Influence of diet enriched with green tea on innate humoral and cellular immune response of kelp grouper (Epinephelus bruneus) to Vibrio carchariae infection

Effect of diet enriched with green tea at 0, 0.01, 0.1 or 1.0% levels on immune responses such as non-specific humoral (lysozyme, antiprotease and complement) and cellular (myeloperoxidase content, production of reactive oxygen, and nitrogen species) and disease resistance on week 1, 2 or 4 in kelp grouper Epinephelus bruneus challenged with Vibrio carchariae (2.47 × 10(8) CFU ml(-1)) was quantified. At all doses green tea supplementation significantly enhanced the serum lysozyme activity from weeks 1 to 4. On the other hand, after week 2 the serum hemolytic complement activity, leucocyte myeloperoxidase content and reactive nitrogen species protection significantly increased in groups fed with 0.01 and 0.1% green tea supplementation diets. The serum antiprotease activity significantly increased in group fed with at 1.0% green tea from week 1 to 4. However, all diets except at 0.01% level resulted in a significant decrease in reactive oxygen species protection during the experimental period. Challenged groups fed with green tea enriched diet at 0.01 and 0.1% level had a higher relative percent survival than with 1.0% diet on week 1, 2 or 4. The results suggest that dietary administration of green tea supplementation at a concentration of 0.01 and 0.1% level positively enhances the non-specific humoral and cellular immune responses and disease resistance of kelp grouper E. bruneus to V. carchariae.     

Dietary supplementation with Cynodon dactylon (L.) enhances innate immunity and disease resistance of Indian major carp, Catla catla (Ham.)

Indian major carp (Catla catla) was subjected to study the immunostimulatory effects when the grass Cynodon dactylon(L) ethanolic extract administrated as feed supplement. C. catla was fed with 0% (Control), 0.05% (group I), 0.5% (group II) and 5% (group III) extract provided for 60 days. Blood samples were collected at every 10 days of interval up to 60 days for analyzing the non-specific humoral (lysozyme activity, antiprotease activity and haemolytic complement) and cellular (production of reactive oxygen and nitrogen species, myeloperoxidase activity) immune response study. The results indicate that C. dactylon ethanolic extract administered as feed supplement significantly (P < 0.05) enhanced most of the non-specific immune parameters tested. Among the experimental diet groups, significantly increased response of non-specific immunity was seen in group III (5%). Disease resistant analysis against Aeromonas hydrophila was performed in control group and plant extract treated fish for 7, 14, 21 and 28 days. Relative percent survival rate (RPS) was observed in treated samples, which is directly proportional to concentration of the extract. Additionally, electron microscopic studies and gelatin zymography for Matrix Metalo Proteinase (MMPs) were examined in spleen at 7th and 28th days of feeding. Administration of C. dactylon mixed diet delayed the lymphocyte destruction with positive ultrastructural changes. An induced stress (A. hydrophila infection) was observed by using MMPs expression, which was reduced in the experimental diet groups than the control. All these experimental results prove that C. dactylon ethanolic extract enhances the immunity of Catla fish.     

Inonotus obliquus containing diet enhances the innate immune mechanism and disease resistance in olive flounder Paralichythys olivaceus against Uronema marinum

The present study describes the effect of diet supplementation with Chaga mushroom, Inonotus obliquus extract at 0%, 0.01%, 0.1%, and 1.0% levels on the innate humoral (lysozyme, antiprotease, and complement), cellular responses (production of reactive oxygen and nitrogen species and myeloperoxidase), and disease resistance in olive flounder, Paralichythys olivaceus against Uronema marinum. The lysozyme activity and complement activity significantly increased in each diet on weeks 2 and 4 against pathogen. The serum antiprotease activity and reactive nitrogen intermediates production significantly increased in fish fed with 0.1% and 1.0% diets from weeks 1-4. However, reactive oxygen species production and myeloperoxidase activity significantly increased in 1.0% and 2.0% diets on weeks 2 and 4. In fish fed with 0.1% and 1.0% diets and challenged with U. marinum the cumulative mortality was 50% and 40% while in 0% and 0.01% diets the mortality was 85% and 55%. The results clearly indicate that supplementation diet with I. obliquus at 0.1% and 1.0% level positively enhance the immune system and confer disease resistance which may be potentially used as an immunoprophylactic in finfish culture.     

