ECHINHIBIN-1 - AN INHIBITOR OF SENDAI VIRUS ISOLATED FROM THE VENOM OF THE SNAKE ECHIS-COLORATUS

The snake venom of Echis coloratus was found to abolish the hemaggluti nating activity, hemolytic activity and in vivo infectivity of Sendai virus. The active factor (Echinhibin-1) was purified by gel filtration on Sephadex G-50, followed by chromatography on DEAE-Sepharose and CM -sepharose. Echinhibin-1 is a protease with a molecular weight of abou t 25 kDa, an isoelectric point of 7 and is stained by PAS, indicating that it is a glycoprotein. It showed a strong azocollase activity that was stable up to 68 degrees C and at pH values of 4.5-10.5. Ten mu ug /ml were sufficient to abolish the hemolytic effect of the virus on hu man erythrocytes when incubation was at 37 degrees C for 2 h, while 20 mu g/ml abolished the hemagglutinating activity. Addition of Echinhib in-1 after the adsorption of Sendai Virions onto washed erythrocytes a t 4 degrees C did not inhibit the subsequently hemolytic activity at 3 7 degrees C, indicating that Echinhibin-1 interferes with virus adsorp tion to the cells. Of various protease inhibitors, only Na-2 EDTA and o-phenanthroline inhibited the antiviral activity of the purified fact or, indicating that it is a metalloproteinase. In vivo, mice inoculate d intranasally with the virus pretreated with Echinhibin-1 developed w ell and gained weight, whereas untreated virus-infected mice lost weig ht and died within 1 week; Intravenous administrations of the purified factor up to 80 mu g/mouse produced no signs of toxicity and subcutan eous injections caused no hemorrhagic activity, while the whole venom is very hemorrhagic with an LD(50) of 250 mu g/kg for mice.