GENETIC ENGINEERING APPROACHES FOR MALARIA VACCINES

针对两种主要疟原虫的亚单位疫苗， 将研制恶性疟原虫和间日疟原虫。 我们有 证明了杂交型B病毒表面抗原（HBVsAg） 多肽（由环子孢子基因的部分插入物组成 插入HBVsAg基因的前S区）在 基因工程酵母载体系统。 这些杂合多肽 组装成具有HBV和HBV抗原性的多聚体颗粒， 疟原虫 我们建议生产杂交HBV多肽 含有部分间日疟原虫环子孢子基因。 我们亦建议 使用酵母表达载体生产完整的环子孢子 两种疟疾的蛋白质。 在第一阶段，抗原性的 在酵母中产生的杂合HBVsAg颗粒和环子孢子蛋白将被 用抗疟疾寄生虫的抗血清评估;超免疫人血清和 将各种动物血清培养成完整的寄生虫或合成的 代表环子孢子抗原的重复单元的肽将 得到考验 此外，这些制剂的免疫原性将是 在啮齿动物和灵长类动物中进行了评估。 这些研究将重点 测量与保护相关的免疫反应。 用于相位 II，表达系统将被优化，纯化程序将 被开发以产生大量的最具免疫原性的形式， 这些疟疾抗原。 攻毒研究将在亚人中进行 灵长类动物 各种免疫程序以及 将测试佐剂。 这些挑战性实验的结果将 用于确定是否存在其他阶段的抗原， 寄生虫的生命周期应包括在内， 持久免疫力 在第一阶段开发的程序，测试使用 混合HBVsAg作为一种载体， 环子孢子抗原和检测整个环子孢子蛋白 在酵母中表达，可以提供增强免疫原性的手段， 疟疾裂殖子和配子体阶段的表面蛋白 寄生虫

Subunit vaccines for the two predominant species of malaria parasites, Plasmodium falciparum and Plasmodium vivax will be developed. We have demonstrated that hybrid Hepatitis B virus surface antigen (HBVsAg) polypeptides (composed of insertions of part of the circumsporozoite gene of P. falciparum into the pre-S region of the HBVsAg gene) are expressed in genetically engineered yeast vector systems. These hybrid polypeptides assemble into multimeric particles that have antigenicities of both HBV and the malaria parasite. We propose to produce hybrid HBV polypeptides containing parts of the circumsporozoite gene of P. vivax. We also propose to use yeast expression vectors to produce the entire circumsporozoite proteins of both malaria species. In Phase I, the antigenicity of the hybrid HBVsAg particles and circumsporozoite proteins made in yeast will be assessed with antisera to the malaria parasite; hyperimmune human sera and various animal sera raised to either intact parasites or to synthetic peptides representing the repeat units of the circumsporozoite antigen will be tested. Also, the immunogenicity of these preparations will be evaluated in rodents and in sub-human primates. These studies will focus on measuring immune responses that correlate with protection. For Phase II, expression systems will be optimized and purification procedures will be developed to produce large quantities of the most immunogenic form of these malaria antigen(s). Challenge studies will be conducted in sub-human primates. Various immunization procedures as well as the effects of adjuvants will be tested. The results of these challenge experiments will be used to determine whether or not antigens of other stages of the parasites' life cycles should be included to stimulate effective and durable immunity. The procedures developed in Phase I, testing the use of hybrid HBVsAg as a carrier for presentation of portions of the circumsporozoite antigen and testing the entire circumsporozoite protein expressed in yeast, may provide the means to augment the immunogenicity of the surface proteins of merozoite and gametocyte stages of malaria parasites.