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）相关腹泻疾病每年导致约40万至80万人死亡。细菌粘附素或定植因子（CFAs）和肠毒素是ETEC腹泻的关键毒力因子。肠毒素，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，这些毒素会破坏体液平衡并刺激体液分泌，从而导致腹泻。然而，在研究个体肠毒素的毒力意义和鉴定肠毒素在ETEC腹泻中的毒力决定因素方面的研究非常有限，这可能直接滞后于利用肠毒素作为抗原来预防或降低人类腹泻疾病严重程度的疫苗开发。研究肠道毒素致病性的主要障碍是缺乏合适的攻毒模型。由于安全风险、伦理和财政扩张的考虑，人体挑战研究非常有限；而啮齿类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疾病的研究价值不大。相反，某些猪对ETEC自然易感，而猪易感的K88毛状ETEC病原体被研究得最广泛，其与腹泻的相关性也得到了最好的表征。本研究拟分别克隆表达LT、STa和STb的estAB、estA和estB基因，并构建模型病原体，以检验每种肠毒素在腹泻中的意义。该项目的总体目标是建立一个通用模型，以检查个体肠毒素在腹泻疾病中的生物学相关性。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，为开发以肠毒素为抗原的人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.