Effect of actinomycin D on plaque formation by mengovirus

Treatment of L cell monolayers with actinomycin D resulted in an increase in both the size and number of mengovirus plaques when compared to untreated cells. Addition of the drug to the agar overlay was as effective as pretreatment provided the addition was immediately after virus adsorption. The increased plaque number observed was apparently not due to rescue of defective particles or inhibition of interferon production. The data indicate that more mengovirus particles can successfully complete the infectious cycle in L cells in the presence of actinomycin. The data also suggest that indigenous C-type particles in L cells may interfere with picornavirus replication.