Milich D R, Peterson D L, Zheng J, Hughes J L, Wirtz R, Schödel F
Department of Molecular Biology, Scripps Research Institute, La Jolla, California 92037, USA.
Ann N Y Acad Sci. 1995 May 31;754:187-201. doi: 10.1111/j.1749-6632.1995.tb44451.x.
The "carrier effect," defined as the provision of T cell recognition sites physically linked to B cell epitopes in order to provide Th cell function for antibody synthesis, is well known. Peptides, proteins, and more recently particulate protein antigens have been used for this purpose. The hepatitis B core antigen represents a highly immunogenic antigen in humans as well as in experimental animal models. Studies in mice have provided insight into this enhanced immunogenicity. For example, HBcAg directly activates B cells (i.e., T cell independence), HBcAg elicits strong T cell responses, and HBcAg is efficiently processed and presented by antigen presenting cells (APCs). These characteristics suggested that HBcAg may be an ideal carrier moiety for B cell epitopes requiring additional Th cell function. Therefore, a number of HBV and non-HBV B cell epitopes have been chemically linked or fused by recombinant methods to HBcAg as a method to increase immunogenicity with significant success. We have designed bacterial expression vectors that allow insertion of heterologous B cell epitopes at various positions within HBcAg particles and permit efficient purification of hybrid HBcAg particles. Studies of positional effects have demonstrated that an internal insertion into a dominant HBcAg-specific B cell site represents a superior location for enhanced antibody production. Immunogenicity studies have been extended to protection against experimental challenge in several systems. For example, a malaria CS repeat sequence derived from P. berghei was inserted into HBcAg at the internal site, and purified hybrid HBcAg/CS particles were highly immunogenic and protected 100% of experimentally challenged BALB/c mice. This system has also been exploited for purposes of oral vaccination by expressing genes coding for hybrid HBcAg particles in live, avirulent vaccine strains of Salmonella species.
“载体效应”是指提供与B细胞表位物理连接的T细胞识别位点，以便为抗体合成提供Th细胞功能，这是众所周知的。肽、蛋白质以及最近的颗粒性蛋白质抗原都已用于此目的。乙肝核心抗原在人类以及实验动物模型中都是一种高度免疫原性的抗原。对小鼠的研究为这种增强的免疫原性提供了深入了解。例如，乙肝核心抗原直接激活B细胞（即T细胞非依赖性），引发强烈的T细胞反应，并且能被抗原呈递细胞（APC）有效加工和呈递。这些特性表明，乙肝核心抗原可能是需要额外Th细胞功能的B细胞表位的理想载体部分。因此，许多乙肝病毒和非乙肝病毒的B细胞表位已通过化学连接或重组方法与乙肝核心抗原融合，作为提高免疫原性的一种方法，并取得了显著成功。我们设计了细菌表达载体，允许在乙肝核心抗原颗粒内的不同位置插入异源B细胞表位，并能有效纯化杂交乙肝核心抗原颗粒。位置效应研究表明，插入到主要的乙肝核心抗原特异性B细胞位点内部是增强抗体产生的优越位置。免疫原性研究已扩展到在多个系统中预防实验性攻击。例如，将源自伯氏疟原虫的疟疾环子孢子蛋白重复序列插入到乙肝核心抗原的内部位点，纯化的杂交乙肝核心抗原/环子孢子蛋白颗粒具有高度免疫原性，并能保护100%经实验攻击的BALB/c小鼠。通过在无毒的沙门氏菌活疫苗菌株中表达编码杂交乙肝核心抗原颗粒的基因，该系统也已被用于口服疫苗接种。
