Multiepitope circumsporozoite P.falciparum malaria subunit vaccine displayed on v

描述（由申请人提供）：鉴于疟疾给许多发展中国家带来的非常高的负担，本提案的总体目标是开发恶性疟原虫疟疾特异性免疫原，其可能用作预防疟疾的负担得起的有效疫苗。目前最有效的疟疾候选疫苗（RTS，S/AS 02 A）是基于使用与疟疾环子孢子（CS）特异性T和B细胞表位融合的颗粒载体平台（HBsAg）。RTS，S疫苗目前的局限性是需要反应原性佐剂和瞬时保护。另一个潜在的并发症是携带者来自人类病原体，即B型肝炎病毒（HBV）。为了避免这些问题，已经开发了非人类病原体衍生的载体平台，特别是来自土拨鼠嗜肝DNA病毒（WHcAg）的核心蛋白。修饰的WHcAg颗粒将被用作疫苗平台有几个原因：CS-WHcAg杂交颗粒引发极高水平的抗CS抗体; HBV慢性携带者（全球4亿人）对HBcAg和HBsAg的免疫耐受性可以通过使用WHcAg平台来规避;并且因为CS-WHcAg杂交颗粒可以在细菌中制备，所以疫苗的生产将相对便宜。已经开发了初步的CS-WHcAg杂合颗粒，其含有插入到环区域（产生最高滴度抗插入物抗体的插入位点）中的两个中和CS重复表位和融合到C末端的两个“通用”疟疾特异性T细胞结构域。该CS-WHcAg杂合颗粒在小鼠中具有很强的免疫原性，并且能够在体内引发预防恶性疟原虫/伯氏疟原虫杂合子子孢子肝感染的中和性抗CS重复序列抗体，因此它是开发用于人用疫苗的理想基础。开发最佳疟疾疫苗的策略分为四个目标：1）掺入额外的CS衍生的B细胞和T细胞中和表位; 2）在杂交恶性疟原虫/伯氏疟原虫子孢子模型中测试疫苗候选物的保护效力，并开发包含额外恶性疟原虫表位的模型; 3）测试重组和化学连接的“分子佐剂”改善疫苗颗粒的保护效力的能力;和4）确定所选疫苗候选物的最佳制剂、途径和剂量。这两种强大的技术，即WHcAg-载体平台和恶性疟原虫/伯氏疟原虫杂交子孢子攻击模型的组合，将使得能够产生多种CS-WHcAg杂交颗粒免疫原，其可以在恶性疟原虫疟疾特异性的体内感染模型系统中测试保护功效。疟疾是世界上最重要的致命热带寄生虫病（每年有150万至270万人死亡），估计每年有3亿至5亿临床新病例。恶性疟原虫的自然感染不会产生有效的免疫力，疟疾控制工作正受到多重抗药性恶性疟原虫传播和按蚊媒介对杀虫剂产生抗药性的阻碍。因此，迫切需要一种预防性疫苗来防止这种疾病的进一步传播。

DESCRIPTION (provided by applicant): Given the very high burden malaria imposes on many developing countries, the overall objective of this proposal is to develop a P. falciparum malaria-specific immunogen that may be useful as an affordable and effective vaccine to prevent malaria. The current most effective malaria vaccine candidate (RTS,S/AS02A) is based on the use of a particulate carrier platform (the HBsAg) fused to malaria circumsporozoite (CS)-specific T and B cell epitopes. Current limitations of the RTS,S vaccine have been a requirement for reactogenic adjuvants and transient protection. A further potential complication is that the carrier is derived from a human pathogen, the hepatitis B virus (HBV). To circumvent these problems a non-human pathogen-derived carrier platform has been developed, specifically the core protein from the woodchuck hepadnavirus (WHcAg). Modified WHcAg particles will be used as the vaccine platform for several reasons: CS-WHcAg hybrid particles elicit extremely high levels of anti-CS antibodies; the immune tolerance to HBcAg and HBsAg in HBV chronic carriers (400 million worldwide) can be circumvented by the use of the WHcAg platform; and because CS-WHcAg hybrid particles can be made in bacteria, production of a vaccine will be relatively inexpensive. A preliminary CS-WHcAg hybrid particle has been developed that contains two neutralizing CS repeat epitopes inserted into the loop region (the insertion site that raises the highest titer anti-insert antibodies) and two "universal" malaria-specific T cell domains fused to the C-terminus. This CS-WHcAg hybrid particle is very immunogenic in mice and is capable of eliciting neutralizing anti-CS repeat antibodies that prevent P. falciparum/P. berghei hybrid sporozoite liver infection in vivo, therefore it is an ideal basis from which to develop a vaccine for human use. The strategy for developing an optimal malaria vaccine is divided into four aims: 1) incorporation of additional CS-derived B cell and T cell neutralizing epitopes; 2) testing the protective efficacy of the vaccine candidates in a hybrid P. falciparum/P. berghei sporozoite model and developing the model to encompass additional P. falciparum epitopes; 3) test recombinant and chemically linked "molecular adjuvants" for their ability to improve protective efficacy of the vaccine particles; and 4) determine optimal formulation, route and dosing of the chosen vaccine candidates. The combination of these two powerful technologies, the WHcAg-carrier platform and the P. falciparum/P. berghei hybrid sporozoite challenge model, will enable the production of a variety of CS-WHcAg hybrid particle immunogens that can be tested for protective efficacy in an in vivo infectious model system specific for P. falciparum malaria. Malaria is the world's most important lethal tropical parasitic disease (1.5 to 2.7 million deaths each year) with an estimated 300-500 million clinical new cases each year. The natural P. falciparum infection does not result in effective immunity, and malaria control efforts are being impeded by the spread of multiple drug resistant P. falciparum and the development of insecticide resistance by the anopheline mosquito vector. Therefore, a prophylactic vaccine is urgently needed to prevent further spread of this disease.