Abstract
Rifampin partially inhibits focus formation and virus production in chick embryo fibroblasts infected with Bryan high-titer Rous sarcoma (RAV-1) virus. This inhibition occurs with exposure to rifampin during a critical period between day 1 and day 2 after infection. This suggests that the drug does not affect formation of the provirus or its transcription or translation after the "fixation" step, but it seems to affect one or more events which take place before fixation and activation of virus production.