Effects of cyclophosphamide on the immune system and disease resistance of Asian catfish Clarias batrachus

Cyclophosphamide (CYP), a multifunctional alkylating agent is known as a potent immunosuppressor in endotherms. Here, an experiment was conducted in an ectothermic Asian catfish species, Clarias batrachus to investigate its effect on non-specific and specific immunity as well as disease resistance against a common bacterial pathogen challenge. CYP was intraperitoneally injected for 3 consecutive days at a rate of 200 mgkg(-1) body weight. After 72 h post-injection, control and CYP-treated fish were screened for superoxide production through nitroblue tetrazolium (NBT) assay, myeloperoxidase (MPO) activity, packed cell volume (PCV) and total protein, lysozyme, alternative complement activity (ACH50) and natural haemagglutinin titre as a measure of non-specific immunity level as well as disease resistance against Aeromonas hydrophila challenge to vaccinated and unvaccinated fish. To study the effect on specific immunity, CYP was injected thrice at an interval of 7 days after bacterin injection and serum antibody titre was measured by bacterial agglutination titre assay. The results showed a significant (P<0.05) decrease in NBT and MPO activities, and percent survival against A. hydrophila challenge (both in unvaccinated and vaccinated fish) in CYP-treated fish, when compared to control fish. The above results support the immunosuppressive action of CYP in freshwater catfish, C. batrachus. The neutrophil activities, as measured through superoxide production and myeloperoxidase levels, might be important contributors during A. hydrophila infection and that treatment with CYP reduces phagocytic killing power and inhibits resistance against aeromoniasis.     

The effect of mistletoe, Viscum album coloratum, extract on innate immune response of Nile tilapia (Oreochromis niloticus)

The purpose of the present study was to evaluate the effect of dietary mistletoe extracts on non-specific immune response and disease resistance of Nile tilapia (Oreochromis niloticus) against Aeromonas hydrophila infection. Tilapia fingerlings were fed with a diet containing 0 mg as a control, 10 mg, 50 mg, and 200 mg mistletoe powder kg(-1) dry diet for 80 days. The immunological parameters, respiratory burst activity, lysozyme activity, alternative complement haemolysis activity (ACH(50)), and phagocytic activity of fish were investigated following 20, 40 and 80 days of feeding. Fish were challenged with A. hydrophila on 80 days after feeding and mortalities were checked over 10 days post-infection. The results show that fish fed with mistletoe extract exhibited an increase in activity in all immunological parameters (P < 0.05) compared to the control group depending on feeding periods and doses of mistletoe. Following challenge with A. hydrophila, 42% less survivability was observed in the control group than in other experimental diet groups. The highest survival rate (83%) was shown in the group fed with a 50 mg mistletoe kg(-1) diet. The results suggest that mistletoe enables tilapia to promote immunity and be more resistant to A. hydrophila infection.     

The auxotrophic aroA mutant of Aeromonas hydrophila as a live attenuated vaccine against A. salmonicida infections in rainbow trout (Oncorhynchus mykiss)

An auxotrophic aroA mutant of the Aeromonas hydrophila AG2 strain is a live attenuated vaccine against A. hydrophila infection in rainbow trout (Oncorhynchus mykiss). The protection conferred by the live attenuated vaccine against A. salmonicida strains is reported here, and several parameters of the specific and non-specific immune response in vaccinated trout were characterised. Vaccination with a dose of 10(7)cells/fish of the aroA mutant elicited significant protection against the Hooke and DK30 strains of A. salmonicida (relative percent survival RPS >60%). This cross-protection correlated moderately with the activation of the humoral and cellular specific immune responses, which show cross-reactivity against antigens shared by the two bacterial species, and a moderate increase in the lysozyme and antiprotease activities in the serum of vaccinated trout.     

