[Fluorescent antibody method in the study of an antiviral agent: 5-sulfamido--isatin-thiosemicarbazone].

Direct immunofluorescence supplied evidence of the antiviral action of a new synthetic derivative (5-sulfamido-ITSC) against vaccina virus in HeLa cell cultures. The antiviral potential of the new derivative is expressed by a 10-18 delay in the appearance of the viral antigen and by the quantitative reduction of synthesis. Administered in a single dose of 40 uM/ml, after infection of the HeLa cells, 5-sulfamido-ITSC does not arrest the infection and bring about elimination of the virus from the cell, in the course of a single viral multiplication cycle.