Extracellular bactericidal functions of porcine neutrophils (133.20)

Abstract

Abstract Neutrophils are one of the main effector cells of innate immunity and were shown to kill bacteria via phagocytosis more than 100 years ago. New developments, however, also show that neutrophils are capable of antimicrobial activity by producing extracellular structures named neutrophil extracellular traps (NETs). The antimicrobial effects of NETs can be attributed to cathelicidins, a category of antimicrobial peptides stored as inactive proforms. These proforms are cleaved by neutrophils elastase during cell activation in response to pathogens. This project focuses on the cathelicidin peptides contained within NETs and their effectiveness in killing several common bacterial pathogens of swine. Subsequent investigations address the contribution of cathelicidins to extracellular bactericidal activity of porcine neutrophils. Activated secretions of neutrophils are effective in killing 100% of Escherichia coli K12, 21% of Streptococcus suis, and 74% of Actinobacillus suis. Pasteurella multocida appears to survive in the presence of activated neutrophil secretions demonstrating a 38% increase in growth when compared to P. multocida exposed to non activated neutrophils secretions. Identification of the contribution of cathelicidins to this bactericidal activity is pending. These data suggest that activated neutrophil secretions have bactericidal activity against common pathogens in swine.