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This review synthesizes the multifaceted role of vitamin A in fish well-being, encompassing immune function, antioxidant capacity and growth regulation, providing a comprehensive understanding of its significance in fish diets and implications for aquaculture. Key objectives include exploring the role of vitamin A in fish immunology, growth impact, oxidative stress status, and future directions. Vitamin A is critical for immune cell development, enhancing both innate and adaptive immune responses. It maintains mucosal integrity and modulates phagocytic activity, crucial for pathogen defense. Growth regulation is influenced by vitamin A through cellular differentiation and morphogenesis, essential for tissue and skeletal development. Studies indicate that vitamin A supplementation improves growth metrics and body composition across various fish species. Vitamin A also combats oxidative stress by scavenging free radicals, enhancing antioxidant enzyme activity, and inducing autophagy, thus protecting cellular components from oxidative damage. Interactions with other vitamins like E, D, and C highlight the importance of balanced nutrition in aquaculture. Integrative management practices, including nutritionally balanced diets, optimal water quality, stress reduction, and environmental enrichment, are recommended to maximize fish health and productivity through adequate vitamin A utilization. [ABSTRACT FROM AUTHOR]

The fermentation products of Astragalus have been acknowledged for their ability to enhance immune functions. This study assessed the impact of incorporating Astragalus, fermented with Lactobacillus plantarum and Bacillus coagulans, on crucian carp's growth, disease resistance, and immunological characteristics. The experimental groups were fed with common feed (C), C + Astragalus (A), A + Lactobacillus plantarum (AL), A + Bacillus coagulans (AB), and AL + Bacillus coagulans (ALB). The fermented products were mixed with common feed at a 1:99 ratio, and crucian carp were fed 2% of their body weight for four weeks, with sampling conducted on days 3, 7, 14, 21, and 28. Disease resistance was evaluated using Aeromonas hydrophila (A. hydrophila) at a concentration of 0.2 mL (1.0×107 CFU/mL). The final weights in the AL, AB, and ALB groups significantly increased compared to the C group. The ALB group exhibited elevated serum albumin levels, alkaline phosphatase, intestinal lipase, protease enzyme, C3, and IgM gene expression compared to the C group. At the same time, alanine aminotransferase, aspartate aminotransferase, and glucose contents were significantly reduced. The survival rate significantly increased in all experimental groups after treatment with A. hydrophila. In conclusion, Astragalus products fermented with Lactobacillus plantarum and Bacillus coagulans could effectively improve crucian carp's growth, disease resistance, and immune response. [ABSTRACT FROM AUTHOR]

The peritoneum is mainly composed of mesothelial cells, fiber cells, and fibers, with many free cells that come from tissue capillaries. Siniperca chuatsi is a valuable fish commodity and important freshwater aquaculture species in China. With the increase in the scale of its breeding, bacterial and viral disease of the S. chuatsi has become increasingly rampant in recent years. This study analyzed the peritoneal gene expression profile using transcriptome technology for the first time. The results showed that 95,711 unigenes were expressed in the peritoneum with an average length of 920.72 bp. In addition to the housekeeping genes, the genes of extracellular matrix protein 1a (ecm1), Angiopoietin-related protein 4-like (angptl4) and cysteine-rich protein 1 (crip1) were highly expressed genes in the peritoneum, and they are key factors in peritoneal development and the maintenance of morphology. Meanwhile, many immune genes were also expressed in the peritoneum, including beta-2-microglobulin (b2m), MHC II invariant chain (cd74), prostate stem cell antigen-like protein (psca), claudin (cldn), heat shock protein 90 (hsp90), complement component 4 (c4), radical S-adenosyl methionine domain-containing protein 2 (rsad2), and cathepsin S (ctss). The RT-PCR results showed that different genes exhibited different expression profiles. The transcriptome data indicated that b2m, cldn, hsp90, c4, and rsad2 were highly expressed in the peritoneum. b2m, cd74, psca, c4, and ctss were highly expressed after embryonic hatching, whereas cldn, hsp90, and rsad2 were expressed at early embryonic stages. Quantitative PCR demonstrated that b2m, cd74, cldn, hsp90, c4, and ctss genes were highly expressed after immunostimulation. This study provides significant data for studying the morphological and functional diversity of fish peritoneum and lays a foundation for research on mandarin fish immunity. [ABSTRACT FROM AUTHOR]

Aquaculture is rapidly becoming one of the pivotal sectors in the farming economy, driven by the increasing demand for high-quality animal protein at an affordable cost, especially with the escalating human population. However, the expansion of high-density fish populations also brings forth a challenge—the rapid transmission and spread of infectious disease agents among them. To combat this, vaccination is emerging as a reliable and standardized method for providing immunity against viral and bacterial outbreaks. The ideal vaccine is expected to be safe, effective, economical, and easily administered. The fish vaccination industry continually publishes new information on fish immunology and vaccinology, contributing to the improvement in vaccine formulation and efficacy. This review aims to offer insights into the current status of bacterial, viral, and parasitic diseases, discuss existing vaccinations, and address potential industry-threatening diseases like infectious edwardsiellosis, motile aeromonas septicemia (MAS), Tilapia Lake Virus (TiLV) disease, infectious salmon anemia (ISA), vibriosis, and white spot disease. Technological advancements have played a crucial role in enhancing our understanding of fish immunological mechanisms, leading to improved vaccine administration and the development of recombinant live attenuated, subunit, DNA, and RNA vaccines. However, challenges such as oral tolerance, vaccine degradation, and stressful environments persist, impacting vaccine efficacy. Addressing these challenges and gaining a deeper understanding of the fish immune system and host–pathogen interactions will be pivotal for future improvements, contributing to the sustainability of aquaculture and enhancing global food security. [ABSTRACT FROM AUTHOR]

This review summarizes the current knowledge on immune defence activities of the European sea bass Dicentrarchus labrax by reporting the consistent amount of work done on this economically-important species. A draft genome sequence is available for this species, together with whole transcriptomes from lymphoid and non-lymphoid tissues. Available full-length coding sequences of many immunoregulatory and immune-related genes allow for targeted quantitative PCR analysis, nowadays needed for -omics data verification, ex vivo and in vitro. The first anti-T cells monoclonal antibody teleost-wise was obtained in sea bass, followed by several monoclonal and polyclonal markers of lymphocyte populations, namely T cells (pan-T, CD3ε, TcRγ, CD45), and B cells (IgM, IgT, IgD). The combined use of molecular and biochemical tools enabled investigations on innate and acquired immune responses of sea bass in unstimulated/stimulated fish, along the development and under variable environmental conditions and food regimes. An overview of sea bass viral and bacterial pathogens and available vaccines against these microorganisms is also provided. The knowledge accumulated in the past 25 years validates the European sea bass as a reference marine model in the field of fish immunology.

