Herpesvirus Interactions With Cell Surface Receptors

单纯疱疹病毒（HSV）进入细胞需要病毒糖蛋白gD与其受体之一结合，然后导致病毒与细胞融合。众所周知，用pH值为3的缓冲液处理与病毒结合的细胞可以阻断HSV的渗透。为了进一步了解HSV进入的分子机制，使用β -半乳糖苷酶报告试验检测了酸失活的影响。用轻度酸性pH预处理的HSV-1 （KOS）无细胞病毒粒子不能进入Vero细胞。因此，低pH值直接影响病毒粒子本身。具体来说，当pH < 6.5时，病毒粒子的进入活性被抑制。失活是快速的、不可逆的和温度依赖性的。酸处理的病毒粒子也不能进入表达gd结合受体疱疹病毒进入介质A （HveA）、nectin-1或nectin-2的CHO细胞。我们证明了这些受体介导病毒与细胞在4？通过添加可溶性gD或可溶性受体来阻断这种结合。这些发现表明，受体对于病毒进入至关重要，部分原因是它们在病毒与细胞融合之前加强HSV与细胞的粘附作用。低pH处理不影响HSV与HveA、nectin-1或nectin-2的稳定结合，也不改变gD的受体结合构象。综上所述，这些数据表明，低pH值干扰了HSV进入过程中的一个步骤，而不是gd受体相互作用。我们提出，低pH预处理使HSV无法与细胞膜融合，是一种解开受体结合和融合进入过程的有用工具。

Entry of herpes simplex virus (HSV) into cells requires binding of viral glycoprotein gD to one of its receptors which then leads to virus-cell fusion. It is known that HSV penetration is blocked by treating cells bound with virus with a buffer at pH 3. To gain further insights into the molecular mechanism of HSV entry, the effects of acid inactivation were examined using a beta-galactosidase reporter assay. Cell-free virions of HSV-1 (KOS) that were pretreated with mildly acidic pH were incompetent for entry into Vero cells. Thus, low pH directly affects the virions themselves. Specifically, entry activity was inhibited when virions was treated with pH < 6.5. Inactivation was rapid, irreversible and temperature-dependent. Acid-treated virions also failed to enter CHO cells expressing the gD-binding receptors herpesvirus entry mediator A (HveA), nectin-1 or nectin-2. We demonstrated that these receptors mediate stable, heparin-resistant binding of virus to cells at 4?C, and that binding was blocked by addition of soluble gD or soluble receptors. These findings suggest that receptors are essential for entry partly due to their role in strengthening HSV adhesion to cells prior to virus-cell fusion. Low pH treatment did not affect stable binding of HSV to HveA, nectin-1 or nectin-2, nor did it alter the receptor-binding conformation of gD. Taken together, the data indicate low pH perturbs a step in the HSV entry process other than the gD-receptor interaction. We propose that low pH pretreatment incapacitates HSV for fusion with cell membranes and is a useful tool to uncouple the entry processes of receptor binding and fusion.