INHIBITION OF HERPES-SIMPLEX VIRUS-REPLICATION BY A 2-AMINO THIAZOLE VIA INTERACTIONS WITH THE HELICASE COMPONENT OF THE UL5-UL8-UL52 COMPLEX

With the use of a high throughput biochemical DNA helicase assay as a screen, T157602, a 2-amino thiazole compound, was identified as a spec ific inhibitor of herpes simplex virus (HSV) DNA replication. T157602 inhibited reversibly the helicase activity of the HSV UL5-UL8-UL52 (UL 5/8/52) helicase-primase complex with an IC50 (concentration of compou nd that yields 50% inhibition) of 5 mu M. T157602 inhibited specifical ly the UL5/8/52 helicase and not several other helicases. The primase activity of the UL5/8/52 complex was also inhibited by T157602 (IC50 = 20 mu M). T157602 inhibited HSV growth in a one-step viral growth ass ay (IC90 = 3 mu M), and plaque formation was completely prevented at c oncentrations of 25 to 50 mu M T157602. Vero, human foreskin fibroblas t (HFF), and Jurkat cells could be propagated in the presence of T1576 02 at concentrations exceeding 100 mu M with no obvious cytotoxic effe cts, indicating that the window between antiviral activity and cellula r toxicity is at least 33-fold. Seven independently derived T157602-re sistant mutant viruses (four HSV type 2 and three HSV type 1) carried single base pair mutations in the UL5 that resulted in single amino ac id changes in the UL5 protein. Marker rescue experiments demonstrated that the UL5 gene from T157602-resistant viruses conferred resistance to T157602-sensitive wild-type viruses. Recombinant UL5/8/52 helicase- primase complex purified from baculoviruses expressing mutant UL5 prot ein showed complete resistance to T157602 in the in vitro helicase ass ay. T157602 and its analogs represent a novel class of specific and re versible anti-HSV agents eliciting their inhibitory effects on HSV rep lication by interacting with the UL5 helicase.