Simpson, Guy Richard; (2004) Optimising therapeutic herpes simplex virus vectors for cancer therapy. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The aim of this thesis was to optimise therapeutic herpes simplex vectors for cancer therapy. In part I, a range of cell lines were developed for the complementation of non-replicating HSV-1 vectors, which have subsequently been used for development of a dendritic cell (DC) mediated vaccine against melanoma. In part II the effects of human sera on HSV-1 vectors, produced from various cell lines, were investigated to determine susceptibility of these vectors to inactivation by natural antibodies and complement. This demonstrated that HSV-1 vectors grown on cells encoding α-l-3-galactosyltransferase are sensitive to Galα1-3Gal antibodies and complement in HSV-1 naive human serum. In conclusion, HSV-1 vectors for human gene and oncolytic therapies should be produced from Galα1-3Gal negative cells. In part III new oncolytic HSV vectors were optimised for maximum local tumour control by the insertion of a pro-drug activating gene and/or a fusogenic retroviral glycoprotein. Our laboratory has developed an oncolytic HSV vector based on a clinical isolate (JS-1), with two deletions that provide enhanced tumour selective replication (ICP34.5- and ICP47-) and an increased level of antigen presentation in infected tumour cells (ICP47-). The prodrug activating gene cytosine deaminase fused to uracil phospo-ribosyltransferase, and/or the truncated glycoprotein from gibbon ape leukaemia virus (GALV env R-) were inserted into this backbone. In vitro testing showed enhanced tumour killing by each of these vectors compared to the backbone vector. However, the vectors containing the prodrug activating gene showed toxicological problems in a nude mice model, when administered with the prodrug, possibly due to very efficient prodrug activation leading to toxic systemic levels of active drug. The viral vector containing the truncated glycoprotein GALV env R- greatly improved the in vivo dose response of killing compared to backbone vector, with no evidence of cytotoxicity in mice.

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