Development of a Preclinical Assay to Predict Efficacy of Ricin Toxin Subunit Vaccines

项目摘要 蓖麻毒素（RT）被国家过敏和传染病研究所（NIAID）归类为 新出现的传染病优先病原体。NIAID和国防部分别是 支持开发有效的RT亚单位疫苗的努力。发展RT的主要障碍 疫苗的最大缺陷是缺乏功能性临床前试验来预测在人体中的功效。虽然很好 建立了对RT的免疫是由抗体介导的，对蓖麻毒素A的免疫应答 基于亚基（RTA）的抗原主要（>90%）由非中和抗体组成。的确， RTA特异性鼠和骆驼单克隆抗体的详细功能和结构分析 单克隆抗体（MAbs）的研究表明，毒素中和活性（TNA）与非常有限数量的B相关 RTA表面的表位“簇”。常规的基于细胞的细胞毒性测定不是 足够敏感，以检测负责的毒素中和抗体的小部分， 保护性免疫从疫苗开发的角度来看，开发一种更有效的疫苗是至关重要的。 灵敏和直接的测定来测量针对关键保护性表位的血清抗体。 因此，本项目的目标是开发一种基于ELISA的临床前竞争测定法， 预测RT亚单位疫苗在人类中的效力。Aim 1将建立原型竞赛 基于ELISA的检测，用于鉴定与保护性免疫相关的血清抗体谱 Aim 2将在NHP模型中鉴定基于竞争ELISA的测定，以确定抗体 最后，目标3将验证 使用来自I期和II期研究的人血清的竞争ELISA。作为该计划的一部分，我们将 建立单克隆抗体竞争和保护性免疫之间的联系， 测量表位特异性中和抗体应答的能力将构成免疫学的一个重大进步。 评估候选RT亚单位疫苗在人类中的功效。

Project Summary Ricin toxin (RT) is classified by the National Institute of Allergy and Infectious Diseases (NIAID) as an Emerging Infectious Disease Priority Pathogen. NIAID and the Department of Defense are each supporting efforts to develop an effective RT subunit vaccine. A major roadblock to developing RT vaccines is the absence of a functional preclinical assay to predict efficacy in humans. While it is well established that immunity to RT is mediated by antibodies, the immune response against ricin toxin A subunit (RTA)-based antigens consists predominantly (>90%) of non-neutralizing antibodies. Indeed, detailed functional and structural analyses of RTA-specific murine and camelid monoclonal antibodies (MAbs) has revealed that toxin-neutralizing activity (TNA) is associated a very limited number of B epitope “clusters” on the surface of RTA. Conventional cell-based cytotoxicity assays are not sufficiently sensitive to detect the small fraction of toxin-neutralizing antibodies responsible for protective immunity. From the standpoint of vaccine development, it is critical to develop a more sensitive and direct assay to measure serum antibodies against the key protective epitopes. Therefore, the goal of this program is to develop a preclinical ELISA-based competition assay that will predict the efficacy of RT subunit vaccines in humans. Aim 1 will e stablish a prototype competition ELISA-based assay that identifies a serum antibody profile associated with protective immunity against RT. Aim 2 will qualify the competition ELISA-based assay in a NHP model to define antibody profile that is associated with protection against aerosolized RT. Finally, Aim 3 will validate the competition ELISA using human sera from Phase I and II studies. As part of this program we will establish the link between MAb competition and protective immunity, with the expectation that the ability to measure epitope-specific neutralizing antibody responses will constitute a major advance in assessing the efficacy of candidate RT subunit vaccines in humans.