Antioxidant effects of the aqueous extract of turmeric against hydrogen peroxide-induced oxidative stress in spotted seabass(Lateolabrax maculatus)

Intensive aquaculture-induced oxidative stress is detrimental to fish health and yield.Medicinal plants show promise as natural health boosters and antioxidants in the aquaculture industry.Therefore,this work investigated the effects of turmeric aqueous extract(TAE)on the growth performance,antioxidant status,and hydrogen peroxide(H2O2)-induced oxidative stress in spotted seabass(Lateolabrax maculatus).Fish were fed diets supplemented with 0(Con),2(TAE2),or 4(TAE4)g/kg TAE for eight weeks,then were injected with H2O2.The results showed that dietary supplementation of TAE did not affect fish growth,feed utilization,or body composition.TAE treatment increased liver antioxidant enzyme activities and decreased liver malondialdehyde content and serum levels of glutamate oxalate transaminase,glutamate pyruvate transaminase,and lactate dehydrogenase.Furthermore,the increases in mortality,liver malondialdehyde content,and serum biomarkers of liver injury in the H2O2-treated fish were inhibited as a consequence of the TAE treatment.In addition,TAE treatment activated the Nrf2/Keap1 pathway in the liver,supported by the up-regulated expression of nrf2,ho-1,and gclc,and down-regulated keap1 expression.Overall,dietary incorporation of TAE protected against H2O2-induced oxidative stress in spotted seabass probably by enhancing antioxidant capacity through the Nrf2/Keap1 pathway.

Selected dietary plant-based proteins for growth and health response of Nile tilapia Oreochromis niloticus

Tilapia culture is one of the largest sectors of global aquaculture.Among the different species of tilapia,Nile tilapia(Oreochromis niloticus)is perhaps the top cultured species.The production of Nile tilapia has been continually increasing throughout the years resulting in genetic deterioration.Several tilapia strains with better growth performance and adaptive capability to survive in different culture conditions have been developed to alleviate the crisis.Increased demand for Nile tilapia implies higher farming cost.Plant-based proteins are utilized as partial or complete fishmeal replacements to reduce feed cost.However,these proteins can adversely affect and alter growth and feed performance,carcass composition and indices,and gut and hepatic health.This review discusses the use of seven plant-based proteins:namely,soybean,copra,pea,corn,palm kernel,microalgae,and seaweed as a Nile tilapia aquafeed.Different processing methods are employed to produce several types of plant-based proteins.Processed plant-protein types,when utilized as an aquafeed ingredient,vary in its effect on the performance,hemato-immunological parameters,and gut and hepatic health of Nile tilapia.Studies have shown that Nile tilapia can effectively maximize plant-based protein diets based on the preparation method,type of plant source,amino acid supplementation,and inclusion levels of the plant proteins.These readily available crops should be considered as primary protein sources for aquaculture.Hindrances to the use of plant-based proteins as a main dietary protein are limiting amino acids,presence of anti-nutritional factors,and the competition between its demand as human food and as animal feed.

Growth performance,fatty acid profile,gut,and muscle histo-morphology of Malaysian mahseer,Tor tambroides post larvae fed short-term host associated probiotics

Host associated probiotics(HAPs)provide health benefits to the host when administered as dietary supplement.However,a short-term probiotics application strategy has yet to be optimized.A 90-days study was conducted to evaluate the response of Malaysian mahseer,Tor tambroides post larvae fed with basal diet enriched HAPs for 30-days,and its response following another 60-days feeding with only basal diet.Three experimental diets(Enterococcus faecalis strain 2674(T1),Aeromonas sp.strain A8-29(T2)and E.faecalis strain FC11682(T3))were prepared by spray-coating each HAPs on a basal diet at 1×108 CFU/g feed.Differences in growth performances,whole-body proximate and fatty acid composition,muscle morphometry,and gut morphology were evaluated.Results showed that after 30 days,T3 fish produced highest growth.All HAP treatment groups showed better muscle distribution profile,improved fatty acid composition,and higher villus length,width and area,than control group.After 90 days,the growth of T3 fish was still the highest.Muscle distribution profile and villus growth were higher in HAP treatments,although only total n-6 PUFA,total MUFA,linoleic acids,and linolenic acids in HAP treated fish remained high after probiotics withdrawal.No difference in whole-body proximate composition was observed in both 30 and 90 days.Collective findings demonstrated that short-term application of HAPs at an early stage could be used to boost T.tambroides growth,with E.faecalis strain FC11682 showing the best efficacy.

