Abstract
The addition of either isatin--thiosemicarbazone (IBT) or its N-methyl derivative effectively inhibited the multiplication of various isolates of infectious bovine rhinotracheitis virus. Treatment of infected cultures with IBT early or late in the log, phase of replication markedly suppressed the production of infectious virus, indicating that the drug inhibits virus maturation. The time course of formation of infectious virus and of synthesis of viral DNA and viral protein was determined with the inhibitors FUdR and cycloheximide, respectively. In radioisotope experiments, IBT inhibited the incorporation of label into both RNA and DNA at a fairly early stage of the virus growth cycle.