MicroRNAs in Giardia Pathogenesis

描述(申请人提供)：蓝氏贾第鞭毛虫是世界上最常见的引起腹泻的原虫。它感染了全球约5亿人，导致营养吸收不良，可能导致儿童认知发育缺陷。贾第鞭毛虫病的发病机制尚不清楚，阻碍了治疗和预防这种疾病的努力。数据表明，免疫反应通过诱导肠上皮细胞上的微绒毛缩短来促进病理，从而为营养吸收提供更大的表面积。其他研究表明，上皮细胞之间的紧密连接发生了变化，导致上皮通透性增加，进一步阻碍了营养的适当吸收。这一建议将检验一个新的假说，即免疫反应诱导一种microRNA的表达，该microRNA减少微绒毛的关键成分的表达，导致微绒毛表面积减少和上皮通透性增加。免疫反应在诱导这种微小RNA产生方面的作用将通过使用遗传免疫缺陷小鼠以及通过过继地将感染小鼠的选定免疫细胞转移到幼稚的个体来测试。微小RNA在发病机制中的作用也将在体内使用缺乏编码这种微小RNA的基因的小鼠身上进行测试，并在体外通过在肠上皮细胞培养中过表达这种转录物来测试。将在体内和体外分析microRNA靶标的表达、上皮通透性和营养吸收。与公共卫生相关：贾第虫是美国最常见的原生动物腹泻原因，也被认为是生物防御B类威胁因子。这项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来改善公共健康。这些信息将为治疗常见疾病，如乳糜泻和炎症性肠病，以及腹泻疾病，如贾第鞭毛虫提供新的战略。

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.