Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/10/2019
Publication Date: N/A
Technical Abstract: Bovine NK-lysins (bNK-lysins), a type of antimicrobial proteins, are primarily produced by cytotoxic T-lymphocytes and NK-cells. We and others have previously demonstrated the potent antimicrobial activities of synthetic bNK-lysin-derived peptides (NK1, NK2A, NK2B, and NK2C) against a variety of microbes, including the bacterial pathogens causing bovine respiratory disease complex in cattle. While immunomodulatory properties of several antimicrobial peptides including chicken NK-lysin have recently been reported, it is unknown whether bNK-lysins also display such immunomodulatory properties. Given the structural and functional similarities of bNK-lysins with chicken NK-lysin, we hypothesized that bNK-lysins also display immunomodulatory activities. To test this hypothesis, one peptide corresponding to the functional region helices 2 and 3 of bNK-lysin NK2A (bNK2A) was synthesized. The immune responses of cattle PBMC to bNK2A peptide were assessed for increase in intracellular calcium concentration ([Ca2+]i) and induction of chemokine/cytokine transcript expression levels (mRNA) by flow cytometry and quantitative RT-PCR, respectively. Immediate elevation of [Ca2+]i, which is a key early feature in immune cell activation, was observed with Fluo-4-AM loaded PBMC when incubated with bNK2A. The bNK2A had a modest effect on the expression levels of chemokines CCL4, CCL5 and IL-8, and cytokines IL-6, and TNF-alpha (2-3-fold increase) in monocytes. The bNK2A treatment increased the expression levels of chemokine CCL20 and cytokine IL-1 beta (4-6-fold) in monocytes. Cells incubated with PBS (negative control) did not show any changes in [Ca2+]i or chemokine/cytokine expression levels. These findings suggest that bNK-lysins appear to have immunomodulatory properties in addition to antimicrobial activities.