The AID/APOBECs are a group of zinc-dependent cytidine deaminases that catalyse the deamination of bases in nucleic acids, resulting in a cytidine to uridine transition. Secreted novel AID/APOBEC-like deaminases (SNADs), characterized by the presence of a signal peptide are unique among all of intracellular classical AID/APOBECs, which are the central part of antibody diversity and antiviral defense. To date, there is no available knowledge on SNADs including protein characterization, biochemical characteristics and catalytic activity. We used various in silico approaches to define the phylogeny of SNADs, their common structural features, and their potential structural variations in fish species. Our analysis provides strong evidence of the universal presence of SNAD1 proteins/transcripts in fish, in which expression commences after hatching and is highest in anatomical organs linked to the immune system. Moreover, we searched published fish data and identified previously, "uncharacterized proteins" and transcripts as SNAD1 sequences. Our review into immunological research suggests SNAD1 role in immune response to infection or immunization, and interactions with the intestinal microbiota. We also noted SNAD1 association with temperature acclimation, environmental pollution and sex-based expression differences, with females showing higher level. To validate in silico predictions we performed expression studies of several SNAD1 gene variants in carp, which revealed distinct patterns of responses under different conditions. Dual sensitivity to environmental and pathogenic stress highlights its importance in the fish and potentially enhancing thermotolerance and immune defense. Revealing the biological roles of SNADs represents an exciting new area of research related to the role of DNA and/or RNA editing in fish biology. [ABSTRACT FROM AUTHOR]

This review summarizes the current knowledge on immune defence activities of the European sea bass Dicentrarchus labrax by reporting the consistent amount of work done on this economically-important species. A draft genome sequence is available for this species, together with whole transcriptomes from lymphoid and nonlymphoid tissues. Available full-length coding sequences of many immunoregulatory and immune-related genes allow for targeted quantitative PCR analysis, nowadays needed for -omics data verification, ex vivo and in vitro. The first anti-T cells monoclonal antibody teleost-wise was obtained in sea bass, followed by several monoclonal and polyclonal markers of lymphocyte populations, namely T cells (pan-T, CD3e, TcR?, CD45), and B cells (IgM, IgT, IgD). The combined use of molecular and biochemical tools enabled investigations on innate and acquired immune responses of sea bass in unstimulated/stimulated fish, along the development and under variable environmental conditions and food regimes. An overview of sea bass viral and bacterial pathogens and available vaccines against these microorganisms is also provided. The knowledge accumulated in the past 25 years validates the European sea bass as a reference marine model in the field of fish immunology. [ABSTRACT FROM AUTHOR]

Fishes are hosts for many microorganisms that provide them with beneficial effects on growth, immune system development, nutrition and protection against pathogens. In order to avoid spreading of infectious diseases in aquaculture, prevention includes vaccinations and routine disinfection of eggs and equipment, while curative treatments consist in the administration of antibiotics. Vaccination processes can stress the fish and require substantial farmer's investment. Additionally, disinfection and antibiotics are not specific, and while they may be effective in the short term, they have major drawbacks in the long term. Indeed, they eliminate beneficial bacteria which are useful for the host and promote the raising of antibiotic resistance in beneficial, commensal but also in pathogenic bacterial strains. Numerous publications highlight the importance that plays the diversified microbial community colonizing fish (i.e., microbiota) in the development, health and ultimately survival of their host. This review targets the current knowledge on the bidirectional communication between the microbiota and the fish immune system during fish development. It explores the extent of this mutualistic relationship: on one hand, the effect that microbes exert on the immune system ontogeny of fishes, and on the other hand, the impact of critical steps in immune system development on the microbial recruitment and succession throughout their life. We will first describe the immune system and its ontogeny and gene expression steps in the immune system development of fishes. Secondly, the plurality of the microbiotas (depending on host organism, organ, and development stage) will be reviewed. Then, a description of the constant interactions between microbiota and immune system throughout the fish's life stages will be discussed. Healthy microbiotas allow immune system maturation and modulation of inflammation, both of which contribute to immune homeostasis. Thus, immune equilibrium is closely linked to microbiota stability and to the stages of microbial community succession during the host development. We will provide examples from several fish species and describe more extensively the mechanisms occurring in zebrafish model because immune system ontogeny is much more finely described for this species, thanks to the many existing zebrafish mutants which allow more precise investigations. We will conclude on how the conceptual framework associated to the research on the immune system will benefit from considering the relations between microbiota and immune system maturation. More precisely, the development of active tolerance of the microbiota from the earliest stages of life enables the sustainable establishment of a complex healthy microbial community in the adult host. Establishing a balanced host-microbiota interaction avoids triggering deleterious inflammation, and maintains immunological and microbiological homeostasis. [ABSTRACT FROM AUTHOR]

Aquaculture is a growing industry worldwide, but it faces challenges related to animal health. These challenges include infections by parasites, bacteria, and viral pathogens. These harmful pathogens have devastating effects on the industry, despite efforts to control them through vaccination and antimicrobial treatments. Unfortunately, these measures have proven insufficient to address the sanitary problems, resulting in greater environmental impact due to the excessive use of antimicrobials. In recent years, probiotics have emerged as a promising solution to enhance the performance of the immune system against parasitic, bacterial, and viral pathogens in various species, including mammals, birds, and fish. Some probiotics have been genetically engineered to express and deliver immunomodulatory molecules. These promote selective therapeutic effects and specific immunization against specific pathogens. This review aims to summarize recent research on the use of probiotics in fish aquaculture, with a particular emphasis on genetically modified probiotics. In particular, we focus on the advantages of using these microorganisms and highlight the main barriers hindering their widespread application in the aquaculture industry. [ABSTRACT FROM AUTHOR]

The CD28-B7 interaction is required to deliver a second signal necessary for T-cell activation. Additional membrane receptors of the CD28 and B7 families are also involved in immune checkpoints that positively or negatively regulate leukocyte activation, in particular T lymphocytes. BTLA is an inhibitory receptor that belongs to a third receptor family. Fish orthologs exist only for some of these genes, and the potential interactions between the corresponding ligands remain mostly unclear. In this work, we focused on the channel catfish (Ictalurus punctatus), a long-standing model for fish immunology, to analyze these co-stimulatory and co-inhibitory receptors. We identified one copy of cd28, ctla4, cd80/86, b7h1/dc, b7h3, b7h4, b7h5, two btla, and four b7h7 genes. Catfish CD28 contains the highly conserved mammalian cytoplasmic motif for PI3K and GRB2 recruitment, however this motif is absent in cyprinids. Fish CTLA4 share a C-terminal putative GRB2-binding site but lacks the mammalian PI3K/GRB2-binding motif. While critical V-domain residues for human CD80 or CD86 binding to CD28/CTLA4 show low conservation in fish CD80/86, C-domain residues are highly conserved, underscoring their significance. Catfish B7H1/DC had a long intracytoplasmic domain with a P-loop-NTPase domain that is absent in mammalian sequences, while the lack of NLS motif in fish B7H4 suggests this protein may not regulate cell growth when expressed intracellularly. Finally, there is a notable expansion of fish B7H7s, which likely play diverse roles in leukocyte regulation. Overall, our work contributes to a better understanding of fish leukocyte co-stimulatory and co-inhibitory receptors. [ABSTRACT FROM AUTHOR]

