A comparative study on innate immunity parameters in the epidermal mucus of Indian major carps

The innate immune system, particularly the external body surface, plays a frontier role in protecting fish from relevant infections. The present study is aimed at understanding and comparing the mucosal immunity of Indian major carp, that is, Labeo rohita, Catla catla and Cirrhinus mrigala, by evaluating different immune parameters such as protein content, lysozyme, myeloperoxidase, proteases and alkaline phosphatase activity in the skin mucus. The protein content of mucus sample of these species was compared, and the highest protein content was found in C. catla among the three Indian major carp species. The levels of proteases (40 ± 0.211 units/ml) and myeloperoxidase OD450 nm (1.525 ± 0.108) were found to be highest in the skin mucus of C. catla. However, lysozyme levels were highest in the skin mucus of L. rohita (10.95 ± 0.330 μg/ml), and C. mrigala had the highest alkaline phosphatase activity (30.74111 ± 0.680 U/l). Besides the enzyme activities, the epidermal mucus samples of three Indian major carp species were also tested and compared for the antibacterial activity against seven bacterial strains. Skin mucus of C. catla showed highest antibacterial activity among the three Indian major carps against all the seven bacterial strain, except that Micrococcus lysodeikticus and Vibrio cholerae, however, showed highest activity against mucus of C. mrigala. Also, the epidermal mucus from all the three species successfully agglutinated three freshwater pathogens, viz. Aeromonas hydrophila, Pseudomonas fluorescens and Edwardsiella tarda, with agglutination titres being the highest for Labeo rohita for all the pathogens. The epidermal mucus samples from the Indian major carp species showed haemagglutination activity and successfully lysed human, chicken and goat RBCs showing highest activity in C. catla. These results provide information for a better understanding of the role of epidermal mucus and its components in the innate immune system of Indian major carps.     

Specific immune response in mucosal and systemic compartments of Cirrhinus mrigala vaccinated against Edwardsiella tarda: In vivo kinetics using different antigen delivery routes

Mucosal immune barriers confer protection against invading fish pathogens. Here, we conducted an experiment for 60 days to assess the mucosal and systemic immune response in Mrigal (Cirrhinus mrigala), an Indian major carp. Fish were immunized with inactivated Edwardsiella tarda by four different routes, namely, oral, immersion, injection, and anal intubation. An indirect enzyme‐linked immunosorbent assay (ELISA) was used to measure the specific immune response (antibody) in serum and mucus (collected from skin, gill, and gut) of the fish on 0, 15, 30, 45, and 60 days postimmunization. For specific immune response in the serum, significantly higher (p < 0.05) optical density (OD) values were obtained in the anal group (0.52 ± 0.03) and in the oral group (0.48 ± 0.03). In the skin mucus, significantly higher OD values were obtained in the oral group (0.48 ± 0.04) and immersion group (0.32 ± 0.03). In the gill mucus, significantly higher OD values were obtained in the oral group (0.82 ± 0.08) and the immersion group (0.73 ± 0.03). In the gut mucus, significantly higher OD values were obtained in the immersion group (0.080 ± 0.007) compared to the rest of the treatments. Fish from all the groups were challenged with LD₅₀ dose of E. tarda at the end of the experiment. We conclude that oral and immersion immunization routes offer better protection of C. mrigala compared to other antigen delivery routes.     

