Multi-ligand merozoite invasion blocking malaria vaccine

描述(申请人提供)：由恶性疟原虫(PF)引起的疟疾每年导致2.5亿多个临床病例，近100万人死亡。疫苗将是降低疟疾发病率和死亡率的理想干预措施。疟疾的所有临床表现和病理都是由寄生虫生命周期的红细胞期引起的，因此疟疾的所有后遗症都是在寄生虫入侵红细胞时开始的。阻断寄生虫对红细胞的入侵将防止寄生虫的复制和所有临床疾病。PF寄生虫通过与特定的红细胞受体结合来入侵红细胞。因此，通过诱导抗体干扰寄生虫在入侵过程中受体-配体的相互作用来阻断寄生虫对红细胞的入侵是疟疾疫苗开发的重要途径。一个研究得很好的PF配体是EBA-175，它将其受体唾液酸结合到血糖蛋白A上。EBA-175的抗体可以阻止寄生虫的入侵。不幸的是，有一些PF菌株通过不涉及唾液酸的替代途径入侵。因此，有效阻止入侵的疫苗的开发必须诱导出针对多个配体的抗体，干扰唾液酸和其他入侵途径的抗体。网织红细胞 结合同源蛋白家族(PfRH)在除唾液酸以外的其他途径与红细胞结合和侵袭中发挥重要作用。我们的目标是评估用PfRH蛋白免疫诱导的抗体与抗EBA-175抗体结合是否能有效地阻止寄生虫对红细胞的入侵。将通过阻断红细胞结合和寄生虫生长侵袭抑制试验系统地进行评估。我们将首先在兔体内表达重组候选蛋白，以产生针对这些候选蛋白的抗体。将对候选PfRH1、2b、4和5以及EBA-175进行评估。我们的近期目标是使用一种多配体疫苗的策略，有效地干扰寄生虫结合和对红细胞的入侵，这种疫苗可以诱导抗体阻断多条入侵途径。对红细胞入侵这一关键步骤进行多方面的干预是我们创新和方法的核心。我们将选择最佳候选组合，并建议在第二阶段将其开发为多配体、入侵阻断疫苗。因此，在第二阶段，我们将创建选定重组候选克隆的生产者克隆，并使用适合人类使用的多种佐剂配方在恒河猴身上进行系统评估，筛选出最佳佐剂配方(S)，并在cGMPs下生产材料，为确定这种多配体裂殖子入侵阻断疫苗的效力而进行的临床试验做准备。 与公共卫生相关：疟疾每年导致4-5亿临床病例和近100万人死亡，每年造成非洲国内生产总值1%的损失，是旅行者和军事人员严重关切的问题。Protein Potential的目标是为初级市场开发和商业化90%保护性疟疾疫苗，年收入可能达到10亿美元；1)来自发达国家的旅行者；2)发展中国家的婴儿、幼儿和少女。该项目的成功将大大降低开发成本，缩短有效疟疾疫苗的上市时间。

DESCRIPTION (provided by applicant): Malaria caused by Plasmodium falciparum (Pf) results in more than 250 million clinical cases, and nearly one million deaths annually. A vaccine would be the ideal intervention for reducing malaria morbidity and mortality. All clinical manifestations and pathology of malaria are caused by the erythrocytic stage of the parasite life cycle, and thus all sequelae of malaria disease begin when the parasite invades erythrocytes. Blocking parasite invasion of erythrocytes would prevent parasite replication and all clinical disease. Pf parasites invade erythrocytes by binding to specific erythrocyte receptors. Thus, blocking parasite invasion of erythrocytes by inducing antibodies that interfere with parasite receptor-ligand interaction during invasion is an important approach to malaria vaccine development. A well-studied Pf ligand is EBA-175 that binds its receptor sialic acids on glycophorin A. Antibodies to EBA-175 can block parasite invasion. Unfortunately there are strains of Pf that invade by alternate pathways not involving sialic acids. Development of vaccines that effectively block invasion must thus induce antibodies against multiple ligands, antibodies that interfere with the sialic acid and alternate pathways of invasion. The reticulocyte binding homolog protein family (PfRH) of proteins has been identified to play a major role in binding and invasion of erythrocytes by alternate pathways excluding sialic acids. We aim to assess if antibodies induced by immunization with the PfRH proteins when combined with antibodies against EBA-175 can effectively block invasion of parasites into erythrocytes. Assessments will be systematically performed using blocking of erythrocyte binding and parasite growth invasion inhibition assays. We will first express recombinant candidate proteins to raise antibodies against these candidates in rabbits. The candidates PfRH 1, 2b, 4 and 5, together with EBA-175 will be assessed. Our immediate goal is to potently interfere with parasite binding and invasion into erythrocytes using the strategy of a multi-ligand vaccine that induces antibodies that block multiple pathways of invasion. Interfering on multiple fronts with the single crucial step of erythrocyte invasion is at the core of our innovation and approach. We will select the best combination of candidates and propose to develop them in Phase II as a multi-ligand, invasion blocking vaccine. Thus in Phase II we will create producer clones of the selected recombinant candidates and systematically assess them in rhesus monkeys with multiple adjuvant formulations suitable for human use, down select the best adjuvant formulation(s), and produce material under cGMPs in preparation for clinical trials designed to determine the efficacy of this multi-ligand merozoite invasion blocking vaccine. PUBLIC HEALTH RELEVANCE: Malaria causes 400-500 million clinical cases and nearly 1 million deaths annually, and is responsible for >1% loss of GDP in Africa annually and is a serious concern for travelers and military personnel. Protein Potential's goal is to develop and commercialize a >90% protective malaria vaccine for primary markets with a potential for >$1 billion annual revenues; 1) travelers from the developed world, and 2) infants, young children, and adolescent girls in the developing world. Success in this project will significantly decrease the cost of development and reduce time to market for an effective malaria vaccine.