USE OF EPSTEIN-BARR-VIRUS NUCLEAR ANTIGEN-1 IN TARGETED THERAPY OF EBV-ASSOCIATED NEOPLASIA

To target expression of toxic genes to Epstein-Barr virus (EBV)-associ ated tumor cells, we have developed an EBV-driven enzyme prodrug syste m (EDEPS) that takes advantage of the trans-activating properties of E BNA1, a latent protein expressed in all EBV-containing cells, to direc t expression of cytosine deaminase (CD) at high levels in those cells only, Plasmids were constructed in which the CD gene or a luciferase r eporter gene were cloned downstream of the herpes simplex virus thymid ine kinase (tk) promoter and the family of repeats (FR) sequence from the oriP region of EBV, Analysis of luciferase activity after transien t transfection into a panel of EBV-negative or -positive human cell li nes showed that the presence of the FR element enhanced transcription from the tk promoter in all EBV-positive cell lines, whereas transcrip tion from tk was repressed in all EBV-negative cell lines, including B , T, and fibroblast cell lines, In clonogenicity assays following tran sfection with the CD vector, the presence of 5-fluorocytosine (5-FC) i n the culture medium completely abolished cell growth in EBV-positive cell lines, but did not affect the growth of EBV-negative cell lines, This vector system should have wide applicability in that it allows ta rgeted expression of any gene of interest to tumors that carry EBV, ir respective of the role EBV plays in their pathogenesis.