大弹涂鱼皮肤黏液的抑菌活性和蛋白质组学

皮肤黏液是鱼类免疫防御的第一道防线。大弹涂鱼皮肤黏液对其免疫防御、渗透压维持以及适应水陆生活等方面具有重要意义。为深入了解大弹涂鱼皮肤黏液的蛋白质分子组成,对其皮肤黏液开展了抑菌活性分析和蛋白质组学分析。通过电刺激法收集大弹涂鱼皮肤黏液,采用打孔法比较了皮肤黏液和血清的抑菌活性差异;进一步利用鳗弧菌对大弹涂鱼进行诱导,采用生长曲线抑制法分析和比较了诱导前后皮肤黏液的抑菌活性差异。利用Shotgun质谱技术,结合大弹涂鱼皮肤转录组数据库,对大弹涂鱼皮肤黏液开展了蛋白质组学分析;进一步利用String软件对所鉴定的蛋白质开展了蛋白质相互作用预测。大弹涂鱼皮肤黏液具有广谱抑菌活性,鳗弧菌诱导后的大弹涂鱼皮肤黏液与诱导前相比,对部分革兰氏阴性菌的抑菌活性明显上升,但对其他菌株的抑菌活性差异不明显。从大弹涂鱼皮肤黏液中共鉴定各类蛋白质分子97种,基本分子组成与其他硬骨鱼类皮肤黏液蛋白相似,但也有少数蛋白如泛素蛋白、胸腺素蛋白等未在其他鱼类皮肤黏液中报道。此外,其他鱼类中所鉴定到的部分蛋白如热休克蛋白、抗菌肽等在大弹涂鱼皮肤黏液中未能鉴定到。大弹涂鱼皮肤黏液中已鉴定的蛋白多数具有与免疫功能相关的结构域,且存在一个以肌动蛋白为核心的相互作用网络。大弹涂鱼皮肤黏液具有明显的广谱抑菌活性,其蛋白质组成与其他鱼类皮肤黏液具有一定的相似性。本研究为深入了解大弹涂鱼皮肤黏液的分子多样性及功能机制奠定了基础。     

Improved performance of Atlantic cod (Gadus morhua L.) larvae following enhancement of live feed using a fish protein hydrolysate

High larval mortalities and anatomical deformities are among the major obstacles restricting the development of Atlantic cod (Gadus morhua) aquaculture. The immune system of cod larvae is poorly developed at hatch, and innate immune parameters are therefore of importance for defence against environmental microorganisms. Two separate experiments were conducted with bioencapsulation of the live feed of cod larvae using a pollock (Pollachius virens) protein hydrolysate. Offering peptide enhanced live feed to larvae during the first weeks of exogenous feeding promoted larval development, with reduced incidence of severe deformities to 3.0% as compared with 9.6% deformities observed in the control group at 160 days posthatch. The production and distribution of IgM and lysozyme were furthermore increased in larvae fed peptide enhanced feed compared with control larvae. IgM was predominantly detected in the foregut and the epithelial lining of the digestive tract as well as in the epidermal mucus of the skin. Lysozyme was mainly detected in the epidermal mucus of the skin and in the foregut. Overall, the results indicate that live feed enhancement using a protein hydrolysate derived from pollock may reduce deformities and promote normal development during early production stages of cod larvae.     

Efficacy of Liriope platyphylla on Hematology and Immune Response in Olive Flounder,Paralichthys olivaceus,Against Flexibacter maritimus Infection

The effect of different solvent‐based (methanol, ethanol, and aqueous) extracts of Liriope platyphylla at 0, 0.1, 1.0, and 2.0 mg doses on hematology and innate immune response in olive flounder, Paralichthys olivaceus, against Flexibacter maritimus is reported. The red blood cells and white blood cells significantly increased with ethanol and aqueous extracts with any dose against F. maritimus while the hematocrit level significantly increased with methanol or ethanol extracts. However, the hemoglobin content significantly increased irrespective of the doses and type of extracts, whereas the mean corpuscular volume, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration significantly decreased. The lymphocytes and monocytes significantly increased in all doses and extracts, whereas neutrophils increased in ethanol or aqueous extracts. However, the thrombocytes level neither the doses nor extracts did not significant changes to the control against pathogen. Total protein and globulin levels significantly increased with all the doses of ethanol extract while does not significant change in methanol extract. The phagocytic activity and complement activity were significantly enhanced with any dose of ethanol extract while with aqueous extract it was only at 1.0 and 2.0 mg doses. At all the doses of each extract significantly enhanced the leucocytes activity against F. maritimus. The results confirm that the ethanolic and aqueous extracts of L. platyphylla stimulate the immune response against F. maritimus in P. olivaceus.     

