Mode of antiviral activity of water soluble components isolated from Elfvingia applanata on vesicular stomatitis virus

A preparation of water soluble components (EA) was made from carpophores of Elfvingia applanata (Pers.) Karst and its in vitro antiviral activity on v esicular stomatitis virus [(Indiana serotype, VSV(IND)] was investigated by plaque reduction assay. EA exhibited potent antiviral activity on VSV(IND) growth and negligible cytotoxicity on Vero cells, 50% effective concentrat ion (EC50) of 104 mug/ml and 50% cytotoxic concentration (CC50) of 3,793 mu g/ml, respectively. Selectivity index (Sl, CC50/EC50) of EA on Vero cell an d VSV(IND) was about 36.5. EA did not display either a direct virucidal eff ect on VSV(IND) or induction of antiviral substance by Vero cells upon its treatment. Thus, the mode of antiviral activity of EA was studied at steps of viral adsorption onto cell. When both EA and virus were added to cell mo nolayers, titer of cell-free virus in culture supernatant increased in ca. 30-40% compared with that of control group and titer of cell-associated vir us was 60-400% higher than that of control group. These results suggested t hat antiviral activity of EA on VSV(IND) might be due to the hindrance of v iral entry to cells at either endocytosis or loss of envelope.