Immunomodulation in infectious diarrhea

描述(由申请人提供)： 首席研究员的目标是继续发展智力、技术和分析技能，成为微生物发病机制中独立资助的医生-科学家研究员，检查细菌产品对免疫系统的影响。实现这一目标的计划将包括基础免疫学、淋巴细胞信号转导以及微生物和分子遗传学方面的额外教学和实验室培训。 细菌免疫调节产品在传染病及其预防中起着至关重要的作用。例如，艰难梭菌毒素A和B与伪膜性小肠结肠炎的发生有关，霍乱毒素在口服免疫中起到佐剂的作用。在这项提案中，我们将继续描述一种来自肠道致病性大肠杆菌(EPEC)的新型毒素，其结果是显著抑制T细胞的激活。抑制基因LifA(淋巴细胞抑制活性)编码一个推测大小为366 kDa的蛋白质。LifA基因产物淋巴抑素与大型梭状芽胞杆菌细胞毒素的N端有很大的相似性，编码一个葡萄糖转移酶基序，这对它们的特殊活性是至关重要的。在相关细菌中也发现了类似的免疫抑制基因和生物活性，包括其他EPEC菌株、肠出血性大肠杆菌和小鼠病原体轮状芽孢杆菌。我们的假设是淋巴抑素中的葡萄糖基转移酶基序对于观察到的免疫抑制是关键的，导致适应性免疫反应的特定淋巴细胞亚群的抑制，并允许牢固地建立肠道革兰氏阴性感染。为了验证这一假设，我们提出：目标1：确定淋巴抑素作用下淋巴细胞中的共底物和靶分子(S)。目的：研究淋巴抑制素抑制IL-2、IL-4和干扰素-γ表达的特定淋巴细胞群的细胞内激活途径。目的：研究淋巴抑素是否抑制黏膜获得性免疫反应，从而在体内巩固轮状芽胞杆菌肠道感染。 拟议的研究项目将有助于理解慢性感染性腹泻和胃肠道炎症的发病机制，如克罗恩病和溃疡性结肠炎。

DESCRIPTION (provided by applicant): The goal of the principal investigator is to continue to develop intellectual, technical, and analytical skills to become an independently funded physician-scientist investigator in microbial pathogenesis, examining the effect of bacterial products on the immune system. The program to achieve this goal will consist of additional didactic and laboratory training in basic immunology, lymphocyte signal transduction, and microbial and molecular genetics. Bacterial immunomodulatory products are of utmost importance in infectious diseases and their prevention. For example, C. difficile toxin A and B are implicated in the development of pseudomembranous enterocolitis, and cholera toxin functions as an adjuvant in oral immunization. In this proposal we will continue to characterize a novel toxin from Enteropathogenic E. coli (EPEC), resulting in marked inhibition of T cell activation. The inhibitory gene, lifA (lymphocyte inhibitory activity), encodes for a protein with the putative size of 366kDa. The lifA gene product, lymphostatin, bears significant similarity to the N-terminus of large Clostridial cytotoxins, encoding for a glucosyltransferase motif, which is critical for their specific activity. Similar immunosuppressive genes and biological activity have been identified in related bacteria, including other EPEC strains, Enterohemorrhagic E. coli, and the mouse pathogen C. rodentium. Our hypothesis is that the glucosyltransferase motif in lymphostatin is critical for the observed immunosuppression, leading to inhibition of defined lymphocyte subpopulations of the adaptive immune response and allowing firm establishment of enteric Gram negative infection. To test the hypothesis, we propose: Aim 1: To identify the co-substrate and target molecule(s) in lymphocytes exposed to lymphostatin. Aim 2: To investigate intracellular activation pathways in defined lymphocyte populations affected by lymphostatin, resulting in suppression of IL-2, IL-4, and IFN-gamma expression. Aim 3: To investigate whether lymphostatin suppresses the mucosal adaptive immune response and firmly establishes C. rodentium enteric infection in vivo. The proposed research project will contribute to the understanding of immune mechanisms involved in the pathogenesis of chronic infectious diarrhea and gastrointestinal inflammation as seen in Crohn's disease and ulcerative colitis.