Ichihashi Y
Department of Virology, Faculty of Medicine, Niigata University, Asahimachi, Japan.
Virology. 1996 Mar 15;217(2):478-85. doi: 10.1006/viro.1996.0142.
The vaccinia virus forms two morphologically distinct infectious virus particles: intracellular mature virus (IMV) and extracellular enveloped virus (EEV). The envelope of EEV is a Golgi-derived membrane (wrapping membrane). A mutant (vRB10) lacks the ability to form the EEV. In medium containing a neutralizing antibody (2D5mAb), the vRB10 mutant was diluted out from infected cells, whereas the IHD-J strain of vaccinia virus replicated well. The result indicated that the 2D5mAb specifically neutralized the IMV. The 2D5-resistant EEV appeared at 6-7 hr postinfection, and over 65% of infectious virus in the culture fluid was EEV at 48 hr after infection. The EEV was resistant not only to the 2D5mAb but also against several neutralizing antibodies, including polyclonal antivaccinia serum reactive with proteins of the wrapping membrane. Freeze-thawing and other procedures that may damage the wrapping membrane converted the EEV to a form susceptible to the antibodies. Since specific infectivity was not affected by the damage or by exposure to antibody against the wrapping membrane proteins, the wrapping membrane did not directly participate in penetration. The infection process of vaccinia virus was analyzed by comparison of responses to acid treatment between normal IMV and trypsin-treated IMV. Proteolytically activated IMV infected rapidly responding to acid. The protected form virus, which was noninfectious under usual conditions, was proteolytically activated on cell membrane then responded to the acid. Proteolysis activated the virus, and an acidic condition accelerated fusion between the activated IMV and plasma membrane. The virus in the EEV wrapping membrane was the activated form that has the capacity to fuse with the cell membrane. However, the infection of intact EEV was more sensitive against lysosomotropic agents (NH4Cl, neutral red) than that of the trypsin-activated IMV. Resistance to the 2D5mAb, sensitivity to lysosomotropic agents, and acceleration of infection by acid suggested that the intact EEV penetrated by virus-endosome membrane fusion. The combined effect of the presence of wrapping membrane and the process of internalization via an endocytic mechanism rendered EEV resistant to neutralizing antibodies.
细胞内成熟病毒（IMV）和细胞外被膜病毒（EEV）。EEV的包膜是源自高尔基体的膜（包裹膜）。一个突变体（vRB10）缺乏形成EEV的能力。在含有中和抗体（2D5mAb）的培养基中，vRB10突变体从感染细胞中被稀释掉，而痘苗病毒的IHD-J株则复制良好。结果表明，2D5mAb特异性中和IMV。抗2D5的EEV在感染后6 - 7小时出现，感染后48小时培养液中超过65%的感染性病毒是EEV。EEV不仅对2D5mAb有抗性，而且对几种中和抗体也有抗性，包括与包裹膜蛋白反应的多克隆抗痘苗血清。冻融和其他可能损伤包裹膜的操作将EEV转化为易受抗体影响的形式。由于比感染性不受损伤或暴露于针对包裹膜蛋白的抗体的影响，包裹膜不直接参与病毒穿透。通过比较正常IMV和胰蛋白酶处理的IMV对酸处理的反应来分析痘苗病毒的感染过程。经蛋白水解激活的IMV对酸快速反应而感染。在通常条件下无感染性的受保护形式病毒在细胞膜上被蛋白水解激活，然后对酸产生反应。蛋白水解激活病毒，酸性条件加速激活的IMV与质膜之间的融合。EEV包裹膜中的病毒是具有与细胞膜融合能力的激活形式。然而，完整EEV的感染比胰蛋白酶激活的IMV对溶酶体促渗剂（NH4Cl、中性红）更敏感。对2D5mAb的抗性、对溶酶体促渗剂的敏感性以及酸对感染的加速作用表明完整的EEV通过病毒-内体膜融合进行穿透。包裹膜的存在和通过内吞机制内化的过程的综合作用使EEV对中和抗体具有抗性。
