title: A Strategy for Cultivation of Retargeted Oncolytic Herpes Simplex Viruses in Non-cancer Cells.
abstract: The oncolytic herpes simplex virus (HSV) that has been approved for clinical practice and those HSVs in clinical trials are attenuated viruses, often with the neurovirulence gene γ134.5 and additional genes deleted. One strategy to engineer nonattenuated oncolytic HSVs consists of retargeting the viral tropism to a cancer-specific receptor of choice, exemplified by HER2 (human epidermal growth factor receptor 2), which is present in breast, ovary, and other cancers, and in detargeting from the natural receptors. Because the HER2-retargeted HSVs strictly depend on this receptor for infection, the viruses employed in preclinical studies were cultivated in HER2-positive cancer cells. The production of clinical-grade viruses destined for humans should avoid the use of cancer cells. Here, we engineered the R-213 recombinant, by insertion of a 20-amino-acid (aa) short peptide (named GCN4) in the gH of R-LM113; this recombinant was retargeted to HER2 through insertion in gD of a single-chain antibody (scFv) to HER2. Next, we generated a Vero cell line expressing an artificial receptor (GCN4R) whose N terminus consists of an scFv to GCN4 and therefore is capable of interacting with GCN4 present in gH of R-213. R-213 replicated as well as R-LM113 in SK-OV-3 cells, implying that addition of the GCN4 peptide was not detrimental to gH. R-213 grew to relatively high titers in Vero-GCN4R cells, efficiently spread from cell to cell, and killed both Vero-GCN4R and SK-OV-3 cells, as expected for an oncolytic virus. Altogether, Vero-GCN4R cells represent an efficient system for cultivation of retargeted oncolytic HSVs in non-cancer cells.IMPORTANCEThere is growing interest in viruses as oncolytic agents, which can be administered in combination with immunotherapeutic compounds, including immune checkpoint inhibitors. The oncolytic HSV approved for clinical practice and those in clinical trials are attenuated viruses. An alternative to attenuation is a cancer specificity achieved by tropism retargeting to selected cancer receptors. However, the retargeted oncolytic HSVs strictly depend on cancer receptors for infection. Here, we devised a strategy forin vitrocultivation of retargeted HSVs in non-cancer cells. The strategy envisions a double-retargeting approach: one retargeting is via gD to the cancer receptor, and the second retargeting is via gH to an artificial receptor expressed in Vero cells. The double-retargeted HSV uses alternatively the two receptors to infect cancer cells or producer cells. A universal non-cancer cell line for growth of clinical-grade retargeted HSVs represents a step forward in the translational phase.
authors.affiliation: Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Bologna, Italy.
authors.forename: Valerio
authors.initials: V
authors.lastname: Leoni
authors.affiliation: Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Bologna, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Gatta
authors.affiliation: Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Bologna, Italy.
authors.forename: Costanza
authors.initials: C
authors.lastname: Casiraghi
authors.affiliation: Nouscom SRL, Rome, Italy.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Nicosia
authors.affiliation: Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Bologna, Italy.
authors.forename: Biljana
authors.initials: B
authors.lastname: Petrovic
authors.affiliation: Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Bologna, Italy gabriella.campadelli@unibo.it.
authors.forename: Gabriella
authors.initials: G
authors.lastname: Campadelli-Fiume
mesh_terms: D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D005818:Genetic Engineering / Q000379:methods; D018259:Herpesvirus 1, Human / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D006801:Humans; D050130:Oncolytic Virotherapy; D050504:Oncolytic Viruses / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000737:chemistry / Q000235:genetics*; D018139:Simplexvirus / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D014709:Vero Cells; D056189:Viral Tropism; D014776:Virus Cultivation / Q000379:methods*
chemical_list: D018719:Erb-b2 Receptor Tyrosine Kinases; C508053:ERBB2 protein, human
keywords: HER2; HSV; Vero; oncolytic viruses; retargeting