Aquaculture species diversification in China

China has been the top aquaculture producer in the world since 2002.Over 800 species and 240 improved varieties have been used in China’s aquaculture,which is the most diverse collection of species on this planet.Species diversification,along with other aquaculture technologies,contributes significantly to the increase of China’s aquaculture production,whereas the use of too many species in aquaculture has resulted in some issues related to the environment and sustainability.We provide an updated overview of the species currently used in Chinese aquaculture in this paper.We examine critically the main drivers of species diversification in China with examples.We also introduce Chinese approaches to improve and certify new species and varieties for commercial production.We believe that further species diversification is not a priority in China’s aquaculture,while further improvement of aquaculture technologies for major and native species is essential for green,profitable,and sustainable(GPS)aquaculture.The implications of China’s experiences with species diversification for global aquaculture species diversification are discussed.

Evaluation of growth performance,feed efficiency and nutrient digestibility of red hybrid tilapia fed dietary inclusion of black soldier fly larvae(Hermetia illucens)

Insects,particularly black soldier fly larvae(BSFM),Hermetia illucens,have been regarded as promising protein and lipid sources in animal feed,including fish.Digestibility is the key factor that affects nutrient utilization,feeding physiology and efficiency.In the present work,the effect of BSFM on the digestibility of red hybrid tilapia(RHT)compared to fish meal(FM)was ultimately unveiled.A 56-day growth trial was performed with 60 RHT(~30 g)randomly distributed into six tanks and fed two experimental diets containing FM as a reference diet and BSFM as a test diet.In addition,faeces were collected to determine their chromium concentration and proximate composition.The apparent digestibility coefficient(ADC)of dry matter,crude protein and energy in the BSFM diet were observed to be significantly higher than those in the FM diet.Besides,the growth performance of fish fed with the BSFM diet exhibited significantly higher(P<0.05)weight gain,specific growth rate,protein efficiency ratio and lower feed conversion ratio than those in the FM group.This study shows that the BSFM feed was well digested by tilapia and improved its growth performance.

Repercussion of salinity on hematological parameters and tissue morphology of gill and kidney at early life of tilapia

This study was attempted to reveal the changes in three hematological parameters such as blood hemoglobin,number of white blood cells(WBCs)and number of red blood cells(RBCs)and one biochemical(e.g.,glucose)parameter along with the changes in histomorphological structures of gills and kidney of Nile tilapia fry reared in saline water.Two experimental set up were used for two different age groups-5 days-after-hatch(5DAH)and 15 days-after-hatch(15DAH)-to test a novel hypothesis:if a little difference in the age during the first exposure to saline water could produce any variation in the results.They were placed into 6 plastic drums having six different salinity levels:0,5,10,15,20 and 25.After 60 days,at least 5 individuals were taken out from each drum to observe the above-hematological and histomorphological parameters.A two-way-ANOVA revealed that,except for hemoglobin,all the observed parameters have been affected the effect of age×salinity interaction(P<0.05).Between the two age groups,only the overall average glucose value and RBC count were significantly different.Among various salinity levels,only RBC and WBC counts differed significantly.Further,the mean glucose value,RBC counts and WBC count at different salinities differed significantly from the base mean value of each parameter.With regard to the histomorphological structure of the gills and kidney,various malformations were evident.Though hypertrophy,epithelial uplifting and epithelial necrosis were present as gill degenerations,hyperplasia was prevalent across almost all salinity levels.On the other hand,glomerular necrosis,pyknotic nucleus,hyaline droplets degeneration,shrinking of the glomeruli,etc.were observed in kidney structures.By assisting to understand the effects of salinity stress,all these data on tilapia fry will help to determine the prospects and scope of culturing the species in high-salinity water.