Dietary Korean mistletoe enhances cellular non-specific immune responses and survival of Japanese eel (Anguilla japonica)

The present study was performed to investigate the immunostimulatory effects of Korean mistletoe extract (KM-110; Viscum album Coloratum) on the non-specific immune response and protection against Aeromonas hydrophila infection in Japanese eel (Anguilla japonica). Eels were fed under 4 regimes, 0%, 0.1%, 0.5% and 1.0% KM-110 mixed diet. On day 14 after feeding, 15 fish from each group were injected i.p. with live A. hydrophila (3 x 10(6)CFU) and the remaining unchallenged fish from each group were used to study the innate immune response. On 14 days post-infection, the total survival rates were 26.6% in control, and 33.3%, 66.6% and 80% in 0.1%, 0.5% and 1% KM-110-treated groups, respectively. The maximum lysozyme activity was observed in the 1% KM-110-treated group. There was no significant difference of lysozyme activity between 0.1% and 0.5% KM-110 group. Superoxide anion (O(2)(-)) production was significantly (p<0.05) augmented in the 0.5% and 1% KM-110 groups compared to the control and 0.1% KM-110 group. No significant difference of (O(2)(-) production was found between 0.5% and 1% KM-110 group. Likewise, there was a significant increase in phagocytic activity in the 0.5% KM-110 group compared with the 0.1% group (p<0.05), but no significant difference between the 0.5% and the 1% KM-110 group indicating that 0.5% KM-110 concentration is suitable for stimulating maximum phagocytic activity resulting in a high amount of ROI production. Considering the present results, KM-110 could be utilized as a promising immunostimulating substance for a diet in aquaculture.     

Effect of Sophora flavescens on non-specific immune response of tilapia (GIFT Oreochromis niloticus) and disease resistance against Streptococcus agalactiae

The paper describes the effect of a diet supplemented with the Chinese traditional herbal medicine Sophora flavescens on the immunity and disease resistance of an Oreochromis niloticus GIFT strain. Experimental diets containing 0.025%, 0.050%, 0.100%, 0.200%, and 0.400% S. flavescens, as well as a control group without S. flavescens were used. We tested the non-specific humoral immune responses (lysozyme, antiprotease, and complement) and cellular immune responses (reactive oxygen species and nitrogen species production and myeloperoxidase), as well as disease resistance against Streptococcus agalactiae. S. flavescens supplementation at all dose significantly enhanced serum lysozyme, antiprotease, and natural hemolytic complement activity. Similarly, all S. flavescens doses enhanced cellular myeloperoxidase activity. The increased production of reactive oxygen species and reactive nitrogen intermediates by peripheral blood leucocytes was observed in most of the treatment groups throughout the test period. The fish fed 0.100% S. flavescens had a percent mortality of 21.1% and a relative percent survival of 73.3% compared with the group fed the basal diet during the S. agalactiae challenge. The results suggest that S. flavescens can be recommended as a tilapia feed supplement to enhance fish immunity and disease resistance against S. agalactiae.     

Chinese herbs (Astragalus radix and Ganoderma lucidum) enhance immune response of carp, Cyprinus carpio, and protection against Aeromonas hydrophila

The effect of Chinese herbs (Astragalus radix and Ganoderma lucidum) on immune response of carp was investigated. Fish were fed diets containing Astragalus (0.5%), Ganoderma (0.5%) and combination of two herbs (Astragalus 0.5% and Ganoderma 0.5%) for 5 weeks. Other groups of fish were vaccinated (i.p.) against Aeromonas hydrophila/Aeromonas salmonicida (Shering Plough, Essex, U.K.) at the beginning of the experiment and fed the same diets as described above. Control fish (negative control) and fish vaccinated only (positive control) were fed basal diets without supplements of herbs. The respiratory burst activity, phagocytosis, lysozyme activity and circulatory antibody titres in plasma were monitored. Following 5 weeks after feeding, fish were infected with A. hydrophila and mortalities were recorded. The results of this study showed that feeding non-vaccinated and vaccinated carp with combination of Astragalus and Ganoderma stimulated respiratory burst activity, phagocytosis of phagocytic cells in blood and lysozyme and circulatory antibody titres in plasma in vaccinated carp. Fish challenged with A. hydrophila had variable survival. The best survival (60%) was in vaccinated group fed with both herbs, while almost 90% of control fish (negative control) and 60% of fish vaccinated only (positive control) died.     

