Metabolism and activities of 3′-azido-2′,3′-dideoxythymidine and 2′,3′-didehydro-2′,3′-dideoxythymidine in herpesvirus thymidine kinase transduced T-lymphocytes

T-lymphocytes transduced with the conditionally toxic herpesvirus thymidine kinase gene (HSV-1 TK) are increasingly becoming important tools in genetic therapy approaches for treating viral infections and cancers. Therefore, the effects of different antiviral nucleoside drugs on the growth inhibition of parental and HSV-1 TK-transduced human T-lymphocyte cell lines (H9 and CEM TK −) were examined. As expected, both transduced cell lines were most sensitive to growth inhibition by ganciclovir (GCV). While the presence of HSV-1 TK did not potentiate 3′-azido-2′,3′-dideoxythymidine (AZT) growth inhibition of H9 cells containing cellular TK; transduction of HSV-1 TK into the cellular TK-deficient CEM cells (CEM TK −) restored sensitivity to AZT. In both transduced cell lines, an HSV-1 TK-dependent growth inhibition with 2′,3′-didehydro-2′,3′-dideoxythymidine (d4T) was observed and a K m of 143 μM for d4T and HSV-1 TK was determined. Metabolic labeling analysis showed that drug metabolism correlated with the observed effects on cell growth. The effects of HIV-1 replication in the CEM TK − cell lines in the presence of AZT or d4T was evaluated. CEM TK − cells are largely resistant to AZT or d4T inhibition of HIV-1 replication, however, transduction of HSV-1 TK into the CEM TK − cells completely restored AZT and d4T inhibition of HIV-1 replication. These studies confirm the requirement for a thymidine kinase activity for the anti-HIV activities of d4T and suggest that AZT, but not d4T, could be potentially administered to patients receiving HSV-1 TK-transduced lymphocytes.