Antimicrobial roles of phagocytosis in teleost fish:Phagocytic B cells vs professional phagocytes

The defense system of teleost fish organized on innate and adaptive immunity protects them against a wide variety of pathogenic microorganisms in the aquatic environment.Phagocytosis is one of the most effective defense strategies against microbial challenge mainly performed by classical‘professional’phagocytes(including monocytes,macrophages and granulocytes).They contain,kill and process the internalized pathogens for antigen presentation by providing antigenic ligands to initiate activation and clonal expansion of T and B cells,which bridge the innate and adaptive immunity.The discovery of phagocytic B cells in teleost fish has broken the paradigm that primary vertebrate B cells are lack of phagocytosis of particulates,as well as led to the investigation of phagocytic activity of mammalian B-1 B cells.The active phagocytic,microbicidal capabilities and antigen presentation in teleost phagocytic B cell have demonstrated to be similar as professional phagocytes,providing a potential impact on development of new vaccination strategies to prevent and control infectious diseases.In this review,we aim to address current progress on the antimicrobial role of phagocytic B cells in teleost fish by comparing it with other professional phagocytes and mammalian B-1 B cells,and provide the application prospect of phagocytic B cells in developing vaccines as well as the prevention of fish diseases.

Microbial,immune and antioxidant responses of Nile tilapia with dietary nano-curcumin supplements under chronic low temperatures

A 56-day feeding period was performed to investigate the possible impacts of dietary nano curcumin(0,50,100,150,and 200 ppm)on the growth,nutrient utilization,non-specific immune parameters,antioxidants in Nile tilapia under chronic low temperature(21.02±0.11◦C).Fishes(n=225;Initial weight=4.39±0.08 g/fish)were randomly stocked at 15 fish/tank for five experimental groups in triplicates.Under low-temperature circumstances,dietary curcumin in nano form showed no notable alteration in growth variable,nutrient efficiency,digestive enzymes efficiency,biometric indices,survival rates,and hematological components.Meanwhile,the serum of fishes with nano curcumin diets under low-temperature stress displayed higher total protein as well as lower glucose,cortisol,and total cholesterol compared with the control group.Moreover,fish fed nano curcumin diets displayed higher lysozyme and bactericidal activities compared to the control group and the best performance was found at dietary nano curcumin level of≥100 ppm.Also,groups fed the basal diet demonstrated the poorest antioxidant capacity,and the best superoxide dismutase(SOD)and glutathione peroxidase(GPx)existed in fish with nano curcumin diets while the best catalase(CAT)efficiency occurred at higher nano curcumin levels≥100 ppm.In addition,higher counts of intestinal microbiota in terms of total bacterial count(TBC),total yeast and molds count(TYMC),and coliform were noticed in fish consumed the basal diet compared to groups fed on nano curcumin diets.In conclusion,incorporating nano curcumin at a level of≥100 mg/kg diet(particularly at 150 mg/kg)improved a non-specific immune response,antioxidant,and healthier gastrointestinal microbiota in Nile tilapia under chronic low-temperature stress.

Effects ofβ-1,3-glucan and ascorbic acid on the nutritional-immune response and antioxidant signaling pathways of live tiger grouper during simulated transport

Transport in water is the most common method for transporting live fish in China,however,transport is a strong stressor.Transport stress could lead to a reduced immune and antioxidant system function of tiger grouper,resulting in sickness and death.Besides,tiger grouper were continuously stressed during transport,which resulted in quality deterioration.It is necessary that find a way to relieve the stress of transportation of tiger grouper.Ascorbic acid is not only a good anti-stress agent,but it is also an effective immunostimulant.β-1,3-glucan is a feed additive that can enhance the immune response of fish.Therefore,this study evaluated the effects ofβ-1,3-glucan and ascorbic acid on the nutritional-immune response and antioxidant signaling pathways of live tiger grouper during simulated transport.Results indicated that addingβ-1,3-glucan and ascorbic acid in transport-water muted the increase of alanine aminotransferase(ALT)and aspartate aminotransferase(AST)activity.In addition,β-1,3-glucan and ascorbic acid activated Nrf2 and mediated TOR expression and then up-regulate related mRNA expression of antioxidant and immune enzymes.We concluded that the application ofβ-1,3-glucan and ascorbic acid inhibit the increase of metabolism enzymes and inflammatory factors and activate immune and antioxidant signaling pathways to relieve oxidant stress,immune response,and apoptosis.Reducing the loss of amino acids provided nutrients to relieve oxidative stress and immune response,which demonstrated immune-nutritional response in live tiger grouper during simulated transport.These results may provide a new solution for alleviating the decline of immune and antioxidant function of tiger grouper caused by transportation stress.