Effect of dimethylglycine and trimethylglycine (Betaine) on the response of Atlantic salmon (Salmo salar L.) smolts to experimental Vibrio anguillarum infection

Atlantic salmon (Salmo salar L.) were fed on a control diet or experimental diets containing betaine (15 mg g^-1) or dimethylglycine (DMG, I mg g^-1 or 5 mg g^-1). After 10 weeks of feeding, resistance to infection was assessed following inoculation with Vibrio anguillarum. Total blood and differential leucocyte counts were made, and plasma lysozyme and ceruloplasmin were assayed as non-specific humoral factors. The mortality during the bacterial exposure was of the same magnitude in all feeding groups. Betaine or DMG had no effect on the 'basal' levels of plasma total protein, lysozyme or ceruloplasmin, but 3 days postinjection the lysozyme and ceruloplasmin levels were higher in the control group compared with the experimental groups. In both DMG groups, the lymphocyte response took place 1-2 weeks earlier than in the control or betaine supplemented group indicating that DMG has an immunomodulating effect on salmon.     

黄连须和小檗碱对草鱼非特异性免疫系统的影响及对嗜水气单胞菌感染的抵抗作用

为了评估黄连须(FRC)和小檗碱(BBR)对草鱼(Ctenopharyngodon idella)的非特异性免疫及对抵抗嗜水气单胞菌感染的影响, 鱼喂食含1.00%、0.50%、0.25%, 0.10%, 0.00%的FRC和0.05%BBR的饲料28d。喂养28d后, 鱼注射嗜水气单胞菌, 记录感染14d后的存活率。检测NBT活性、血清溶菌酶活性、吞噬活性和补体C3水平来评价药物对草鱼的免疫反应。结果表明, 与模型组相比, 喂养饲料含有FRC和BBR的各组提高NBT活性、血清溶菌酶活性、吞噬活性和草鱼补体C3水平。喂食0.50%FRC组感染细菌后的存活率最高, 与模型组比较增加44%。FRC和BBR的体外抗菌活性采用最小抑菌浓度的方法进行了研究, 并显示出较强的抑制作用。结果表明, FRC和BBR可以用作免疫刺激剂以提高草鱼非特异性免疫和对嗜水气单胞菌引起疾病的抵抗。       

The immunomodulatory effects of tuftsin on the non-specific immune system of Indian Major carp, Labeo rohita

The purpose of this study was to determine if injections of different dosages of tuftsin would enhance the immune response and disease resistance against the infections due to the opportunistic pathogens Aeromonas hydrophila and Edwardsiella tarda in Labeo rohita fingerlings. Hence, four different dosages of tuftsin in PBS suspension at the rate of 0, 5, 10, 15 mg kg(-1) body weight of fish were injected intraperitoneally to the fingerlings of L. rohita at 2-week intervals for four times. After every 2-week interval, different serum biochemical, haematological and immunological parameters of fish were evaluated. Biochemical and haematological parameters including serum total protein content, albumin content, globulin content, albulin:globulin ratio, glucose content, leucocyte counts etc.; cellular immune parameters including superoxide anion production, phagocytic activities, lymphokine production index etc.; humoral immune parameters including lysozyme activity, complement activity, serum bactericidal activity etc., in the fish were evaluated after every 2-week interval. After 56 days, fish were divided into two subgroups under each major treatment group for challenge with two pathogens A. hydrophila and E. tarda. The mortality (%) and agglutinating antibody titre was recorded on 28th day post challenge. Most of the immune parameters including leucocyte count, phagocytic ratio, phagocytic index, lysozyme activity, complement activity, and serum bactericidal activity were significantly (p相似文献   

ERKs activation and calcium signaling are both required for VEGF induction by vanadium in mouse epidermal Cl41 cells

