Herpesvirus Interactions With Cell Surface Receptors

单纯疱疹病毒(HSV)感染许多培养细胞，如Vero细胞，是通过受体结合和与细胞表面融合而启动的。对HSV进入不同细胞系的调查表明，中国仓鼠卵巢(CHO)和HeLa细胞支持HSV的内吞、pH依赖的进入途径。在这些细胞类型中，但不是Vero细胞，溶酶体促进剂，如弱碱性氯化铵和缓冲细胞器低pH的离子载体Monensin，以剂量依赖的方式阻止HSV进入。在感染这两种血清型的几个菌株期间，这些药物的非细胞毒性浓度在结合后的早期阶段起作用。HSV细胞受体HveA、Nectin-1或Nectin-2介导的CHO细胞进入被这些药物阻断。在感染后30min，电子显微镜(EM)很容易在囊泡中检测到被包被的病毒粒子。耗尽细胞能量，阻止内吞作用，防止细胞摄取和感染HSV在CHO和HeLa细胞。进入Vero细胞不受能量耗尽的影响，正如预期的那样，病毒与Vero细胞表面融合的EM图像很常见。HSV进入所有三个细胞系的动力学相似，这表明无论采用何种途径，进入都是同样有效的。许多病毒的pH依赖的融合功能被病毒粒子的酸预处理灭活。在pH 5.5处理后，HSV进入所有细胞类型的机会减少了50%。这种失活是快速的(1分钟)，依赖于温度，并且不可逆。酸处理对受体结合糖蛋白gD的抗原构象没有影响，对放射性标记的病毒粒子与细胞受体的结合也没有影响。这表明，温和的酸性pH会使进入过程中的结合后事件失活，如膜融合。我们认为HSV有能力通过内吞和低pH触发的步骤有效地进入细胞。

Herpes simplex virus (HSV) infection of many cultured cells, such as Vero cells, is initiated by receptor-binding and fusion with the cell surface. A survey of HSV entry into diverse cell lines indicated that Chinese hamster ovary (CHO) and HeLa cells support an endocytic, pH-dependent entry pathway for HSV. In these cell types, but not Vero cells, lysosomotropic agents, such as the weak base ammonium chloride and the ionophore monensin which buffer the low pH of organelles, blocked HSV entry in a dose-dependent manner. Noncytotoxic concentrations of these agents acted at an early, postbinding step during infection by several strains of both serotypes. CHO cell entry mediated by the HSV cellular receptors HveA, nectin-1 or nectin-2 was blocked by these agents. Enveloped virions were readily detected in vesicles by electron microscopy (EM) at < 30 min post-infection. Depletion of cellular energy, which blocks endocytosis, prevented cellular uptake and infection by HSV in CHO and HeLa cells. Entry into Vero cells was unaffected by energy depletion, and as expected, EM images of virus fusion with the Vero cell surface were prevalent. The kinetics of HSV entry into all three cell lines was similar, which suggests that entry is equally efficient regardless of the pathway utilized. The pH-dependent fusion function of many viruses is inactivated by acid pre-treatment of virions. Entry of HSV into all cell types was reduced by 50% following treatment with pH 5.5. This inactivation was rapid (< 1 min), temperature-dependent, and irreversible. Acid pretreatment had no detectable effect on the antigenic conformation of gD, the receptor-binding glycoprotein, and no effect on binding of radiolabelled virions to cellular receptors. This suggests that mildly acidic pH inactivates a post-binding event in entry such as membrane fusion. We propose that HSV has the capacity to efficiently enter cells by endocytic uptake followed by a low pH-triggered step.