Effect of ethanolic extract of Zingiber officinale on growth performance and mucosal immune responses in rainbow trout (Oncorhynchus mykiss)

This study was conducted to examine the effect of ethanolic ginger (Zingiber officinale) extract on growth performance and some skin mucus immune parameters in rainbow trout (Oncorhynchus mykiss). A total of 600 rainbow trout fingerling (10.07 ± 0.21 g) were randomly assigned to four groups in triplicate and fed for 45 days with 1, 2.5 and 5 g kg^?1 of ginger extract and with unsupplemented basal diet as the control. The total protein content and lysozyme, alkaline phosphatase and protease activities of skin mucus were investigated following 15, 30 and 45 days of feeding. Results showed that administration of 2.5 and 5 g kg^?1 of ethanolic ginger extract for 45 days improved weight gain, feed utilization efficiency and feed conversion ratio of O. mykiss (P < 0.05). Significantly higher (P < 0.05) skin mucus lysozyme, alkaline phosphatase and protease activity and protein level were observed in the 2.5 and 5 g kg^?1 ginger extract groups on the 30th and 45th day compared to the controls. The findings suggest that ethanolic extract of ginger enhances growth performance and skin mucus immune parameters of rainbow trout.     

Supplementation of dietary apple cider vinegar as an organic acidifier on the growth performance,digestive enzymes and mucosal immunity of green terror (Andinoacara rivulatus)

The present study was designed to investigate the effects of dietary apple cider vinegar (ACV) on digestive enzyme activity and growth performance as well as immune responses and antibacterial activity of skin mucus in green terror (Andinoacara rivulatus). Fish were fed diets supplemented with 0%, 1%, 2% and 4% of ACV (40.830 ppm acetic acid concentration) for 63 days. The final weight and weight gain values were observed to be significantly higher in fish fed with 2% of ACV compared to the control group (p < .05). ACV inclusion in the diets had significant effects on SGR (%) and FCR values (p > .05). ACV treatment resulted in a significant increase in the intestinal protease, α‐amylase, lipase and alkaline phosphatase activities compared to control (p < .05). The activities of digestive enzymes in fish fed with 2% and 4% of ACV diets were significantly higher than the other groups (p < .05). The total protein content, alternative haemolytic complement, alkaline phosphatase, total immunoglobulins and lysozyme activities of skin mucus increased significantly in fish fed with ACV diets (p < .05). In conclusion, administration of ACV enhanced digestive enzyme activity, growth performance, immune responses and the immune properties of skin mucus, and it can be used as a natural growth promoter and immunostimulant in green terror culture.     

Comparative analysis of innate immune parameters of the skin mucous secretions from certain freshwater teleosts, inhabiting different ecological niches

The innate immune system of fish is considered first line of defense against a broad spectrum of pathogens. Being a component of innate immunity and lying at the interface between fish and the aqueous environment, skin mucus plays a frontier role in protecting fish from infections. In the present study, skin mucus of Cirrhinus mrigala, Labeo rohita, Catla catla, Rita rita and Channa punctata, inhabiting different ecological niches, was analyzed to characterize potential innate immune factors such as lysozyme, proteases, phosphatases, esterase and sialic acid. The enzyme activities were high in bottom dweller species, C. punctata and C. mrigala, and low in clean water inhabiting species, L. rohita and C. catla. An inverse relationship was observed between the level of enzyme activity and the sialic acid content in these fish species. In R. rita, however, the levels of all factors were found to be low. Zymographic analysis with labeled Micrococcus lysodeikticus revealed three isoforms of lysozyme in C. punctata and two in each species, C. mrigala, L. rohita and C. catla. In R. rita, lysozyme could not be detected. Gelatin zymography revealed that serine and metalloproteases were the major mucus proteases in all fish species investigated. In addition, trypsin-like protease and Ca(++)-specific serine proteases were observed in skin mucus. Increased knowledge of these parameters could be useful in understanding the role of skin mucus in the innate immune system of fish species inhabiting different ecological niches.     

