Essential elements of the capsid protein for self-assembly into empty virus-like particles of hepatitis E virus
Essential elements of the capsid protein for self-assembly into empty virus-like particles of hepatitis E virus
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DOI：
10.1128/jvi.79.20.12999-13006.2005
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发表时间：
2005-10-01
影响因子：
5.4
通讯作者：
Cheng, RH
中科院分区：
文献类型：
--
作者：
Li, TC;Takeda, N;Cheng, RH
戊型肝炎病毒（HEV）是一种不可培养的病毒，可引起人类急性肝功能衰竭。该病毒的主要衣壳蛋白由开放阅读框2（ORF 2）基因编码。当用重组杆状病毒表达由ORF 2的氨基酸（aa）残基112至660组成的重组蛋白质时，蛋白质自组装成病毒样颗粒（VLP）（T. C. Li，Y. Yamakawa，K.铃木，M。Tatsumi，M. A. Razak，T. Uchida，N. Takeda和T. Miyamura，J. Virol. 71：7207-7213，1997）。在感染的Tn 5细胞的培养基中可以发现VLP，但在Sf 9细胞的培养基中没有发现，并且主要的VLP已经失去了C-末端52 aa。为了研究HEV VLP形成所需的蛋白质，我们制备了14个杆状病毒重组体来表达在N末端、C末端或两者处截短的衣壳蛋白。由氨基酸残基112至608组成的衣壳蛋白在Sf 9细胞中形成VLP，表明颗粒形成依赖于ORF 2蛋白的修饰过程。在本研究中，电子低温显微镜和图像处理的VLP产生的Sf 9和Tn 5细胞表明，他们具有相同的配置和结构。空VLP被发现在Tn 5和Sf 9细胞感染的重组含有一个N-末端截短氨基酸残基125和C-末端氨基酸残基601，证明氨基酸残基126至601是VLP装配的启动所需的基本要素。重组HEV VLP是潜在的粘膜疫苗载体，用于呈递外源抗原表位，也可作为载体用于将基因递送至粘膜组织用于DNA疫苗接种和基因治疗。本研究结果为构建具有新功能的重组HEV VLP提供了有用的信息。
Hepatitis E virus (HEV) is a noncultivable virus that causes acute liver failure in humans. The virus's major capsid protein is encoded by an open reading frame 2 (ORF2) gene. When the recombinant protein consisting of amino acid (aa) residues 112 to 660 of ORF2 is expressed with a recombinant baculovirus, the protein self-assembles into virus-like particles (VLPs) (T.-C. Li, Y. Yamakawa, K. Suzuki, M. Tatsumi, M. A. Razak, T. Uchida, N. Takeda, and T. Miyamura, J. Virol. 71:7207-7213, 1997). VLPs can be found in the culture medium of infected Tn5 cells but not in that of Sf9 cells, and the major VLPs have lost the C-terminal 52 aa. To investigate the protein requirement for HEV VLP formation, we prepared 14 baculovirus recombinants to express the capsid proteins truncated at the N terminus, the C terminus, or both. The capsid protein consisting of aa residues 112 to 608 formed VLPs in Sf9 cells, suggesting that particle formation is dependent on the modification process of the ORF2 protein. In the present study, electron cryomicroscopy and image processing of VLPs produced in Sf9 and Tn5 cells indicated that they possess the same configurations and structures. Empty VLPs were found in both Tn5 and Sf9 cells infected with the recombinant containing an N-terminal truncation up to aa residue 125 and C-terminal to aa residue 601, demonstrating that the aa residues 126 to 601 are the essential elements required for the initiation of VLP assembly. The recombinant HEV VLPs are potential mucosal vaccine carrier vehicles for the presentation of foreign antigenic epitopes and may also serve as vectors for the delivery of genes to mucosal tissue for DNA vaccination and gene therapy. The results of the present study provide useful information for constructing recombinant HEV VLPs having novel functions.