Two novel muramidases from skin mucosa of rainbow trout (Oncorhynchus mykiss)

Assessing the impacts of in-feed probiotic on the growth performance and health condition of pangasius (Pangasianodon hypophthalmus) in a farm trial

The effects of in-feed probiotics on growth performance, haematological parameters, gut microbial content, and morphological changes to pangasius fish were assessed. The trial had three phases, i.e., larvae to fry (20 days), fry to fingerlings (45 days), and grow-out phase from fingerlings to marketing (90 days). The stocking densities were 400 m^-3, 200 m^-3, and 12 m^-3 for phases 1, 2, and 3, respectively. Phases 1 and 2 were conducted in hapas in the same pond, whereas phase 3 was performed in concrete tanks. The in-feed probiotic was administered at a rate of 0.2 g kg^-1 of feed three times per day in phases 1 and 2 only. In phase 3, in-feed probiotics was not applied to any groups. The treated group exhibited higher growth performances (p < 0.05) than the control in all three phases of experiment. The survival % in phase 1 and 2 were found significantly (p < 0.05) higher in treatment groups. This indicates that pangasius nurserers would benefit from using probiotics as a safeguard to increase fry survival to a greater extent. Two haematological parameters including red blood cells (RBC) and white blood cells (WBC) levels were found significantly (p < 0.05) higher in treated groups in phase 2 and 3, while glucose and hemoglobin level were found significantly (p < 0.05) higher in the treated groups during phases 2 and 3, respectively. The gut microbiota content was relatively higher in the treated groups in phase 2 and 3. Histological findings indicate that the use of probiotics during the nursing phases of pangasius induced a positive change in the intestinal morphological structures. The positive impacts of probiotics on the phase 3 confirmed an immediate and long-term growth performance and health of pangasius.

Extracellular vesicles from cod (Gadus morhua L.) mucus contain innate immune factors and deiminated protein cargo

Extracellular vesicles are released from cells and participate in cell communication via transfer of protein and genetic cargo derived from the parent cells. EVs play roles in normal physiology and immunity and are also linked to various pathological processes. Peptidylarginine deiminases (PADs) are phylogenetically conserved enzymes with physiological and pathophysiological roles. PADs cause post-translational protein deimination, resulting in structural and, in some cases, functional changes in target proteins and are also linked to EV biogenesis. This study describes for the first time EVs isolated from cod mucosa. Mucosal EVs were characterised by electron microscopy, nanoparticle tracking analysis and EV-specific surface markers. Cod mucosal EVs were found to carry PAD, complement component C3 and C-reactive proteins. C3 was found to be deiminated in both whole mucus and mucosal EVs, with some differences, and further 6 deiminated immune and cytoskeletal proteins were identified in EVs by LC-MS/MS analysis. As mucosal surfaces of teleost fish reflect human mucosal surfaces, these findings may provide useful insights into roles of EVs in mucosal immunity throughout phylogeny.

Post-translational protein deimination in cod (Gadus morhua L.) ontogeny novel roles in tissue remodelling and mucosal immune defences?

Peptidylarginine deiminases (PADs) are calcium dependent enzymes with physiological and pathophysiological roles conserved throughout phylogeny. PADs promote post-translational deimination of protein arginine to citrulline, altering the structure and function of target proteins. Deiminated proteins were detected in the early developmental stages of cod from 11 days post fertilisation to 70 days post hatching. Deiminated proteins were present in mucosal surfaces and in liver, pancreas, spleen, gut, muscle, brain and eye during early cod larval development. Deiminated protein targets identified in skin mucosa included nuclear histones; cytoskeletal proteins such as tubulin and beta-actin; metabolic and immune related proteins such as galectin, mannan-binding lectin, toll-like receptor, kininogen, Beta2-microglobulin, aldehyde dehydrogenase, bloodthirsty and preproapolipoprotein A-I. Deiminated histone H3, a marker for anti-pathogenic neutrophil extracellular traps, was particularly elevated in mucosal tissues in immunostimulated cod larvae. PAD-mediated protein deimination may facilitate protein moonlighting, allowing the same protein to exhibit a range of biological functions, in tissue remodelling and mucosal immune defences in teleost ontogeny.

