Introduction
Host defense peptides (HDPs) have garnered significant attention as innovative alternatives to conventional antibiotics. These peptides are notable not only for their antimicrobial properties but also for their capacity to modulate immune responses. Piscidins are amphiphilic, cationic peptides characterized by an α-helical secondary structure, potent antimicrobial activity against a broad spectrum of pathogens, and notable immunomodulatory properties [1]. However, their oral administration is constrained by limited stability and vulnerability to enzymatic degradation [2].
Methodology
To address these limitations, we encapsulated piscidin 1 (P1) within carrageenan and pectin microparticles, thereby developing an oral delivery system. P1 is an HDP of gilthead seabream (Sparus aurata). Gilthead seabream specimens were fed for 17 days a commercial diet (Skretting) supplemented with 0%, 0.05%, or 0.1% encapsulated P1. The scanning electron microscope was used to determine the size of the microparticles. Serum and head-kidney leucocytes were collected on days 4 and 17 to assess humoral and innate immune parameters (peroxidase, anti-protease, lysozyme, and respiratory burst activities and phagocytosis). Additionally, muscle samples were collected on day 17 for texture profile analysis (TPA; hardness, adhesiveness, springiness, cohesiveness, gumminess, chewiness, and resilience) and proximate composition analysis (carbohydrates, protein, fat, ash, fiber, water).
Results
The results indicated that serum peroxidase activity significantly increased on day 4 in fish fed the 0.05% encapsulated P1 diet. Respiratory burst activity decreased in fish fed with encapsulated P1 at both day 4 and day 17. Phagocytic ability increased in fish fed the 0.1% diet at both sampling points, while only the 0.05% diet group exhibited an increase in phagocytosis capability on day 4. TPA results demonstrated that adhesiveness decreased in fish fed the 0.1% encapsulated P1 diet, while resilience increased in both groups receiving encapsulated P1. The diet had no effect on the proximate composition of the fish.
Conclusion
Therefore, this study suggests that encapsulated peptides may hold potential as an oral delivery system to stimulate the immune system and enhance muscle quality in aquaculture.
Acknowledgments
Claudia Marín-Parra (PRE2021-098414) has PhD grant. This study was funded by the Proyecto de investigación PID2020-113637RB-C21 financiado por MCIN/ AEI /10.13039/501100011033 and forms part of the ThinkInAzul programme supported by MCIN with funding from European Union Next Generation EU(PRTR-C17.I1) and by the Comunidad Autónoma de la Región de Murcia-Fundación Séneca (Spain).
Bibliography
[1] S.V. Raju, P. Sarkar, P. Kumar, J. Arockiaraj, Piscidin, Fish Antimicrobial Peptide: Structure, Classification, Properties, Mechanism, Gene Regulation and Therapeutical Importance, International Journal of Peptide Research and Therapeutics 27(1) (2021) 91-107.
[2] A.P. de Amorim, Y. Alessandra Santana Moura, K. Mirella Soares de Souza, A.L.F. Porto, R.P. Bezerra, Encapsulation of peptides inhibitors of the angiotensin-converting enzyme: A systematic review, Materials Today Communications 36 (2023) 106850.