Studies were conducted to determine the immunomodulatory effects of high dietary ascorbic acid (vitamin C) on growth, serum concentration, non-specific immune response and disease resistance of a commercially important Asian catfish, Clarias batrachus. Four practical diets were formulated to contain 0, 500, 1000 and 2000 mg ascorbic acid (AA) equivalent/kg diet, supplied as L-ascorbyl-2-polyphosphate (LAPP) and were fed for 2, 4, 6 and 8 weeks. Each diet was fed to triplicate groups of catfish with initial body weight of 15.47± 0.59 g. After 2, 4, 6 and 8 weeks, growth, serum concentration of AA, oxidative respiratory burst, lysozyme and natural hemolytic complement activities, myeloperoxidase (MPO) content and natural haemagglutination titre were measured. Ten numbers of fish in duplicate were challenged with Aeromonas hydrophila to measure the level of protection against aeromoniasis at each one of the assayed times. The results showed that AA concentration in serum correlated positively with those in the diets and reached its saturation level after the time period directly proportional to the increase in dose level. Fish fed AA-supplemented diets showed significantly (p < 0.05) higher specific growth rate after 2 weeks of feeding. The superoxide production was enhanced after 8 weeks of feeding fish at a supplemented dose level of 2000 mg/kg. Similarly, MPO content, haemagglutination titre and alternative complement activity in serum enhanced with the increase of dietary AA levels at different duration of feeding. The lysozyme activity was not affected by the dietary AA treatment. On the other hand, feeding of AA at all concentrations significantly increased percent survival against A. hydrophila challenge after 4 weeks compared to control. The non-specific immune parameters as well as percent survival were enhanced as a result of high AA supply particularly at 500 mg/kg diet, although the increase was not maintained but returned to the initial levels after 4 weeks. These results support the possible use of AA as an immunostimulant at a dose of 500 mg/kg diet for a period of 4 weeks in catfish farming. (Mol Cell Biochem xxx: 25–33, 2005)     

Immunostimulatory effect of Tinospora cordifolia Miers leaf extract in Oreochromis mossambicus

Immunostimulatory effect of leaf extract of T. cordifolia on (i) specific immunity (antibody response), (ii) non-specific immunity (neutrophil activity) and (iii) disease resistance against Aeromonas hydrophila was investigated in O. mossambicus. Ethanol and petroleum ether extracts of the leaves were used. Both ethanol and petroleum ether extracts administered at doses of 0.8, 8 or 80 mg/kg body weight, prolonged the peak primary antibody titres upto one to three weeks. Ethanol extract at the dose of 8 mg/kg and petroleum ether extract at the doses of 0.8 or 8 mg/kg enhanced the secondary antibody response. All the doses of ethanol extract significantly enhanced neutrophil activity. Fish injected with petroleum ether or ethanol extract at a dose of 8 mg/kg were protected against experimental infection with virulent A. hydrophila. The results indicates the potential of T. cordifolia leaf extracts for use as an immunoprophylactic to prevent diseases in finfish aquaculture.     

Influence of feeding the leucine metabolite β-hydroxy-β-methylbutyrate (HMB) on the non-specific cellular and humoral defence mechanisms of rainbow trout (Oncorhynchus mykiss)

Previous studies have shown that leucine metabolite β‐hydroxy‐β‐methylbutyrate (HMB) increases the immune function in animals as measured by cellular and humoral immune responses. In the present study the influence of feeding HMB on the nonspecific cellular and humoral defence mechanisms and protection against furunculosis in rainbow trout (Oncorhynchus mykiss) was examined. HMB was fed in a pelleted ration at either 0 (control), 10, 25 or 50 mg  kg^?1 bw day^?1 for 8 weeks. Blood and pronephros cells were taken at random from 10 fish in each group for the analyses. The respiratory burst activity (RBA) and potential killing activity (PKA) of phagocytes, lymphocyte proliferation stimulated by either concanavalin (ConA) or lipopolysaccharide (LPS), lysozyme activities and total immunoglobulin (Ig) levels in plasma were analysed at 0, 1, 2, 3, 4, 6 and 8 weeks. After 4 weeks of feeding HMB, a challenge test was performed by injection of Aeromonas salmonicida into the fish. HMB approximately doubled the respiratory burst activity and potential killing activity ability of polymorphonuclear (PMN) and morphonuclear (MN) cells (P < 0.01) and increased the mitogen‐stimulated lymphocyte proliferation (P < 0.01) when compared with the control group. HMB feeding also increased (P < 0.01) the lysozyme activity in plasma and total Ig levels in serum. During the 14‐day challenge test, mortality was decreased (P < 0.01) by up to 62% in HMB‐fed fish compared with the control group mortality. In conclusion, the non‐specific immune enhancement by HMB resulted in protection against furunculosis in the rainbow trout.     

