On the antiviral activity of diffusomycin (oxazolomycin)

The effect of the beta-lactone antibiotic diffusomycin (oxazolomycin) was investigated against vaccinia (Lister), herpes simplex type 1 (Kupka), influenza A (WSN; H1N1), and Coxsackie A9 viruses. Diffusomycin reduced significantly the plaque formation of enveloped DNA and RNA viruses by more than 90% in the range of the maximally tolerated dose. As could be shown with vaccinia virus, the antiviral action was not caused by virucidal effect on virions or by interaction with virus adsorption and penetration. In one-step growth cycle assays diffusomycin prevented the replication of herpes simplex type 1, vaccinia and influenza A viruses in a dose-dependent manner. The replication of influenza A viruses was blocked immediately after addition of the compound during zero to six hr p.i. Partial reversibility of the antiviral action was established by washing off the antibiotic from chicken embryo cells (CEC) infected with influenza A virus. Finally, replication of Coxsackie A9 virus was not inhibited by diffusomycin. Electron-optical studies revealed a reduced synthesis of HSV-1 nucleocapsids in dependence on the concentration of the compound.