Gatta Valentina, Petrovic Biljana, Campadelli-Fiume Gabriella
Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Bologna, Italy.
PLoS Pathog. 2015 May 21;11(5):e1004907. doi: 10.1371/journal.ppat.1004907. eCollection 2015 May.
Herpes simplex virus (HSV) enters cells by means of four essential glycoproteins - gD, gH/gL, gB, activated in a cascade fashion by gD binding to one of its receptors, nectin1 and HVEM. We report that the engineering in gH of a heterologous ligand - a single-chain antibody (scFv) to the cancer-specific HER2 receptor - expands the HSV tropism to cells which express HER2 as the sole receptor. The significance of this finding is twofold. It impacts on our understanding of HSV entry mechanism and the design of retargeted oncolytic-HSVs. Specifically, entry of the recombinant viruses carrying the scFv-HER2-gH chimera into HER2+ cells occurred in the absence of gD receptors, or upon deletion of key residues in gD that constitute the nectin1/HVEM binding sites. In essence, the scFv in gH substituted for gD-mediated activation and rendered a functional gD non-essential for entry via HER2. The activation of the gH moiety in the chimera was carried out by the scFv in cis, not in trans as it occurs with wt-gD. With respect to the design of oncolytic-HSVs, previous retargeting strategies were based exclusively on insertion in gD of ligands to cancer-specific receptors. The current findings show that (i) gH accepts a heterologous ligand. The viruses retargeted via gH (ii) do not require the gD-dependent activation, and (iii) replicate and kill cells at high efficiency. Thus, gH represents an additional tool for the design of fully-virulent oncolytic-HSVs retargeted to cancer receptors and detargeted from gD receptors.
单纯疱疹病毒（HSV）通过四种必需糖蛋白——gD、gH/gL、gB进入细胞，这些糖蛋白通过gD与其中一种受体nectin1和疱疹病毒侵入介质（HVEM）结合以级联方式被激活。我们报告称，在gH中构建一种异源配体——一种针对癌症特异性HER2受体的单链抗体（scFv），可将HSV嗜性扩展至以HER2作为唯一受体的细胞。这一发现具有双重意义。它影响我们对HSV进入机制的理解以及靶向性溶瘤HSV的设计。具体而言，携带scFv-HER2-gH嵌合体的重组病毒在不存在gD受体的情况下，或在删除构成nectin1/HVEM结合位点的gD关键残基后，仍能进入HER2阳性细胞。实质上，gH中的scFv替代了gD介导的激活作用，使得功能性gD对于通过HER2进入细胞而言不再必要。嵌合体中gH部分的激活是由顺式排列的scFv完成的，而不像野生型gD那样通过反式排列激活。关于溶瘤HSV的设计，以往的靶向策略完全基于在gD中插入癌症特异性受体的配体。当前的研究结果表明：（i）gH能够接受异源配体。通过gH进行靶向的病毒（ii）不需要gD依赖性激活，并且（iii）能够高效复制并杀死细胞。因此，gH是设计靶向癌症受体且不靶向gD受体的完全毒性溶瘤HSV的一种额外工具。
