Jiang Hai-Fei, Wang Wei, Jiang Xuan, Zeng Wen-Bo, Shen Zhang-Zhou, Song Yi-Ge, Yang Hong, Liu Xi-Juan, Dong Xiao, Zhou Jing, Sun Jin-Yan, Yu Fei-Long, Guo Lin, Cheng Tong, Rayner Simon, Zhao Fei, Zhu Hua, Luo Min-Hua
State Key Laboratory of Virology, CAS Center for Excellence in Brain Science, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China.
University of Chinese Academy of Sciences, Beijing, China.
J Virol. 2017 May 26;91(12). doi: 10.1128/JVI.00127-17. Print 2017 Jun 15.
Although a varicella-zoster virus (VZV) vaccine has been used for many years, the neuropathy caused by VZV infection is still a major health concern. Open reading frame 7 (ORF7) of VZV has been recognized as a neurotropic gene , but its neurovirulent role remains unclear. In the present study, we investigated the effect of ORF7 deletion on VZV replication cycle at virus entry, genome replication, gene expression, capsid assembly and cytoplasmic envelopment, and transcellular transmission in differentiated neural progenitor cells (dNPCs) and neuroblastoma SH-SY5Y (dSY5Y) cells. Our results demonstrate that the ORF7 protein is a component of the tegument layer of VZV virions. Deleting ORF7 did not affect viral entry, viral genome replication, or the expression of typical viral genes but clearly impacted cytoplasmic envelopment of VZV capsids, resulting in a dramatic increase of envelope-defective particles and a decrease in intact virions. The defect was more severe in differentiated neuronal cells of dNPCs and dSY5Y. ORF7 deletion also impaired transmission of ORF7-deficient virus among the neuronal cells. These results indicate that ORF7 is required for cytoplasmic envelopment of VZV capsids, virus transmission among neuronal cells, and probably the neuropathy induced by VZV infection. The neurological damage caused by varicella-zoster virus (VZV) reactivation is commonly manifested as clinical problems. Thus, identifying viral neurovirulent genes and characterizing their functions are important for relieving VZV related neurological complications. ORF7 has been previously identified as a potential neurotropic gene, but its involvement in VZV replication is unclear. In this study, we found that ORF7 is required for VZV cytoplasmic envelopment in differentiated neuronal cells, and the envelopment deficiency caused by ORF7 deletion results in poor dissemination of VZV among neuronal cells. These findings imply that ORF7 plays a role in neuropathy, highlighting a potential strategy to develop a neurovirulence-attenuated vaccine against chickenpox and herpes zoster and providing a new target for intervention of neuropathy induced by VZV.
尽管水痘带状疱疹病毒（VZV）疫苗已使用多年，但VZV感染所致神经病变仍是一个重大的健康问题。VZV的开放阅读框7（ORF7）已被确认为一个嗜神经基因，但其神经毒力作用仍不清楚。在本研究中，我们研究了ORF7缺失对VZV在分化的神经祖细胞（dNPCs）和成神经细胞瘤SH-SY5Y（dSY5Y）细胞的病毒进入、基因组复制、基因表达、衣壳装配和胞质包被以及跨细胞传播等复制周期阶段的影响。我们的结果表明，ORF7蛋白是VZV病毒体被膜层的一个组成部分。删除ORF7不影响病毒进入、病毒基因组复制或典型病毒基因的表达，但明显影响VZV衣壳的胞质包被，导致包膜缺陷颗粒显著增加，完整病毒体减少。在dNPCs和dSY5Y的分化神经元细胞中，这种缺陷更为严重。ORF7缺失也损害了ORF7缺陷病毒在神经元细胞之间的传播。这些结果表明，ORF7是VZV衣壳胞质包被、病毒在神经元细胞之间传播以及可能是VZV感染所致神经病变所必需的。水痘带状疱疹病毒（VZV）再激活引起的神经损伤通常表现为临床问题。因此，鉴定病毒神经毒力基因并表征其功能对于缓解VZV相关神经并发症很重要。ORF7先前已被鉴定为一个潜在的嗜神经基因，但其在VZV复制中的作用尚不清楚。在本研究中，我们发现ORF7是分化神经元细胞中VZV胞质包被所必需的，并且ORF7缺失导致的包被缺陷导致VZV在神经元细胞之间的传播不佳。这些发现意味着ORF7在神经病变中起作用，突出了开发一种针对水痘和带状疱疹的神经毒力减弱疫苗的潜在策略，并为干预VZV诱导的神经病变提供了一个新靶点。
