Molecular and Cellular Biology, University of California, 1 Shields Ave., Davis, CA 95616, USA.
J Virol. 2011 Jan;85(2):1117-24. doi: 10.1128/JVI.00657-10. Epub 2010 Nov 10.
Hepatitis E virus (HEV) is a human pathogen that causes acute hepatitis. When an HEV capsid protein containing a 52-amino-acid deletion at the C terminus and a 111-amino-acid deletion at the N terminus is expressed in insect cells, the recombinant HEV capsid protein can self-assemble into a T=1 virus-like particle (VLP) that retains the antigenicity of the native HEV virion. In this study, we used cryoelectron microscopy and image reconstruction to show that anti-HEV monoclonal antibodies bind to the protruding domain of the capsid protein at the lateral side of the spikes. Molecular docking of the HEV VLP crystal structure revealed that Fab224 covered three surface loops of the recombinant truncated second open reading frame (ORF2) protein (PORF2) at the top part of the spike. We also determined the structure of a chimeric HEV VLP and located the inserted B-cell tag, an epitope of 11 amino acids coupled to the C-terminal end of the recombinant ORF2 protein. The binding site of Fab224 appeared to be distinct from the location of the inserted B-cell tag, suggesting that the chimeric VLP could elicit immunity against both HEV and an inserted foreign epitope. Therefore, the T=1 HEV VLP is a novel delivery system for displaying foreign epitopes at the VLP surface in order to induce antibodies against both HEV and the inserted epitope.
戊型肝炎病毒（HEV）是一种引起急性肝炎的人类病原体。当在昆虫细胞中表达包含 C 末端 52 个氨基酸缺失和 N 末端 111 个氨基酸缺失的 HEV 衣壳蛋白时，重组 HEV 衣壳蛋白可以自我组装成保留天然 HEV 病毒粒子抗原性的 T=1 病毒样颗粒（VLP）。在这项研究中，我们使用冷冻电子显微镜和图像重建来显示抗 HEV 单克隆抗体结合在刺突侧的衣壳蛋白突出结构域。HEV VLP 晶体结构的分子对接显示 Fab224 覆盖了 Spike 顶部重组截断第二开放阅读框（ORF2）蛋白（PORF2）的三个表面环。我们还确定了嵌合 HEV VLP 的结构，并定位了插入的 B 细胞标签，这是一个连接到重组 ORF2 蛋白 C 末端的 11 个氨基酸的表位。Fab224 的结合位点似乎与插入的 B 细胞标签的位置不同，这表明嵌合 VLP 可以引发针对 HEV 和插入的外源表位的免疫反应。因此，T=1 HEV VLP 是一种新型的递送系统，可在 VLP 表面展示外源表位，以诱导针对 HEV 和插入表位的抗体。