Neutrophils in Atlantic salmon(Salmo salar L.)are MHC class II^(+)and secret IL-12p40 upon bacterial exposure

Antigen-presentation via major histocompatibility complex(MHC)to T cells is the key event to initiate adaptive immune responses.In teleosts,as in mammals,the main types of professional antigen-presenting cells(APCs)are dendritic cells(DCs),monocytes/macrophages,and B cells.In the current study,flow cytometry,immunostaining and qPCR have been used to show that neutrophils in the teleost fish Atlantic salmon(Salmo salar L.)have antigen-presenting properties.The neutrophils were positive for MHC class II,CD83 and CD80/86,and upon in vitro bacterial exposure,gene expression analysis of purified neutrophils showed that IL-12p40,which is essential for proliferation of naïve T cells,was highly upregulated at both 6 and 24 h post bacterial exposure.Based on presence of MHC class II and upregulation of molecules involved in antigen presentation and T cell activation,we suggest that neutrophils in Atlantic salmon have potential to function as professional APCs.This work makes an important basis for further exploring the potential of using neutrophils to develop new,targeted immunoprophylactic measures.

The roles of polysaccharides in tilapia farming:A review

Impairment of fish growth and immune system due to stress and disease are major constraints in aquaculture industry.Traditionally,antibiotic was used as prophylactic agent in the health management of aquaculture species.However,antibiotic only provide a temporary solution to the problem of disease outbreak.Over-reliance on antibiotic also has led to the increasing cases of antibiotic resistance among pathogenic bacteria from aquaculture sites and contamination of antibiotic residues into human food chain.Probiotic,prebiotic and symbiotic are therefore suggested as alternatives to prophylactic antibiotic to be used in the aquaculture industry.A potential prophylactic agent is polysaccharide that could be developed into an alternative antibiotic for aquatic animals.In this review paper,definition,sources,and mode of action of polysaccharide are presented.The roles of polysaccharides in fish farming with emphasis on growth improvement,immune system enhancement,disease resistance stimulation in tilapia farming,and the effects of polysaccharides on abiotic stressors are summarized and discussed.

Historic,pre-stock enhancement,demographic conditions of exploited populations of dusky flathead,Platycephalus fuscus,in eastern Australia

Responsible stock enhancement initiatives require baseline data of wild population demographic conditions that can be used in testing management outcomes.This study provides the first fishery-independent assessment of length-and age-based biological characteristics of exploited populations of Platycephalus fuscus in eastern Australia prior to stock enhancement.Sampling was conducted over seven estuaries spanning seven degrees of latitude and the geographical range of proposed stock enhancements.Populations in all estuaries showed evidence of length and age truncation,especially those subject to commercial fisheries where young individuals of both sexes dominated populations.Maximum longevities were 12 and 11 years for females and males respectively,but few females>5 years and males>3 years were generally sampled.Females dominated populations,and on average,the mean lengths and ages of females were greater than males within each estuary and across all age classes.Sexually dimorphic variation in growth was evident across all estuaries,with females attaining greater maximum lengths than males.Estuary-specific differences in individual growth were not identified.On average,over 50%of females sampled in each estuary were>the minimum legal length(MLL),but the opposite was evident for males.In contrast,over 25%of males in each estuary were>the mean length at maturity(L50),whereas in all but one estuary<13%of the females were>the L50.Stocked male and female P.fuscus should recruit to the fishery in 2 and 3 years,and contribute to the spawning stock in 1.5 and 4.5 years,respectively.This study provides important historical baseline data that can contribute to testing stock enhancement outcomes on populations.

