Differential Effects of TcdB1 and TcdB2 in C. difficile disease

摘要 最近的报告表明，艰难梭菌是40多万例 胃肠道疾病和近30，000人死亡。C. 艰难梭菌是TcdB，一种使靶细胞中的小GTP酶葡糖基化的细胞内细菌毒素。 我们的研究集中在确定TcdB 1和TcdB 2的关键差异，这两个主要的 TcdB的变体。TcdB 1由C.艰难梭菌和TcdB 2是由 C.高毒力/流行株很难了解这两种形式的TcdB， 具有92%的同一性，在中毒和免疫原性的关键步骤上存在差异， 历史菌株和流行菌株之间毒力的潜在差异。很难几 研究，包括我们小组的许多研究，发现TcdB 1和TcdB 2在它们的 与靶细胞的相互作用、向性、细胞毒性和免疫原性。我们的工作目标 是识别和表征这些因素的潜在分子和细胞细节， 解释了TcdB 1和TcdB 2活性的这些差异。为了继续这条线， 调查，三个具体的目标，i）确定潜在的差异，在分子 TcdB 1和TcdB 2受体结合和细胞渗透的机制，ii）确定TcdB 2 破坏抗原呈递并限制对共同施用的疫苗抗原的体液免疫 TcdB 2 Δ1769-1787，和iii）C.艰难梭表达TcdB 1突变体 而TcdB 2将被追踪。这些研究将进一步深入了解TcdB 1 和TcdB 2，确定TcdB对导致复发的无效免疫记忆的贡献， 并在C.艰难 感染总的来说，这项工作的结果将加强我们对C。难治性疾病 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.