Antarctic Fish Antimicrobial Peptides Active Against Bacterial and Viral Pathogens of Aquacultural Importance

Background/Objectives: The aquaculture industry represents a fundamental food sector. One of the main limiting factors for this sector is related to bacterial diseases, for which antibiotics have been widely used worldwide for decades. In recent years, a more conscious approach to the use of antimicrobials within the framework of the One Health approach has increased the need for alternatives capable of helping with disease management while avoiding the onset of antimicrobial resistance phenomena. Antimicrobial peptides, which have a broad spectrum of action against pathogens, are a promising solution. Methods: In this work, we investigated the capability of three peptides (Trematocine, Chionodracine, and Cnd-m3) isolated from Antarctic fish to target bacterial and viral pathogens affecting aquaculture. Successively, we investigated their cytotoxicity versus a continuous embryonic cell line (DLEC) derived from European sea bass and their haemolytic activity against fish erythrocytes. Moreover, we evaluated their immunomodulatory effect. Results: Regarding antibacterial properties, Cnd-m3 was identified as the best peptide, demonstrating good bactericidal and bacteriostatic activity against various bacterial strains, including Lactococcus garvieae. Concerning this bacterium, ANS permeability assays showed that the Cnd-m3 peptide has a great ability to interact with its outer membrane, while TEM analysis revealed that the peptide, after destabilization of the cell membrane, interacts with nucleic structures. Considering the antiviral activity, Trematocine was effective against two tested pathogenic enveloped viruses. Moreover, the toxicity of Trematocine and Cnd-m3 was evaluated by investigating their cytotoxicity against a cell line derived from Dicentrarchus labrax and haemolysis against sea bass erythrocytes. Both revealed good selectivity towards pathogens at the lowest concentration. Finally, Cnd-m3 manifested light in vitro immunomodulatory properties. Conclusions: Overall, these data provide a solid basis for future studies assessing the potential applications of two of the tested peptides in aquaculture.