PACAP Is Lethal to Flavobacterium psychrophilum Through Either Direct Membrane Permeabilization or Indirectly, by Priming the Immune Response in Rainbow Trout Macrophages

Conclusions Antimicrobial peptides (AMPs) are promising alternatives to antibiotics in the ongoing battle between aquaculture facilities and infectious agents. One AMP that has received a lot of attention due to its pleiotropic effects in aquatic species is PACAP. The results of the present study revealed that PACAP derived from the teleost C. gariepinus acts as a potent antimicrobial peptide against the causative agent of BCWD, F. psychrophilum. Furthermore, its mode of action was confirmed to be permeabilization of the bacterial membrane. When a live infection model was developed with this pathogen and the monocyte/macrophage-like cell line, RTS11, 24 h pre-exposure of PACAP appeared to protect RTS11 by significantly reducing the number of viable bacteria in the culture system. Based on transcript levels of pro-inflammatory cytokines and receptors for the AMP, PACAP was also shown to have an immunostimulatory effect on RTS11 whether exposed to the AMP alone or exposed to both PACAP and live F. psychrophilum challenge. Overall, this study was able to provide further validation regarding the antimicrobial effect of PACAP on aquatic pathogens as well as its immunomodulatory activity on teleost immune cells. As a promising candidate for use in aquatic models, future studies should focus on confirming these valuable functions of PACAP throughout live infection models in vivo. Author Contributions SS performed majority of experiments, contributed to experimental design, and wr...
Source: Frontiers in Immunology - Category: Allergy & Immunology Source Type: research