Dietary vitamin C and its derivatives affect immune responses in grass shrimp, Penaeus monodon

Effects of L-ascorbic acid on growth, non-specific immunity, antioxidant capacity, and intestinal and hepatopancreatic histology of red swamp crayfish, Procambarus clarkii

This study investigated the dietary effects of coated L-ascorbic acid (LA) on growth, feed utilization, survival, serum biochemical indices, immunity, antioxidant capacity, and intestinal and hepatopancreatic histology of the pre-adult red swamp crayfish. Four isoproteinous and isolipidic diets were formulated to contain several LA levels as 0, 1300, 1600, and 1900 mg/kg and designated as control (LA0), LA13, LA16, and LA19, respectively. However, the analyzed LA concentrations in diets were 0.00, 199.57, 360.45, and 487.50 mg/kg in LA0, LA13, LA16, and LA19, respectively. Triplicate treatments of crayfish (21.60 ± 0.14 g) were fed the test diets and reared in fiberglass tanks with a density of 20 individuals per each for eight weeks. Results revealed that all LA treatments had significantly enhanced growth performance compared to the control. Of interest, the LA16 treatment recorded the highest final tank biomass, biomass gain, total feed intake, condition factor, and muscle yield among the other treatments. The tank feed conversion ratio was significantly decreased in LA treatments compared to the control. Moreover, dietary LA16 and LA19 had significantly higher survival rates (93.3%) compared to (85.0%) in the LA0 group. All dietary doses of LA significantly increased serum parameters (total protein, albumin, globulin, lysozyme activity) and respiratory burst activity compared to the LA0 treatment. Dietary LA16 significantly boosted the hepatopancreatic antioxidant capacity, manifested by decreased malondialdehyde concentrations, increased catalase, superoxide dismutase, and glutathione peroxidase enzyme activities, and reduced glutathione content compared to the LA-free diet. A normal histoarchitecture of the hepatopancreatic tubules was found in all LA treatments except with some minor degenerative changes in the tubular lumen, and hepatopancreatic cells associated with enlarged nuclei were found in the LA19. However, normal intestinal histoarchitecture was found in all treatments with no recorded intestinal lesions. Of interest, the polynomial regression performed on the analyzed LA concentrations suggested that 380 mg/kg would be suitable to provide maximal biomass gain for pre-adult crayfish. In conclusion, results revealed that coated LA could enhance the growth, immunity, and antioxidant capacity of pre-adult red swamp crayfish, suggesting its potential as a functional and necessary micronutrient for crayfish diets.

Ascorbic Acid Regulates the Immunity, Anti-Oxidation and Apoptosis in Abalone Haliotis discus hannai Ino

The present study was conducted to investigate the roles of ascorbic acid (AA) in immune response, anti-oxidation and apoptosis in abalone (Haliotis discus hannai Ino). Seven semi-purified diets with graded levels of AA (0, 50, 100, 200, 500, 1000 and 5000 mg/kg) were fed to abalone (initial weight: 12.01 ± 0.001 g, initial shell length: 48.44 ± 0.069 mm) for 100 days. The survival, weight gain rate and daily increment in shell length were not affected by dietary AA. The AA content in the gill, muscle and digestive glands of abalone was significantly increased by dietary AA. In terms of immunity, dietary AA significantly improved the total hemocyte count, respiratory burst and phagocytic activity in hemolymph, and lysozyme activity in cell-free hemolymph (CFH). In the digestive gland, the TLR-MyD88-dependent and TLR-MyD88-independent signaling pathways were suppressed by dietary AA supplementation. The mRNA levels of β-defensin and arginase-I in the digestive gland were significantly increased by dietary AA. In the gill, only the TLR-MyD88-dependent signaling pathway was depressed by dietary AA to reduce inflammation in abalone. The level of mytimacin 6 in the gill was significantly upregulated by dietary AA. After Vibrio parahaemolyticus infection, the TLR signaling pathway in the digestive gland was suppressed by dietary AA, which reduced inflammation in the abalone. In terms of anti-oxidation, superoxide dismutase, glutathione peroxidase and catalase activities, as well as total anti-oxidative capacity and reduced glutathione content in CFH, were all significantly upregulated. The malondialdehyde content was significantly downregulated by dietary AA. The anti-oxidative capacity was improved by triggering the Keap1-Nrf2 pathway in abalone. In terms of apoptosis, dietary AA could enhance the anti-apoptosis ability via the JNK-Bcl-2/Bax signaling cascade in abalone. To conclude, dietary AA was involved in regulating immunity, anti-oxidation and apoptosis in abalone.

