Identification of an aprotinin antiviral domain

Digestion of the proteinase inhibitor aprotinin, by clostripain, a cysteine proteinase, yielded five oligopeptide fragments. Two fragments exhibited both antiviral and antibacterial activities, two fragments only antiviral activity, and one fragment showed no antimicrobial activity. One of the former oligopeptides showed antiviral activity against human herpes simplex virus type 1 and bovine parainfluenza virus type 3. It consisted of the hexapeptide Y‐F‐Y‐N‐A‐K corresponding to amino acids 21–26 of intact aprotinin. An identical synthetic peptide had the same antiviral spectrum as the natural hexapeptide, exhibited no antibacterial activity, and was also devoid of trypsin inhibiting activity. Intact aprotinin, in contrast, is ineffective against human herpes simplex virus 1 and bovine parainfluenza virus 3 but possesses antibacterial properties against several bacterial species [(1992) J. Appl. Bact. 72, 180–187].