Interferon pretreatment inhibits simian virus 40 infections by blocking the onset of early transcription.

CV-1 cells treated with human leukocyte interferon before infection with simian virus 40 (SV40) are protected from virus-induced cytopathic effects. Accumulation of viral mRNA is inhibited markedly. If T antigen is present in interferon-treated cells before infection, viral DNA replication is inhibited only slightly. These results show that many SV40 virions reach the nucleus in a form which can be replicated but not transcribed. Accumulation of SV40 mRNA is not inhibited in cells treated with interferon after infection. Thus the block mediated by interferon is specific for the onset of transcription. Infections with SV40 DNA rather than virions are insensitive to treatment with interferon, showing that the inhibition involves an interaction between viral nucleoprotein complexes and cellular factors.