Histological assessments of intestinal immuno-morphology of tiger grouper juvenile, Epinephelus fuscoguttatus

Histological assessments on the intestinal morphology and immunity of tiger grouper juveniles, Epinephelus fuscoguttatus help in determining the earliest age to start an oral vaccination. This study describes the morphological development of the intestinal immunity of tiger grouper of various ages. Clinically healthy tiger groupers were selected and divided into 4 groups of 20 fish per group. Groups 1, 2, 3 and 4 consisted of juveniles of 30, 60, 90 and 120 days old, respectively. The whole intestine was collected and divided into three regions, the anterior, mid and posterior intestine and fixed in 10% buffered formalin before slides were prepared for microscopic examinations. It was found that the histological structures of the anterior intestine were for absorption of nutrient from digested food particles. The significantly (p < 0.05) higher number and length of the intestinal villi and smaller gap between villi were observed in the anterior intestine, which were structures for absorption. Structures of the posterior intestine were for immunity especially the adaptive immunity with included significantly (p < 0.05) higher numbers of the lymphoid and goblet cells, and significantly (p < 0.05) thicker lamina propria, which were structures for immunity. The mid intestine was the transition structure that involved in both absorption and innate immunity. The results also revealed that leukocytes existed in the lamina propria of 30-days old tiger groupers, an indication that the immune system was present at that particular age.

Conventional and unconventional antimicrobials from fish, marine invertebrates and micro-algae

All eukaryotic organisms, single-celled or multi-cellular, produce a diverse array of natural anti-infective agents that, in addition to conventional antimicrobial peptides, also include proteins and other molecules often not regarded as part of the innate defences. Examples range from histones, fatty acids, and other structural components of cells to pigments and regulatory proteins. These probably represent very ancient defence factors that have been re-used in new ways during evolution. This review discusses the nature, biological role in host protection and potential biotechnological uses of some of these compounds, focusing on those from fish, marine invertebrates and marine micro-algae.

Complete amino acid sequence of three reptile lysozymes

To study the structure and function of reptile lysozymes, we have reported their purification, and in this study we have established the amino acid sequence of three egg white lysozymes in soft-shelled turtle eggs (SSTL A and SSTL B from Trionyx sinensis, ASTL from Amyda cartilaginea) by using the rapid peptide mapping method. The established amino acid sequence of SSTL A, SSTL B, and ASTL showed substitutions of 43, 42, and 44 residues respectively when compared with the HEWL (hen egg white lysozyme) sequence. In these reptile lysozymes, SSTL A had one substitution compared with SSTL B (Gly126Asp) and had an N-terminal extra Gly and 11 substitutions compared with ASTL. SSTL B had an N-terminal extra Gly and 10 residues different from ASTL. The sequence of SSTL B was identical to soft-shelled turtle lysozyme from STL (Trionyx sinensis japonicus). The Ile residue at position 93 of ASTL is the first report in all C-type lysozymes. Furthermore, amino acid substitutions (Phe34His, Arg45Tyr, Thr47Arg, and Arg114Tyr) were also found at subsites E and F when compared with HEWL. The time course using N-acetylglucosamine pentamer as a substrate exhibited a reduction of the rate constant of glycosidic cleavage and increase of binding free energy for subsites E and F, which proved the contribution for amino acids mentioned above for substrate binding at subsites E and F. Interestingly, the variable binding free energy values occurred on ASTL, may be contributed from substitutions at outside of subsites E and F.

Isolation and cDNA cloning of an antibacterial L-amino acid oxidase from the skin mucus of the great sculpin Myoxocephalus polyacanthocephalus

