Novel antigen designs and delivery platforms to enhance the protective ability of Tpr-based vaccines for syphilis

摘要 在过去的二十年里，我们开发梅毒疫苗的努力已经鉴定出两种 在免疫/攻击实验中对梅毒提供高度但不完全保护的抗原 兔子模型。这两种候选疫苗来自选定成员的保守区域 梅毒螺旋体重复序列 (Tpr) 抗原 TprC/D2 和 TprK。对这些抗原的免疫力 显示可通过调理吞噬作用增强病原体清除作用，并提供实质性保护 与对照相比，挑战部位下疳的发展。然而，在这些早期的疫苗设计中， TprC 和 TprD2 蛋白的几个预测表面表位被省略，因为它们显示出 抗原变异程度有限，尽管我们证明它们可以提供额外的 如果与激活的巨噬细胞结合使用，则可成为病原体调理作用和吞噬作用的目标 诱导Th1型反应的佐剂。 为了获得完全保护性的梅毒疫苗，我们的目标是修改我们的早期疫苗设计，以包括额外的 TprC 和 TprD2 蛋白的保护性表位。首先（目标 1），我们将评估 使用旨在涵盖所有抗原变体的抗原混合物的全长重组 TprC 和 TprD2 这些蛋白质，其中也将包含 TprK 保守片段。与此同时，我们将开展一系列 绘制 TprC 和 TprD2 的 T 细胞表位和保护性 B 细胞表位的实验，以提供信息 开发用于抗原递送的替代平台，其目标是递送选定的表位而不是 比全长抗原。对于这些映射实验（也在目标 1 中计划），我们将使用 TprK 作为 对照抗原，因为过去已经鉴定出该蛋白质的 B 细胞和 T 细胞表位。代替 重组蛋白，我们将设计和测试嵌合串联体（目标 2）和基于 HPV 的嵌合体 病毒样颗粒（VLP，目标 3）。这些替代递送平台将专门诱导免疫 密螺旋体表面调理抗体的目标，并可能增强病原体清除 传染性的挑战。在目标 4 中，我们将结合我们的结果和卡梅伦博士（项目 1）获得的结果 与她选择的候选疫苗 (Tp0751) 结合我们最具保护性的疫苗设计和交付 平台。随后，将使用我们的 fila 疫苗设计进行最终免疫/激发实验 使用现代梅毒分离株来评估总体保护水平和免疫力的持久性 兔子免疫后攻击免疫动物。

ABSTRACT Over the last two decades, our efforts to develop a syphilis vaccine have allowed identification of two antigens that confer high but not complete protection to syphilis in immunization/challenge experiments in the rabbit model. These two vaccine candidates were derived from conserved regions of selected members of the Treponema pallidum repeat (Tpr) antigens TprC/D2 and TprK. Immunity to these antigens has been shown to enhance pathogen clearance by opsonophagocytosis and provide substantial protection from chancre development at challenge sites compared to controls. In these early vaccine designs, however, several predicted surface epitopes of the TprC and TprD2 proteins were omitted because they showed a limited degree of antigenic variation, even though we demonstrated that they could provide additional targets for pathogen opsonization and phagocytosis by activated macrophages if used in combination with adjuvants inducing a Th1-type response. To attain a fully protective syphilis vaccine we aim to modify our early vaccine design to include additional protective epitopes of the TprC and TprD2 proteins. First (Aim 1), we will evaluate the protective activity of full-length recombinant TprC and TprD2 using a cocktail of antigens designed to cover all antigenic variants of these proteins, which will also contain the TprK conserved fragment. In parallel, we will conduct a series of experiments to map T-cell epitopes and protective B-cell epitopes of TprC and TprD2 to inform development of alternative platforms for antigen delivery, with the goal of delivering selected epitopes rather than on full length antigens. For these mapping experiments (also planned in Aim 1), we will use TprK as a control antigen, as B-and T-cell epitopes were already identified for this protein in the past. In lieu of recombinant proteins, we will engineer and test chimeric concatemers (Aim 2) and chimeric HPV-based viral-like particles (VLPs, Aim 3). These alternative delivery platforms will specifically induce immunity to targets of opsonizing antibodies on the treponemal surface, and likely enhance pathogen clearance upon infectious challenge. In Aim 4, we will combine our results and those obtained by Dr. Cameron (Project 1) with her selected vaccine candidate (Tp0751) to combine our most protective vaccine designs and delivery platform. Subsequently, a final immunization/challenge experiment with our fila vaccine design will be performed to assess overall level of protection and durability of immunity using a modern syphilis isolate to challenge immunized animals following rabbit immunization.