Malaria Vaccine Based on Self-Assembling Polypeptide Nanoparticles (SAPN)

描述（由申请人提供）：恶性疟原虫疫苗的开发已被证明是一项艰巨的生物工程挑战。疟疾折磨着全世界5亿人，每年造成大约300万人死亡，其中大多数是儿童。“RTS，S”是迄今为止最成功的疟疾候选疫苗，在临床和实地挑战研究中仅对人类提供约40%的保护效力，并且需要加入佐剂才能实现保护性免疫原性。该申请的广泛、长期目标是开发自组装多肽纳米颗粒（SAPN），作为恶性疟原虫疟疾疫苗的基础，这种疫苗可能比目前临床试验中的疫苗更具保护作用，表现出优异的热稳定性，并且可以在没有佐剂的情况下递送，这可能与适合在没有冷链的情况下递送的配方一致。SAPN由线性多肽（LP）构建块组装。每个LP由五聚体和三聚体线圈结构域组成，由连接器分隔，表位抗原在内部和N-和C-末端显示。本研究旨在确定B细胞和T细胞表位在SAPN上的最佳结构，以产生最有效的免疫原性和保护性免疫反应。显示柏氏疟原虫CSP表位的SAPN（类似于RTS，S中的恶性疟原虫CSP b细胞表位）已被证明在柏氏疟原虫小鼠疟疾模型中刺激对致命孢子虫攻击的持久保护性免疫反应，而无需佐剂。SAPN颗粒已被证明具有佐剂活性。这表明SAPN平台可能优于迄今为止使用的其他蛋白质疫苗技术，因为这些技术都需要添加外部佐剂才能起到保护作用。我们正在开发的SAPN疫苗将评估其免疫增强机制（佐剂性）；表达恶性疟原虫（人疟）CSP基因的伯黑氏疟原虫（鼠疟）对攻毒的保护作用利用人HLA转基因小鼠，在人HLA背景下通过特异性恶性疟原虫T细胞表位提供免疫原性/保护性反应。具体目标是：(1)设计和生产SAPN，以确定免疫优势PfCSP b细胞表位的最佳密度，以刺激有效的抗体反应；(2)以优化的免疫优势型PfCSP B细胞表位密度，确定向SAPN添加泛等位基因HTL和CTL表位对免疫应答的增强作用；(3)在非人灵长类动物（NHP）模型中评估PfCSP SAPN先导疫苗的安全性、反应原性和免疫应答。该研发计划预计将推进一个创新的疫苗平台，并开发一种基于恶性疟原虫CSP的B细胞和T细胞表位抗原的疟疾疫苗，该疫苗已经在临床和现场试验中显示出成功的（尽管有限的）保护效果，如在AS02A中的RTS，S。研究的成功应该使拟议的研究有资格获得进一步资助，用于人类使用的产品开发和疫苗试验。公共卫生相关性：将基于一种新技术开发一种疟疾疫苗，这种新技术是自组装肽纳米粒子，它显示了疟疾寄生虫免疫原，这种免疫原以前被证明可引起对疟疾的保护性免疫。这个新的疫苗平台有望最终为发展中国家生产一种廉价的疟疾疫苗。

DESCRIPTION (provided by applicant): The development of a vaccine against P. falciparum has proven to be a difficult bioengineering challenge. Malaria afflicts 500 million people worldwide and annually kills about 3 million people, mostly children. "RTS,S", the most successful malaria vaccine candidate to date, provides only about 40% protective efficacy in humans in clinical and field challenge studies, and it requires formulation with an adjuvant to achieve protective immunogenicity. The application's broad, long-term objective is to develop self-assembling polypeptide nanoparticles (SAPN) as the basis for a P. falciparum malaria vaccine that is potentially more protective than those currently in clinical trials, shows excellent heat stability, and can be delivered without an adjuvant, which is likely to be consistent with formulations suited for delivery without a cold chain. SAPN assemble from linear polypeptide (LP) building blocks. Each LP consists of pentameric and trimeric coiled-coil domains separated by a linker, with epitope antigens displayed internally and on the N- and C- termini. The proposed work aims to identify the best configuration for the display of B cell and T cell epitopes on SAPN for producing the most potent immunogenic and protective immune response. SAPN displaying the P. berghei CSP epitope (analogous to the P. falciparum CSP B-cell epitope in RTS,S) have been shown to stimulate a long lasting protective immune response against a lethal sporozoite challenge in the P. berghei mouse malaria model without the need for an adjuvant. The SAPN particles have been shown themselves to have adjuvant activity. This suggests that the SAPN platform is potentially superior to other protein vaccine technologies used to date as these have all required the addition of extraneous adjuvants to be protective. The SAPN vaccines in our development pipeline will be evaluated for their mechanism of immune enhancement (adjuvanticity); protective efficacy against challenge with a strain of P. berghei (mouse malaria) expressing the CSP transgene from P. falciparum (human malaria); and immunogenic/protective response provided by specific P. falciparum T cell epitopes in human HLA backgrounds using human-HLA transgenic mice. The Specific Aims are to: (1) Design and produce SAPN in order to determine the optimal density of the immunodominant PfCSP B-cell epitope to stimulate a potent antibody response; (2) Determine the enhancement to the immune response provided by the addition of pan allelic HTL and CTL epitopes to SAPN with the optimized density of immunodominant PfCSP B cell epitope; and (3) Evaluate the safety, reactogenicity and immune response to the lead PfCSP SAPN vaccine candidate in a non-human primate (NHP) model. This R&D plan is expected to advance an innovative vaccine platform and to develop a malaria vaccine based on B cell and T cell epitope antigens from P. falciparum CSP that have already demonstrated successful, though limited, protective efficacy in clinical and field trials as RTS,S in AS02A. Success should qualify the proposed research for further funding for human- use product development and vaccine trials. PUBLIC HEALTH RELEVANCE: A malaria vaccine will be developed based on a new technology, self-assembling peptide nanoparticles, that display malaria parasite immunogens previously shown to elicit protective immunity to malaria. This new vaccine platform holds promise for ultimately producing an inexpensive malaria vaccine for the developing world.