Submitted to: Infection and Immunity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/19/1999
Publication Date: N/A
Interpretive Summary: Respiratory tract diseases are a leading cause of loss from disease in the cattle, sheep and goat industries. Annual loss in the United States is estimated to exceed one billion dollars. Losses are from mortality, reduced feed efficiency, and slaughter condemnations, as well as prevention and treatment measures. Currently, not all the factors preventing infectious disease in normal animals are known by scientists and veterinarians. As part of our ongoing studies to understand the natural, innate immune system, we isolated 2 unique antimicrobial peptides from white blood cells in the blood of sheep and goats. While the peptides remained active against bacteria like E. coli, P. aeruginosa, B. subtilis and L. monocytogenes in salt solutions, they lost activity against bacteria like S. aureus and fungi like C. albicans under these conditions. On the basis of our findings, it appears that this would be an important factor in npreventing infection and averting the disease process. Our findings are a important first step in finding new ways to better control shipping fever of cattle. Corollary benefits include an increase in the profitability and international competitiveness of the U. S. cattle industry, a stronger rural economy, and a continued supply of inexpensive, wholesome beef, and beef products for the American consumer.
Technical Abstract: Two proline-rich peptides, OaBac5alpha and ChBac5, were purified from elastase-treated extracts of sheep and goat leukocytes. The peptides were homologous to each other and to bovine Bac5. Both exhibited potent, broad-spectrum antimicrobial activity under low salt conditions. While the peptides remained active against E. coli, P. aeruginosa, B. subtilis and L. .monocytogenes in 100 mM NaCl, they lost activity against S. aureus and C. albicans under these conditions. ChBac5 showed moderate affinity for LPS, which may contribute to its ability to kill Gram-negative bacteria. Proline-rich Bac5 peptides are highly conserved in ruminants, and may contribute significantly to their innate, neutrophil-mediated host defense mechanisms.