Marine actinomycetes Nocardiopsis alba MCCB 110 has immunomodulatory property in the tiger shrimp Penaeus monodon

Shrimp farming constitutes an important source of revenue and employment in many developing countries. However, the shrimp industry has always been plagued with infectious diseases having varied aetiologies. Dominated by non - specific immune mechanism, preventive health care strategy is the most appropriate approach to protect the crop. The present study evaluated the efficacy of an actinomycete, Nocardiopsis alba MCCB 110 in eliciting non - specific immune mechanism in Penaeus monodon having Vibrio harveyi as the challenge organism. Haemocyte count, total protein, phenoloxidase, reactive oxygen intermediates, acid and alkaline phosphatase as well as the gene expression of proPO, peroxinectin, transglutaminase, alpha 2-macroglobulin, astakine, crustin, and penaeidin-3 were evaluated. The results demonstrated that the phenoloxidase, respiratory burst, total protein, acid and alkaline phosphatases were higher in the haemolymph of shrimps fed with Nocardiopsis alba MCCB 110 incorporated feed before and after challenge with Vibrio harveyi, compared to those of placebo fed animals. Up-regulation of six immune genes (alpha 2 macroglobulin, penaeidin -3, transglutaminase, proPO, crustin and peroxinectin) during the post-challenge were recorded. Survival of shrimp among the Nocardiopsis alba administered ones was 83% while it was 50% in placebo fed group. The elevated levels of nonspecific immune gene transcripts and concurrent increase in non specific immunity besides the higher survival rate in the Nocardiopsis alba administered group demonstrated the immunomodulatory property of the marine actinomycete Nocardiopsis alba MCCB 110 in the tiger shrimp Penaeus monodon, and on administering it through diet shrimp could be protected from vibriosis especially of V. harveyi.

Characterization of an inducible HSP70 gene in Chilo suppressalis and expression in response to environmental and biological stress

The highly conserved heat shock protein 70 (HSP70) contributes to survival at a cellular level and greatly enhances stress tolerance in many organisms. In this study, we isolate and characterize Cshsp702, which encodes an inducible form of HSP70 in the rice stem borer, Chilo suppressalis. Cshsp702 does not contain introns; the translational product is comprised of 629 amino acids with an isoelectric point of 5.69. Real-time quantitative PCR revealed that Cshsp702 was expressed at maximal levels in hemocytes and was minimally expressed in the midgut. Expression of Cshsp702 in response to a range of temperatures (-11 to 43 °C) indicated significant induction by extreme cold and hot temperatures, with maximum expression after 2 h at 42 °C. The induction of Cshsp702 in response to the endoparasite Cotesia chilonis was also studied; interestingly, Cshsp702 expression in C. suppressalis was significantly induced at 24 h and 5 days, which correspond to predicted times of C. chilonis feeding and growth, respectively. The potential induction of Cshsp702 as an inflammatory response due to parasitic stress is discussed. In conclusion, Cshsp702 is induced in response to both environmental and biotic stress and plays an important role in the physiological adaptation of C. suppressalis.

Beta 1,3/1,6-glucan and vitamin C immunostimulate the non-specific immune response of white shrimp (Litopenaeus vannamei)

This study mainly evaluated the effects of orally administered beta 1,3/1,6-glucan and vitamin C on the nonspecific immune responses of white shrimp (Litopenaeus vannamei). In this study, we found that the white shrimp oral administration with 1 g/kg of beta 1,3/1,6-glucan effectively enhanced O2(-) production and phenoloxidase and superoxide dismutase activity. Shrimp were oral administration with 0.2 g/kg of vitamin C presented beneficial nonspecific immune responses and enzyme activity and also observed in the beta 1,3/1,6-glucan treatment groups. Consequently, we compared the alterations in the immune activity between the beta 1,3/1,6-glucan and vitamin C groups and the evidence illustrated that combination of beta 1,3/1,6-glucan and vitamin C presented an additive effect on inducing the nonspecific immune responses of white shrimp.

