Inhibition of late influenza virus genome expression by diamidinophenylindole.

The growth cycle of influenza virus strain FPV, Ulster 73, was altered by treatment of LLC-MK2 cells with diamidinophenylindole. Viral protein synthesis was restricted to the early pattern of virus multiplication, and post-treatment experiments showed the ability of the drug to block virus replication until the 4th hour p.i. Drug addition (followed by removal) revealed the inhibition of synthesis of late viral products, and especially of membrane protein. Kinetic studies on the production of viral RNA indicated a decrease in the synthesis of late virus-induced RNA species, suggesting that the target of DAPI is probably the late transcription of the virus genome. The nonpermissive condition mediated by the drug could represent a suitable model to study cellular intervention during viral growth.