Gene therapy against cancer and HIV infection using the gene encoding herpes simplex virus thymidine kinase

The expression of the gene encoding herpes simplex virus thymidine kinase (HSV-TK) in eukaryotic cells confers sensitivity to antiherpetic drugs such as acyclovir and ganciclovir. This property has been proposed for use in gene therapy approaches to kill either cancer cells or HIV-infected cells. Several animal experiments have shown the regression of tumors after in vivo transfer of the HSV-TK gene followed by ganciclovir treatment. Furthermore, CD4(+) T cells harboring the HSV-TK gene under the control of HIV regulatory sequences are protected from HIV spreading in the presence of acyclovir. Thus, the HSV-TK gene has potential applications in gene therapy for the treatment of cancer and HIV infection.