温度对牙鲆皮肤黏液抗体产生的影响

在9℃、15℃、21℃和26℃4种不同水温下,用淋巴囊肿病毒(LCDV)灭活疫苗腹腔注射牙鲆,应用间接酶联免疫吸附试验(ELISA)研究了其皮肤黏液中特异性抗体水平的变化,以分析温度对牙鲆皮肤黏液抗体产生的影响.ELISA结果表明,9℃和15℃水温下牙鲆黏液OD值分别在注射LCDV后第9周和第7周达到峰值(9℃:OD=0.179; 15℃:OD=0.233); 21℃水温下OD值上升最快,5周达到峰值(0.316); 26℃水温下OD值较21℃无显著差异,也于5周达到峰值(0.295).采用硫酸铵分步盐析等技术粗提不同温度下OD值最高时的牙鲆皮肤黏液中的免疫球蛋白(Ig),SDS-PAGE检测发现,各温度组黏液蛋白中均含有72 kD和26 kD蛋白条带.Western blotting结果显示,抗牙鲆血清Ig重链的单克隆抗体只与黏液蛋白中72 kD条带发生反应,确定为牙鲆皮肤黏液Ig重链.综上结果表明,牙鲆在最适生活温度(21℃)下,抗体应答强度最大.牙鲆粗提黏液蛋白中Ig的初步确定,为探索牙鲆黏液免疫机制提供了材料.     

The immune response of turbot, Scophthalmus maximus (L.), skin to high water temperature

The immune responses of mucus from the skin of turbot, Scophthalmus maximus, were studied in relation to changing water temperature. Groups of fish were exposed to a programmed increase of 3 °C per 48 h, until the experimental water temperatures of 16, 20, 23, 25, 27 or 28 °C were reached. After 48 h at the relevant temperature, the expressions of immune‐related factors were determined, including immunoglobulin M (IgM), IL‐1β, hepcidin, transferrin, lysozyme, acid/alkaline phosphatase and superoxide dismutase using RT–PCR and spectrophotometric methods. Significant changes in mucus immunity were observed, which paralleled with those previously reported for serum in other fish species. Hence, it is suggested that the serum and mucus immune system of turbot have a similar regulatory system. This information could be useful in better understanding the role of the mucus as a component of the innate immune system.     

Effects of Panax ginseng extract in practical diets for rainbow trout (Oncorhynchus mykiss) on growth performance,immune response and resistance to Yersinia ruckeri

In a preliminary in vitro study, a Panax ginseng extract exhibited an evident antibacterial activity against Yersinia ruckeri and Lactococcus garvieae and affected the respiratory burst and proliferation of rainbow trout Oncorhynchus mykiss leukocytes. Subsequently, the effects of a dietary ginseng extract supplementation on growth, blood biochemical profile, innate immune response and resistance against Y. ruckeri infection were investigated in vivo in rainbow trout juveniles. Four experimental diets were obtained by adding 0.0%, 0.01%, 0.02%, 0.03% of ginseng ethanolic extract to a commercial feed. Each diet was fed to triplicate groups of fish (mean body weight 30.5 ± 0.15 g) at 1% of body weight day^?1 for 10 weeks. The dietary supplementation with ginseng extract did not affect growth performance, feed utilization, biometric traits and fish whole body composition (P > 0.05). No major changes due to graded levels of ginseng extract in the diet were observed in blood biochemical parameters except for increasing plasma triglycerides and non‐esterified fatty acids in fish fed diets including 0.01% and 0.02% of extract (P < 0.05). The innate immune response was barely modulated by the dietary addition of ginseng extract. Serum lysozyme and leukocytes respiratory burst activities were just slightly increased in fish fed all the ginseng extract‐supplemented diets compared with controls, whereas serum antiproteases and leukocyte MPO were not affected (P > 0.05). The dietary administration of ginseng extract induced a reduction in mortality of rainbow trout infected with Y. ruckeri, although no significant differences between treated and control groups were observed (P > 0.05).     

