Antiviral effect of interferon in vivo may be mediated by the host [16]

INTERFERON has antiviral effects both in vivo and in vitro. Viral replication is inhibited in interferon-treated cells in vitro because the reproductive cycle of the virus is inhibited at the transcriptional or translational level, depending on the virus-cell system studied¹. This direct inhibition of viral replication has been assumed to also be the mechanism by which interferon exerts its antiviral effect in vivo. We report here results that indicate protection by interferon against viral infection in vivo without inhibition of the viral replication of the same virus in vitro.