Integrating a pre-erythrocytic component into a multistage malaria vaccine

疟疾控制继续引起国际关注。虽然目前的综合控制努力是 如果要进一步减少全球疟疾负担，就需要增加新的工具。 有效疫苗的开发和引进具有成为此类工具的巨大潜力。但是，在这方面， 迄今为止，疟疾疫苗工作的成功有限。虽然有几个挑战， 必须解决的两个关键问题一再出现。一是亚单位疫苗的免疫原性 必须改进。其次，没有迹象表明，对这些复杂的，多阶段的疟原虫的免疫力， 寄生虫是针对单一的保护性抗原。疫苗候选抗原将需要配制 组合使用，而不会降低单个组分的免疫原性。我们之前的努力 重点关注血液阶段和性阶段疫苗靶点，其中抗体依赖性机制 免疫力是必需，但其中中和B细胞表位的免疫原性不是最佳的。在我们 方法，我们设计了一个保守的，高度免疫原性的，恶性疟原虫特异性载体蛋白， 裂殖子表面蛋白8，促进疫苗生产，并诱导有效的CD 4 + T细胞帮助 中和抗体的产生。我们证明了它作为恶性疟原虫血液阶段载体的实用性 候选疫苗包括裂殖子表面蛋白1、裂殖子表面蛋白2、网织红细胞结合 蛋白同源物5和25 kDa性阶段抗原。重要的是，中和抗体对 靶向结构域保持在多抗原、多阶段制剂的范围内。一个前- 红细胞期疫苗组分目前在我们的制剂中缺乏。在这个项目中，我们将测试 PfMSP 8是重组恶性疟原虫环子孢子表面有效载体蛋白的假设 基于蛋白质的疫苗，以引发针对多个保护性B细胞表位的有效、持久的抗体应答（重复 和非重复结构域）。目的1：表达和纯化四种重组蛋白 基于PfCSP的疫苗旨在增加对相关表位的免疫应答的广度，其中一些 这是目前基于PfCSP的RTS，S疫苗所缺乏的。在目标2中，我们将确定 用GLA-SE配制的每种基于rPfCSP的疫苗引发的T和B细胞应答的表位特异性 作为佐剂。在向下选择之后，我们将评估疫苗诱导的， 用表达伯氏疟原虫的转基因伯氏疟原虫寄生虫的啮齿动物攻击模型中的PfCSP特异性IgG。 恶性疟原虫这项工作的成功将为随后的非临床试验奠定基础。 人灵长类动物以确定rPfCSP* 疫苗是否可以与现有的rPfMSP 1/8组合配制， rPfMSP 2/8、rPfRh 5/8和rPfs 25/8疫苗，而不损害对单个组分的应答。

Malaria control continues to attract international attention. While current integrated control efforts are being maintained, new tools need to be added if further reduction in the global malaria burden is to be realized. The development and introduction of an efficacious vaccine has great potential to be one such tool. However, successes in the malaria vaccine effort to date have been limited. While there are several challenges that must be addressed, two key issues have repeatedly emerged. First, the immunogenicity of subunit vaccines must be improved. Second, there is no indication that immunity to these complex, multi-stage plasmodial parasites is directed toward a single protective antigen. Vaccine candidate antigens will need to be formulated in combination, without any reduction in the immunogenicity of individual components. Our prior efforts have focused on both blood-stage and sexual stage vaccine targets where antibody-dependent mechanisms of immunity are essential, but where immunogenicity of neutralizing B cell epitopes has not been optimal. In our approach, we engineered a well-conserved, highly immunogenic, P. falciparum specific carrier protein based on merozoite surface protein 8 that facilitates vaccine production and induces potent CD4+ T cell help for the production of neutralizing antibodies. We demonstrated its utility as a carrier for P. falciparum blood-stage vaccine candidates including merozoite surface protein 1, merozoite surface protein 2, reticulocyte-binding protein homologue 5 and the 25 kDa sexual stage antigen. Of importance, neutralizing antibody responses to targeted domains were maintained within the context of a multi-antigen, multi-stage formulation. A pre- erythrocytic stage vaccine component is currently lacking from our formulation. In this project, we will test the hypothesis that PfMSP8 is an effective carrier protein for a recombinant P. falciparum circumsporozoite surface protein-based vaccine to elicit potent, durable antibody responses to multiple protective B cell epitopes (repeat and non-repeat domains) that neutralize sporozoites. In aim 1, we will express and purify four recombinant PfCSP-based vaccines designed to increase the breadth of immune responses to relevant epitopes, some of which are lacking in the current PfCSP-based RTS,S vaccine. In aim 2, we will determine the magnitude and epitope specificity of T and B cell responses elicited by each rPfCSP-based vaccine formulated with GLA-SE as adjuvant. Following down-selection, we will evaluate the functionality and durability of vaccine-induced, PfCSP-specific IgG in a rodent challenge model with transgenic Plasmodium berghei parasite expressing P. falciparum CSP. Success in this effort will provide the foundation for subsequent preclinical testing in non- human primates to determine if a rPfCSP* vaccine can be formulated in combination with existing rPfMSP1/8, rPfMSP2/8, rPfRh5/8 and rPfs25/8 vaccines without compromising responses to individual components.