DEVELOPMENT OF THE HBCAG AS A VACCINE CARRIER PLATFORM

最近能够映射蛋白质抗原上的中和B细胞表位，这使得人们对这些“半抗原样”抗原在疫苗开发中的潜在用途产生了很大的兴趣。然而，肽抗原通常需要与免疫原性载体缀合以获得有效的免疫原性。适合于人免疫的最佳蛋白质载体部分是不可用的。该提案的目的是开发B型肝炎核衣壳作为多价载体平台的潜力，以增强对弱肽抗原的免疫应答。我们最近使用HBcAg作为啮齿动物的载体（即，伯氏疟原虫，约氏疟原虫）和人（即，恶性疟原虫）疟疾疫苗的开发。啮齿动物疫苗具有90-100%的保护性，而人类候选疫苗在小鼠中激发出前所未有的子孢子中和抗体水平。天然HBCAG的许多独特的免疫学特征和用杂合HBcAg-疟疾候选疫苗获得的成功表明，这种颗粒蛋白将可用作将各种抗原递送至免疫系统的手段。提出了三个具体项目。(1)研究HBcAg-疟疾杂交颗粒增强免疫原性的基本免疫机制。理解调节对HBcAg-CS杂交颗粒增强的免疫应答的细胞机制将使未来的合理疫苗设计成为可能。这将在小鼠中完成并涉及B细胞识别的检查（即，T细胞非依赖性，共刺激分子的诱导）和Th细胞识别（即，HBcAg-杂交颗粒的精细特异性、遗传限制、细胞因子产生、Th细胞亚群分布）以及杂交颗粒的抗原呈递和加工。(2)HBcAg作为疫苗载体平台的优化。待检查变量：B细胞/Th细胞插入物的最佳数目、HBcAg内最佳容纳B细胞以及Th细胞表位的插入位点、颗粒稳定性的重要性、包含未甲基化CpG二核苷酸的影响以及多重或组合疫苗设计的可能性。还将探索蛋白抗原与HBCAG的化学缀合。(3)HBcAg平台技术应用于除恶性疟原虫外的其他表位。我们预计，在疟疾候选疫苗开发过程中获得的经验和信息将适用于其他可能受益于使用HBcAg作为平台的疫苗。具体地，将来自病原体如流感、间日疟原虫、FMDV、HCV和HIV-1的选定表位（B和Th）细胞掺入杂合HBcAg颗粒中，以确定HBcAg载体系统的普遍适用性。

The recent ability to map neutralizing B cell epitopes on protein antigens has created much interest in the potential use of these "hapten-like" antigens in vaccine development. However, peptide antigens often require conjugation to an immunogenic carrier for efficient immunogenicity. An optimal protein carrier moiety suitable for human immunization is not available. The objective of the proposal is to exploit the potential of the hepatitis B nucleocapsid to function as a multi-valent carrier platform to enhance the immune response to weak peptide antigens. We recently used the HBcAg as a carrier for rodent (i.e., P. berghei, P. yoelii) and human (i.e., P. falciparum) malarial vaccine development. The rodent vaccines are 90-100% protective and the human candidate vaccine elicits unprecedented levels of sporozoite-neutralizing antibody in mice. A number of unique immunologic characteristics of the native HBCAG and the success achieved with the hybrid HBcAg-malaria candidate vaccines suggest that this particulate protein will be useful as a means of delivering a variety of antigens to the immune system. Three specific projects are proposed. (1) Examine basic immunologic mechanisms responsible for the enhanced immunogenicity of HBcAg- malaria hybrid particles. Understanding the cellular m4echanisms regulating the enhanced immune response to HBcAg-CS hybrid particles will enable future rational vaccine design. This will be accomplished in mice and involve examination of B cell recognition (i.e., T cell- independence, induction of co-stimulatory molecules) and Th cell recognition (i.e., fine specificity, genetic restriction, cytokine production, Th cell subset distribution) of HBcAg-hybrid particles as well as the antigen presentation and processing of hybrid particles. (2) Optimization of the HBcAg as a vaccine carrier platform. Variables to be examine: the optimal number of B cell/Th cell inserts, the insertion sites within HBcAg that best accommodate B cell as well as Th cell epitopes, the importance of particle stability, the effects of inclusion of unmethylated CpG dinucleotides, and the potential for multiple or combination vaccine design. Chemical conjugation of protein antigens to the HBCAG will also be explored. (3) Application of the HBcAg platform technology to other epitopes in addition to P. falciparum. We anticipate that the experience and information gained during the development of malaria candidate vaccines will be applicable to other vaccines which may benefit from the use of HBcAg as a platform. Specifically, selected epitopes (B and Th) cell from pathogens such as Influenza, P. vivax, FMDV, HCV and HIV-1 will be incorporated into hybrid HBcAg particles to determine the general applicability of the HBcAg carrier system.