The skin mucus of the great sculpin Myoxocephalus polyacanthocephalus showed both antibacterial and L-amino acid oxidase (LAO) activities. Antibacterial LAOs were purified from the skin mucus of the M. polyacanthocephalus by column chromatography and named MPLAO1, MPLAO2, and MPLAO3, based on the order of elution by ion-exchange high performance liquid chromatography. cDNA cloning of MPLAO3 revealed that the full-length cDNAwas 2659 bp and encoded the signal peptide (Met1-Ala26) and the mature protein (Val28-Phe520). A homology search using the BLAST program revealed that MPLAO3 shared sequence identity with LAO family proteins, and had 74% identity with the antibacterial LAO from the skin mucus of the rockfish Sebastes schlegeli. MPLAO3 catalyzed the oxidation of only L-lysine with a Km of 0.16 mM. MPLAO3 exhibited potent antibacterial activity against both Gram-positive and Gramnegative bacteria, and was most active against Aeromonas salmonicida JCM7874 with a minimum inhibitory concentration of 0.02 microg/mL. The antibacterial activity was attributable to H2O2, because the activity was completely lost in the presence of catalase. The antibacterial LAOs may be involved in the innate immunity of the great sculpin M. polyacanthocephalus skin.

Modulation of the immune system of fish by their environment

The environment impacts on the physiology and psychology of animals in a wide variety of ways. If we can develop an understanding of how different environmental factors affect different processes we may be able to predict these changes and avoid or moderate deleterious events and the resultant changes in fish health and disease resistance. In this review, advances in the understanding of environmental impacts were identified in relation to specific areas of immune function. The trends, where they can be identified, showed that increases in light, temperature, salinity, oxygen, pH or particulates results in a general increase in immune function.

Purification, characterization and comparison of reptile lysozymes

Cation exchange column chromatography and gel filtration chromatography were used to purify four reptile lysozymes from egg white: SSTL A and SSTL B from soft shelled turtle (Trionyx sinensis), ASTL from Asiatic soft shelled turtle (Amyda cartilagenea) and GSTL from green sea turtle (Chelonia mydas). The molecular masses of the purified reptile lysozymes were estimated to be 14 kDa by SDS-PAGE. Enzyme activity of the four lysozymes could be confirmed by gel zymograms and showed charge differences on native-PAGE. SSTL A, SSTL B and ASTL had sharp pH optima of about pH 6.0, which contrasts with that of GSTL, which showed dual pH optima at about pH 6.0 and pH 8.0. The activities of the reptile lysozymes rapidly decreased within 30 min of incubation at 90 degrees C except for ASTL, which was more stable. Partial N-terminal amino acid sequencing and peptide mapping strongly suggested that the enzymes were C-type lysozymes. Interestingly, the mature SSTL lysozymes show an extra Gly residue at the N-terminus, which was previously found in soft-shelled turtle lysozyme. The reptile lysozymes showed lytic activity against several species of bacteria, such as Micrococcus luteus and Vibrio cholerae, but showed only weak activity to Pseudomonas aeruginosa and lacked activity towards Aeromonas hydrophila.

Comparison of select innate immune mechanisms of fish and mammals

The study of innate immunity has become increasingly popular since the discovery of homologs of many of the innate immune system components and pathways in lower organisms including invertebrates. As fish occupy a key position in the evolution of the innate and adaptive immune responses, there has been a great deal of interest regarding similarities and differences between their defense mechanisms and those of higher vertebrates. This review focuses on describing select mechanisms of the innate immune responses of fish and the implications for evolution of immunity in higher vertebrates.

Apolipoproteins A-I and A-II are potentially important effectors of innate immunity in the teleost fish Cyprinus carpio

We have previously shown that high density lipoprotein is the most abundant protein in the carp plasma and displays bactericidal activity in vitro. Therefore the aim of this study was to analyze the contribution of its principal apolipoproteins, apoA-I and apoA-II, in defense. Both apolipoproteins were isolated by a two step procedure involving affinity and gel filtration chromatography and were shown to display bactericidal and/or bacteriostatic activity in the micromolar range against Gram-positive and Gram-negative bacteria, including some fish pathogens. In addition, a cationic peptide derived from the C-terminal region of carp apoA-I was synthesized and shown to possess antimicrobial activity (EC(50) = 3-6 micro m) against Planococcus citreus. This peptide was also able to potentiate the inhibitory effect of lysozyme in a radial diffusion assay at subinhibitory concentrations of both effectors. Finally, limited proteolysis of HDL-associated apoA-I with chymotrypsin in vitro was shown to generate a major truncated fragment, which indicates that apoA-I peptides liberated in vivo through a regulated proteolysis could also be involved in innate immunity.