Epitope-Based CSP Vaccines Optimized to Achieve Long-Term Sterile Immunity

摘要 鉴于疟疾给许多发展中国家带来了非常沉重的负担，以及继续需要 有效疫苗，这项建议的目的是开发恶性疟原虫(PF)疫苗，通过服用 过去几年获得的隔离和表征保护性人类的知识的优势 针对寄生虫主要外壳蛋白的单抗，环子孢子(CS)蛋白。这个 目前在临床上最先进的疟疾候选疫苗RTS、S和R21只针对主要的NANP 在C-末端区域重复PFC蛋白和T细胞表位。实时测试系统的当前局限性，S 疫苗已有30-50%的疗效和暂时性保护作用。另一个潜在的复杂情况是预先存在的 对来自人类病原体的乙肝表面抗原携带者的免疫力/耐受性。为了绕过这些 问题我们已经开发了一个非人类病原体衍生的载体平台，特别是核心蛋白 来自土拨鼠庚型肝炎病毒(WHcAg)。用改良的WHcAg VLP作为疫苗平台 几个原因：WHC-CS杂交VLP诱导极高水平的抗CS保护性抗体；新的 可以简单地添加保护性表位；由于WHC-CS杂交VLP可以在细菌中制造，因此疫苗 将具有较低的商品成本。在初步研究中，我们开发了一种WHC-CS杂交VLP，它包含两个 中和PF-CS重复B细胞表位和三个疟疾特异性T细胞结构域。这条西隧-CS 杂合VLP(命名为VLP-162)在小鼠和兔体内具有很强的免疫原性，并能诱导中和抗CS 重复抗体可预防伯氏肺孢子虫/PF杂交子孢子肝体内感染并产生无菌 90-100%的小鼠对血液期感染有免疫力。我们的做法是扩大范围，保护 添加由保护性人单抗Cis43、313/317、L9和L9定义的B细胞表位对VLP-162的疗效 5D5，外加扩大VLP提供的CS特异性T细胞表位。开发最优产品的策略 下一代疟疾疫苗分为三个目标：目标1)在VLP-162基础上加入新的 定义CS来源的保护性B细胞表位并扩大CS特异性T细胞表位的数量；目的 2)通过在多个小鼠品系中评估佐剂配方来优化免疫原性；以及目标3)进行 PbPf杂交子孢子在PF小鼠攻击模型中的体内保护效果测试 完整的PF CS或工程的PF CS蛋白，使我们能够测量每个表位对 保护功效。这两种技术的组合，WHcAg平台和PbPf混合 子孢子挑战模型，将允许在感染模型中确定体内保护效果 系统。

Abstract Given the very high burden malaria imposes on many developing countries and the continued need for an effective vaccine, the objective of this proposal is to develop a Plasmodium falciparum (Pf) vaccine by taking advantage of the knowledge gained in the last few years isolating and characterizing protective human monoclonal antibodies specific for major coat protein of the parasite, circumsporozoite (CS) protein. The malaria vaccine candidates currently most advanced in the clinic, RTS,S and R21, target only the major NANP repeat of the PfCS protein plus T cell epitopes in the C-terminal domain. Current limitations of the RTS,S vaccine have been the 30-50% efficacy and transient protection. A further potential complication is pre-existing immunity/tolerance to the HBsAg carrier, which is derived from a human pathogen. To circumvent these problems we have developed a non-human pathogen-derived carrier platform, specifically the core protein from the woodchuck hepadnavirus (WHcAg). Modified WHcAg VLPs are used as the vaccine platform for several reasons: WHc-CS hybrid VLPs elicit extremely high levels of anti-CS protective antibodies; new protective epitopes can be added simply; and since WHc-CS hybrid VLPs can be made in bacteria, the vaccine will have a low cost-of-goods. In preliminary studies we developed a WHc-CS hybrid VLP that contains two neutralizing Pf-CS repeat B cell epitopes and three “universal” malaria-specific T cell domains. This WHc-CS hybrid VLP (designated VLP-162) is very immunogenic in mice and rabbits and elicits neutralizing anti-CS repeat antibodies that prevent P. berghei/Pf hybrid sporozoite liver infection in vivo and produces sterile immunity to blood stage infection in 90-100% of mice. Our approach is to expand the scope and protective efficacy of VLP-162 by adding B cell epitopes defined by the protective human Mabs CIS43, 313/317, L9 and 5D5, plus expand the CS-specific T cell epitopes delivered by the VLP. The strategy for developing an optimal next-generation malaria vaccine is divided into 3 aims: Aim 1) build on VLP-162 by incorporation of the newly defined CS-derived protective B cell epitopes and broadening the number of CS-specific T cell epitopes; Aim 2) optimize immunogenicity by assessing adjuvant formulations in multiple mouse strains; and Aim 3) conduct in vivo protective efficacy tests in Pf mouse challenge models using PbPf hybrid sporozoites that contain the entire Pf CS or engineered Pf CS proteins that allow us to measure the contribution of each epitope to protective efficacy. Combination of these two technologies, the WHcAg platform and the PbPf hybrid sporozoite challenge models, will allow in vivo protective efficacy to be determined in infectious model systems.