Sea bass Dicentrarchus labrax (L.) bacterial infection and confinement stress acts on F-type lectin (DlFBL) serum modulation

An Update of Lectins from Marine Organisms: Characterization, Extraction Methodology, and Potential Biofunctional Applications

Lectins are a unique group of nonimmune carbohydrate-binding proteins or glycoproteins that exhibit specific and reversible carbohydrate-binding activity in a non-catalytic manner. Lectins have diverse sources and are classified according to their origins, such as plant lectins, animal lectins, and fish lectins. Marine organisms including fish, crustaceans, and mollusks produce a myriad of lectins, including rhamnose binding lectins (RBL), fucose-binding lectins (FTL), mannose-binding lectin, galectins, galactose binding lectins, and C-type lectins. The widely used method of extracting lectins from marine samples is a simple two-step process employing a polar salt solution and purification by column chromatography. Lectins exert several immunomodulatory functions, including pathogen recognition, inflammatory reactions, participating in various hemocyte functions (e.g., agglutination), phagocytic reactions, among others. Lectins can also control cell proliferation, protein folding, RNA splicing, and trafficking of molecules. Due to their reported biological and pharmaceutical activities, lectins have attracted the attention of scientists and industries (i.e., food, biomedical, and pharmaceutical industries). Therefore, this review aims to update current information on lectins from marine organisms, their characterization, extraction, and biofunctionalities.

Seasonal changes of hydrolytic enzyme activities in the skin mucus of rainbow trout, Oncorhynchus mykiss at different body sizes

The innate immune factors in the skin mucus of fish are affected by the ecological and physiological conditions such as developmental stage and seasonal cycle. The aim of this study was to investigate the seasonal changes in soluble protein and the hydrolytic enzyme activities of the skin mucus of rainbow trout including lysozyme, alkaline phosphatase (ALP) and proteases at different body sizes. Skin mucus samples were collected over three consecutive season periods including winter, spring and late summer. In each season, sampling was performed separately from three different weight groups including 2-20 g (W1), 100-200 g (W2) and 400-600 g (W3) fish. Our results showed a significant increase of soluble protein in all three weight groups from winter to spring when water temperature elevated from 9 °C to 14 °C. Moreover lysozyme activity was remarkably elevated in W1 fish from winter to late summer. In all three seasons, the activity of lysozyme was significantly decreased along with increasing the fish size. Contrary to lysozyme, the activity of proteases and ALP showed a decreasing trend from winter to late summer. A significant positive correlation was found between the proteases and ALP activity, proposing that both proteases and ALP might have important synergic roles in the mucosal innate immune function of rainbow trout. Moreover, using reverse transcription PCR (RT-PCR) analysis of some proteases genes including cathepsin-L and cathepsin-D, we demonstrated that the proteases are transcribed and likely synthesized in epidermal mucus cells of rainbow trout. The present study confirmed seasonal changes of hydrolytic enzyme activities in the skin mucus of rainbow trout across all three weight groups, with the highest variation in juvenile fish.

Vaccines and immune protection of principal Mediterranean marine fish species

This review describes and summarizes the knowledge on established and experimental vaccines developed against viral and bacterial pathologies affecting the most important farmed marine finfish species present in the Mediterranean area, namely European seabass Dicentrarchus labrax, sea bream Sparus aurata, turbot Psetta maxima and meagre Argyrosomus regius. The diseases that have been recorded in seabass, sea bream and meagre are caused by bacteria Vibrio anguillarum, Photobacterium damselae, Tenacibaculum maritimum as well as by viruses such as Viral Encephalopathy and Retinopathy/Viral Nervous Necrosis and Lymphocystic disease. The main pathologies of turbot are instead bacteriosis provoked by Tenacibaculum maritimum, Aeromonas sp. and Vibrio anguillarum, and virosis by viral hemorrhagic septicaemia virus. Some vaccines have been optimized and are now regularly available for the majority of the above-mentioned pathogens. A measurable immune protection has been conferred principally against Vibrio anguillarum, Photobacterium damselae sub. piscicida and VER/VNN.

