Characterization and transduction of a retroviral vector encoding human interleukin-4 and herpes simplex virus-thymidine kinase for glioma tumor vaccine therapy

Vaccination with cytokine-transduced tumor cells represents a potentially i mportant approach to the treatment of central nervous system tumors. We hav e recently demonstrated the therapeutic efficacy of tumor cell vaccines exp ressing the murine interleukin 4 (IL-4) and the herpes simplex virus-thymid ine kinase in a rat brain tumor model in which nonirradiated vaccine cells can be eliminated by the subsequent administration of ganciclovir. In this report, we demonstrate the construction and characterization of a retrovira l vector that encodes human IL-4, neomycin phosphotransferase, and herpes s implex virus-thymidine kinase genes for use in human clinical trials. An MF G-based retroviral vector was used to generate the recombinant retrovirus, TFG-hIL4-Neo-Tk, in which a long terminal repeat-driven polycistronic trans cript encodes three cDNAs that are linked and coexpressed using two interve ning internal ribosome entry site fragments from the encephalomyocarditis v irus. The amphotropic retroviral vector TFG-hIL4-Neo-Tk was then used to in fect human primary glioma cultures and skin-derived fibroblasts. After infe ction and G418 selection, cells produced 89-131 ng/10(6) cells/48 hours of human IL-4, which was determined to be biologically active. Transduced glio ma cells were highly sensitive to the cytotoxic effect of ganciclovir. Thes e data demonstrate the suitability of the TFG-hIL4-Neo-Tk vector for therap eutic studies of cytokine-transduced autologous tumor vaccination in patien ts with malignant gliomas.