Multiepitope circumsporozoite P.falciparum malaria subunit vaccine displayed on v

说明(申请人提供)：鉴于疟疾对许多发展中国家造成的沉重负担，本提案的总体目标是开发一种针对恶性疟原虫的免疫原，可用作负担得起的有效疫苗来预防疟疾。目前最有效的疟疾候选疫苗(RTS，S/AS02A型)是基于融合了疟疾环子孢子(CS)特异性T和B细胞表位的颗粒载体平台(乙肝表面抗原)。目前RTS、S疫苗的局限性已成为反应性佐剂和暂时性保护的要求。另一个潜在的并发症是，携带者来自一种人类病原体，即乙肝病毒(HBV)。为了绕过这些问题，已经开发了一种非人类病原体衍生的载体平台，特别是土拨鼠庚型肝炎病毒(WHcAg)的核心蛋白。改良的WHcAg颗粒将被用作疫苗平台，原因有几个：CS-WHcAg杂化颗粒可诱导极高水平的抗CS抗体；使用WHcAg平台可以规避慢性乙肝携带者(全球4亿人)对HBcAg和HBs Ag的免疫耐受；由于CS-WHcAg杂化颗粒可以在细菌中制造，疫苗的生产将相对便宜。一种初步的CS-WHcAg杂合颗粒已经被开发出来，它含有两个插入环区(提高最高滴度抗插入抗体的插入部位)的中和CS重复表位，以及两个融合到C末端的疟疾特异性T细胞域。这种CS-WHcAg杂合颗粒在小鼠体内具有很强的免疫原性，能够诱导中和抗CS重复抗体，防止恶性疟原虫/伯氏疟原虫杂交子孢子肝感染，是研制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)加入额外的CS来源的B细胞和T细胞中和表位；2)在恶性疟原虫/伯氏疟原虫混合子孢子模型中测试候选疫苗的保护效力，并开发该模型以包含更多的恶性疟原虫表位；3)测试重组和化学连接的“分子佐剂”提高疫苗颗粒保护效力的能力；以及4)确定所选候选疫苗的最佳配方、路线和剂量。这两项强大的技术，即WHcAg载体平台和恶性疟原虫/伯氏疟原虫杂交子孢子挑战模型的结合，将使各种CS-WHcAg杂交颗粒免疫原的生产能够在针对恶性疟原虫的体内感染模型系统中测试保护效果。疟疾是世界上最重要的致命性热带寄生虫病(每年有150万至270万人死亡)，每年估计有3亿至5亿临床新病例。恶性疟原虫的自然感染不能产生有效的免疫，恶性疟原虫多重抗药性的传播和按蚊媒介对杀虫剂的抗药性的发展阻碍了疟疾控制工作。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.