Antiviral activity of various 1-beta-D-arabinofuranosyl-E-5-halogenovinyluracils and E-5-bromovinyl-2'-deoxyuridine against salmon herpes virus, Oncorhynchus masou virus (OMV).

1-beta-D-Arabinofuranosyl-E-5-bromovinyluracil (BVaraU), 1-beta-D-arabinofuranosyl-E-5-iodovinyluracil (IVaraU), 1-beta-D-arabinofuranosyl-E-5-chlorovinyluracil (CVaraU) and 1-beta-D-arabinofuranosyl-5-vinyluracil (VaraU) were examined for antiviral activity against salmon herpesvirus, Oncorhynchus masou virus (OMV) in vitro using Yamame (Oncorhynchus masou) kidney cells (YNK). BVaraU, IVaraU, CVaraU and VaraU were highly active against OMV; 50% inhibitory concentration (IC50): 0.01, 0.003, 0.003, 0.003 microgram/ml, respectively. The IC50 of 5-bromovinyl-2'-deoxyuridine (BVDU) was 0.3 microgram/ml. The lower activity may be due to cleavage of it N-glycosyl linkage by pyrimidine nucleoside phosphorylases (i.e. thymidine phosphorylase) during the incubation period. The arabinofuranosyl counterparts are resistant to this (these) enzyme(s). Both OMV-induced DNA polymerase and cellular DNA polymerase alpha were strongly inhibited by BVaraU 5'-triphosphate (BVaraUTP). In an in vivo study, daily immersion of OMV-infected chum salmon (Oncorhynchus keta) fry into aqueous solution of BVaraU (5 micrograms/ml, 30 min/day, 30 times) did not increase the life span of infected fish.