Simple Summary: The study of the innate immune system's (IIS) properties is one of the key tasks of modern immunology, since it could help enhance the quality of therapy and drug discovery. This system remains understudied for nonmammalians, and teleost fish are promising model organisms for fundamental studies of IIS organization. The recent single-cell transcriptomics (scRNAseq) experiments carried out on zebrafish and other teleosts brought fundamental knowledge about their innate immunity organization. The aim of this review is to summarize information about the available IIS-related scRNAseq experiments for teleosts and outline further perspectives for studies in this field. We found 89 scRNAseq datasets for zebrafish in different stages and organs suitable for the further meta-analysis of IIS properties and six experiments for other teleosts. Therefore, the obtained data for zebrafish could be further generalized and compared with that of mammals, while for other teleosts, we still have a large gap in knowledge. We believe that in the coming years, new scRNAseq data obtained for nonmodel teleosts will be of particular value and interest in the context of animal immunology. The innate immune system is the first line of defense in multicellular organisms. Danio rerio is widely considered a promising model for IIS-related research, with the most amount of scRNAseq data available among Teleostei. We summarized the scRNAseq and spatial transcriptomics experiments related to the IIS for zebrafish and other Teleostei from the GEO NCBI and the Single-Cell Expression Atlas. We found a considerable number of scRNAseq experiments at different stages of zebrafish development in organs such as the kidney, liver, stomach, heart, and brain. These datasets could be further used to conduct large-scale meta-analyses and to compare the IIS of zebrafish with the mammalian one. However, only a small number of scRNAseq datasets are available for other fish (turbot, salmon, cavefish, and dark sleeper). Since fish biology is very diverse, it would be a major mistake to use zebrafish alone in fish immunology studies. In particular, there is a special need for new scRNAseq experiments involving nonmodel Teleostei, e.g., long-lived species, cancer-resistant fish, and various fish ecotypes. [ABSTRACT FROM AUTHOR]

Fishes are hosts for many microorganisms that provide them with beneficial effects on growth, immune system development, nutrition and protection against pathogens. In order to avoid spreading of infectious diseases in aquaculture, prevention includes vaccinations and routine disinfection of eggs and equipment, while curative treatments consist in the administration of antibiotics. Vaccination processes can stress the fish and require substantial farmer’s investment. Additionally, disinfection and antibiotics are not specific, and while they may be effective in the short term, they have major drawbacks in the long term. Indeed, they eliminate beneficial bacteria which are useful for the host and promote the raising of antibiotic resistance in beneficial, commensal but also in pathogenic bacterial strains. Numerous publications highlight the importance that plays the diversified microbial community colonizing fish (i.e., microbiota) in the development, health and ultimately survival of their host. This review targets the current knowledge on the bidirectional communication between the microbiota and the fish immune system during fish development. It explores the extent of this mutualistic relationship: on one hand, the effect that microbes exert on the immune system ontogeny of fishes, and on the other hand, the impact of critical steps in immune system development on the microbial recruitment and succession throughout their life. We will first describe the immune system and its ontogeny and gene expression steps in the immune system development of fishes. Secondly, the plurality of the microbiotas (depending on host organism, organ, and development stage) will be reviewed. Then, a description of the constant interactions between microbiota and immune system throughout the fish’s life stages will be discussed. Healthy microbiotas allow immune system maturation and modulation of inflammation, both of which contribute to immune homeostasis. Thus, immune equilibrium is closely linked to microbiota stability and to the stages of microbial community succession during the host development. We will provide examples from several fish species and describe more extensively the mechanisms occurring in zebrafish model because immune system ontogeny is much more finely described for this species, thanks to the many existing zebrafish mutants which allow more precise investigations. We will conclude on how the conceptual framework associated to the research on the immune system will benefit from considering the relations between microbiota and immune system maturation. More precisely, the development of active tolerance of the microbiota from the earliest stages of life enables the sustainable establishment of a complex healthy microbial community in the adult host. Establishing a balanced host-microbiota interaction avoids triggering deleterious inflammation, and maintains immunological and microbiological homeostasis.

Aquaculture is rapidly becoming one of the pivotal sectors in the farming economy, driven by the increasing demand for high-quality animal protein at an affordable cost, especially with the escalating human population. However, the expansion of high-density fish populations also brings forth a challenge—the rapid transmission and spread of infectious disease agents among them. To combat this, vaccination is emerging as a reliable and standardized method for providing immunity against viral and bacterial outbreaks. The ideal vaccine is expected to be safe, effective, economical, and easily administered. The fish vaccination industry continually publishes new information on fish immunology and vaccinology, contributing to the improvement in vaccine formulation and efficacy. This review aims to offer insights into the current status of bacterial, viral, and parasitic diseases, discuss existing vaccinations, and address potential industry-threatening diseases like infectious edwardsiellosis, motile aeromonas septicemia (MAS), Tilapia Lake Virus (TiLV) disease, infectious salmon anemia (ISA), vibriosis, and white spot disease. Technological advancements have played a crucial role in enhancing our understanding of fish immunological mechanisms, leading to improved vaccine administration and the development of recombinant live attenuated, subunit, DNA, and RNA vaccines. However, challenges such as oral tolerance, vaccine degradation, and stressful environments persist, impacting vaccine efficacy. Addressing these challenges and gaining a deeper understanding of the fish immune system and host–pathogen interactions will be pivotal for future improvements, contributing to the sustainability of aquaculture and enhancing global food security.

Comparative animal models generate fundamental scientificknowledgeof immune responses. However, these studies typically are conducted in mammals because of their biochemical and physiological similarity to humans. Presently, there has been an interest in using teleost fish models to study intestinal immunology, particularly intestinal mucosa immune response. Instead of targeting the pathogen itself, a preferred approach for managing fish health is through nutrient supplementation, as it is noninvasive and less labor intensive than vaccine administrations while still modulating immune properties. Amino acids (AAs) regulate metabolic processes, oxidant-antioxidant balance, and physiological requirements to improve immune response. Thus, nutritionists can develop sustainable aquafeeds through AA supplementation to promote specific immune responses, including the intestinal mucosa immune system. We propose the use of dietary supplementation with functional AAs to improve immune response by discussing teleost fish immunology within the intestine and explore how oxidative burst is used as an immune defense mechanism. We evaluate immune components and immune responses in the intestine that use oxidant-antioxidant balance through potential selection of AAs and their metabolites to improve mucosal immune capacity and gut integrity. AAs are effective modulators of teleost gut immunity through oxidant-antioxidant balance. To incorporate nutrition as an immunoregulatory means in teleost, we must obtain more tools including genomic, proteomic, nutrition, immunology, and macrobiotic and metabonomic analyses, so that future studies can provide a more holistic understanding of the mucosal immune system in fish. [ABSTRACT FROM AUTHOR]

Aquaculture is a growing industry worldwide, but it faces challenges related to animal health. These challenges include infections by parasites, bacteria, and viral pathogens. These harmful pathogens have devastating effects on the industry, despite efforts to control them through vaccination and antimicrobial treatments. Unfortunately, these measures have proven insufficient to address the sanitary problems, resulting in greater environmental impact due to the excessive use of antimicrobials. In recent years, probiotics have emerged as a promising solution to enhance the performance of the immune system against parasitic, bacterial, and viral pathogens in various species, including mammals, birds, and fish. Some probiotics have been genetically engineered to express and deliver immunomodulatory molecules. These promote selective therapeutic effects and specific immunization against specific pathogens. This review aims to summarize recent research on the use of probiotics in fish aquaculture, with a particular emphasis on genetically modified probiotics. In particular, we focus on the advantages of using these microorganisms and highlight the main barriers hindering their widespread application in the aquaculture industry.