Immune related transcriptional responses and performance of Litopenaeus vannamei post-larvae fed on dietary probiotic PrimaLac(®)

The present study investigated the effects of various levels of multi-strain probiotic on the immune related gene expression, digestive enzyme activity, growth performance, body chemical composition and survival of Litopenaeus vannamei post-larvae. After transferring post-larvae of L. vannamei to indoor conditions and subsequent acclimation to laboratory condition for 14 days, the shrimp were fed multi-strain probiotic at four different doses of 0, 0.25, 0.5 and 1.0 g kg(-1) for eight weeks. Shrimp fed 0.5 and 1.0 g kg(-1) probiotic PrimaLac(®) exhibited significantly (p < 0.05) higher weight gain, specific growth rate, body crude protein as well as lower FCR compared to other groups. Feeding on 0.5 and 1 g kg(-1) dietary multi-strain probiotic significantly (p < 0.05) increased the level of body crude protein. Oral administration of 0.5 and 1.0 g kg(-1) multi-strain probiotic significantly (p < 0.05) decreased body crude lipid and body moisture respectively. 30 days after feeding, protease, amylase and lipase activity increased in groups fed 0.5 and 1.0 g kg(-1) probiotic PrimaLac(®). However, on the 60th day, specific protease and amylase activity in all treatment groups were significantly higher than control group (p < 0.05) but lipase activity was higher (p < 0.05) in groups fed 0.5 and 1.0 g kg(-1) multi-strain probiotic. Oral administration of 1.0 g kg(-1) probiotic increased (p < 0.05) the level of prophenoloxidase and g-type lysozyme gene on day 30th and 60th after treatment. On day 30th and 60th, penaeidin gene expression was significantly higher in all treatment groups compared to the control group (p < 0.05). In general, findings of this study demonstrated that oral administration of 0.5 and 1.0 g kg(-1) multi-strain probiotic improved the performance of the fish and increased the expression of immune related genes.

White spot disease risk factors associated with shrimp farming practices and geographical location in Chanthaburi province, Thailand

Over the past 2 decades, shrimp aquaculture in Thailand has been impacted by white spot disease (WSD) caused by white spot syndrome virus (WSSV). Described here are results of a survey of 157 intensive shrimp farms in Chanthaburi province, Thailand, to identify potential farm management and location risk factors associated with the occurrence of WSD outbreaks. Logistic regression analysis of the survey responses identified WSD risks to be associated with farms sharing inlet water and culturing shrimp year round and with a single owner operating more than 1 farm. The analysis also showed WSD risks to be reduced at farms that used probiotics and applied lime to pond bottoms when fallow to neutralize acidity and kill microorganisms. Regression modeling identified no association of geographical location with WSD. The data should assist shrimp farms in mitigating the effects of WSD in Thailand.

Binding Specificity of Philyra pisum Lectin to Pathogen-Associated Molecular Patterns, and Its Secondary Structure

We recently reported a Philyra pisum lectin (PPL) that exerts mitogenic effects on human lymphocytes, and its molecular characterization. The present study provides a more detailed characterization of PPL based on the results from a monosaccharide analysis indicating that PPL is a glycoprotein, and circular dichroism spectra revealing its estimated α-helix, β-sheet, β-turn, and random coil contents to be 14.0%, 39.6%, 15.8%, and 30.6%, respectively. These contents are quite similar to those of deglycosylated PPL, indicating that glycans do not affect its intact structure. The binding properties to different pathogen-associated molecular patterns were investigated with hemagglutination inhibition assays using lipoteichoic acid from Gram-positive bacteria, lipopolysaccharide from Gram-negative bacteria, and both mannan and β-1,3-glucan from fungi. PPL binds to lipoteichoic acids and mannan, but not to lipopolysaccharides or β-1,3-glucan. PPL exerted no significant antiproliferative effects against human breast or bladder cancer cells. These results indicate that PPL is a glycoprotein with a lipoteichoic acid or mannan-binding specificity and which contains low and high proportions of α-helix and β-structures, respectively. These properties are inherent to the innate immune system of P. pisum and indicate that PPL could be involved in signal transmission into Gram-positive bacteria or fungi.

Effects of different dietary lipid level on the growth, survival and immune-relating genes expression in Pacific white shrimp, Litopenaeus vannamei

Five feeding trials based on the isonitrogenous and isoenergetic experimental diets containing 34% protein, 6%, 8%, 10%, 12% or 14% lipid respectively in the circulating water culture system for both 30 and 60 days were conducted to investigate the effect of the dietary lipid level on the growth and immunity in white shirmp, Litopenaeus vannamei adults. The body weight and specific growth rate of white shrimp in different treatments indicated that shrimps fed the diet of 12% lipid level for 30d and 10% lipid level for 60d had the best developmental status. The ability of respiratory burst in hemocytes was improved as the increase of dietary lipid level. The transcripts of LGBP and pPO were sensitive to the dietary lipid in hemocyte and hepatopancreas respectively. The activities of CAT, GPx and AKP were increased to a certain extend according to dietary lipid level. Qualification of MDA showed the lowest level in the sample subjected to 12% lipid level diet, indicating an optimal utilization of the dietary lipid and an efficient clearance of MDA in vivo. These results suggested that dietary lipid level of 10-12% significantly tunes the growth and enhance the immune abilities mainly via ROS pathway of L. vannamei.

