ANTIBACTERIAL PROTEINS FROM PORCINE POLYMORPHONUCLEAR NEUTROPHILS

Antibacterial peptides were purified from porcine neutrophil granules collected from healthy pigs. Granule proteins, extracted with 0.2 mol/ L sodium acetate, were subjected to ion-exchange chromatography and fi ve peaks (designated A to E) were detected. Individual porcine neutrop hil granule proteins were shown to inhibit the growth of target organi sms Escherichia coli and Staphylococcus aureus. The antimicrobial acti vity was shown to be concentration and time dependent. Peak D showed s trong antimicrobial activity against S. aureus and peak C (with a grea ter number of eluted proteins) was shown to be active against both S. aureus and E. coli. One of the peptides was purified further by revers e-phase HPLC from peak fraction C. The MW of this peptide was approxim ately 5500 Da as determined by SDS-PAGE and mass spectral analysis and was active against both E. coli and S. aureus in vitro sustaining a > 90% decrease, respectively, in CFU after a 2 h exposure with 50 mu g of this peptide. Amino acid analysis showed the peptide was rich in as partate/aspartic acid, glutamine/glutamic acid, proline, arginine and threonine. The antimicrobial activity of this peptide and other novel proteins in porcine neutrophilic granules demonstrates the probable ro le of these proteins and peptides in host defence of porcine neutrophi ls against bacterial infection.