Simple Summary: Protecting the welfare of animals and the 3Rs rule are very relevance, and for this reason cell culture is an important tool. In fish it has importance in several fields such as virology, toxicology, pathology and immunology. The objective was to carry out a primary culture of the head kidneys of Atlantic salmon (Salmo salar), Pacific salmon (Oncorhynchus kisutch) and rainbow trout (Oncorhynchus mykiss), and to characterize how they respond to bacterial and viral stimuli by analyzing molecules that participate in the innate and adaptive immune response. The primary cell cultures of the head kidney (HK) from the three salmonids studied were cultured and exposed to two substances that mimic molecular patterns of different pathogens, i.e., Lipopolysaccharide (LPS) and Polyinosinic: polycytidylic acid (POLY I:C). The HK primary cell cultures from the three species grown in vitro responded differently to POLY I:C and LPS. This is the first study to demonstrate and characterize the expression of immune genes in head kidney primary cell cultures isolated from three salmonid species. It also indicates their potential role in developing immune responses as defense response agents and targets of immunoregulatory factors. Fish cell culture is a common in vitro tool for studies in different fields such as virology, toxicology, pathology and immunology of fish. Fish cell cultures are a promising help to study how to diagnose and control relevant viral and intracellular bacterial infections in aquaculture. They can also be used for developing vaccines and immunostimulants, especially with the ethical demand aiming to reduce and replace the number of fish used in research. This study aimed to isolate head kidney primary cell cultures from three Chilean salmonids: Salmo salar, Oncorhynchus kisutch, and Oncorhynchus mykiss, and characterize the response to bacterial and viral stimuli by evaluating various markers of the innate and adaptive immune response. Specifically, the primary cell cultures of the head kidney from the three salmonids studied were cultured and exposed to two substances that mimic molecular patterns of different pathogens, i.e., Lipopolysaccharide (LPS) (bacterial) and Polyinosinic: polycytidylic acid (POLY I:C). Subsequently, we determined the mRNA expression profiles of the TLR-1, TLR-8, IgM, TLR-5, and MHC II genes. Head kidney primary cell cultures from the three species grown in vitro responded differently to POLY I:C and LPS. This is the first study to demonstrate and characterize the expression of immune genes in head kidney primary cell culture isolated from three salmonid species. It also indicates their potential role in developing immune responses as defense response agents and targets of immunoregulatory factors. [ABSTRACT FROM AUTHOR]

Further studies should focus not only on the fish immune response but also on the pathogen strain, going deeper into the pathogenesis and depicting the pathogen or fish determinants for susceptibility/resistance. In addition, lamprey BCAP protein levels, and its tyrosine kinase activity, were increased in peripheral blood lymphocytes, gills, and supraneural myeloid bodies upon bacterial infection as well as via lipopolysaccharide (LPS) stimulation, but not phytohemagglutinin (PHA), thus pointing to a role in the B-cell/LPS-mediated immune response [[4]]. Fish is the first group of vertebrates to appear during animal evolution. [Extracted from the article]

Fingerlings (0.23 g) and juveniles (267.04 g) of African catfish (Clarias gariepinus) were reared for 32 days under experimental aquarium conditions and were exposed to either 0.75 mg/L or 3.0 mg/L diethylenetriaminepentaacetic acid-iron(II) (Fe-DTPA) and 3.0 mg/L or 12.0 mg/L Fe-DTPA in the water, respectively. These treatment groups were compared to a control group without additional Fe-DTPA. The growth, mortality, ethological indicators (activity, agonistic interactions, air-breathing), leukocyte distribution, histopathological changes in liver and gills, and genetic biomarkers were evaluated for each group. While the growth, mortality, and behavior were not significantly different between the groups, the lymphocyte count in the fish's blood increased significantly in all groups during the course of the experiment, but independently from the treatments. A similar trend (p > 0.05) was observed in monocytes. The number of granulocytes decreased significantly, but independently from the treatments. These changes indicated the possibility of an ongoing immune response in the fish from all treatments that might be caused by the increasing aggressive behavior of the fish. However, the Fe-DTPA treatments did not cause a notable suppression or enhancement of the immune reactions. Fe3+ accumulations in liver tissues were detected at the tested concentrations, and further changes occurred in the cells of the gills. Gene-expression biochips were used to simultaneously quantify the transcript levels of 34 genes associated with iron metabolism and stress physiology in head kidney samples. The obtained gene-expression profiles did not reveal any significant differences across either the different treatments or the time points. The results indicate that Fe-DTPA supplementation in the tested concentrations can be considered relatively harmless for the health and welfare of African catfish. [ABSTRACT FROM AUTHOR]

Cuttlefish are sensitive to the breeding environment, and the low-salinity environment significantly impacts their growth and immunity. So far, it is difficult to breed this species artificially. This study was conducted in Sepia lycidas. And the aim was to investigate the differences in protein phosphorylation in the intestine of S. lycidas under different salinity conditions. Firstly, 999 phosphoproteins (specific peptide = 1), 1928 phosphopeptides, and 2727 phosphorylation sites were identified. Among them were 284 down-regulated expression phosphorylation sites (corresponding to 115 phosphoproteins) and 674 up-regulated expression phosphorylation sites (corresponding to 408 phosphoproteins) in the intestine under a low salinity environment compared with that under a natural salinity environment. Next, GO analysis found that more phosphoproteins corresponding to differentially expressed phosphorylation sites were related to anatomical structure development, multicellular organism development, regulation of the cellular process, etc. The molecular functions of these proteins mainly contain protein binding, transferase activity, catalytic activity, and heterocyclic compound binding. And they are mainly involved in the cellular components of intracellular anatomical structure, organelle, and cytoplasm. KEGG enrichment analysis of the differential phosphoproteins suggested that many significantly enriched pathways were related to the phosphatidylinositol signaling system, cell junction (adherens junction and tight junction), and inositol phosphate metabolism. Finally, changes in environmental salinity can affect the intestinal structure, metabolism, and immune homeostasis of S. lycidas. [ABSTRACT FROM AUTHOR]