Effect of dietary vitamin C on the growth performance and innate immunity of juvenile cobia (Rachycentron canadum)

This study was conducted to evaluate the effects of dietary vitamin C on growth performance, hematologic parameters and innate immune responses in juvenile cobia, Rachycentron canadum. Seven practical diets were formulated to contain 0.0 (as the basal diet), 13.6, 27.2, 54.4, 96.6, 193.4 and 386.5 mg ascorbic acid equivalent kg(-1) diet. Each diet was fed to triplicate groups of juvenile cobia with initial body weight of 5.5 g in 500-L cylindrical fiberglass tank. The results of 8 weeks feeding trial showed that typical vitamin C-deficient signs such as spinal deformation and body nigrescence were observed in the fish fed the basal diet. Fish fed the basal diet had significantly lower weight gain, specific growth rate (SGR), protein efficiency ratio (PER) and feed efficiency (FE) than those fed the diets supplemented with vitamin C, but no significant differences were observed among diets supplemented with vitamin C. However, survival rate was significantly affected by the dietary vitamin C levels, fish fed the basal diet had lower survival rate than those fed the diets supplemented with vitamin C. The ascorbic acid concentration in liver was correlated positively with the dietary vitamin C levels, however, the thiobarbituric acid reactive substances (TBARS) concentrations in liver was not significantly affected by the dietary vitamin C levels, although, fish fed the basal diet had the highest TBARS values among all treatments. The activities of serum lysozyme, superoxide dismutase (SOD), alkaline phophatase (AKP) and total immunoglobulin (Ig) were significantly influenced by the dietary vitamin C levels, fish fed the basal diet had lower lysozyme, SOD, AKP and total Ig than those fed diets supplemented with vitamin C. The serum glucose and triglyceride concentrations were significantly affected by the dietary vitamin C levels. Fish fed the basal diet had lower red blood cell and hemoglobin values than those fed the vitamin C supplemented diets. The challenge experiment with Vibrio harveyi showed that lower cumulative survival was in fish fed the unsupplemented diet, the cumulative survival were significantly increased with increase of the dietary ascorbic acid levels from 13.6 to 96.6 mg kg(-1), while the cumulative survival reached plateau when dietary ascorbic acid levels increased from 96.6 to 386.5 mg kg(-1). These results indicated that dietary vitamin C did significantly influence on growth performance and immune response of juvenile cobia.

Functional analysis of C-type lysozyme in penaeid shrimp

Lysozyme is an enzyme that cleaves the β-1,4-glycosidic linkages between N-acetylmuramic acid and N-acetylglucosamine in peptidoglycan, leading to bacterial lysis. Recently, lysozyme has been found to have anti-HIV and anti-cancer properties in mammals. However, most functional analyses were done in vitro using purified or recombinant lysozyme protein. Here, we used RNA interference to silence c-type lysozyme expression in penaeid shrimp, Marsupenaeus japonicus, to analyze the function of lysozyme in vivo. Silencing of lysozyme expression by dsRNA lysozyme (dsLYZ) led to 100% mortality without any artificial bacterial infection in 5 days. Lysozyme deficiency caused the number of hemocytes in hemolymph to decrease from 1.3 × 10(7) to 2.3 × 10(6) cells/ml and caused the number of bacteria to increase from 78 to 764 colony-forming units/ml. Suppression of bacterial growth using oxytetracycline and kanamycin showed improvement in mortality, suggesting that shrimp mortality post- dsLYZ injection can be attributed to bacterial growth in the shrimp hemolymph. The majority of the bacteria, identified by 16 S rRNA analysis, were Gram-negative species such as Vibrio and Pseudomonas. Furthermore, PKH26 staining showed that the dsLYZ-injected shrimp were unable to eliminate non pathogenic Escherichia coli or Staphylococcus aureus in 24 h. These data suggest that c-type lysozyme in shrimp serves to regulate the growth of bacterial communities, particularly Gram-negative bacteria, in the hemolymph.

