MECHANISM OF ANTIVIRAL ACTION OF (E)-5-(2-BROMOVINYL)-2'-DEOXYURIDINE(BVDU) - DIRECT EVIDENCE WITH [C-14] BVDU IN HERPES-SIMPLEX VIRUS-INFECTED CELLS

The mechanism of action of (E)-5-(2-bromovinyl)-2'deoxyuridine (BVDU) was investigated using a C-14-radiolabelled derivative. A remarkable a ccumulation of [C-14]BVDU was detected in herpes simplex virus type 1 (HSV-l)-infected cells, in greater quantities (18-fold) than in uninfe cted cells. Furthermore, selective incorporation of [C-14]BVDU was mea sured exclusively into HSV-1 DNA. Further studies on the cellular kine tic and metabolic fate of BVDU indicated that in HSV-l-infected cells it was phosphorylated intracellularly to its mono(BVDU-MP) and triphos phate (BVDU-TP) derivatives. The amount of BVDU-MP was 10 times higher than BVDU-TP. BVDU entered infected cells very quickly and was rapidl y converted into BVDU-MP which, in turn, was further metabolized to BV DU-TP. After 5 h incubation, 13% of initial radioactivity was found in the SDS phase, representing mainly DNA and proteins, of HSV-1-infecte d cells and only 2% in uninfected cells, further confirming the select ive incorporation of the compound into viral DNA. Following removal of BVDU from culture medium, the cellular decay of BVDU-phosphorylated d erivatives was rather slow, with an estimated half-life of 10 h, and t heir disappearance from the cytosol was paralleled by a progressive ac cumulation of radioactivity in the SDS phase. These results give direc t evidence for the selective cellular uptake, metabolism and viral DNA accumulation of BVDU in HSV-1-infected cells, representing the major Factors for its powerful and specific anti-herpesvirus activity.