Genetically Engineered Vesicular Stomatitis Virus in Gene Therapy: Application for Treatment of Malignant Disease

Abstract

We report here the generation of recombinant vesicular stomatitis virus (VSV) able to produce the suicide gene product thymidine kinase (TK) or cytokine interleukin 4 (IL-4). In vitro cells infected with the engineered viruses expressed remarkably high levels of biologically active TK or IL-4 and showed no defects in replication compared to the wild-type virus. Recombinant viruses retained their ability to induce potent apoptosis in a variety of cancer cells, while normal cells were evidently more resistant to infection and were completely protected by interferon. Significantly, following direct intratumoral inoculation, VSV expressing either TK or IL-4 exhibited considerably more oncolytic activity against syngeneic breast or melanoma tumors in murine models than did the wild-type virus or control recombinant viruses expressing green fluorescent protein (GFP). Complete regression of a number of tumors was achieved, and increased granulocyte-infiltrating activity with concomitant, antitumor cytotoxic T-cell responses was observed. Aside from discovering greater oncolytic activity following direct intratumoral inoculation, however, we also established that VSV expressing IL-4 or TK, but not GFP, was able to exert enhanced antitumor activity against metastatic disease. Following intravenous administration of the recombinant viruses, immunocompetent BALB/c mice inoculated with mammary adenocarcinoma exhibited prolonged survival against lethal lung metastasis. Our data demonstrate the validity of developing novel types of engineered VSV for recombinant protein production and as a gene therapy vector for the treatment of malignant and other disease.

Systemic therapy of experimental breast cancer metastases by mutant vesicular stomatitis virus in immune-competent mice

“…24,25 Recombinant VSVs expressing the herpes simplex virus thymidine kinase or the cytosine deaminase suicide genes have been reported by Barber's group. 32,33 Their results suggest that the use of the prodrug-suicide gene strategy may add synergy to the effectiveness of oncolytic VSV in cancer treatment. An alternative strategy of cytotoxic gene therapy was recently introduced by Bateman et al, 34 demonstrating that plasmid-mediated expression of viral fusogenic membrane glycoprotein efficiently killed tumor cells through induction of fusion to form large multinucleated syncytia.…”

VSV-tumor selective replication and protein translation

“…The mechanism of VSV oncolysis also involves the induction of apoptosis by as yet undetermined mechanisms, though predominantly utilizes the caspase-9 pathway (Balachandran et al, 2000b). Studies by a number of groups have now shown robust proapoptotic oncolytic ability against tumors in athymic nude mice as well as in syngeneic tumors in immunocompetent animals (Balachandran and Barber, 2000;Balachandran et al, 2001;Fernandez et al, 2002;Obuchi et al, 2003;Stojdl et al, 2003;Ebert et al, 2004). VSV has also been shown capable of exerting its antitumor effects against metastatic breast adenocarcinoma when inoculated at sites distant from the tumor and when introduced intravenously (Balachandran and Barber, 2000;Balachandran et al, 2001).…”

“…For instance, VSV harboring a mutant M is defective in the ability to suppress host antiviral responses including the IFN response, compared to wild-type viruses (Stojdl et al, 2003). A major advantage of using VSV as an oncolytic agent includes that this virus is genetically malleable and large gene inserts/ genes can be placed inside the genome for heterologous expression (Schnell et al, 1996;Fernandez et al, 2002;Porosnicu et al, 2003). The ability to modify VSV through genetic engineering, obviously affords the prospect of creating new generations of custom-made VSV vectors that contain immunomodulatory and/or suicide cassettes designed to increase their antitumor activity.…”

Enhancing VSV oncolytic activity with an improved cytosine deaminase suicide gene strategy

“…Recombinant VSV carrying the Herpes virus TK enzyme has been shown to phosphorylate the non-toxic prodrug ganciclovir, facilitating its DNA integration and subsequent local toxicity. 13,15 A similar strategy was employed with VSV expressing the human sodium iodine symporter that resulted in the accumulation of radioactive iodine at the tumor site. 16 Both of these recombinant VSV strategies were shown to delay tumor growth in murine models; however, their action is restricted to cells that are directly infected by VSV.…”