Molecular characterisation and biological activity of an antiparasitic peptide from Sciaenops ocellatus and its immune response to Cryptocaryon irritans

Harnessing marine antimicrobial peptides for novel therapeutics: A deep dive into ocean-derived bioactives

Marine antimicrobial peptides (AMPs) are potent bioactive compounds with broad-spectrum activity against bacteria, viruses, and fungi, offering a promising alternative to traditional antibiotics. These small, cationic, and amphiphilic peptides (3-50 amino acids) are key components of marine organisms' immune defenses, adapted to harsh oceanic environments. Discovered in the 1980s, marine AMPs have garnered interest for their unique structures and potential applications in human health. However, despite the ocean's vast biodiversity, they remain underexplored compared to land-based AMPs. This review emphasizes the therapeutic potential of marine AMPs, including their modes of action, structural variety, and applications in drug development, tissue regeneration, and cancer treatment. Moreover, it discusses their antibacterial, antiviral, antifungal, and antiparasitic properties. Additionally, the review addresses strategies to enhance the therapeutic potential of marine AMPs and the challenges associated with their development. By examining the promising future of marine AMPs, this review aims to pave the way for new approaches to combat antimicrobial resistance and develop innovative treatments for various infectious diseases. The potential of marine AMPs as the "medicine bank of the new millennium" remains vast, providing a valuable resource for future drug discovery and sustainable practices across industries.

Embracing the era of antimicrobial peptides with marine organisms

Covering: 2018 to Jun of 2023The efficiency of traditional antibiotics has been undermined by the proliferation of antibiotic-resistant pathogenic microorganisms, necessitating the pursuit of innovative therapeutic agents. Antimicrobial peptides (AMPs), which are part of host defence peptides found ubiquitously in nature, exhibiting a wide range of activity towards bacteria, fungi, and viruses, offer a highly promising candidate solution. The efficacy of AMPs can frequently be augmented via alterations to their amino acid sequences or structural adjustments. Given the vast reservoir of marine life forms and their distinctive ecosystems, marine AMPs stand as a burgeoning focal point in the quest for alternative peptide templates extracted from natural sources. Advances in identification and characterization techniques have accelerated the discoveries of marine AMPs, thereby stimulating AMP customization, optimization, and synthesis research endeavours. This review presents an overview of recent discoveries related to the intriguing qualities of marine AMPs. Emphasis will be placed upon post-translational modifications (PTMs) of marine AMPs and how they may impact functionality and potency. Additionally, this review considers ways in which marine PTM might support larger-scale, heterologous AMP manufacturing initiatives, providing insights into translational applications of these important biomolecules.

Two duplicated piscidin genes from gilthead seabream (Sparus aurata) with different roles in vitro and in vivo

From the discovery of pleurocidin in skin mucus of winter flounder, many new related sequences have been found, forming a fish-exclusive family of antimicrobial peptides (AMP) called piscidin. Their mature peptides have a broad-spectrum antimicrobial activity and can be involved in the innate immune response. In the present work, two paralogous tripartite piscidin genes are formally described for the first time in gilthead seabream (Sparus aurata), an important marine farmed fish. Gene synteny and protein phylogeny clearly indicated a massive pisc gene expansion in a cluster of the chromosome 22 as well as a special evolution of piscidin in gilthead seabream compared to the rest of piscidins studied in other fish species. Despite being highly similar genes, they show totally different expression patterns in tissues and head-kidney leucocytes under both naïve and Vibrio/nodavirus-stimulated conditions. Moreover, these paralogous genes coded very different proteins according to their physicochemical properties. In this way, these piscidin genes have distinct roles not only related to their microbicide activity but also to their immune modulation. In addition, the present study improves the knowledge of duplication of AMP genes and adaptative diversification of teleost immune system.

Outbreak of Cryptocaryon irritans infection in silver pomfret Pampus argenteus cultured in China

Silver pomfret Pampus argenteus is a major cultivated marine fish species with a high market value. In summer 2021, Cryptocaryon irritans, a ciliate parasite, infected the cultured silver pomfret in aquaculture ponds in Ningbo, Zhejiang Province, China. The symptoms of infected fish include white spots on the skin and fins, increased body surface mucus, loss of appetite, irritability, and shedding of scales. After collecting white spots from moribund fish, the 18S ribosomal RNA sequence of the pathogen on the fish skin was amplified by PCR; phylogenetic analysis showed that it was closely related to C. irritans strains from Ningde, Fujian, China. Four groups of silver pomfret were tested in an artificial infection experiment over the course of 72 h, consisting of 3 infected groups (1600, 4000, and 8000 theronts fish-1) and 1 healthy group. White spots were observed on the skin and fins of the infected fish, but not on their gills. Samples were taken from the gills, liver, kidney, and spleen of both infected and healthy fish and were compared to evaluate any significant histopathological differences. As the dose of infection increased, symptoms became more pronounced. At 72 h, mortality rates were 8.3, 50, and 66.7% for the 3 different concentrations, respectively. The median lethal concentration was calculated to be 366 theronts g-1 at 72 h, 298 theronts g-1 at 84 h, and 219 theronts g-1 at 96 h. This study emphasizes the importance of developing early diagnosis methods and appropriate prevention strategies to decrease the impact of C. irritans infection in the silver pomfret aquaculture industry.

Expression of the Antimicrobial Peptide Piscidin 1 and Neuropeptides in Fish Gill and Skin: A Potential Participation in Neuro-Immune Interaction

Antimicrobial peptides (AMPs) are found widespread in nature and possess antimicrobial and immunomodulatory activities. Due to their multifunctional properties, these peptides are a focus of growing body of interest and have been characterized in several fish species. Due to their similarities in amino-acid composition and amphipathic design, it has been suggested that neuropeptides may be directly involved in the innate immune response against pathogen intruders. In this review, we report the molecular characterization of the fish-specific AMP piscidin1, the production of an antibody raised against this peptide and the immunohistochemical identification of this peptide and enkephalins in the neuroepithelial cells (NECs) in the gill of several teleost fish species living in different habitats. In spite of the abundant literature on Piscidin1, the biological role of this peptide in fish visceral organs remains poorly explored, as well as the role of the neuropeptides in neuroimmune interaction in fish. The NECs, by their role as sensors of hypoxia changes in the external environments, in combination with their endocrine nature and secretion of immunomodulatory substances would influence various types of immune cells that contain piscidin, such as mast cells and eosinophils, both showing interaction with the nervous system. The discovery of piscidins in the gill and skin, their diversity and their role in the regulation of immune response will lead to better selection of these immunomodulatory molecules as drug targets to retain antimicrobial barrier function and for aquaculture therapy in the future.