal effects of virulence gene expression during pneumonic plague

描述（由申请人提供）：鼠疫耶尔森菌是造成毁灭性疾病鼠疫的原因，由于其传播潜力高、疾病进展迅速、发病率和死亡率高，特别是通过气溶胶途径，被列为a类精选药剂。原发性肺鼠疫发生在个人吸入带有鼠疫杆菌的气溶胶或飞沫时，因此具有高度传染性，几乎总是致命的。小鼠感染模型显示，原发性肺鼠疫是一种令人惊讶的双相综合征，其中感染在最初的24-36小时内以静止或抗炎状态开始，随后在48小时内过渡到高度促炎状态。因此，为了生存、复制和传播给新的宿主，鼠疫杆菌必须能够控制和应对快速变化的宿主环境。在感染过程中，耶尔森菌毒力的一个必要组成部分是基于质粒的YscType III分泌系统（T3SS），它将六种效应蛋白直接递送到宿主细胞的细胞质中。这些被称为Yops的蛋白质被认为可以调节宿主的反应，以防止吞噬、炎症和激活对耶尔森氏菌的有效免疫，特别是在感染的早期。由于T3SS对肺内鼠疫毒力的要求以及感染过程中效应体Yops基因表达模式的差异，我预测随着宿主细胞类型和肺部炎症状态的改变，Yops对肺部感染的相对贡献会发生变化。因此，本研究的目的是：1)在小鼠感染模型中，通过从完全毒力菌株中靶向删除这些基因，确定六种效应Yops中的每一种如何参与鼠疫杆菌的毒力和改变宿主炎症状态；2)利用外源诱导启动子系统改变Yop表达，研究细菌基因表达的时机如何影响鼠疫杆菌调节肺中抗炎和促炎状态转换的能力。在这样做的过程中，我期望更好地了解鼠疫杆菌如何能够成功地感染肺部并引起疾病，这将有助于确定针对这一公共卫生威胁的疫苗开发和治疗目标。

DESCRIPTION (provided by applicant): Yersinia pestis, the cause of the devastating disease plague, is classified as a Category A select agent due to its elevated potential for transmissibility, rapid disease progression, and high morbidity and mortality, particularly by the aerosol route. Primary pneumonic plague results when an individual inhales aerosols or droplets carrying Y. pestis, and as such is highly contagious and almost always fatal. A mouse model of infection shows that primary pneumonic plague is a surprisingly biphasic syndrome, in which the infection begins with a quiescent or anti-inflammatory state in the first 24-36 hours that subsequently transitions to a highly pro-inflammatory state by 48 hours. Thus, in order to survive, replicate, and be transmitted to new hosts, Y. pestis must be able to control and respond to a rapidly changing host environment. A necessary component of Yersinia virulence during infection is the plasmid-based YscType III secretion system (T3SS) that delivers six effector proteins directly into the cytosol of host cells. Together these proteins, termed Yops, are thought to modulate the host response to prevent phagocytosis, inflammation, and activation of effective immunity against Yersinia species, particularly early in the infection. Due to the requirement of the T3SS to plague virulence in the lung and the differential gene expression pattern of the effector Yops during infection, I predict that the relative contributions of the Yops to the pulmonary infection change as the types of host cells and inflammatory state of the lungs are altered. Therefore, the goals of this study are 1) to determine how each of the six effector Yops contribute to the virulence of Y. pestis and changing host inflammatory state during primary pneumonic plague in the mouse model of infection via the targeted deletion of these genes from a fully virulent strain, and 2) to examine how the timing of bacterial gene expression affects the ability of Y. pestis to modulate the transition between the anti- and pro-inflammatory states in the lung by altering Yop expression using an exogenously inducible promoter system. In so doing, I anticipate developing a better understanding of how Y. pestis is able to successfully infect the lungs and cause disease, which will facilitate the identification of targets for vaccine development and treatment for this public health threat.