Abstract
The induction of interferon in chick embryo cells by human adenovirus types 1, 5 and 12 has been examined. Rifampicin, at a concentration of 100 µg./ml., added either immediately or within 24 hr after infection, completely inhibited interferon induction by all three adenoviruses. Up to 24 hr after infection, the inhibitory effect was reversible, and when the drug was removed, interferon production resumed. Rifampicin at 100 µg./ml. also inhibited interferon induction by Semliki Forest virus in chick cells at 37° and 42°, although it had no effect on virus growth at 37°. We conclude that the antibiotic inhibits either a non-essential virus function involved in induction, or alternatively a cellular function. The antiviral action of chick cell interferon against Semliki Forest virus or vaccinia virus was not affected by rifampicin. The drug inhibited chick cell growth, but did not appear to injure cell viability over 48 to 72 hr periods. Rifampicin significantly depressed the incorporation of [3H]-thymidine into chick cell DNA, but had a much lesser effect on incorporation of [3H]-uridine and [3H]-leucine into RNA and protein respectively.