A Humanized Mouse Model of Typhoid Fever

性状（由申请方提供）：肠道沙门氏菌Sv.伤寒（S.伤寒（Typhi）是人类伤寒的病原体，可在正常宿主中引起危及生命的感染。目前的伤寒疫苗只有中等免疫原性和保护性。由于缺乏小动物模型，疫苗技术的改进受到限制。S.伤寒对人类高度适应，在正常小鼠中不会引起进行性感染。S.鼠伤寒-鼠相互作用用于模拟S.伤寒-人的相互作用，但鼠伤寒和人伤寒表现出病原体和宿主决定因素的重大差异。在应用中，我们报告了一个突破性的发展，一个小动物模型的研究，人类伤寒，使用NOD-scid IL 2 rgamma空小鼠移植CD 34+人造血干细胞从T细胞耗尽的脐带血。初步研究表明，S.伤寒Ty 2可以在腹腔内接种后在移植小鼠体内复制，引起致命感染，重现了人类伤寒的关键特征。相反，S.伤寒不能在非移植的NOD-scid IL 2 r γ无效动物或免疫活性NOD对照中引起生产性感染。本申请描述了一个试点项目，以评估这一新的模型，并严格测试的假设，S。伤寒需要人类单核细胞在体内复制。该项目的具体目标是： 1.人源化小鼠伤寒模型的表征。新模型将使用微生物学、组织病理学和流式细胞术方法来表征，以确定感染过程、先天免疫应答和细胞凋亡的重要性。 2. S的鉴定。人源化小鼠中复制所需的伤寒杆菌基因。一种基于微阵列的方法将被用于识别损害S的转座子突变。伤寒毒力。 我们的模型提供了一个前所未有的机会，以获得新的见解伤寒发病机制，确定新的S。伤寒疫苗候选人和制定新的战略，预防沙门氏菌。伤寒感染。 公共卫生相关性：本提案的目的是描述一种新的人源化小鼠伤寒模型，并使用该模型来鉴定伤寒沙门氏菌毒力的遗传决定因素。模拟人类伤寒的小动物模型代表了开发更有效的伤寒疫苗的重大进展。公共卫生声明：伤寒沙门氏菌仍然是一种严重的人类病原体，估计每年造成16，000，000例感染，并导致600，000多人死亡。目前可用的两种伤寒疫苗并不完全有效，只能提供短期保护。伤寒疫苗的开发一直受到缺乏小动物模型的限制。在本申请中，我们报告了人源化小鼠模型的突破性发展，该模型重现了人类伤寒的关键方面。 伤寒沙门氏菌能够在移植了从脐带血中获得的人类免疫细胞的小鼠中复制，产生进行性致命感染。这是第一次提供了一个实验系统来分析伤寒临床结果的宿主和微生物决定因素。本研究将为S.伤寒与人体免疫系统的关系，并确定构建安全有效伤寒疫苗的新策略。

DESCRIPTION (provided by applicant): Salmonella enterica sv. Typhi (S. Typhi) is the etiologic agent of typhoid fever in humans and can cause life-threatening infection in normal hosts. Current typhoid vaccines are only moderately immunogenic and protective. Improvements in vaccine technology have been constrained by the lack of a small animal model. S. Typhi is highly adapted to humans and fails to cause progressive infection in normal mice. S. Typhimurium- murine interactions are used to model S. Typhi-human interactions, but murine typhoid and human typhoid exhibit major differences in both pathogen and host determinants. In the application, we report a breakthrough in the development of a small animal model for the study of human typhoid fever, using NOD-scid IL2rgamma null mice engrafted with CD34+ human hematopoietic stem cells from T-cell depleted umbilical cord blood. In preliminary studies, we have shown that S. Typhi Ty2 can replicate in vivo within engrafted mice following intraperitoneal inoculation to cause lethal infection that recapitulates crucial features of human typhoid. In contrast, S. Typhi is unable to cause productive infection in non-engrafted NOD-scid IL2rgamma null animals or immunocompetent NOD controls. This application describes a pilot project to evaluate this new model and rigorously test the hypothesis that S. Typhi requires human mononuclear cells to replicate in vivo. The specific aims of the project are: 1.Chacterization of the Humanized Mouse Typhoid Model. The novel model will be characterized using microbiologic, histopathologic, and flow cytometric methods to define the course of infection, innate immune response, and importance of apoptosis. 2. Identification of S. Typhi Genes Required for Replication in Humanized Mice. A microarray-based method will be used to identify transposon mutations that impair S. Typhi virulence. Our model provides an unprecedented opportunity to gain new insights into typhoid pathogenesis, identify new S. Typhi vaccine candidates and devise new strategies for the prevention of S. Typhi infections. PUBLIC HEALTH RELEVANCE: The goals of this proposal are to characterize a novel humanized mouse model of human typhoid and to use this model to identify genetic determinants of Salmonella Typhi virulence. A small animal model that mimics human typhoid represents a major advance toward the development of more effective typhoid vaccines. Public Health Statement: Salmonella Typhi remains a serious human pathogen, estimated to cause 16,000,000 infections each year and resulting in more than 600,000 deaths. The two currently available typhoid vaccines are not completely effective and provide only short-term protection. Typhoid vaccine development has been constrained by the lack of a small animal model. In this application, we report the breakthrough development of a humanized mouse model that recapitulates critical aspects of human typhoid. Salmonella Typhi is able to replicate in mice engrafted with human immune cells obtained from umbilical cord blood, producing a progressive lethal infection. For the first time, this provides an experimental system to analyze the host and microbial determinants of clinical outcomes in typhoid fever. The studies described in this proposal will provide new insights into the interaction of S. Typhi with the human immune system and identify new strategies for the construction of safe and effective typhoid vaccines.