[Potentiating effect of cycloheximide on viral interference]

The degradation of the antiviral state can be delayed in vitro by antimetabolites, when added between 5-7 hours after interferon. We explore in this chronological order whether antiviral resistance induced by Newcastle disease virus (N.D.V.) in vivo could be modified by an antimetabolite. Cycloheximide was selected for this study because of its reversible biological effect and lack of toxicity in our experimental conditions. The model system employed was Syrian Hamsters, using N.D.V. as an interferon inducer and encephalomyocarditis virus (E.M.C.) as a challenge virus. A constant and significant increase in survival of animals treated with N.D.V.+cycloheximide is probably related to a delay in the degradation of the antiviral state and not to interferon superinduction.