Modulation and Interaction of Immune-Associated Parameters with Antioxidant in the Immunocytes of Crab Scylla paramamosain Challenged with Lipopolysaccharides

Invertebrates are dependent on cellular and humoral immune defences against microbial infection. Scylla paramamosain is an important commercial species, but the fundamental knowledge on its immune defense related to the antioxidant and immune-associated reactions is still lacking. The study was to differentiate the responses of immune-associated parameters of haemolymph components in S. paramamosain when challenged with bacterial lipopolysaccharides (LPSs). The immunostimulating effects of LPS in crab by triggering various immune parameters (phagocytosis, lysozyme, antibacterial activity, phenoloxidase, and the generation of superoxide and nitric oxide) were investigated. Results showed that the generation of free radicals, phenoloxidase, lysozyme and antibacterial activities was significantly increased through the exposure periods. Conversely, total hemocyte count and lysosomal membrane stability decreased significantly as the exposure period extended to 96 h. The relationship between the antioxidant enzymes and immune reactions due to LPS was highly significant. In addition, ROS production was positively correlated with antioxidant showing immediate response of antioxidant defense to the oxyradicals generated. Overall, the study indicated that nonspecific immune components in hemocytes of crab showed active response to the LPS stimulation, and their responses suggested that many immune-associated parameters could be modulated and interrelated with the influence of antioxidants in crustaceans.

Is activated hemocyanin instead of phenoloxidase involved in immune response in woodlice?

In the Common woodlouse Porcellio scaber (Crustacea: Isopoda: Oniscidea), experimental immune challenge did not induce the expression of pro-phenoloxidase that, in most other invertebrates studied thus far, can be activated into phenoloxidase via an activation cascade upon immune challenge. Instead, Porcellio hemocyanin proved to exhibit catecholoxidase activity upon activation. However, none of the activating factors known from other invertebrates other than SDS-treatment resulted in activation of hemocyanin into a functional phenoloxidase in vitro. The distinct characteristics of isopod hemocyanin are reflected by the quaternary structure of the hemocyanin dodecamers that differs from that of other crustacean hemocyanins in that the two hexamers share a common 3-fold rotation axis and have an angular offset of 60 degrees against each other. Accordingly, the sequence of Porcellio hemocyanin can be distinguished clearly from other crustacean hemocyanins and in a phylogenetic analysis forms a cluster with other isopod and amphipod hemocyanins. We propose a peracarid-type hemocyanin that may have evolved in response to its required multiple functions in respiration and immune response, while phenoloxidase sensu strictu is lacking.

Effect of environmental parameters on immune response of the Indian spiny lobster, Panulirus homarus (Linnaeus, 1758)

The high export value of the Indian spiny lobster Panulirus homarus increasingly attracts the aquaculturists for farming and fattening. However, lack of knowledge on the effect of environmental parameters on the immune system of this animal could result in high mortality, which ultimately may cause major loss to the industry. Here, we report the effect of salinity (20, 25, 35, 40, and 45 per thousand), pH (5.0, 8.0, and 9.5), dissolved oxygen (DO) (1 and 5 mg L(-1)), and ammonia-N concentration (0, 0.5, 1.5 and 3 mg L(-1)) on the immune response of P. homarus measured in the haemolymph in terms of Total Haemocyte Count (THC), phenoloxidase (PO) activity, and NBT-reduction. Our data showed significant reduction (P<0.05) in THC, and NBT-reduction at lower (20 per thousand) and higher (45 per thousand) salinities. However, PO activity showed significant disparity, showing an increasing trend from 20 to 45 per thousand. Significant reduction (P<0.05) in THC and PO activity under acidic and alkaline conditions, under hypoxic condition (1 mg L(-1)), and at the higher ammonia-N concentrations than their respective optimal conditions were observed. Thus, suggesting that extreme environmental parameters can induce modifications in the immune system of the spiny lobster P. homarus, which may enhance their susceptibility to opportunistic pathogens. The humoral parameters such as THC, PO activity, and NBT-reduction can be used as potential stress indicators for healthy management of spiny lobsters.