Effect of dietary beta-1,3 glucan on immune responses and disease resistance of healthy and aflatoxin B1-induced immunocompromised rohu (Labeo rohita Hamilton).

The immunostimulant beta-1,3 glucan was fed at 0.1% in feed for 7 days to healthy and aflatoxin B1 (AFB1)-induced immunocompromised fish, Labeo rohita (one of the major tropical carp species), in a 60 day trial. The effects of AFB1, glucan and their interactions on non-specific and specific immunity levels and disease resistance of fish were studied. A single intraperitoneal injection of AFB1 at 1.25 mg kg(-1) body weight) caused a significant (P < 0.05) reduction in non-specific immunity as measured through neutrophil phagocytic indices, serum bactericidal activity, and specific immunity as measured through bacterial agglutination titre against Edwardsiella tarda, as well as reduced protection against Aeromonas hydrophila challenge in comparison to control fish which were exposed neither to aflatoxin nor to glucan. Feeding of glucan to healthy fish raised the non-specific and specific immunity level and protection against bacterial infection compared with the control. Feeding of glucan to AFB1-induced immunocompromised fish for 7 days significantly raised the degree of resistance against A. hydrophila challenge and the non-specific immunity level in comparison to non-treated AFB1 exposed fish. Although feeding of glucan was able to increase specific immunity, all measured through haemagglutination titre against sheep red blood cells, and bacterial (E. tarda) agglutination titre in healthy fish in comparison to all other groups, no significant increase in specific immunity to the aflatoxin-exposed group was seen.     

Coriolus versicolor polysaccharides enhance the immune response of crucian carp (Corassius auratus gibelio) and protect against Aeromonas hydrophila

To investigate the effect of Coriolus versicolor polysaccharides (CVPS) on the immune response of crucian carp (Corassius auratus gibelio), fish were fed diets containing CVPS at different concentrations including 0.5, 1.0 and 2.0 g kg^?1 for 5 weeks. Other groups of fish were vaccinated by intraperitoneal injection (i.p.) against Aeromonas hydrophila with a killed bacterin at the beginning of the experiment and fed the same diets as described above. Additionally, control fish and vaccinated‐only fish were fed basal diets without CVPS supplementation. The phagocytosis, lysozyme activity, complement components C3 and C4, E‐C3bRR (Erythrocyte‐C3b rosette rate) and E‐CIRR (Erythrocyte‐immune complex rosette rate) levels and circulating antibody titers in the serum were monitored. Five weeks after feeding the prescribed diet, fish were challenged with A. hydrophila and the mortalities recorded. Results showed that feeding non‐vaccinated and vaccinated crucian carp with CVPS stimulated the phagocytosis of leukocytes, lysozyme, complement components C3 and C4, erythrocyte immune adherence, and circulatory antibody titers in serum in vaccinated crucian carp. Immune parameters increased to their highest levels after 3 weeks of feeding the diet containing 0.5 or 1.0 g kg^?1 CVPS. These doses also resulted in the highest protection in the challenge experiment. Best survival (85%) was in the vaccinated group fed the diet containing 1.0 g kg^?1 CVPS, whereas almost 80% of control fish (negative control) and 50% of vaccinated‐only fish (positive control) died.     

Studies on Bacillus subtilis and Lactobacillus acidophilus, as potential probiotics, on the immune response and resistance of Tilapia nilotica (Oreochromis niloticus) to challenge infections