Complement (C) is a serum protein with immunity-related functions and enzymatic activities. It can induce inflammatory responses and antibody formation following activation by substances such as pathogens. Moreover, it is a crucial molecule in the congenital immune defense system. Complement manifests earlier than immunoglobulin in the evolutionary process of fish's immune system. Therefore, the complement system of fish is vital for congenital and acquired immunities. A complement system is a polymolecule system comprising more than 30 soluble proteins, membrane-bound proteins, and complement receptors. It can be activated through three pathways for immunoregulation, the clearance of the immune complex, etc. The liver primarily produces the fish complement C3, which is a significant component of the complement system of fishes. C3 is the hub of three activation pathways. Research works concerning the structure, generation process, expression, and functions of C3 in fishes are reviewed in this study. [ABSTRACT FROM AUTHOR]

Galectin-4 belongs to the galactoside-binding protein family and is a type of tandem repeat galectin. Despite previous studies indicating its importance in fish immunology, a comprehensive investigation is necessary to fully understand its role in immunomodulatory functions and cellular dynamics. Therefore, this study aimed to explore the immunomodulatory functions of galectin-4 with a particular focus on its antimicrobial and cellular proliferative properties. The open reading frame of PhGal4 spans 1092 base pairs and encodes a soluble protein of 363 amino acids with a theoretical isoelectric point (IEP) of 6.39 and a molecular weight of 39.411 kDa. Spatial expression analysis under normal physiological conditions revealed ubiquitous expression of PhGal4 across all examined tissues, with the highest level observed in intestinal tissue. Upon stimulation with poly I:C, LPS, and L. garvieae , a significant increase (p < 0.05) in PhGal4 expression was observed in both blood and spleen tissues. Subsequent subcellular localization assay demonstrated that PhGal4 was predominantly localized in the cytoplasm. The recombinant PhGal4 (rPhGal4) exhibited specific binding capabilities to pathogen-associated molecular patterns (PAMPs), including LPS and peptidoglycan, but not poly I:C. The rPhGal4 negatively affected the bacterial growth kinetics. Additionally, rPhGal4 demonstrated complete hemagglutination of fish erythrocytes, which could be inhibited by the presence of D-galactose and α-lactose. The overexpression of PhGal4 in FHM epithelial cells demonstrated a significant suppression of viral replication during VHSV infection. Furthermore, the in vitro scratch assay and WST-1 assay demonstrated a wound healing effect of PhGal4 overexpression in FHM cells, potentially achieved through the promotion of cell proliferation by activating genes involved in cell cycle regulation. In conclusion, the responsive expression to immune stimuli, antimicrobial properties, and cell proliferation promotion of PhGal4 suggest that it plays a crucial role in immunomodulation and cellular dynamics of red-lip mullet. The findings in this study shed light on the multifunctional nature of galectin-4 in teleost fish. • Exposure to poly I:C, LPS, and L. garviae significantly increased PhGal4 expression (p < 0.05). • The recombinant PhGal4 (rPhGal4) demonstrated specific binding to LPS, and peptidoglycan with no affinity for poly I:C. • The rPhGal4 negatively affects bacterial growth kinetics and induces erythrocyte haemagglutination. • Overexpression of PhGal4 in fish cells significantly suppressed VHSV virus replication. • Scratch and WST-1 assays demonstrated in vitro wound-healing effects attributed to PhGal4 overexpression. [ABSTRACT FROM AUTHOR]

In recent years, studies on circadian control in immunity have been actively conducted in mammals, but little is known about circadian rhythms in the field of fish immunology. In this study, we aimed to analyse the regulation of the diel oscillation of inflammatory cytokine interleukin-1β (il1b) gene expression by core components of the circadian clock in Japanese medaka (Oryzias latipes). The expression of il1b and clock genes (bmal1 and clock1) in medaka acclimated to a 12:12 light (L): dark (D) cycle showed diel rhythm. Additionally, higher expression of il1b was detected in medaka embryo cells (OLHdrR-e3) overexpressing bmal1 and clock1. A significant decrease in il1b expression was observed in OLHdrR-e3 cells after bmal1 knockdown using morpholino oligos. These changes may be mediated by transcriptional regulation via clock proteins, which target the E-box sequence in the cis -element of il1b as identified using luciferase reporter assays. Moreover, LPS stimulation and pathogenic bacterial infection at different zeitgeber time (ZT) under LD12:12 conditions affected the degree of il1b expression, which showed high and low responsiveness to both immuno-stimulations at ZT2 and ZT14, respectively. These results suggested that fish IL-1β exhibited diel oscillation regulated by clock proteins, and its responsiveness to immune-stimulation depends on the time of day. • Medaka il1b is expressed in a circadian rhythm. • Medaka clock genes bmal1 and clock1 regulate il1b expression. • Immuno-stimulation at different time point impacts il1b expression magnitude. [ABSTRACT FROM AUTHOR]

Immunoglobulin M (IgM) shows potential as a significant immunological marker in Asian seabass (Lates calcarifer), accentuating the importance of developing specific monoclonal antibodies (mAbs) for immunological studies. In this study, we investigated the antigenicity of the IgM heavy chain (IgMH), particularly the Cμ3 region of IgMH (IgMHCμ3), and synthesized a peptide for anti-IgMHCμ3 mAb production. The synthesized peptide was used to generate a specific mAb in rabbits. The produced mAb demonstrated high specificity and affinity for Asian seabass IgMH, as confirmed through indirect ELISA, Western blot analysis, indirect immunofluorescence assay (IIFAT) and flow cytometry analysis. In addition, an indirect ELISA was developed and optimized to measure anti- Flavobacterium covae and anti- Streptococcus iniae antibody titers in Asian seabass serum. The monoclonal antibody (mAb) was subsequently used to assess the health status of Asian seabass post-vaccination and challenge with these pathogens, demonstrating its potential as a valuable tool for immunological studies and health assessments in Asian seabass. Vaccination and postchallenge fish exhibited a pronounced increase in specific antibodies and total serum IgM and IgM+ cell populations. Thus, this study establishes a foundational platform for using the anti-IgMHCμ3 mAb as an essential tool for evaluating and understanding the immune responses and health status of Asian seabass, especially in the context of bacterial infections and vaccinations, and paves the way for more studies in fish immunology. • Specific monoclonal antibody to Asian seabass IgM heavy chain (mAb-IgM) was successfully developed. • The specificity and affinity of mAb-IgM were effectively confirmed through ELISA and Western blot analysis. • Indirect immunofluorescence assay (IIFA) and flow cytometry demonstrated IgM+ B cell population in Asian seabass. • The mAb-IgM effectively demonstrated its efficacy in monitoring the health status of fish during vaccination. [ABSTRACT FROM AUTHOR]