Characterization of carboxylesterase in skin mucus of Cirrhinus mrigala and its assessment as biomarker of organophosphate exposure

Presence of carboxylesterase (CbE) activity in the skin mucus of Cirrhinus mrigala was investigated. CbE activity in skin mucus showed higher substrate preference for α-naphthyl acetate over p-nitrophenyl acetate. Four CbE isozymes—CbE-1, CbE-2, CbE-3, and CbE-4 were observed in skin mucus during zymography. The isozyme CbE-4 was characterized as typical serine esterase, whereas CbE-1, CbE-2, and CbE-3 were identified as sulphhydryl group-dependent serine esterases. In vitro treatment of skin mucus with the organophosphorus insecticide, Nuvan^® showed strong inhibition of CbE activity. In vivo exposure of the fish to sublethal test concentrations (5 and 15 mg/l) of the insecticide also revealed significant inhibition of CbE activity in mucus. After the cessation of exposure, CbE activity recovered to its control level during the recovery periods. Thus, CbE activity in skin mucus could be considered a biomarker of the organophosphorus insecticide exposure to fish and a useful tool in monitoring environmental toxicity.     

鱼类组蛋白核苷酸的多态性及其在杀鱼爱德华氏菌感染中的作用

组蛋白是染色体核小体的重要组分,在调控染色质结构、基因转录、个体发育等不同生物学过程中起着重要作用。为了研究鱼类组蛋白基因是否存在核苷酸的多态性以及组蛋白核苷酸多态性是否会影响鱼类的抗病力,本实验以斑马鱼和草鱼为研究对象,通过PCR扩增克隆了组蛋白H2A的全长开放阅读框;利用过表达技术、菌落平板计数、感染存活分析以及荧光定量PCR技术,研究了斑马鱼和草鱼组蛋白H2A核苷酸多态性不同变异体在杀鱼爱德华氏菌感染中的作用。在本研究中,实验发现鱼类组蛋白H2A存在着丰富的核苷酸多态性。序列分析结果显示斑马鱼和草鱼组蛋白H2A核苷酸多态性的变异体核苷酸序列相似性为90%～100%;而两两H2A核苷酸多态性变异体氨基酸序列之间最多只有3个位点存在差异。通过体内和体外抗菌实验可知,斑马鱼和草鱼组蛋白H2A核苷酸的多态性显著影响H2A的抗菌活性。此外,筛选出的抗菌组蛋白H2A核苷酸多态性的变异体在斑马鱼体内的过表达,不仅具有免疫增强的作用,还能显著增强斑马鱼对杀鱼爱德华氏菌感染的抗病力。本研究为筛选具有抗病作用的组蛋白H2A免疫保护原奠定了重要基础。     

Identification of histones as endogenous antibiotics in fish and quantification in rainbow trout (<Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>) skin and gill

Antimicrobial polypeptides (AMPPs) are increasingly recognized as a critical component of innate host defense. Among the AMPPs, polypeptides related to histones have been identified from many animals. Using peptide mapping, we further confirm the identity of two histone-like proteins from fish as members of the H2B (sunshine bass) and H1 (rainbow trout) histone groups. We optimized the conditions for measuring rainbow trout HLP-1/H2B via sandwich ELISA. We used two antibodies, one to the amino terminus and one to the carboxyl terminus, of trout histone H2B, as the capture antibodies, and we used peroxidase-labeled antibody raised to calf histone H2B as the secondary antibody. Specificity of the detecting antibody was confirmed by specific reactivity with histone H2B in tissue extracts via western blotting. The test was reproducible and capable of detecting as little as 5 ng of histone H2B (0.05 μg/ml). Histone H2B levels expressed in gill tissue of juvenile, healthy rainbow trout were well within concentrations that are lethal to important fish pathogens. However, there was a significant, age (size)-dependent decline in histone H2B concentrations as fish matured, until levels became virtually undetectable in market-size fish. In contrast, levels in skin appeared to remain high and unchanged in small versus large fish. Antibacterial activity in skin and gill tissues was closely correlated with histone H2B concentration measured via ELISA, which supports our previous finding that histones are the major AMPPs in rainbow trout skin and gill.     