Effects of dietary supplementation with tropical microfungi Mucor circinelloides and Trichoderma harzianum powder on growth performance,bacterial communities,and the biomass nutritional profile of white shrimp grow-out culture(Litopenaeus vannamei)

Microfungi have been explored further as supplement constituents in shrimp culture due to their rich protein,lipid,essential amino acids,fatty acids,and various bioactive compounds.The researchers have evaluated the effects of two microfungi powders(Mucor circinelloides and Trichoderma harzianum)as feed supplements on growth performance,bacterial communities,and the biomass nutritional profile of white shrimp(Litopenaeus vannamei).The results showed that commercial/artificial feed(Feng-Li)with supplementation microfungi powder had a different effect on white shrimp growth performance than control after 62 days of the grow-out period.Supplementation with 1.5%M.circinelloides powder(M-2)could improve the growth performance of white shrimp,especially the survival rate(81.33%),final body weight(5.21 g),and shrimp biomass(211.35 g).In contrast,supplementation with 1.5%T.harzianum powder(T-2)did not improve the growth performance of white shrimp compared to control(p>0.05).Furthermore,it also affected the profile of the bacterial community in culture water as well as in shrimp intestines.Supplementation with both microfungi could reduce the total number of bacteria in culture water at the end of the experiment,where the lowest number was obtained in treatment T-2(3.9×10^(5)CFU/mL),followed by M-2(9.9×10^(5)CFU/mL)and control(4.4×10^(6)CFU/mL).In the culture water,20 isolates of culturable bacteria were found during the trial,with the dominant bacteria in M-2:Bacillus cereus,Bacillus velezensis,Gordonia polyisoprenivorans,T-2:Acinetobacter sp.,Gordonia polyisoprenivorans,Micrococcus luteus.Based on average well colour development(AWCD),the highest bacterial activity was in the M-2(0.297-0.707),followed by T-2(0.226-0.717)and control(0.094-0.694).The highest substrate group utilised in M-2 and T-2 were polymers(0.896 and 1.348)and control:amines(0.100).The highest Shannon diversity index was obtained in the M-2(2.508),followed by control(2.286)and the T-2(2.157).As many as 11 isolates of culturable bacteria were found in the shrimp intestine,with dominant bacteria in M-2:Bacillus velezensis,Micrococcus luteus,Bacillus cereus,T-2:Bacillus velezensis,Micrococcus sp.2,Demequina activiva.The highest bacterial activity was in M-2(2.259),followed by control(2.020)and T-2(0.050).The highest substrate group utilisation was in M-2:polymers(2.564),T-2:carbohydrates(0.094),and control:polymers(2.185).The highest Shannon diversity index was in the M-2(3.234),followed by control(3.230)and the T-2(0.751).In addition,1.5%M.circinelloides and T.harzianum supplementation increased white shrimp muscle protein content up to 79.21%and 80.40%,respectively,compared to control(76.73%).In conclusion,using Mucor circinelloides powder as a feed supplement can improve the growth performance of white shrimp,increase the functional/probiotic bacteria:B.cereus and B.velezensis in cultur and shrimp’s intestine,and increase the protein content in shrimp muscle tissue.However,more in-depth research is needed,especially on anti-nutritional compounds from fungi that affect shrimp growth.

Marine yeast Rhodotorula paludigena VA 242 a pigment enhancing feed additive for the Ornamental Fish Koi Carp

Skin colour is an important criterion in determining the aesthetic appeal of ornamental fishes,and thus their market worth.Hence the pigment enhancement in ornamental fishes has been the subject of extensive research by using various synthetic as well as natural pigment sources.Dietary composition is one of the most important elements that influence the development of pigmentation in fish.This study is an attempt to assess the possibility of using carotenogenic marine yeast as pigment enhancer in fish diet for Koi carp,Cyprinus carpio.The 60 days feeding experiment was done by using feed incorporated with mangrove associated marine yeast Rhodotorula paludigena VA242.Greater pigmentation in the scales of fishes fed with experimental feed was observed than that fed with the control diet(normal pellet feed).Furthermore the improved growth rate and general wellbeing in fishes fed with experimental feed provides scope for further studies in this field with respect to the growth and survival of fishes.

