The Influence of Proflavine on the Synthesis of Foot-and-Mouth Disease Virus

Abstract

Infective ribonucleic acid (RNA) can be extracted with phenol from virus-infected pig kidney tissue-culture cells before the appearance of new complete virus. In the early stages of multiplication, however, infective RNA cannot be obtained from the cells if they are incubated with ribonuclease before treatment with phenol. This suggests that the infective RNA is in a "free" enzyme-sensitive form at this time. At the end of the lag phase, as the RNA is incorporated into complete virus, there is a decrease in the proportion of infective RNA in the cells which is sensitive to the enzyme. Nine hours after infection all the material in the cells which yields infective RNA on treatment with phenol is insensitive to ribonuclease. Incorporation of low concentrations of proflavine into the incubation medium decreases considerably the yield of infective virus, although the amounts of infective RNA and specific complement-fixing antigen are not proportionately reduced. In the presence of proflavine the RNA in the cells remains sensitive to ribonuclease throughout the growth cycle indicating that the compound prevents the incorporation of RNA into complete virus. The complement-fixing antigen produced in the proflavine inhibited system is the 7 mu non-infective component of the virus.