HERPESVIRUS INTERACTIONS WITH CELL SURFACE RECEPTORS

病毒感染易感细胞需要与细胞受体相互作用。许多病毒在进入细胞之前经历与细胞的双相结合。 通常，当病毒以4度加入细胞时，可以检测到初始的低亲和力相互作用。 随后移动到37度通常伴随着结合力的加强。疱疹病毒似乎与其他病毒家族不同，因为与细胞的初始附着和稳定粘附都可以在4度下发生，并且不需要生理温度。由于迄今为止测试的所有包膜病毒的膜融合都需要37度，因此HSV提供了一种新颖的温度依赖性系统，用于解剖触发病毒-细胞融合过程的事件。目前的单纯疱疹病毒（HSV）进入模型归因于与细胞表面糖胺聚糖（GAG）的初级低亲和力附着。尚未确定哪种细胞分子介导随后HSV与细胞的稳定结合。确定对稳定结合重要的细胞因子将有助于理解导致HSV穿透宿主细胞的分子事件。稳定结合在实验上定义为结合病毒抵抗通过选择性、严格洗涤（例如高盐、PBS-肝素）去除的能力。最近，几种分子被鉴定为允许HSV进入非允许细胞并结合HSV感染所需的病毒糖蛋白D（gD）。这些疱疹病毒进入介体（Hve）被命名为HveA（或HVEM）、HveB和HveC（或nectin 1）。为了确定这些分子是否具有稳定病毒与细胞结合的功能，评估了肝素洗涤对纯化的、放射性标记的病毒粒子与细胞结合的影响。HSV与表达HveA或HveC的细胞的结合具有肝素抗性（稳定）。病毒不能稳定地与表达HveB的细胞结合，这与HveB不能介导野生型HSV-1进入一致。稳定的结合被可溶性辅助受体和可溶性重组gD阻断，表明HSV的肝素抗性附着是由gD结合辅助受体如HveA和HveC特异性介导的。结果表明，在病毒进入期间，HSV与细胞的GAG依赖性结合通过随后与gD结合辅助受体的相互作用而稳定。

Virus infection of susceptible cells requires interaction with cellular receptors. Many viruses undergo a biphasic binding to cells prior to entry. Typically an initial low affinity interaction can be detected when virus is added to cells at 4 degrees. A subsequent shift to 37 degrees is often accompanied by a strengthening of binding. Herpesviruses appear to be distinct from other virus families in that both initial attachment and stable adhesion to cells can occur at 4 degrees and does not require physiological temperature. Since membrane fusion requires 37 degrees in all enveloped viruses tested to date, HSV provides a novel, temperature-dependent system for dissecting the events that trigger the poorly understood process of virus-cell fusion. Current models of herpes simplex virus (HSV) entry attribute primary, low affinity attachment to cell surface glycosaminoglycans (GAGs). It has not been established which cellular molecule(s) mediates subsequent stable binding of HSV to cells. Determination of the cellular factors important for stable binding will facilitate understanding of molecular events leading up to HSV penetration of the host cell. Stable binding is defined experimentally as the ability of bound virus to resist removal by a selective, stringent wash (e.g. high salt, PBS-heparin). Recently, several molecules were identified which allow entry of HSV into nonpermissive cells and bind to viral glycoprotein D (gD) which is required for HSV infection. These herpesvirus entry mediatiors (Hve) are designated HveA (or HVEM), HveB, and HveC (or nectin1).To determine whether these molecules function to stabilize virus binding to cells, the effect of a heparin wash on purified, radiolabelled virions bound to cells was assessed. Binding of HSV to cells that expressed HveA or HveC was heparin-resistant (stable). Virus did not stably bind to HveB-expressing cells, which is consistent with the inability of HveB to mediate wild type HSV-1 entry. Stable binding was blocked by soluble coreceptors and by soluble recombinant gD, indicating that heparin-resistant attachment of HSV is specifically mediated by gD-binding coreceptors such as HveA and HveC . The results suggest that during virus entry, GAG-dependent binding of HSV to cells is stabilized by subsequent interaction with gD-binding coreceptors.