Atlantic salmon and rainbow trout are the most important commercial species in Chile. However, the annual productivity of these species has been reduced mainly by the virulence of microorganisms. Given this, the salmon industry resorts to vaccines, but there are still doubts about their effectiveness, while antibiotics, given its overuse, generate multiresistant bacteria. An alternative strategy is the application of therapeutic molecules based on host defense peptides (HDPs). In 2018, our research group identified and characterized IL-8 derived salmonid peptides called ssIL-8α and omIL-8γ with potential antimicrobial and immunomodulatory activities, respectively. The finding of these different functions indicated that kinocidins like IL-8 has a modular configuration, where different effectors may be deployed, for example, through enzymatic proteolysis, which makes the study of this chemokine attractive. Therefore, in this work we developed and evaluated a protide composed by the effectors ssIL-8α and omIL-8γ linked through an activating sequence on the salmonid’s monocyte/macrophage-like cell line. For this purpose, we determined, by bioinformatic analysis, potential salmonid MMP-9 enzyme cleavage sites, obtained protides with previously selected MMP-9 enzyme cleavage sites and demonstrated that RTS-11 cell line releases MMP-9 enzyme that is capable of cleaving protides. Through the results obtained we were able to synthesize and characterize by HPLC, mass spectrometry and circular dichroism, a protide with the cleavage site for the MMP-9 enzyme. In addition, we detect MMP-9 enzyme in RTS-11 cell line stimulated with bacterial LPS at 24 h by Gelatin zymograms and Western blot. In both cases a band was observed close to 70 kDa. With these results we expect to contribute with a strategy for anti-infective therapy against antibiotic-resistant pathogens, being potentially capable of restoring or enhancing deficient immune functions of fish to favor the production of salmonids.

Acknowledgment: FONDECYT N°1231088.