The Antiviral Activity of Caprochlorone

Summary Caprochlorone demonstrates clear-cut or suggestive activity in cell culture systems against 15 myxoviruses and vaccinia, while 9 other virus strains are insensitive. The action mechanism of caprochlorone against influenza A/WSN, A/PR8, and B/Maryland was compared with that of 1-adamantanamine · HCl, ammonium phosphate, viral antiserum, and acidification. The time at which viral replication could be inhibited, up to 15 minutes after addition of virus, was similar in all cases. This inhibition resulted from failure of virus to penetrate the cell membrane as indicated by sensitivity of virus to neutralization by antiserum even 2 hours after addition of virus and inhibitor. Reversal of inhibition of A/WSN and A/PR8-infected cultures treated for 2 hours is accomplished by removing the compounds and replacing with medium; at this time, acidification inactivates A/WSN, whereas A/PR8 is refractory. Inhibition of B/Maryland-infected cultures with ammonium phosphate is reversed by removal of compound after 2 hours, but resistance to acidification is shown. By contrast, caprochlorone or I-adamantanamine · HCl inhibition of B/Maryland-infected cultures could not be reversed. In addition to inhibition of cell penetration by virus, capro-chlorone delayed release of newly formed virus from the cell, whereas l-adamantana-mine · HCl and ammonium phosphate did not. We wish to acknowledge the excellent technical assistance of Edward Flannery, Janice Wagner, and especially Barbara Zappala.