Epithelial Glycoconjugates as Barriers against Enteric Infections

描述(申请人提供)：肠道感染仍然是五岁以下儿童发病率和死亡率的主要原因。影响这一年龄组的病原体通常使用凝集素样粘附素附着于小肠肠细胞和/或M细胞上表达的宿主糖蛋白和糖脂。因此，这些糖结合物的表达模式可以影响宿主对感染的潜在易感性。多种因素包括年龄、激素、饮食和具有特定共生微生物区系的定植影响上皮糖结合蛋白的表达。我们已经证明，无菌(GnotoBiotic)成虫与共生类杆菌thetaiotaomicron共栖，通过上调肠道细胞特异性的1，2岩藻糖基转移酶的表达，诱导成熟模式。岩藻糖基转移酶将岩藻糖连接到末端的半乳糖和N-乙酰-氨基葡萄糖残基，从而掩蔽上皮表面的潜在配体。这些数据表明，选择共生体的定植可以用来在治疗上刺激易感人群上皮糖共轭表达的有益变化。这项提议将检验这样一种假设，即选择微生物群，特别是B.thaiotaomicron，刺激肠细胞和M细胞顶端表面的糖结合物的发展，从而降低致病细菌、病毒和/或毒素感染/毒化肠道上皮的能力。目标1和目标2将确定B.thetaiotaomicron对小肠和大肠上皮糖结合物表达和可获得性的全面影响。这些目标直接响应了RFA HD 08-004(第5项)：“调查肠细胞表面的糖偶联物，以发现可用作致病和非致病细菌配体的寡糖。”目的3将使用霍乱毒素、蓖麻毒素、呼肠孤病毒和鼠伤寒沙门氏菌感染的成熟小鼠模型来具体验证所提出的假设。

DESCRIPTION (provided by applicant): Enteric infections remain a leading cause of morbidity and mortality in children under the age of five. Pathogens affecting this age group commonly use lectin-like adhesins to adhere to host glycoproteins and glycolipids expressed on small intestinal enterocytes and/or M cells. The expression patterns of these glycoconjugates can thus impact the host's underlying susceptibility to infection. A variety of factors including age, hormones, diet, and colonization with specific commensal microflora impacts epithelial glycoconjugate expression. We have shown that colonization of adult germ-free (gnotobiotic) with the commensal Bacteroides thetaiotaomicron induces a mature pattern by up-regulating enterocyte-specific expression of a 1,2 fucosyltransferase. Fucosyltransferases link fucose to terminal galactose and N-acetyl-glucosamine residues, and thereby mask potential ligands on epithelial surfaces. These data suggest that colonization with select commensals could be used to therapeutically stimulate beneficial changes in epithelial glycoconjugate expression in susceptible populations. This proposal will test the hypothesis that select microflora, notably B. thetaiotaomicron, stimulate the development of glycoconjugates on the apical surfaces of enterocytes and M cells that reduces the capacity of pathogenic bacteria, viruses and/or toxins to infect/intoxicate the intestinal epithelium. Aims 1 and 2 will determine the full impact of B. thetaiotaomicron on expression and accessibility of epithelial glycoconjugates in the small and large intestines. These aims are directly responsive to RFA HD 08-004 (Item 5) "Surveying glycoconjugates on the surface of enterocytes to discover oligosaccharides that may serves as ligands for pathogenic and non-pathogenic bacteria." Aim 3 will specifically test the proposed hypothesis using well-established mouse models of cholera toxin, ricin toxin, reovirus and Salmonella typhimurium infection.