Inhibition of Moloney leukaemia virus production by N-methylisatin-beta-4':4-diethylthiosemicarbazone.
N-methylisatin-beta-4':4'-diethylthiosemicarbazone (M-IBDET) inhibited the production of Moloney leukaemia virus (MLV). Virus inhibition was related to drug concentrations and time of treatment. The effective antiviral drug concentrations ranged between 3.4 muM and 34 muM. Virus reverse transcriptase activity even at concentrations of 34 muM-M-IBDET was not inhibited. At virus inhibitory concentrations the drug reduced RNA synthesis only very slightly and did not affect protein synthesis at all, although growth and DNA synthesis of host cells were suppressed. The inhibition of cellular DNA synthesis was reversible. Comparison of M-IBDET with actinomycin D, cycloheximide and alpha-amanitin in terms of their inhibitory effect on the release of MLV into the culture medium showed that M-IBDET was comparable to the other antimetabolites. The inhibition of MLV production by M-IBDET was confirmed by various parameters of virus assay. It was concluded from the experimental evidence that M-IBDET specifically inhibits MLV-production.