Differential Effects of TcdB1 and TcdB2 in C. difficile disease

 描述(由申请人提供)：艰难梭菌是发达国家医院获得性疾病的主要原因。艰难梭菌感染(CDI)的治疗因抗生素耐药性、复发(RCDI)和新出现的菌株的超强毒力而变得复杂，这些菌株产生一种剧毒的TcdB变种。TcdB是艰难梭菌的主要毒力因子，可导致胃肠道损伤、炎症和全身损伤。在这些研究中，实验将表征TcdB(TcdB1)的历史形式和较温和形式与高毒性TcdB2之间的差异。我们小组发表的初步数据显示，TcdB2具有更广泛的趋向性，并且比TcdB1具有更强的细胞毒性。此外，抗TcdB1的抗体不能交叉中和TcdB2，这表明目前针对TcdB的疫苗和治疗性抗体可能不能对多种艰难梭菌提供广泛的保护。这项研究将检查TcdB1和TcdB2之间的分子差异，以确定这些差异如何影响细胞毒性、抗原性和影响RCDI。目标1将描述以下方面的差异 TcdB1和TcdB2之间的双受体相互作用，评估这如何影响内吞作用，并确定影响这些事件的关键残基。目标2将探索TcdB2掩盖TcdB1中暴露的中和表位的机制。本项目目标3中的实验将确定TcdB1和TcdB2的差异如何使患者易患RCDI。本项目的研究结果将对TcdB_1和Tcd_2的区别作用以及Tcd_2的S增强毒性和抗原性改变对艰难梭菌超强毒力株出现的影响提供新的见解。

 DESCRIPTION (provided by applicant): Clostridium difficile is a leading cause of hospital-acquired illness in developed countries. Treating C. difficile infection (CDI) is complicated by antibiotic resistance, recurrence (RCDI), and hypervirulence of emerging strains that produce a highly toxic variant of TcdB. TcdB is a major C. difficile virulence factor that contributes to gastrointestinal damage, inflammation, and systemic damage. In these studies experiments will characterize the differences between the historical and milder form of TcdB (TcdB1) and the hypertoxic TcdB2. Published and preliminary data from our group shows that TcdB2 has a broader tropism and is more cytotoxic than TcdB1. In addition, antibodies to TcdB1 do not cross-neutralize TcdB2, suggesting that current vaccines and therapeutic antibodies targeting TcdB may not provide broad protection against multiple strains of C. difficile. The study will examine molecular differences between TcdB1 and TcdB2 to determine how these impact cellular intoxication, antigenicity, and influence RCDI. Aim 1 will characterize the differences in dual-receptor interactions between TcdB1 and TcdB2, assess how this impacts endocytosis, and identify key residues that influence these events. Aim 2 will explore a mechanism through which TcdB2 cloaks neutralizing epitopes which are otherwise exposed in TcdB1. Experiments in aim 3 of this project will determine how the differences in TcdB1 and TcdB2 predispose patients to RCDI. The results from this project will provide the first insights into the differentil effects of TcdB1 and TcdB2 and the impact of TcdB2's heightened toxicity and altered antigenicity on the emergence of hypervirulent strains of C. difficile.