Enhanced oncolytic activity of vesicular stomatitis virus encoding SV5-F protein against prostate cancer

Purpose: Vesicular stomatitis virus has been investigated as an oncolytic agent for cancer therapy because it preferentially replicates in tumor but not in normal cells due to the lack of a robust interferon antiviral system in transformed cells. However, wild-type vesicular stomatitis virus can induce a strong systemic immunological response and replicate in the central nervous system, potentially limiting its clinical usefulness. We report the construction of the recombinant, replication restricted vesicular stomatitis virus encoding SV5-F, which can induce syncytial formation with enhanced oncolytic properties against TRAMP-C2 tumors in an immunocompetent mouse model of prostate cancer.

Materials and methods: We constructed the SV5-F recombinant restricted virus vector by replacing the vesicular stomatitis virus G gene with that of the SV5-F transgene to generate rVSV-DeltaG-SV5-F. Morphological changes and DNA fragmentation induced by rVSV-DeltaG-GFP or rVSV-DeltaG-SV5-F were determined by phase contrast microscopy and gel electrophoresis. In vitro cytotoxicity by recombinant vesicular stomatitis virus was done by MTT assay. In vivo study of rVSV treatment was done in immunocompetent mice by subcutaneous administration of TRAMP-C2 cells.

Results: In vitro characterization of the recombinant fusogenic VSV-DeltaG vector on TRAMP-C2 cells showed significantly enhanced apoptotic and cytotoxic effects relative to a similar virus encoding green fluorescent protein, that is rVSV-DeltaG-GFP. Regardless of initial tumor size intratumor rVSV-DeltaG-SV5-F administration in mice bearing subcutaneous TRAMP-C2 tumors resulted in a significantly reduced tumor load over that of the nonfusogenic green fluorescent control virus and of heat inactivated recombinant vesicular stomatitis virus in treated animals (p <0.01).

Conclusions: Results show that G complemented recombinant VSV-DeltaG vectors, especially rVSV-DeltaG-SV5-F, are an effective oncolytic agent against mouse prostate cancer cells in vitro and in an in vivo immunocompetent mouse model system.