Development of an additive model to study the significance of heat-labile and hea

描述（由申请方提供）：产肠杆菌性大肠杆菌（ETEC）相关性腹泻病每年造成约40万至80万例死亡。细菌粘附素或定植因子（CFA）和肠毒素是ETEC腹泻的关键毒力因子。肠毒素、热不稳定毒素（LT）和热稳定毒素（STa、STb）是ETEC产生的主要肠毒素，这些毒素破坏体液平衡，刺激体液分泌，导致腹泻。然而，已经进行了非常有限的研究来研究单个肠毒素的毒力意义，并鉴定ETEC腹泻中的毒力决定簇的肠毒素，这可能直接滞后于使用肠毒素作为抗原的疫苗开发，以预防或降低人类腹泻病的严重程度。肠毒素致病性研究的主要障碍是缺乏合适的攻毒模型。由于安全性风险、伦理学和经济扩张方面的考虑，人类受试者挑战研究非常有限;而啮齿动物是大多数传染病研究的首选模型，对ETEC不敏感，因此研究ETEC疾病的价值不大。相比之下，某些猪对ETEC天然易感，对猪易感的K88菌毛ETEC病原体的研究最为广泛，其与腹泻的相关性也得到了最好的表征。本研究提出分别克隆estAB、estA和estB基因，以表达LT、STa和STb，并构建模型病原体，这将使我们能够检查每种肠毒素在腹泻中的意义。本计画的总体目标是发展一个多功能的模型，以检视个别肠毒素在腹泻疾病中的生物相关性。该研究将阐明LT、STa和STb在ETEC腹泻中的作用，并确定关键的肠毒素，这可能为开发基于肠毒素作为抗原的人类ETEC疫苗铺平道路。

DESCRIPTION (provided by applicant): Enterotoxigenic Escherichia coli (ETEC) associated diarrheal disease are responsible for an estimated 400,000 to 800,000 deaths annually. Bacterial adhesins or colonization factors (CFAs) and enterotoxins are the key virulence factors in ETEC diarrhea. Enterotoxins, heat-labile toxin(LT) and heat stable toxins (STa, STb) are the main enterotoxins produced by ETEC, these toxins cause disruption of fluid homeostasis and stimulate fluid secretion, which results in diarrhea. However, very limited studies have been done to study virulence significance of individual enterotoxin and to identify enterotoxin(s) of virulence determinant in ETEC diarrhea, which might directly lag vaccine development using enterotoxin(s) as antigens to prevent or decrease the severity of diarrheal disease in humans. The major obstacle to study the pathogenicity of enterotoxins is the lack of a suitable challenge model. Human subject challenge studies have been very limited because of concerns of safety risk, ethnics, and financial expanses; while rodents, the preferred models of most infectious disease research, show no susceptibility to ETEC, and therefore have little value to study ETEC disease. In contrast, certain pigs are naturally susceptible to ETEC, and K88 fimbrial ETEC pathogens to which pigs are susceptible have been studied most extensively and their correlative relationships with diarrhea are best characterized. This research proposes to clone estAB, estA, and estB genes separately for expression of LT, STa and STb, and to construct model pathogens which will allow us to examine significance of each individual enterotoxin in diarrhea. The overall goal of this project is to develop a versatile model to examine the biological relevance of individual enterotoxin in diarrhea disease. The study will elucidate the roles of LT, STa and STb in ETEC diarrhea, and determine the key enterotoxins that may pave the way for development of human ETEC vaccines based on enterotoxins as antigens.