Pompano fishes have been widely farmed worldwide. As a representative commercial marine species of the Carangidae family, the golden pompano (Trachinotus blochii) has gained significant popularity in China and worldwide. However, because of rapid growth and high-density aquaculture, the golden pompano has become seriously threatened by various diseases. Cell lines are the most cost-effective resource for in vitro studies and are widely used for physiological and pathological research owing to their accessibility and convenience. In this study, we established a novel immortal cell line, GPF (Golden pompano fin cells). GPF has been passaged over 69 generations for 10 months. The morphology, adhesion and extension processes of GPF were evaluated using light and electron microscopy. GPF cells were passaged every 3 days with L-15 containing 20 % fetal bovine serum (FBS) at 1:3. The optimum conditions for GPF growth were 28 °C and a 20 % FBS concentration. DNA sequencing of 18S rRNA and mitochondrial 16S rRNA confirmed that GPF was derived from the golden pompano. Chromosomal analysis revealed that the number pattern of GPF was 48 chromosomes. Transfection experiments demonstrated that GPF could be utilized to express foreign genes. Furthermore, heavy metals (Cd, Cu, and Fe) exhibited dose-dependent cytotoxicity against GPF. After polyinosinic-polycytidylic acid (poly I:C) treatment, transcription of the retinoic acid-inducible gene I-like receptor (RLR) pathway genes, including mda5 , mita , tbk1 , irf3 , and irf7 increased, inducing the expression of interferon (IFN) and anti-viral proteins in GPF cells. In addition, lipopolysaccharide (LPS) stimulation up-regulated the expression of inflammation-related factors, including myd88 , irak1 , nfκb , il1β , il6 , and cxcl10 expression. To the best of our knowledge, this is the first study on the immune response signaling pathways of the golden pompano using an established fin cell line. In this study, we describe a preliminary investigation of the GPF cell line immune response to poly I:C and LPS, and provide a more rapid and efficient experimental material for research on marine fish immunology. • GPF was established and became a stable fin cell line of Trachinotus blochii. • GPF can be used to assess the cytotoxicity of heavy metals. • GPF can be utilized to express foreign genes with 32 % transfection efficiency. • GPF's immune response to LPS and poly I: C challenge proved it can be used for in vitro immunology study. [ABSTRACT FROM AUTHOR]

A permanent epithelial‐like cell line, named GrB, was established from brain tissues of the rare minnow (Gobiocypris rarus). GrB cells grow well at temperatures between 22℃ and 27℃ in L‐15 medium supplemented with 10% FBS. Chromosome analysis revealed that GrB cells possessed a diploid chromosome number of 2n = 50 at passage 50, consistent with the number of chromosomes reported for G. rarus. Partial amplification and sequence analysis of the cytochrome oxidase subunit I (COI) confirmed that GrB cells are originated from G. rarus. The cell lines also successfully expressed green fluorescence protein from plasmid pEGFP‐N1 and which makes them suitable for transfection studies. A cytolytic cytopathic effect was observed in the cells after infection with tilapia lake virus 2017A (TiLV‐2017A). A large number of virus particles were detected by electron microscopy. Immunofluorescence and virus titration assays indicated that TiLV‐2017A titres reached 105.67 TCID50/ml at 7 days post‐infection (dpi). Healthy adult rare minnows were challenged with virus obtained from these cells showed that they can be infected by TiLV‐2017A, which causes low mortality but clinical signs. The GrB cell line may represent a valuable model as basics for fish virology and fish immunology. [ABSTRACT FROM AUTHOR]

Piscirickettsiosis (SRS) has been the most important infectious disease in Chilean salmon farming since the 1980s. It was one of the first to be described, and to date, it continues to be the main infectious cause of mortality. How can we better understand the epidemiological situation of SRS? The catch-all answer is that the Chilean salmon farming industry must fight year after year against a multifactorial disease, and apparently only the environment in Chile seems to favor the presence and persistence of Piscirickettsia salmonis. This is a fastidious, facultative intracellular bacterium that replicates in the host's own immune cells and antigen-presenting cells and evades the adaptive cell-mediated immune response, which is why the existing vaccines are not effective in controlling it. Therefore, the Chilean salmon farming industry uses a lot of antibiotics—to control SRS—because otherwise, fish health and welfare would be significantly impaired, and a significantly higher volume of biomass would be lost per year. How can the ever-present risk of negative consequences of antibiotic use in salmon farming be balanced with the productive and economic viability of an animal production industry, as well as with the care of the aquatic environment and public health and with the sustainability of the industry? The answer that is easy, but no less true, is that we must know the enemy and how it interacts with its host. Much knowledge has been generated using this line of inquiry, however it remains insufficient. Considering the state-of-the-art summarized in this review, it can be stated that, from the point of view of fish immunology and vaccinology, we are quite far from reaching an effective and long-term solution for the control of SRS. For this reason, the aim of this critical review is to comprehensively discuss the current knowledge on the interaction between the bacteria and the host to promote the generation of more and better measures for the prevention and control of SRS. [ABSTRACT FROM AUTHOR]

The immune system is a complex and sophisticated biological system, spanning multiple levels of complexity, from the molecular level to that of tissue. Our current understanding of its function and complexity, of the heterogeneity of leukocytes, is a result of decades of concentrated efforts to delineate cellular markers using conventional methods of antibody screening and antigen identification. In mammalian models, this led to in-depth understanding of individual leukocyte subsets, their phenotypes, and their roles in health and disease. The field was further propelled forward by the development of single-cell (sc) RNA-seq technologies, offering an even broader and more integrated view of how cells work together to generate a particular response. Consequently, the adoption of scRNA-seq revealed the unexpected plasticity and heterogeneity of leukocyte populations and shifted several long-standing paradigms of immunology. This review article highlights the unprecedented opportunities offered by scRNA-seq technology to unveil the individual contributions of leukocyte subsets and their crosstalk in generating the overall immune responses in bony fishes. Single-cell transcriptomics allow identifying unseen relationships, and formulating novel hypotheses tailored for teleost species, without the need to rely on the limited number of fish-specific antibodies and pre-selected markers. Several recent studies on single-cell transcriptomes of fish have already identified previously unnoticed expression signatures and provided astonishing insights into the diversity of teleost leukocytes and the evolution of vertebrate immunity. Without a doubt, scRNA-seq in tandem with bioinformatics tools and state-of-the-art methods, will facilitate studying the teleost immune system by not only defining key markers, but also teaching us about lymphoid tissue organization, development/differentiation, cell-cell interactions, antigen receptor repertoires, states of health and disease, all across time and space in fishes. These advances will invite more researchers to develop the tools necessary to explore the immunology of fishes, which remain non-conventional animal models from which we have much to learn. [ABSTRACT FROM AUTHOR]

