Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/19/2017
Publication Date: N/A
Technical Abstract: Antimicrobial peptides (AMPs) are a diverse group of molecules which play an important role in the innate immune response in various organisms, including cattle. Bovine NK-lysins, a type of AMP, have been predominantly found in the granules of cytotoxic T-lymphocytes and NK-cells. Collective results from our lab and others have previously reported antimicrobial activity of bovine NK-lysins on various bacterial pathogens, including several involved in bovine respiratory disease complex (BRDC) in cattle; however, such studies are yet to be performed with one important contributor to the BRDC, Mycoplasma bovis. Therefore, the goal of this study was to assess the antimicrobial activity of bovine NK-lysins on M. bovis. Synthetic peptides corresponding to the functional region of helices 2 and 3 of the bovine NK-lysins NK1, NK2A, NK2B and NK2C were assessed for killing activity on two M. bovis bovine isolates. Among four peptides tested, NK2A-derived peptide showed the highest antimicrobial activity, while NK1-derived peptide showed the least antimicrobial activity against both M. bovis isolates as determined by a bacterial killing assay. Flow cytometric analysis of NK-lysin-treated M. bovis after staining with a live/dead bacterial viability indicator (Syto 9/propidium iodide) suggested damage to the cell membrane based on staining of nuclear material within the cells. Electron microscopic examination of M. bovis treated with NK-lysin peptides confirmed damage to the cell membrane. The results of this study suggest that bovine NK-lysins in general, and NK2A in particular, show antimicrobial activity against M. bovis by directly causing damage to the cell membrane. Taken together, findings in this study along with previous studies, we can now conclude that bovine NK2A is highly effective against most bacterial pathogens involved in BRDC.