Evaluation of the nutritional value of Artemia nauplii for European seabass(Dicentrarchus labrax L.)larvae

Adapted European seabass(Dicentrarchus labrax L.)larvae at 25 days post-hatching(dph)with a primary weight and length of 23 mg and 9.92 mm,start the weaning up to 46 dph using the weaning micro-diet(54%crude protein from fish meal,powder milk,and poultry egg)concurrently with Artemia enriched with fortification emulsions(0.6 g/L)of DHA selco®as a control group(DHAS)or Fish oil+20%Vitamin C(FOVC),or Fish oil+20%Vitamin E(FOVE),or Fish oil+10%Vit.C+10%Vit.E(FOCE),or Fish oil only(FO).At 46 dph,groups of larvae fed enriched Artemia with DHAS and FOVE exhibited the highest final body weight,weight gain,average daily gain,specific growth rate,feed intake,protein efficiency ratio,and survival%as well as the lowest feed conversion ratio.Meanwhile,larvae in FOVC displayed the lowest final body weight,total length,weight gain,average daily gain,specific growth rate,feed intake,protein efficiency ratio,and survival%as well as the highest feed conversion ratio.Gastrointestinal histological assessment exhibited no pathological alteration as well as an improvement in the structure with DHAS,FOVE,FOVC,and FOCE co-additives compared to FO.Glutathione peroxidase enzyme(GPx)recorded the highest rates(P<0.05)in groups fed Artemia supplemented with DHAS and FOVE followed by FOCE and FOVC.While the lowest record for GPx activity was noted in the FO group.In conclusion,Using augmented Artemia nauplii with fish oil+vitamin E in single or in companion with vitamin C as cheap antioxidants support D.labrax larval growth,survival,and antioxidant efficacy during the critical weaning period.

Artificial enhancement of sturgeon stock in freshwater reservoirs:A case study on sterlet Acipenser ruthenus of the Kama reservoir

The paper presents the results of the sterlet sturgeon Acipenser ruthenus reintroduction into the Kama Reservoir(Perm Krai,Russia)by sterlet fry from hatcheries into the reservoir since 2001.The effectiveness of hatchery releases was evaluated by monitoring gillnet sampling 2014-2020.The results showed that the species was reported throughout entire Kama Reservoir,which contrasts with 1988-1994 data,when the species was registered only at the upper part of the reservoir near the Kama River mouth.The highest number and biomass values of catch per unit effort(CPUE)of the sterlet were found in submerged river channels-the deepest habitats with flow conditions which are close to the ecological requirements of the species.The distribution of the sterlet within the channel biotopes of the reservoir is defined by reduced variability.The biggest individuals and the widest size range of the sterlet were typical for the upper area of the reservoir and Chusovskoy Bay,which have the greatest flow.The smallest sizes were typical for fish from catches near the dam of the reservoir,which is consistent with the published data on the distribution of sterlet in reservoir conditions.The presented results may indicate the artificial formation of the sterlet stock in the Kama Reservoir maintained by hatchery releases.The revealed distribution of the sterlet in the reservoir determines the direction of further research on natural reproduction and thus formation of an artificially formed population.Also,future studies are required to assess the possibility of hybridization of the sterlet of artificial origin with natural populations of the species,since the low genetic diversity of the sterlet released into the Kama Reservoir which can lead to irreversible loss of genetic individuality of the natural stocks of the species in the catchment of upper course of the Kama River.

Assessing the pomfret stock for setting catch limits in the northern Bay of Bengal,Bangladesh

Pampus argenteus and Pampus chinensis form the high-value demersal Pomfret fishery of Bangladesh.But,due to a monotonic decline in catches over the last five years,it is essential to explore the current stock status concerning the removal rate to ensure the sustainability of this fishery.Therefore,given the reliability and minimal data requirements,this study employed an extended Bayesian State-Space Surplus Production Model,JABBA(Just Another Bayesian Biomass Assessment),to assess the stock rigorously.The results revealed that the stock biomass of the Pomfret fishery in the final year of the time series is significantly lower than BMSY,the biomass required to produce MSY.Consequently,this study recommends a yearly catch limit(TAC)of 10,000 metric tons to prevent further depletion of the stock biomass.Furthermore,to avoid growth overfishing by allowing all immature fishes to reproduce at least once before being caught,this study also calculated the optimum length(Lopt)for catch for both species at which biologically maximum yield and revenue can be obtained.The estimated Lopt is 25 cm for P.argenteus and 30 cm for P.chinensis,and not to capture fishes with lengths lower than these limits,this study further calculated the minimum mesh size limits for gill and set bag nets is 7.5 cm.Though the mesh size regulation was estimated using length-based reference points derived from an empirical equation,this regulation can be used as an associate reference point when TAC is applied to assure the sustainability of this fishery.