The probiotic activity of two bacteria (Bacillus subtilis and Lactobacillus acidophilus) was evaluated by its effect on the immune response of Nile tilapia (Oreochromis niloticus), beside its protective effect against challenge infections. Furthermore, their in-vitro inhibitory activity was evaluated. The in-vitro antimicrobial assay showed that Bacillus subtilis and Lactobacillus acidophilus inhibited the growth of A. hydrophila. The B. subtilis inhibited the development of P. fluorescens while L. acidophilus inhibited the growth of Strept. iniae. The B. subtilis and L. acidophilus proved harmless when injected in the O. niloticus. The feed, containing a mixture of B. subtilis and L. acidophilus or B. subtilis alone, showed significantly greater numbers of viable cells than feed containing L. acidophilus only after 1, 2, 3 and 4 weeks of storage at 4 degrees C and 25 degrees C. The survival rate and the body-weight gain were significantly increased in the fish given B. subtilis and L. acidophilus for one and two months after application. The hematocrit values showed a significant increase in the group that received the mixture of B. subtilis and L. acidophilus compared with the control group. The nitroblue tetrazolium (NBT) assay, neutrophil adherence and lysozyme activity, showed a significant increase in all the probiotic-treated groups after 1 and 2 months of feeding, when compared with the untreated control group. The serum bactericidal activity was high in the group that was given a mixture of the two bacteria. The relative level of protection (RLP) was significantly higher against A. hydrophila, in the bacterial mixture treated group and against P. fluorescens in the L. acidophilus treated group, after one month of the feeding trial. A significantly higher RLP, against A. hydrophila or P. fluorescens, was noticed after 2 months of the feeding trial in the group given a mixture of the two bacteria, and against Strept. iniae in the group fed a diet containing L. acidophilus.     

Enhancement of the immune response and protection induced by probiotic lactic acid bacteria against furunculosis in rainbow trout (Oncorhynchus mykiss)

We analysed the effect of probiotic strains on the cellular and humoral immune responses of rainbow trout (Oncorhynchus mykiss), and their capacity to prevent furunculosis during a challenge trial. Probiotic strains (Lactococcus lactis ssp. lactis CLFP 100, Leuconostoc mesenteroides CLFP 196, and Lactobacillus sakei CLFP 202) were administered orally to fish for 2 weeks at 10(6) CFU g(-1) of feed. In comparison to untreated control fish, the phagocytic activity of head kidney leukocytes and the alternative complement activity in serum were significantly greater in all probiotic groups at the end of the second week. With the exception of the group fed with Lactobacillus sakei, superoxide anion production was also significantly increased in the probiotic groups. Analysis of lysozyme activity did not exhibit any significant difference in the probiotic and control groups. Fifteen days after the start of the probiotic feeding, fish were challenged with Aeromonas salmonicida ssp. salmonicida. The fish supplemented with probiotics exhibited survival rates ranging from 97.8% to 100%, whereas survival was 65.6% in fish not treated with the probiotics. These results demonstrate that probiotic supplementation to fish can reduce the severity of furunculosis, and suggest that this reduction may be associated with enhanced humoral and cellular immune response.     

Immune response and disease resistance of Oreochromis mossambicus to Aeromonas hydrophila after exposure to hexavalent chromium

The objective of this study was to investigate the effect of chronic exposure to sublethal concentrations of hexavalent chromium (K2Cr2O7) on the immune response and disease resistance of Oreochromis mossambicus (Peters) to bacterial Aeromonas hydrophila infection. Fish (45 to 50 g) were exposed to 0.005, 0.05, 0.5, and 5 mg l(-1) [0.01, 0.1, 1, and 10% LC50, respectively] of hexavalent chromium Cr (VI) for 28 d. The specific immune response was assessed by antibody response to A. hydrophila by bacterial agglutination assay, and to sheep red blood cells (SRBC) by plaque forming cell (PFC) assay. In addition, nonspecific immune mechanisms were assessed by serum lysozyme activity and reactive nitrogen intermediates, the latter in terms of nitric oxide (NO) production by peripheral blood leucocytes. Overall immunity was assessed by disease resistance against live virulent A. hydrophila. The study clearly indicated that chronic exposure of fish to 0.5 and 5 mg l(-1) of chromium (VI) decreased both nonspecific and specific parameters of the immune system, which resulted in a lower disease resistance to A. hydrophila. Interestingly, 0.05 mg l(-1) of Cr (VI) enhanced disease resistance and both nonspecific and specific immune responses to A. hydrophila. Our study revealed a concentration-dependent modulation of the immune system by chromium (VI), as demonstrated by suppressive or stimulatory effects on lymphocytes, lysozyme, phagocytic killing mechanisms, and disease resistance in O. mossambicus.