Nuove strategie di reindirizzamento nel disegno di virus Herpes Simplex oncolitici

Oncolytic virotherapy exploits the ability of viruses to infect and kill cells and is envisioned as treatment for tumors that respond poorly to the current therapeutic approaches. The attenuated herpes simplex virus 1 (HSV-1), named T-Vec, is the only oncolytic virus approved so far for clinical practice. Safety was obtained at the expense of virulence. To overcome the attenuation limits, an alternative strategy consists in altering the host range of a virus. The binding of membrane-bound glycoprotein D (gD) of HSV-1 to one of its receptors activates the downstream glycoproteins gH/gL and gB. The latter executes the fusion virion-cell. So far, gD was the only glycoprotein that successfully enabled the retargeting of HSV-1. The work of this thesis focuses on the the development of oncolytic herpes simplex viruses (o-HSVs), retargeted to tumor-specific receptors, in order to bring retargeted o-HSVs to the translational phase. The tropism of HSV-1 has been modified by engineering a heterologous ligand in gH (in virus R-809) or in gB (in R-909). The selected heterologous ligand was a single chain variable fragment antibody (scFv) directed against HER2, a receptor overexpressed in several cancers. The retargeting achieved via gB or gH confers to HSV-1 very similar properties to the retargeting achieved via gD, in terms of virus growth and oncolytic activity in vitro. The changes in gB or gH were combined with those in gD, leading, for the first time, to two HSV-1 simultaneously redirected to two distinct receptors. R-805, directed simultaneously to HER2 and EGFR, has been characterized in vitro. An in vivo model to study its oncolytic efficacy was developed. R-313 was designed to enable the production of an oncolytic vector into a non-tumor cell line. R-313 is capable to use alternately two receptors, and to infect the tumor cells and the non-tumor-producing cells.