Bleomycin, an inhibitor of vaccinia virus replication

Bleomycin inhibits vaccinia virus replication in infected HeLa cells and in mice. Viral DNA synthesis and core RNA polymerase activity are significantly inhibited by the antibiotic. Synthesis of messenger RNA in isolated vaccinia cores is inhibited, but synthesis of poly(A) is unaffected. Vaccinia core DNA is degraded during the course of the RNA polymerase reaction in the presence of bleomycin. The presence of ribonucleoside triphosphates accelerates the degradation of vaccinia core DNA by bleomycin. Effects on DNA synthesis, in particular, the induced degradation of template DNA, may be responsible for the observed antiviral activity of bleomycin.