Synthetic microparticle malaria vaccine

描述(申请人提供)：该第二阶段项目将开发一种新型的合成微粒疟疾疫苗，使用人类疟疾的病原体恶性疟原虫的环子孢子(CS)蛋白的T1BT*表位。目前还没有获得批准的疟疾疫苗，这种疾病每年在发展中国家造成多达5亿新感染和100万人死亡。临床前和临床研究表明，寄生虫子孢子阶段的CS蛋白表位可以诱导保护性免疫。保护性免疫包括作用于感染部位和血液中的寄生虫中和抗体，以及防止红细胞期寄生虫从宿主肝脏释放的特定细胞机制。在成功的第一阶段项目中，我们利用逐层(LBL)法制备了负载T1BT*的合成微粒，T1BT*是一个包含中心重复区(B)抗体表位和两个T细胞表位的融合肽：T1表位与B重叠，在所有恶性疟原虫株中都是保守的；T*表位位于CS的C末端附近，是多种HLA单倍型识别的通用表位。LBL颗粒是由完全合成的原材料(不含生物成分)制成的，可激发强大的适应性免疫反应，并将炎症不良反应降至最低。我们的第一阶段工作表明，携带T1BT*的微粒在小鼠中具有强大的免疫原性，可以激发寄生虫中和抗体和T细胞，包括T细胞表位特异性的效应器细胞毒细胞。用T1BT*微粒免疫的小鼠可抵抗疟原虫攻击。我们还表明，用天然免疫刺激剂TLR2配体Pam3Cys对微粒进行简单的修饰，可以增加候选疫苗的效力和效力，而不会引发明显的炎症事件。在目前的项目中，我们将通过检测携带T1BT*或Pam3Cys.T1BT*的微粒在小鼠和恒河猴模型中的免疫原性和有效性来选择最终的开发候选。在恒河猴模型中的疗效将通过用纯化的猴子Ig被动免疫NA�ve小鼠并攻击感染疟原虫的小鼠来测试。我们将选择引起最高寄生虫中和抗体活性和干扰素？+细胞反应的候选者，因为这两种机制似乎负责预防疟原虫感染。选定的候选者将被推进到临床前开发，其中将包括开发分析释放分析和制造工艺，以及在符合GLP的兔子研究中评估安全性和耐受性。第二阶段开发工作的具体方法和战略将通过与食品和药物管理局(FDA)的讨论来指导，以准备GMP生产和药品产品的发布，并在随后的第三阶段项目中提交研究性新药(IND)申请。

DESCRIPTION (provided by applicant): This Phase II project will develop a novel synthetic microparticle vaccine for malaria, using the T1BT* epitopes of the circumsporozoite (CS) protein of Plasmodium falciparum, the causative agent of human malaria. There is no approved vaccine for malaria, a disease that causes up to 500 million new infections and 1 million deaths each year in the developing world. Preclinical and clinical research has demonstrated that epitopes of the CS protein of the parasite sporozoite stage can elicit protective immunity. The protective immunity consists of parasite-neutralizing antibodies that act at the site of infection and in the bloodstream, and specific cellular mechanisms which prevent release of erythrocytic stage parasite from the host liver. In the successful Phase I project, we utilized layer-by-layer (LbL) fabrication to produce synthetic microparticles loaded with T1BT*, a fusion peptide comprising the antibody epitope of the central repeat region (B) and two T-cell epitopes: the T1 epitope which overlaps B and is conserved in all strains of P. falciparum, and the T* epitope which is located near the C-terminus of CS and is a universal epitope recognized by multiple HLA haplotypes. LbL particles are made with entirely synthetic raw materials (no biological components) and elicit potent adaptive immune responses with minimal inflammatory adverse events. Our Phase I work showed that microparticles bearing T1BT* were potently immunogenic in mice, eliciting parasite-neutralizing antibodies and T-cells including effector cytotoxic cells specific for the T-cell epitopes. Mice immunized with T1BT* microparticles were protected from Plasmodium challenge. We also showed that a simple modification of the microparticles with an innate immune stimulator, TLR2 ligand Pam3Cys, increased the potency and efficacy of the vaccine candidate without triggering overt inflammatory events. In the current project, we will select the final development candidate by examining immunogenicity and efficacy of microparticles loaded with T1BT* or Pam3Cys.T1BT*, in both the mouse and rhesus macaque models. Efficacy in the rhesus model will be tested by passively-immunizing na�ve mice with purified Ig from the monkeys, and challenging the mice with Plasmodium. We will select the candidate that elicits the highest parasite-neutralizing antibody activity and IFN?+ cellular responses, since these two mechanisms appear to be responsible for protection against Plasmodium infection. The selected candidate will be advanced to preclinical development which will include development of analytical release assays and a manufacturing process, and assessment of safety and tolerability in a GLP-compliant rabbit study. The specific methods and strategies of the Phase II development efforts will be guided by discussions with the Food and Drug Administration (FDA) in preparation for GMP manufacturing and release of drug product and submission of an Investigational New Drug (IND) application in a subsequent Phase III project.