Antiviral Activity of N-Ethylisatin beta-Thiosemicarbazone in Vaccinia-Infected Mice

The anti-viral effect of N-ethylisatin β-thiosemicarbazone was determined in mice infected i.c. with vaccinia virus. The findings indicated that a single dose of 4 mg given as early as 72 hours before infection produced a 1 to 2 log lower PFU and LD50 titer and 80 to 100% net survival. When drug was given after virus inoculation, anti-viral efficacy was related to dose and time of treatment. In general, elementary or inclusion bodies were not observed in the brains of surviving drug-treated mice, and inflammatory changes were not suppressed. The absence of antibody or interferon in the brains of drug-treated mice prior to the 10th day following infection showed that protection was solely due to the virostatic action of N-ethylisatin β-thiosemicarbazone.