Harson R, Grose C
Department of Microbiology, University of Iowa College of Medicine, Iowa City 52242, USA.
J Virol. 1995 Aug;69(8):4994-5010. doi: 10.1128/JVI.69.8.4994-5010.1995.
The pathway of envelopment and egress of the varicella-zoster virus (VZV) and the primary site of viral production within the epidermal layer of the skin are not fully understood. There are several hypotheses to explain how the virus may receive an envelope as it travels to the surface of the monolayer. In this study, we expand earlier reports and provide a more detailed explanation of the growth of VZV in human melanoma cells. Human melanoma cells were selected because they are a malignant derivative of the melanocyte, the melanin-producing cell which originates in the neural crest. We were able to observe the cytopathic effects of syncytial formation and the pattern of egress of virions at the surfaces of infected monolayers by scanning electron microscopy and laser-scanning confocal microscopy. The egressed virions did not appear uniformly over the syncytial surface, rather they were present in elongated patterns which were designated viral highways. In order to document the pathway by which VZV travels from the host cell nucleus to the outer cell membrane, melanoma cells were infected and then processed for examination by transmission electron microscopy (TEM) at increasing intervals postinfection. At the early time points, within minutes to hours postinfection, it was not possible to localize the input virus by TEM. Thus, viral particles first observed at 24 h postinfection were considered progeny virus. On the basis of the TEM observations, the following sequence of events was considered most likely. Nucleocapsids passed through the inner nuclear membrane and acquired an envelope, after which they were seen in the endoplasmic reticulum. Enveloped virions within vacuoles derived from the endoplasmic reticulum passed into the cytoplasm. Thereafter, vacuoles containing nascent enveloped particles acquired viral glycoproteins by fusion with vesicles derived from the Golgi. The vacuoles containing virions fused with the outer plasma membrane and the particles appeared on the surface of the infected cell. Late in infection, enveloped virions were also present within the nuclei of infected cells; the most likely mechanism was retrograde flow from the perinuclear space back into the nucleus. Thus, this study suggests a role for the melanocyte in the pathogenesis of VZV infection, because all steps in viral egress can be accounted for if VZV subsumes the cellular pathways required for melanogenesis.
水痘-带状疱疹病毒（VZV）的包膜化和释放途径以及皮肤表皮层内病毒产生的主要部位尚未完全明确。有几种假说试图解释病毒在向单层细胞表面移动时如何获得包膜。在本研究中，我们扩展了早期报告，并对VZV在人黑色素瘤细胞中的生长情况给出了更详细的解释。选择人黑色素瘤细胞是因为它们是黑素细胞的恶性衍生物，黑素细胞是起源于神经嵴的产生黑色素的细胞。通过扫描电子显微镜和激光扫描共聚焦显微镜，我们能够观察到感染单层细胞表面的合胞体形成的细胞病变效应以及病毒粒子的释放模式。释放出的病毒粒子并非均匀地出现在合胞体表面，而是呈细长状分布，被称为病毒高速公路。为了记录VZV从宿主细胞核到细胞膜外的移动途径，黑色素瘤细胞被感染，然后在感染后不同时间间隔进行处理，以便通过透射电子显微镜（TEM）检查。在感染后的早期时间点，即感染后数分钟到数小时内，通过TEM无法定位输入的病毒。因此，在感染后24小时首次观察到的病毒粒子被视为子代病毒。基于TEM观察结果，以下事件序列被认为最有可能。核衣壳穿过内核膜并获得包膜，之后在内质网中被观察到。源自内质网的液泡中的包膜病毒粒子进入细胞质。此后，含有新生包膜粒子的液泡通过与源自高尔基体的囊泡融合而获得病毒糖蛋白。含有病毒粒子的液泡与外质膜融合后，粒子出现在感染细胞的表面。在感染后期，包膜病毒粒子也存在于感染细胞的细胞核内；最可能的机制是从核周间隙逆行流入细胞核。因此，本研究表明黑素细胞在VZV感染的发病机制中起作用，因为如果VZV利用黑素生成所需的细胞途径，那么病毒释放的所有步骤都可以得到解释。
