Isolation and characterization of a γ thiochromanone 4 thiosemicarbazone resistant mutant of vaccinia virus

γ Thiochromanone 4 thiosemicarbazone (TCT) inhibits the growth of vaccinia virus in BSCl cells by interfering with viral maturation. A mutant of the virus (TCT(R)) which is resistant to this drug was isolated. This mutant also exhibits resistance to another thiosemicarbazone related compound, isatin β thiosemicarbazone (IBT). There is a good correlation between the cross resistance of the two mutants IBT(R) and TCT(R) to TCT and IBT, respectively and the similar antipoxvirus activity of these two thiosemicarbazone related compounds.