Differential Effects of TcdB1 and TcdB2 in C. difficile disease

摘要 最新报告表明，艰难梭状芽胞杆菌是40多万例肺炎的病因。 每年有近30,000人死于胃肠道疾病。致病性的主要因素是C。 艰难梭菌是TcdB，一种细胞内的细菌毒素，它能使靶细胞中的小GTP酶糖基化。 我们的研究集中在确定TcdB1和TcdB2这两个主要的 Tcdb的变体。TcdB1是由艰难梭菌的历史菌株产生的，TcdB2是由 艰难梭菌的超强毒力/流行菌株。了解这两种形式的Tcdb是如何 92%的同一性，在中毒和免疫原性的关键步骤上的不同提供了洞察 艰难梭菌历史菌株和流行菌株之间毒力的潜在差异。几个 包括我们小组的许多研究发现，TcdB1和TcdB2在他们的 与靶细胞的相互作用、趋向性、细胞毒性和免疫原性。我们的工作目标是 就是识别和表征这些因子的潜在分子和细胞细节 解释了TcdB1和TcdB2活性的这些差异。要继续这条线 调查，三个具体目标：i)确定分子中潜在的差异 TcdB1和TcdB2受体结合和细胞穿透的机制，II)决定TcdB2是否 颠覆抗原递呈，限制对联合接种疫苗抗原的体液免疫 TcdB2Δ1769-1787；III)艰难梭菌表达TcdB1突变株的构建和检测 和TcdB2将被追查。这些研究将进一步深入了解TcdB1的差异 和TcdB2，确定TcdB对导致复发的无效免疫记忆的贡献， 并在艰难梭菌的背景下测试与特定TcdB功能活动有关的假设 感染。总体而言，这项工作的发现将加强我们对艰难梭菌病的了解 并提供预防和治疗这一严重人类疾病所需的信息。

ABSTRACT The most recent reports indicate Clostridioides difficile is the cause of over 400,000 cases of gastrointestinal illness and nearly 30,000 deaths annually. A major factor in the virulence of C. difficile is TcdB, an intracellular bacterial toxin that glucosylates small GTPases in targeted cells. Our studies focus on determining the critical differences in TcdB1 and TcdB2, the two major variants of TcdB. TcdB1 is produced by historical strains of C. difficile and TcdB2 is produced by hypervirulent/epidemic strains of C. difficile. Understanding how these two forms of TcdB, which share 92% identity, differ in critical steps in intoxication and immunogenicity provides insight into underlying differences in virulence between historical and epidemic strains of C. difficile. Several studies, including many from our group, have found that TcdB1 and TcdB2 differ in their interactions with target cells, tropism, cytotoxicity, and immunogenicity. The objective of our work is to identify and characterize the underlying molecular and cellular details of the factors accounting for these differences in TcdB1 and TcdB2 activity. To continue this line of investigation, three specific aims to i) Determine the underlying differences in the molecular mechanism of TcdB1 and TcdB2 receptor binding and cell penetration, ii) Determine if TcdB2 subverts antigen presentation and limits humoral immunity to co-administered vaccine antigen TcdB2Δ1769-1787, and iii) Construct and test strains of C. difficile expressing mutants of TcdB1 and TcdB2 will be pursued. These studies will provide further insight into the differences in TcdB1 and TcdB2, determine the contribution of TcdB to ineffective immune memory leading to relapse, and test hypotheses related to specific TcdB functional activities in the context of C. difficile infection. Overall, the findings from this work will enhance our understanding of C. difficile disease at multiple levels and provide information needed to prevent and treat this serious human illness.