MicroRNAs in Giardia Pathogenesis

描述（由申请人提供）：贾第鞭毛虫是世界上最常见的引起腹泻的原生动物。它感染了全世界约5亿人，导致营养吸收不良，从而导致儿童认知发育缺陷。贾第虫病的发病机制尚不清楚，这阻碍了治疗和预防该病的努力。数据表明，免疫应答通过诱导肠上皮细胞上的微绒毛缩短而促进病理，从而增加营养吸收的表面积。其他研究表明，上皮细胞之间的紧密连接发生变化，导致上皮通透性增加，进一步阻碍营养物质的适当吸收。这一提议将检验一个新的假设，即免疫应答诱导microRNA的表达，从而减少微绒毛关键元件的表达，导致微绒毛表面积的减少和上皮通透性的增加。免疫反应在诱导产生这种microRNA中的作用将通过遗传免疫缺陷小鼠以及通过过继性地将从感染小鼠中选择的免疫细胞转移到幼稚个体中来进行测试。microRNA在发病机制中的作用也将在体内用缺乏该microRNA编码基因的小鼠进行测试，并在体外通过在肠上皮细胞培养物中过表达该转录物进行测试。将在体内和体外分析microRNA靶点的表达、上皮通透性和营养吸收。公共卫生相关性：贾第鞭毛虫是美国最常见的引起腹泻的原生动物，也被认为是生物防御B类威胁因子。本提案中的研究将通过检查这种感染如何导致营养吸收不良，从而导致认知发育缺陷，从而改善公众健康。这一信息将为治疗乳糜泻、炎症性肠病以及贾第鞭毛虫等腹泻性疾病等常见疾病提供新的策略。

DESCRIPTION (provided by applicant): Giardia lamblia is the most common protozoan cause of diarrhea in the world. It infects ~500 million people worldwide resulting in nutrient malabsorption which can lead to cognitive developmental defects in children. Mechanisms of pathogenesis in giardiasis are poorly understood, hindering efforts to both treat and prevent this disease. Data suggest that immune responses contribute to pathology by inducing shortening of the microvilli on intestinal epithelial cells that provide an enhanced surface area for nutrient absorption. Other studies indicate that changes occur in the tight junctions between epithelial cells resulting in increased epithelial permeability further hindering proper absorption of nutrients. This proposal will examine a novel hypothesis, that immune responses induce expression of a microRNA which reduces expression of key elements of the microvilli, resulting in both the reduction of microvillous surface area and increases in epithelial permeability. The role of immune responses in inducing production of this microRNA will be tested using genetically immunodeficient mice as well as by adoptively transferring select immune cells from infected mice to naive individuals. The role of the microRNA in pathogenesis will also be tested in vivo using mice which lack the gene encoding this microRNA and in vitro by overexpressing this transcript in intestinal epithelial cell cultures. Expression of microRNA targets, epithelial permeability and nutrient absorption will be analyzed both in vivo and in vitro. PUBLIC HEALTH RELEVANCE: Giardia is the most common protozoan cause of diarrhea in the US and is also considered a Biodefense Category B threat agent. The studies in this proposal will improve public health by examining how this infection causes nutrient malabsortion that can lead to defects in cognitive development. This information will provide new strategies for treating common diseases like celiac disease and inflammatory bowel disease as well as diarrheal diseases like Giardia.