Abstract The immunomodulatory and growth promoter effects of brown propolis ethanolic extract (PEE) were determined in pacu. Fish (28.4±0.4 g) were randomly distributed into 12 polyethylene circular tanks (250 L, 30 fish per tank) and fed for 60 days with a commercial diet (32% crude protein) supplemented with 0.0, 1.5, 3.0 and 4.5% (v/w) of PEE in a totally randomized experimental design (n=3). Fish organic defense cells numbers such as thrombocytes and neutrophils increased (p0.05) by treatments. Moreover, dietary PEE decreased (p

Akin to their mammalian counterparts, teleost fish possess a complex assortment of highly specialized immune cells that are capable of unleashing potent innate immune responses to eradicate or mitigate incoming pathogens, and also differentiate into memory lymphocytes to provide long-term protection. Investigations into specific roles and functions of fish immune cells depend on the precise separation of each cell type. Commonly used techniques, for example, density gradient centrifugation, rely on immune cells to have differing sizes or densities and thus fail to separate between similar cell types (e.g. T and B lymphocytes). Furthermore, a continuously growing database of teleost genomic information has revealed an inventory of cellular markers, indicating the possible presence of immune cell subsets in teleost fish. This further complicates the interpretation of results if subsets of immune cells are not properly separated. Consequently, monoclonal antibodies (mAbs) against specific cellular markers are required to precisely identify and separate novel subsets of immune cells in fish. In the field of fish immunology, mAbs are largely generated using the hybridoma technology, resulting in the development of mAbs against specific cellular markers in different fish species. Nevertheless, this technology suffers from being labour-intensive, time-consuming and most importantly, the inevitable loss of diversities of antibodies during the fusion of antibody-expressing B lymphocytes and myeloma cells. In light of this, the focus of this review is to discuss the potential applications of fluorescence-activated cell sorting and droplet-based microfluidics, two emerging technologies capable of screening and identifying antigen-specific B lymphocytes in a high-throughput manner, in promoting the development of valuable reagents for fish immunology studies. Our main goal is to encourage the incorporation of alternative technologies into the field of fish immunology to promote the production of specific antibodies in a high-throughput and cost-effective way, which could better allow for the precise separation of fish immune cells and also facilitate the identification of novel immune cell subsets in teleost fish. [ABSTRACT FROM AUTHOR]

The mall heterodimer partner (SHP) plays an important regulatory role in mammal inflammation. The main objective of this study was to investigate the response of SHP to inflammatory stimulation and its underlying mechanism. The shp gene from large yellow croakers, was cloned, and this gene is mainly expressed in the liver and intestine. Lipopolysaccharide (LPS) stimulation induced the mRNA expression and protein level of SHP in macrophages of large yellow croakers. Overexpression of SHP significantly decreased mRNA expression of tnfα , il-1β , il-6 and cox2 induced by LPS treatment in macrophages. LPS stimulation increased the phosphorylation level of Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) in macrophages. AMPK inhibitor treatment significantly decreased the expression of SHP induced by LPS while AMPK activator significantly increased the expression of SHP. The nuclear factor-erythroid 2-related factor 2 (NRF2) increased the promoter activity of SHP in large yellow croakers and the level of nuclear NRF2 was increased by LPS stimulation and AMPK activation. NRF2 inhibitor treatment significantly decreased mRNA expression of shp induced by LPS and AMPK activator. In conclusion, LPS can induce SHP expression by activating the AMPK-NRF2 pathway while SHP could negatively regulate LPS-induced inflammation in large yellow croakers. This study may be benefit to the development of immunology of marine fish and provide new ideas for inflammation-related diseases. [ABSTRACT FROM AUTHOR]

In jawed vertebrates, two major T cell populations have been characterized. They are defined as α/β or γ/δ T cells, based on the expressed T cell receptor. Salmonids (family Salmonidae) include two key teleost species for aquaculture, rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar) which constitute important models for fish immunology and important targets for vaccine development. The growing interest to decipher the dynamics of adaptive immune responses against pathogens or vaccines has resulted in recent efforts to sequence the immunoglobulin (IG) or antibodies and T cell receptor (TR) repertoire in these species. In this context, establishing a comprehensive and coherent locus annotation is the fundamental basis for the analysis of high-throughput repertoire sequencing data. We therefore decided to revisit the description and annotation of TRA/TRD locus in Atlantic salmon and two strains of rainbow trout (Swanson and Arlee) using the now available high-quality genome assemblies. Phylogenetic analysis of functional TRA/TRD V genes from these three genomes led to the definition of 25 subgroups shared by both species, some with particular feature. A total of 128 TRAJ genes were identified in Salmo , the majority with a close counterpart in Oncorhynchus. Analysis of expressed TRA repertoire indicates that most TRAV gene subgroups are expressed at mucosal and systemic level. The present work on TRA/TRD locus annotation along with the analysis of TRA repertoire sequencing data show the feasibility and advantages of a common salmonid TRA/TRD nomenclature that allows an accurate annotation and analysis of high-throughput sequencing results, across salmonid T cell subsets. [ABSTRACT FROM AUTHOR]

This study evaluated the dietary supplementation of ginger Zingiber of ficinale essential oil for the Neotropical catfish Pseudoplatystoma reticulatum, its effects on fish hematology, immunology, the response of these variables to induction of stress (exposition to air for 3 min), and a bacterial challenge with Aeromonas hydrophila, and the effects on liver histomorphometry. Three levels of the ginger essential oil were evaluated (0.5, 1.0 and 1.5%) in addition to a control group (0%) in a feeding trial for 65 days in triplicate. Fish hematology and immunology were assessed at five different moments: after the feeding trial (0), after the stress induction (stress), and three points after the bacterial challenge (3, 6 and 24 h post-challenge). Fish fed the ginger essential oil supplemented diets did not exhibit significant differences between the hematocrit at the 0-sample point and the 24 h post-challenge point (P = 0.05), while fish fed the control diet presented significantly lower values for the hematocrit when comparing those same two moments (P < 0.05). The thrombocytes count for fish fed the 0.5% essential oil supplemented diet was significantly higher than all other groups after the feeding trial (P < 0.05), and their total leukocytes count after the stress induction was also significantly higher than the other treatments (P < 0.05). Although the results mentioned above indicate that the ginger essential oil had positive health effects on the fish, no significant differences in survival after the challenge with A. hydrophila were observed (P = 0.05). Lastly, histomorphometry suggests that the essential oil did not negatively impact fish hepatocytes. [ABSTRACT FROM AUTHOR]

