Central nervous system toxicity of two adenoviral vectors encoding variants of the herpes simplex virus type 1 thymidine kinase : reduced cytotoxicity of a truncated HSV1-TK

• Published in: Gene therapy Vol. 7; no. 8; pp. 679 - 685
• Main Authors: COWSILL, C, SOUTHGATE, T. D, CASTRO, M. G, MORRISSEY, G, DEWEY, R. A, MORELLI, A. E, MALENIAK, T. C, FORREST, Z, KLATZMANN, D, WILKINSON, G. W. G, LÖWENSTEIN, P. R
• Format: Journal Article
• Language: English
• Published: Basingstoke Nature Publishing Group 01-04-2000
• Subjects: Adenoviridae - drug effects; Adenovirus; Animals; Antiviral Agents - therapeutic use; Biological and medical sciences; Biotechnology; Brain cancer; Brain Neoplasms - therapy; Brain tumors; Cells, Cultured; Central nervous system; Central Nervous System - virology; Cytotoxicity; Edema; Expression vectors; Fundamental and applied biological sciences. Psychology; Ganciclovir; Ganciclovir - therapeutic use; Gene therapy; Genetic Therapy - adverse effects; Genetic Vectors - adverse effects; Glial cells; Glioma; Glioma - therapy; Health. Pharmaceutical industry; Herpes simplex; herpes simplex virus 1; Herpes viruses; Herpesvirus 1, Human - enzymology; Humans; Industrial applications and implications. Economical aspects; N-Terminus; Neostriatum; Neurodegeneration; Neuroglia; Neuronal-glial interactions; Neurons; Rats; Thymidine; Thymidine kinase; Thymidine Kinase - genetics; Antineoplastic agent; Thymidine kinase; Adenoviridae; Enzyme; Herpesviridae; Transferases; Alphaherpesvirinae; Central nervous system; Cytotoxicity; Suicide gene; Virus; Chemotherapy; Ganciclovir; Tumor; Herpesvirus hominis; Mutation; Gene therapy; Vector
• ISSN: 0969-7128; 1476-5462
• DOI: 10.1038/sj.gt.3301147

Herpes simplex virus type 1-thymidine kinase (HSV1-TK) in combination with ganciclovir is an efficient and widely used strategy in brain tumour gene therapy. Recently, we have shown effective inhibition of glioma growth in a syngeneic rat model using recombinant adenoviruses expressing the full-length HSV1-TK and an N-terminus truncated variant, HSV1-DeltaTK in the presence of ganciclovir. We also showed active chronic brain inflammation in the long-term survivors (3 months) treated with HSV1-TK plus GCV. Furthermore, our results indicated loss of myelinated fibres, oedema and indices of ongoing axonal degeneration. In this study, we assessed the cytotoxicity of both HSV1-TK variants in the presence or absence of ganciclovir, in primary cultures of neurones and glia, and in the rat brain in vivo. Our results indicate that, at viral doses where tumour cells are sensitive to the enzyme/prodrug system, (1) there is no major cytotoxicity for either neurones or glial cells grown in primary cultures, (2) on its own the full-length HSV1-TK is more cytotoxic than its truncated version HSV1-DeltaTK for a population of non-neuronal and non-glial cells within neocortical primary cultures, and (3) in vivo, when delivered into the striatum, RAds encoding HSV1-TK are more cytotoxic than RAds encoding HSV1-DeltaTK, after administration of ganciclovir. The effectiveness of HSV1-DeltaTK in preventing brain tumour growth in vivo, combined with its reduced cytotoxicity, both in vivo and in primary cultures of CNS cells, could represent an advantage for treatment of brain tumours using gene therapy.