Effects of dietary retinol acetate on growth performance,skin mucus immune responses and haematological parameters of Caspian roach (Rutilus caspicus)

Three retinol acetate (vitamin A)‐supplemented diets containing 0, 5,000, 10,000 IU kg^?1 diet (in dry weight) were fed twice daily to triplicate groups (50 fish/group) of Caspian roach (Rutilus caspicus) (1.91 ± 0.07 g) for 40 days. At the end of feeding trial, skin mucus antimicrobial activity against Streptococcus faecium, Serratia marcescens, Staphylococcus aureus and Escherichia coli as well as soluble protein level, growth performance and haematological parameters was evaluated. Growth performance including final weight, weight gain, specific growth rate and food conservation ratio as well as the survival rate showed no significant differences between vitamin A‐supplemented diets and control groups (p > .05). The results revealed that the administration of 10,000 IU vitamin A kg^?1 significantly increased skin mucus antibacterial activity (p < .05). Furthermore, the soluble protein level of skin mucus was found to be significantly elevated in roach fed diet containing 10,000 IU vitamin A kg^?1 (p < .05). Evaluation of haematological parameters revealed no significant difference (p > .05), except white blood cell counts that were significantly higher in vitamin A‐fed roach (p < .05). The results of the present study indicate that dietary vitamin A can modulate mucosal immune response of Caspian roach.     

Possible effect of lesser galangal (Alpinia officinarum) extracts encapsulated into mesoporous silica nanoparticles on the immune status of rainbow trout (Oncorhynchus n)

Using plant extracts as immunostimulants in aquaculture has prove effectiv in resisting infectious disease, in addition to being safe and inexpensive. The present study is concerned about the prospective mode of action of using lesser galangal extract (Alpinia officinarum) encapsulated into amine surface functionalized mesoporous silica nanoparticles (MSN) in order to elevate the immune status of rainbow trout (Oncorhynchus mykiss). Fish were randomly divided into 6 groups and fed for 4 weeks with commercial diets supplemented with 0% (control), 0.5% and 1.5% of lesser galangal extract, and with previous concentrations encapsulated with MSN (0.5% + MSN, 1.5% + MSN) and MSN (without extract). The effects of the feeding trial on the innate humoural immune parameters (total protein, myeloperoxidase content, lysozyme antiproteases and bactericidal activities) in rainbow trout were examined. Also, the influence of dietary supplement on some immune‐related genes in rainbow trout head kidney (TNF, IL‐8, IL‐1b, LYZ2 and CD4) after challenge with Yersinia ruckeri was examined. The results revealed enhancement in immune parameters in all treatment groups compared to the control, especially in the fish group fed with 1.5% + MSN which showed the highest significant difference (p < .05) in total protein, lysozyme and antiproteases activities. Also, feeding lesser galangal extract encapsulated into MSN led to an increase in myeloperoxidase content and bactericidal activity. An improvement in the expression of immune‐related genes has been recorded in fish groups fed doses of lesser galangal extract and lesser galangal extract encapsulated into MSN compared to the control or to the group fed with MSN only. Particularly, the group fed with 0.5% + MSN showed a significant up‐regulation in most of the immune‐related genes. The current investigation supports using lesser galangal extract encapsulated into MSN in fish diets as a supplement to enhance the immune response of rainbow trout and elevate its resistance to infectious diseases.     

Immunomodulatory effect of Guavarine®, aqueous guava leaf extract,on ornamental Koi carp Cyprinus carpio var. koi L. 1758

The leaves and bark of guava (Psidium guajava) have a long history of medicinal uses. The immunomodulatory effect of Guavarine®, an aqueous guava leaf extract, was investigated on Cyprinus carpio var. koi L. The fish (8.33 ± 1.02 g) were injected with guava leaf extracts (10 or 100 µg/fish) intraperitoneally, and the innate immune parameters were monitored for 28 days. In fish injected with guava leaf extracts, the lymphocyte proliferation, nitric oxide production, and respiratory burst activity increased until the 14th day and decreased thereafter. The results indicated an elevation in the innate immune status of fish, possibly due to the presence of flavonoids in the leaf extracts.     

