STUDIES ON ANTIVIRAL AND ANTITUMOR ANTIBIOTICS .12. EFFECT OF GEODIN ON VIRUS MULTIPLICATION

Antiviral activity of geodin obtained from a soil fungus was studied employing the Newcastle disease virus—chick embryo fibroblasts culture system. In a plate assay method, the minimum inhibitory concentration was about 9 μg/ml and cytotoxicity was detected at 36 μg/ml. Hemagglutinin synthesis was completely suppressed in a tube assay method when 4 μg/ml of geodin was added after the infection (50 plaque forming units/cell), but at this concentration cytotoxic effect of the antibiotic was observed. At sub-inhibitory concentrations, a dose response was shown in the yield of hemagglutinin and infective virus at 16 hr after the infection, and at this time cytopathic effect was partially or completely arrested depending on the antibiotic concentrations even when complete inhibition of hemagglutinin synthesis was not observed. Geodin did not have any effect on the activity of free virus particles and their adsorption to host cells. The inhibition site of geodin exists somewhere between viral adsorption and viral maturation. © 1961 Taylor & Francis Group, LLC.