Characterisation of IL-21 and IL-21Rαin grass carp:IL-21-producing cells are upregulated during Flavobacterium columnare infection

Interleukin-21(IL-21)is produced mainly by activated CD4^(+)T cells and promotes the proliferation,survival and differentiation of immune cells.This study characterised a high affinity binding receptor of IL-21(IL-21 Rα)from grass carp(Ctenopharyngodon idella,Ci)and analyzed the expression of CiIL-21 and CiIL-21 Rα.It has been shown that they were modulated by PAMPs and during infection with bacterial and viral pathogens.Recombinant CiIL-21 protein produced in bacteria was active in inducing the expression of genes involved in Th responses.A monoclonal CiIL-21 antibody was generated against the rCiIL-21 and showed good reactive specificity with the rCiIL-21 proteins expressed in E.coli cells,and HEK293 T cells and the native protein from PHA-stimulated kidney leukocytes.In addition,the IL-21-producing cells detected by the CiIL-21 monoclonal antibody were found to be increased to in the kidney,spleen and hindgut after infection with Flavobacterium columnare.Our data indicate that IL-21 is involved in the regulation of immune response to bacterial and viral infection.

RNA-seq analysis of a zebrafish caudal fin cell line in response to infection with spring viraemia of carp virus

A cell line,termed ZFIN,was established from the caudal fin of zebrafish and was shown to be susceptible to spring viremia of carp virus(SVCV).The ZFIN cells are epithelial like cells and have a moderate plasmid transfection efficiency of 13.9%.Using an RNA-seq approach,differentially expressed genes(DEGs)regulated by SVCV were identified.Infection of SVCV gave rise to 3931 DEGs and up-regulated DEGs were mostly enriched into the biological regulation and cellular processes,among which pathways for the type I interferon signaling and the response to exogenous dsRNA were the top two GO terms.Several KEGG signaling pathways including TLR signaling pathway,RLR receptor signaling pathway,cytosolic DNA-sensing pathway,NLR signaling pathway,cytokine-cytokine receptor interaction and ferroptosis were significantly enriched.Antiviral genes including ifnφ1,isg15 and mx were significantly up-regulated.In addition,key DEGs involved in autophagy were identified.The results indicate that the ZFIN cell line provides a useful in vitro tool for study on the gene functions and cellular responses to viral infection in fish.

Production and characterization of monoclonal antibodies against grass carp CD4-1 and CD4-2

CD4 T helper cells are an important group of cells in the immune system of vertebrates and express CD4 receptor on the cell surface.In mammals,the CD4 receptor is encoded by a single copy gene,whilst in fish,two copies of cd4 genes,namely cd4-1 and cd4-2,are found.In this study,the ectodomains of grass carp(Ctenopharyngodon idella,Ci)CD4-1 and CD4-2 were expressed in the E.coli cells and used to generate monoclonal antibodies in mice.Western blotting,confocal microscopy and flow cytometry were performed to characterize the monoclonal antibodies.It has been shown that the CiCD4-1 and CiCD4-2 monoclonal antibodies had good specificity to react with the recombinant ectodomains of CiCD4-1 and CiCD4-2 expressed in the CHO-S cells and the native CD4 molecules of grass carp.The CiCD4-1 monoclonal antibody did not recognize CiCD4-2 and verse versa.In addition,the CD4-1 and CD4-2 monoclonal antibodies specifically recognized the CD4-1 and CD4-2 receptors expressed in the HEK293 cells and native molecules of fish cells.Further,the percentages of lymphocytes in immune tissues of healthy fish were analyzed by flow cytometry.It was found that 17.6%of lymphocytes were CD4-1^(+)cells and 22.5%were CD4-2^(+)in the head kidney.In the spleen,13.1%of lymphocytes were CD4-1^(+)and 18.6%were CD4-2^(+)while 7.3%of blood lymphocytes were CD4-1^(+)cells and 8.8%were CD4-2^(+)cells.The availability of the CD4-1 and CD4-2 monoclonal antibodies provides antibody-based tools for further elucidation of the functions of CD4 T cells in grass carp.