Fish gut-liver immunity during homeostasis or inflammation revealed by integrative transcriptome and proteome studies

The gut-associated lymphoid tissue, connected with liver via bile and blood, constructs a local immune environment of both defense and tolerance. The gut-liver immunity has been well-studied in mammals, yet in fish remains largely unknown, even though enteritis as well as liver and gallbladder syndrome emerged as a limitation in aquaculture. In this study, we performed integrative bioinformatic analysis for both transcriptomic (gut and liver) and proteomic (intestinal mucus and bile) data, in both healthy and infected tilapias. We found more categories of immune transcripts in gut than liver, as well as more adaptive immune in gut meanwhile more innate in liver. Interestingly reduced differential immune transcripts between gut and liver upon inflammation were also revealed. In addition, more immune proteins in bile than intestinal mucus were identified. And bile probably providing immune effectors to intestinal mucus upon inflammation was deduced. Specifically, many key immune transcripts in gut or liver as well as key immune proteins in mucus or bile were demonstrated. Accordingly, we proposed a hypothesized profile of fish gut-liver immunity, during either homeostasis or inflammation. Current data suggested that fish gut and liver may collaborate immunologically while keep homeostasis using own strategies, including potential unique mechanisms.

Changes in the levels of humoral immune activities after storage of gilthead seabream (Sparus aurata) skin mucus

Skin mucus is increasingly used as a source for determining immunity-related proteins and enzymes. However, the ability to accurately measure some activities may be modified by inadequate handling and storage of the samples. This study aims to measure the effect of freezing and lyophilization at the time of collection on such activities. Fresh, frozen (immediately after collection at -20 °C and -80 °C) and lyophilized skin mucus samples obtained from the same groups of fish specimens of gilthead seabream (Sparus aurata L.) were analysed in the assays. The amount of total proteins and sugar residues (determined by lectin binding) present in skin mucus samples fell after both freezing and lyophilization of the samples. While no significant differences were exhibited in the levels of some proteins or enzymes (immunoglobulin M, antiprotease, peroxidase, esterase and alkaline phosphatase) determined in fresh or frozen mucus samples, protease and lysozyme activities were lower in frozen mucus samples than in fresh samples. Lyophilization of the mucus samples drastically decreased the total level of proteins obtained, as well as of protease, peroxidase, lysozyme and alkaline phosphatase activities. The results suggest that freezing skin mucus samples is more suitable than lyophilization if samples are stored before determining enzymatic activities.

Genome-wide association analysis reveals loci associated with resistance against Piscirickettsia salmonis in two Atlantic salmon (Salmo salar L.) chromosomes

Background

Pisciricketssia salmonis is the causal agent of Salmon Rickettsial Syndrome (SRS), which affects salmon species and causes severe economic losses. Selective breeding for disease resistance represents one approach for controlling SRS in farmed Atlantic salmon. Knowledge concerning the architecture of the resistance trait is needed before deciding on the most appropriate approach to enhance artificial selection for P. salmonis resistance in Atlantic salmon. The purpose of the study was to dissect the genetic variation in the resistance to this pathogen in Atlantic salmon.

Methods

2,601 Atlantic salmon smolts were experimentally challenged against P. salmonis by means of intra-peritoneal injection. These smolts were the progeny of 40 sires and 118 dams from a Chilean breeding population. Mortalities were recorded daily and the experiment ended at day 40 post-inoculation. Fish were genotyped using a 50K Affymetrix® Axiom® myDesign^TM Single Nucleotide Polymorphism (SNP) Genotyping Array. A Genome Wide Association Analysis was performed on data from the challenged fish. Linear regression and logistic regression models were tested.

Results

Genome Wide Association Analysis indicated that resistance to P. salmonis is a moderately polygenic trait. There were five SNPs in chromosomes Ssa01 and Ssa17 significantly associated with the traits analysed. The proportion of the phenotypic variance explained by each marker is small, ranging from 0.007 to 0.045. Candidate genes including interleukin receptors and fucosyltransferase have been found to be physically linked with these genetic markers and may play an important role in the differential immune response against this pathogen.

Conclusions

Due to the small amount of variance explained by each significant marker we conclude that genetic resistance to this pathogen can be more efficiently improved with the implementation of genetic evaluations incorporating genotype information from a dense SNP array.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-2038-7) contains supplementary material, which is available to authorized users.