DEVELOPMENT OF THE HBCAG AS A VACCINE CARRIER PLATFORM

最近将中和B细胞表位映射到蛋白质抗原上的能力引起了人们对这些“半抗原样”抗原在疫苗开发中的潜在用途的极大兴趣。然而，多肽抗原通常需要结合到免疫原性载体上才能有效地免疫原性。目前还没有一种适合人类免疫的最佳蛋白质载体。这项建议的目的是开发乙肝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反应。我们最近将HBcAg用作啮齿动物(即伯氏疟原虫、约氏疟原虫)和人类(即恶性疟原虫)疟疾疫苗的载体。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诱导出前所未有的子孢子中和抗体水平。天然HBCAG的一些独特的免疫学特征以及HBcAg-疟疾混合候选疫苗取得的成功表明，这种颗粒蛋白将作为一种将各种抗原输送到免疫系统的手段。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学机制。了解调节对HBcAg-CS杂合颗粒增强免疫反应的细胞m4机制将使未来的合理疫苗设计成为可能。这将在小鼠身上完成，涉及HBcAg杂合颗粒的B细胞识别(即T细胞独立性、共刺激分子的诱导)和Th细胞识别(即良好的特异性、遗传限制、细胞因子产生、Th细胞亚群分布)以及杂合颗粒的抗原呈递和处理。(2)优化HBcAg作为疫苗载体平台。要检查的变量：B细胞/Th细胞插入的最佳数量，HBcAg内最适合B细胞和Th细胞表位的插入位置，颗粒稳定性的重要性，包含未甲基化的CpG二核苷酸的影响，以及多重或联合疫苗设计的可能性。还将探索蛋白质抗原与HBCAG的化学偶联。(3)HBcAg平台技术在恶性疟原虫以外的其他表位的应用。我们预计，在开发疟疾候选疫苗期间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。具体地说，来自流感、间日疟原虫、口蹄疫病毒、丙型肝炎病毒和HIV-1等病原体的选定表位(B和Th)细胞将被掺入杂交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.