HSV as A Platform for the Generation of Retargeted, Armed, and Reporter-Expressing Oncolytic Viruses

Abstract

Previously, we engineered oncolytic herpes simplex viruses (o-HSVs) retargeted to the HER2 (epidermal growth factor receptor 2) tumor cell specific receptor by the insertion of a single chain antibody (scFv) to HER2 in gD, gH, or gB. Here, the insertion of scFvs to three additional cancer targets—EGFR (epidermal growth factor receptor), EGFRvIII, and PSMA (prostate specific membrane antigen)—in gD Δ6–38 enabled the generation of specifically retargeted o-HSVs. Viable recombinants resulted from the insertion of an scFv in place of aa 6–38, but not in place of aa 61–218. Hence, only the gD N-terminus accepted all tested scFv inserts. Additionally, the insertion of mIL12 in the US1-US2 intergenic region of the HER2- or EGFRvIII-retargeted o-HSVs, and the further insertion of Gaussia Luciferase, gave rise to viable recombinants capable of secreting the cytokine and the reporter. Lastly, we engineered two known mutations in gB; they increased the ability of an HER2-retargeted recombinant to spread among murine cells. Altogether, current data show that the o-HSV carrying the aa 6–38 deletion in gD serves as a platform for the specific retargeting of o-HSV tropism to a number of human cancer targets, and the retargeted o-HSVs serve as simultaneous vectors for two molecules.

Replicative conditioning of Herpes simplex type 1 virus by Survivin promoter, combined to ERBB2 retargeting, improves tumour cell-restricted oncolysis

“…With the aim to improve our current HSV-1 oncolytic platform, we generated and characterized a virulent oncolytic herpesvirus, SurE_oHSV, bearing two independent features i.e., replication conditioning by Survivin/BIRC5 promoter control of the viral ICP4 gene, and a combination of de-targeting (from common entry receptors) and re-targeting (guided by ERBB2 receptor expression) approach 14 . Retargeting by engineered glycoprotein D has been already demonstrated to ensure de-targeting from natural receptors of HSV-1 and new tropism for selected tumour-associated receptors 15 . Unfortunately, tumour-associated receptors do not clearly differentiate tumour from non-tumour cells, making retargeting approaches potentially not exempt from on-target, off-tumour toxicity, similarly to CAR-T cells [57][58][59][60] .…”

“…Different strategies have been devised in order to maintain selectivity of infection for cancer cells, while keeping an effective replicative and lytic potential of OVs. Among these, engineered oHSV with specific tropism for cancer cells have been generated on virulent, non-attenuated genomes [14][15][16] . Transcriptional retargeting is based on substitution of endogenous promoters, controlling the expression of viral genes, such as ICP4 and ICP27, with cellular promoters which confer tumour-restricted expression and lead to viral selective replication in cancer cells [17][18][19][20][21][22] .…”

“…Several tumours, indeed, express selected cell surface receptors, which can be recognized by engineered viral glycoproteins fused to antibody fragments or receptor ligands. ERBB2 retargeted viruses have been extensively characterized for the specific tropism for ERBB2 positive tumours 14,15 ; fully virulent oHSV with restricted tropism to ERBB2 expressing tumours proved to be efficacious in preclinical models 26 . Very recently, a ERBB2-retargeted oHSV armed with IL-12 proved to be efficacious in subcutaneous and glioblastoma tumour models 27,28 .…”

Oncolytic Virus Encoding a Master Pro-Inflammatory Cytokine Interleukin 12 in Cancer Immunotherapy

“…To address this issue, a recent nextgeneration retargeted IL-12-expressing OHSV known as R-115 has been developed. This OHSV contains no major mutation or deletion and expresses mouse IL-12 under a CMV promoter [38,89]. The OHSV M002 and M032 have deletion of both copies of γ-34.5, with murine and human IL-12 cDNA (p35 and p40 subunits, connected by an IRES), respectively, inserted into each of the γ-34.5 deleted regions [83][84][85][86].…”

“…To address this issue, a recent next-generation retargeted IL-12-expressing OHSV known as R-115 has been developed. This OHSV contains no major mutation or deletion and expresses mouse IL-12 under a CMV promoter [38,89]. IL-12-armed R-115 is a derivative of R-LM113 [90].…”