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

描述(由申请人提供)：产肠毒素大肠杆菌(ETEC)相关性腹泻疾病每年估计导致40万至80万人死亡。细菌黏附素或定植因子(CFAs)和肠毒素是ETEC腹泻的关键毒力因子。肠毒素、耐热毒素(LT)和耐热毒素(StA、STB)是ETEC产生的主要肠毒素，这些毒素可破坏体液平衡，刺激体液分泌，导致腹泻。然而，研究单个肠毒素的毒力意义以及鉴定ETEC腹泻毒力决定簇的肠毒素(S)的研究非常有限，这可能直接滞后于以S肠毒素为抗原的疫苗的研制，以预防或减轻人类腹泻病的严重程度。研究肠毒素致病性的主要障碍是缺乏合适的攻击模型。由于对安全风险、伦理学和经济扩张的担忧，人类的受试者挑战研究非常有限；而啮齿动物作为大多数传染病研究的首选模型，对ETEC没有易感性，因此对ETEC疾病的研究价值很小。相比之下，某些猪对ETEC自然易感，其中对猪易感的K88菌毛ETEC病原体研究最广泛，并最好地刻画了它们与腹泻的相关性。本研究建议分别克隆表达LT、STA和STB的ESTAB、ESTA和ESTB基因，并构建模型病原体，使我们能够检测每个单独的肠毒素在腹泻中的意义。这个项目的总体目标是开发一个通用的模型来检查单个肠毒素在腹泻疾病中的生物学相关性。本研究将阐明LT、StA和STB在ETEC腹泻中的作用，并确定关键的肠毒素，为以肠毒素为抗原的人ETEC疫苗的研制奠定基础。

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.