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，是由受体结合和与细胞表面融合引起的。一项对HSV进入多种细胞系的调查表明，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（而不是Vero细胞），溶酶性收缩剂，如缓冲低pH细胞器的弱碱氯化铵和离子载体莫能菌素，以剂量依赖的方式阻止HSV进入。在两种血清型的几种菌株感染期间，这些药物的无细胞毒性浓度在结合后的早期阶段起作用。由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30分钟内，通过电子显微镜（EM）很容易在囊泡中检测到包膜病毒粒子。在CHO和HeLa细胞中，细胞能量的消耗会阻断内吞作用，从而阻止HSV的细胞摄取和感染。进入Vero细胞不受能量消耗的影响，正如预期的那样，病毒与Vero细胞表面融合的EM图像很普遍。HSV进入这三种细胞系的动力学是相似的，这表明无论采用何种途径，进入的效率都是一样的。许多病毒的ph依赖性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数量减少了50%。这种失活是快速的（< 1分钟），温度依赖性的，不可逆的。酸预处理对gD（受体结合糖蛋白）的抗原构象没有检测到的影响，对放射性标记病毒粒子与细胞受体的结合没有影响。这表明轻度酸性的pH值使进入的结合后事件失活，如膜融合。我们提出HSV具有通过内吞摄取和低ph触发步骤有效进入细胞的能力。

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.