Effect of <Emphasis Type="Italic">Cratoxylum formosum</Emphasis> on innate immune response and disease resistance against <Emphasis Type="Italic">Streptococcus agalactiae</Emphasis> in tilapia <Emphasis Type="Italic">Oreochromis niloticus</Emphasis>

The effect of aqueous extract of Cratoxylum formosum on innate immune response and disease resistance in tilapia Oreochromis niloticus was investigated. The fish were fed diets containing 0% (control), 0.5% (diet 1), 1% (diet 2), and 1.5% (diet 3) of C. formosum aqueous extract for 30 days. At the end of the experimental period, parameters of innate immune response including phagocytosis of blood leukocytes, lysozyme activity in plasma, and respiratory bust activity were examined. Feeding the fish with diet 2 and diet 3 for 20 days enhanced phagocytic activity and for 30 days stimulated lysozyme and respiratory burst activities. Diet 1 increased the phagocytic activity at 30 days, but did not affect the other measured parameters. All parameters were not significantly changed (P > 0.05) in the control group throughout the experiment. Following 30 days of feeding, fish were infected with S. agalactiae. The cumulative mortalities of bacterial-infected tilapia that were fed diet 1, diet 2, and diet 3 were 56, 12, and 10%, respectively, compared with 85% in the control group. These results indicate that the aqueous extract of C. formosum may elevate the innate immune response and enhance disease resistance in tilapia.     

Effects on mortality and stress response in European sea bass, Dicentrarchus labrax (L.), fed mannan oligosaccharides (MOS) after Vibrio anguillarum exposure

The effects of dietary mannan oligosaccharides (MOS; 4 g kg^?1; Bio‐Mos, Alltech Inc, USA) in diets for European sea bass, Dicentrarchus labrax (L.), juveniles in relation to disease and stress resistance, combining intestinal infection with Vibrio anguillarum and stress challenge by confinement, were assessed in this study. After 8 weeks of MOS supplementation, fish were exposed to a pathogen challenge test against V. anguillarum by direct gut inoculation combined with a confinement stressor panel. Cumulative mortality of fish fed MOS caused by anally inoculated V. anguillarum decreased from 66% to 12.5% and from 54.1% to 25% in infected and infected + stressed fish, respectively, compared to fish fed control diet. Results for European sea bass revealed a positive effect of MOS dietary inclusion on disease resistance, in terms of cumulative mortality, against gut inoculated V. anguillarum, as well as reduced effects of stress on microbiota diversity. Both of these findings, together with the enhanced innate immune response and the higher gut mucus production and density of eosinophil granulocytes in gut mucosa obtained in previous studies after MOS supplementation ( Torrecillas et al. 2007, 2011a,b ) suggest that general reinforcement of the innate immune system, and particularly of the intestinal barrier efficiency, is the main defence mechanism of European sea bass fed MOS against pathogenic microorganisms.     

Inhibitory effects of edible marine algae extracts on degranulation of RBL-2H3 cells and mouse eosinophils

Inhibitory effects on degranulation of rat basophilic leukemia (RBL-2H3) cells and mouse eosinophils by marine algae extracts were examined. More than 50% of the degranulation of RBL-2H3 cells was inhibited by water extracts of Ecklonia cava and Chrysymenia wrightii at a concentration of 100 μg/mL. More than 50% of the degranulation of RBL-2H3 cells was inhibited by methanol extracts of Petalonia binghamiae, Scytosiphon lomentaria, Undaria pinnatifida, Porphyra dentata, Codium fragile and Ulva japonica at a concentration of 200 μg/mL. Most inhibitory substances in the methanol extracts were partitioned into ethyl acetate and hexane layers. The ethyl acetate-partitioned layer of methanol extract of Petalonia binghamiae had higher inhibitory effects than the hexane-partitioned layer on the degranulation of RBL-2H3 cells. By contrast, the hexanepartitioned layer of the same extract had a higher inhibitory effect than the ethyl acetate-partitioned layer on the degranulation of mouse eosinophils. The ethyl acetate-partitioned layer of methanol extract of Petalonia binghamiae was further separated into eight fractions by silica gel column chromatography. Most inhibited the degranulation of RBL-2H3 cells, but not that of mouse eosinophils significantly. These results suggest methanol extract of Petalonia binghamiae contains materials that inhibit the degranulation of basophils and eosinophils differentially.