Antiviral Chemotherapeutic Activity of Isatin β-thiosemicarbazone in Mice infected with Rabbit-pox Virus

Abstract

ISATIN β-thiosemicarbazone has been found to have a very powerful chemotherapeutic effect in mice infected intracerebrally with the IHD strain of neurotropic vaccinia virus¹, and will give complete protection against death after infection with doses of virus as high as 100,000 LD50². The compound is inactive against ectromelia infection in mice, however³, and it is therefore of interest to investigate its action against other members of the pox group. The present work was carried out with the Utrecht strain of rabbit-pox virus⁴, presented by Dr. E. A. Boulter, of the Microbiological Research Establishment, Porton. In view of the similarity of this virus to vaccinia and the uncertainty as to its origin, a preliminary investigation was undertaken to ascertain whether it does in fact differ in biological characteristics from the IHD strain of neurovaccinia used in previous work. That a distinction does exist was shown by the failure of rabbit-pox virus to kill mice of weight greater than 15 gm. when inoculated intracerebrally. Differences were observed also in tissue culture. Propagation of both viruses in the cell strain ERK I⁵ yielded fluids of high titre; but whereas the cytopathic effect of neuro-vaccinia consisted of granularity and swelling of individual cells followed by rounding and detachment from the glass, that of rabbit-pox virus manifested itself as the formation of syncytial sheets of cells which later became filled with large vacuoles.