Studies on the mechanism of entry of the envelope virus and its inhibitor.

糖蛋白B（gB）是疱疹病毒中最保守的糖蛋白，在病毒的感染性中起重要作用。大多数疱疹病毒（包括伪狂犬病病毒（PrV））的糖蛋白被细胞蛋白酶切割成两个二硫键连接的亚基。在本研究中，我们证明了在人结肠癌Lo Vo细胞中产生的糖蛋白，缺乏普遍存在的蛋白酶弗林蛋白酶，仍然是未切割的形式，并且病毒在Lo Vo细胞中复制而没有细胞融合。未切割的gB在弗林蛋白酶消化后转化为亚基。该病毒也复制在Madin-Darby牛肾细胞中的肽弗林蛋白酶抑制剂的存在下，没有细胞融合，虽然显着的合胞体形成在没有抑制剂。组成型表达弗林蛋白酶的Lo Vo细胞在感染病毒后出现细胞融合。穿透动力学分析显示，携带未切割的gB的病毒以与携带切割的gB的病毒相同的速率穿透细胞。这些结果表明PrV gB被弗林蛋白酶切割，并且切割对于病毒体外复制是不稳定的。gB裂解参与合胞体的形成，但不是在渗透动力学，这表明不同的机制之间的细胞-细胞融合和病毒-细胞融合的PrV。电子显微镜检查在马疱疹病毒1型（EHV-1）的入境阶段表明，病毒颗粒存在于马脑微血管内皮细胞（EBMEC）的细胞质中的无涂层囊泡。虽然疱疹病毒被认为是在质膜上进入细胞，但这些结果可能表明EHV-1通过内体进入EBMEC。

Glycoprotein B (gB) is the most conserved glycoprotein of herpesviruses and plays important roles in virus infectivity. The glycoprotein of most herpesviruses, including psuedorabies virus (PrV), is cleaved by a cellular protease into two disulfide-linked subunits. In the present study, we demonstrated that the glycoprotein generated in human colon carcinoma Lo Vo cells, which lack the ubiquitous protease furin, remained the uncleaved form and that the virus replicated in Lo Vo cells without cell fusion. The uncleaved gB was converted into the subunits after furin digestion. The virus also replicated in Madin-Darby bovine kidney cells in the presence of a peptide furin inhibitor without cell fusion although distinguished syncytia were formed in the absence of the inhibitor. Lo Vo cells constitutively expressing furin showed cell fusion when they were infected with the virus. The penetration kinetics assays revealed that the virus carrying uncleaved gB penetrated the cells at the same rate as that carrying cleaved gB. These results indicate that PrV gB was cleaved by furin and that the cleavage was dispensable for virus replication in vitro. gB cleavage was involved in syncytium formation but not in penetration kinetics, suggesting that different mechanisms operated between cell-cell fusion and virus-cell fusion by PrV.Electron microscopic examination at the stage of entry of equine herpesvirus 1 (EHV-1) showed that viral particles were present within uncoated vesicles in the cytoplasm of equine brain microvascular endothelial cells (EBMECs). Although herpesviruses are thought to enter the cells on the plasma membrane, these results might show that EHV-1 enter EBMECs through endosome.