Abstract
The antiviral effect of interferon was studied in a number of experimental virus infections in the rat. Interferon was shown to protect rats infected with pseudorabies virus, herpes simplex virus or vesicular stomatitis virus. The antiviral activity was not inhibited by immune suppression induced by azothioprine, prednisolone or cyclosporin A treatment. Cyclophosphamide completely blocked the in vivo activity of interferon in rats.