The aquaculture industry's rapid growth to meet commercial demand can trigger an outbreak of infectious diseases due to high-density farming. Antibiotic overuse and misuse in fish farming and its global health consequences have led to searching for more natural alternatives such as medicinal plants. In this sense, garlic (Allium sativum) has different bioactive compounds with biological properties for animal health. Among them are the ajoene, alliin, and allicin, which confer biological properties such as growth promotion, antimicrobial, antiviral, antioxidant, and antiparasitic. Ways to use garlic in aquaculture include oil, fresh mash, aqueous extract, and garlic powder. The powder presentation is the most used in aquaculture; it is generally applied by oral administration, adding to the feed, and the dose used ranges from 0.05 to 40 g/kg of feed. Garlic has been used in the aquaculture of different species such as rainbow trout (Oncorhynchus mykiss), spotted grouper (Epinephelus coioides), catfish (Clarias gariepinus), tilapia (Oreochromis niloticus), guppy fish (Poecilia reticulata), goldfish (Carassius auratus), and barramundi (Lates calcarifer). In addition to its properties, garlic's usage became popular, thanks to its low cost, easy incorporation into food, and little environmental impact. Therefore, its application can be an effective solution to combat diseases, improve organisms' health using natural supplies, and as an alternative to antibiotics. This review reports and discusses plant-derived products' beneficial properties, emphasizing garlic and its usages in fish aquaculture. [ABSTRACT FROM AUTHOR]

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Antimicrobial peptides (AMPs) are an essential part of the vertebrate innate immune system. Piscidins are a family of AMPs specific in fish. In our previous investigation, we identified four paralogous genes of piscidins in the orange-spotted grouper (Epinephelus coicodes), which exhibited distinct activities against bacteria, fungi, and parasitic ciliated protozoa. Piscidins demonstrated their capability to modulate the expression of diverse immune-related genes; however, their precise immunoregulatory functions remain largely unexplored. In this study, we examined the immunomodulatory properties of putative mature peptides derived from four E. coicodes piscidins (ecPis1S, ecPis2S, ecPis3S, and ecPis4S) in head kidney leukocytes (HKLs) or monocytes/macrophages (MO/MΦ)-like cells isolated from E. coicodes. Our data demonstrate that E. coicodes piscidins exhibit immunomodulatory activities supported by multiple lines of evidence. Firstly, all four piscidins displayed chemotactic activities towards HKLs, with the most potent chemotactic activity observed in ecPis2S. Secondly, stimulation with E. coicodes piscidins enhanced respiratory burst and phagocytic activity in MO/MФ-like cells, with ecPis3S showing the highest efficacy in increasing phagocytosis of MO/MΦ-like cells. Thirdly, mRNA expression levels of chemokine receptors, Toll-like receptors, T cell receptors, and proinflammatory cytokines were modulated to varying extents by the four piscidins in E. coicodes HKLs. Overall, our findings indicate that the immunological activities of these four paralogous piscidins from E. coicodes are exhibited in a paralog-specific and concentration-dependent manner, highlighting their distinct and versatile immunomodulatory properties. This study makes a significant contribution to the field of fish AMPs immunology by elucidating the novel mechanisms through which members of the piscidin family exert their immunomodulatory effects. Moreover, it provides valuable insights for further exploration of fish immunomodulating agents. • E. coicodes paralogous piscidins show the versatile immunomodulatory activities. • E. coicodes piscidin 2 exhibits the strongest chemotactic activity for leucocytes. • E. coicodes piscidin 3 shows the strongest activity to enhance the phagocytosis of MO/MΦ. • Piscidins regulate expression of immune-related genes widely and in paralog-specific manner. [ABSTRACT FROM AUTHOR]

Granulins are conserved in nearly all metazoans, with an intriguing loss in insects. These pleiotropic peptides are involved in numerous physiological and pathological processes yet have been overwhelmingly examined in mammalian systems. While work in other animal models has been informative, a richer understanding of the proteins should be obtained by integrating knowledge from all available contexts. The main bodies of work described here include 1) the structure-function relationships of progranulin and its cleavage products, 2) the role of expanded granulin gene families and different isoforms in fish immunology, 3) the release of granulin peptides to promote host angiogenesis by parasitic worms, 4) a diversity of molluscan uses for granulins, including immune activation in intermediate hosts to trematodes, 5) knowledge gained on lysosomal functions from C. elegans and the stress-related activities of granulins. We provide an overview of functional reports across the Metazoa to inform much-needed future research. • Granulins are conserved and pleiotropic, yet the evolution of functions is unclear. • Functional patterns and novelties across animal granulins are detailed. • The loss of granulins in some insects is addressed. • Granulin can be released from parasites and hosts simultaneously. • Future directions for each type of organism are suggested throughout. [ABSTRACT FROM AUTHOR]

In this study, we investigated a new application of bubble-eye goldfish (commercially available strain with large bubble-shaped eye sacs) for immunological studies in fishes utilizing the technical advantage of examining immune cells in the eye sac fluid ex vivo without sacrificing animals. As known in many aquatic species, the common goldfish strain showed an increased infection sensitivity at elevated temperature, which we demonstrate may be due to an immune impairment using the bubble-eye goldfish model. Injection of heat-killed bacterial cells into the eye sac resulted in an inflammatory symptom (surface reddening) and increased gene expression of pro-inflammatory cytokines observed in vivo, and elevated rearing temperature suppressed the induction of pro-inflammatory gene expressions. We further conducted ex vivo experiments using the immune cells harvested from the eye sac and found that the induced expression of pro-inflammatory cytokines was suppressed when we increased the temperature of ex vivo culture, suggesting that the temperature response of the eye-sac immune cells is a cell autonomous function. These results indicate that the bubble-eye goldfish is a suitable model for ex vivo investigation of fish immune cells and that the temperature-induced infection susceptibility in the goldfish may be due to functional impairments of immune cells. [ABSTRACT FROM AUTHOR]

Nile tilapia (Oreochromis niloticus) is a freshwater fish, which is extensively cultivated worldwide and constitutes one of the model species for the study of fish immunology. Monoclonal antibodies are very advantageous molecular tools for studying teleost immune system. Specifically, monoclonal antibodies that react with immunoglobulins are used successfully in the study of the humoral immune response of several fish species. In the present study, we produced and characterized a monoclonal antibody against tilapia IgM heavy chain using a peptide-based strategy. The peptide sequence was selected from the surface-exposed region between CH3–CH4 domains. The specificity of the polyclonal serum and the hybridoma culture supernatant obtained by immunization with the peptide conjugated to keyhole limpet hemocyanin were evaluated by western blotting, both showing reactivity against tilapia serum IgM. The purified mAb was able to recognize secreted IgM by western blotting and ELISA and membrane IgM by flow cytometry. We also demonstrated that the antibody doesn't cross-react with a recombinant IgT fragment. This tool allowed us to study for the first time the stimulation of mucosal immunity after Pituitary Adenylate Cyclase Activating Polypeptide administration. Overall, the results demonstrated the utility of this mAb to characterize humoral immune response in O. niloticus. • MAb against Nile tilapia IgM using a peptide-based strategy was produced and characterized. • Nile tilapia IgM purified from serum was successfully identified by mass spectrometry analysis. • The produced mAb was specific for IgM and doesn't cross-react with a recombinant IgT fragment. • The prepared mAb is applicable for IgM detection and quantification by western blotting, ELISA and flow cytometry. • IgM and IgT concentrations increased in tilapia skin mucus after injection of synthetic C. gariepinus PACAP-38. [ABSTRACT FROM AUTHOR]