In vivo effects of adding singular or combined anti-oxidative vitamins and/or minerals to diets on the immune system of tilapia (Oreochromis hybrids) peripheral blood monocyte-derived, anterior kidney-derived, and spleen-derived macrophages

Macrophage function is an important factor for resistance to infection and anti-oxidative vitamins and minerals can affect how macrophages function in fish. We report the in vivo effect of adding singular or combined vitamins (A, C, and E) and/or minerals (Se, Zn, Cu, Mn, and Fe) in diets on the immune system of tilapia (Oreochromis hybrids) peripheral blood monocyte-derived, anterior kidney-derived, and spleen-derived macrophages. An optimal dose of vitamins and/or minerals in diets increased macrophage proliferation and protective activity, maintained macrophage viability, increased body weight and length, and increased lysozyme activity, however, at improper doses and combinations of vitamins or minerals a decrease was observed. Furthermore, vitamins and/or minerals at any doses and combinations in diets decreased superoxide and nitric oxide production. Therefore, appropriate doses and combinations of vitamins and/or minerals in diets may increase tilapia macrophages immunity.

In vitro generation of superoxide anion by the hemocytes ofMacrobrachium rosenbergii: possible mechanism and pathways

The hemocytes from the giant freshwater prawn Macrobrachium rosenbergii were examined for their ability to generate superoxide anion (O(2) (-)) in vitro upon exposure to various components derived from microbial cell wall components. Among the test molecules, laminarin (a polymer of beta-1, 3 glucans), mannan and LPS from five different bacterial species produced a differential response in terms of stimulated O(2) (-) production in prawn hemocytes, suggesting the ability of the hemocytes to differentiate non-self. This response was almost completely inhibited by superoxide dismutase (SOD) suggesting SOD-inhibitable O(2) (-) generation by prawn hemocytes. Phorbol 12-myristate 13-acetate (PMA) and Ca ionophore led to enhanced O(2) (-) generation by the hemocytes and this suggests the possible role of protein kinase C and Ca(2+) ions in such generation. Cytochemical analysis using nitroblue tetrazolium (NBT)-staining revealed the importance of granular hemocytes in O(2) (-) generation in these prawns. Inhibition of O(2) (-) generation by inhibitors of NADPH-oxidase and phenoloxidase pathways clearly reveal the involvement of two different pathways in non-self stimulated O(2) (-) generation by the prawn hemocytes. These findings demonstrate the importance of O(2) (-) generation and role of possible pathways in hemocyte mediated cellular immune response of a crustacean.

Engulfed pathogen-induced apoptosis in haemocytes of giant freshwater prawn, Macrobrachium rosenbergii

Haemocytes of the giant freshwater prawn, Macrobrachium rosenbergii, were investigated for the induction of apoptosis after phagocytosis of pathogenic yeasts, bacteria and non-pathogenic latex beads in vitro. Isolated haemocytes of M. rosenbergii were cultured at a ratio of 1:50 haemocytes to pathogen with the yeast Debaryomyces hansenii, the bacteria Aeromonas hydrophila or Enterococcus faecium, or with latex beads at 25 degrees C for 2 h, followed by washing to remove free particles. At least 200 haemocytes were counted to determine the phagocytosis rate, and the results showed that haemocytes engulfed latex beads at a higher rate than the aquatic pathogens. By transmission electron microscopy, the yeast- or bacterium-engulfing haemocytes displayed morphological changes characteristic of apoptosis, including formation of cytoplasmic vacuoles, chromatin condensation and fragmentation of nuclei. This pathogen-induced apoptosis was further confirmed by DNA laddering and TUNEL (terminal deoxynucleotidyl transferase-mediated deoxy-UTP nick-end-labelling) assays. Neither haemocytes treated with latex beads nor uninfected haemocytes (control group) showed signs of apoptosis after 48 h in culture.

The protective effect of chitin and chitosan against Vibrio alginolyticus in white shrimp Litopenaeus vannamei

White shrimp, Litopenaeus vannamei, which had been injected with chitin at 4, 6 and 8 microg g(-1) or chitosan at 2, 4 and 6 microg g(-1), were challenged with pathogen Vibrio alginolyticus at 2 x 10(6) colony-forming units (cfu) shrimp(-1) and then placed in seawater of 34 per thousand. The survival of shrimp that received chitin or chitosan at either dose was significantly higher than that of control shrimp after 1 day, and at the termination of the experiment (6 days after the challenge). In another experiment, the total haemocyte count (THC), phenoloxidase activity, respiratory burst, superoxide dismutase (SOD) activity, and phagocytic activity to V. alginolyticus were measured when L. vannamei (10.4 +/- 0.7 g) were injected individually with chitin at 4 and 6 microg g(-1) or chitosan at 2 and 4 microg g(-1). L. vannamei received chitin at 6 microg g(-1) or chitosan at 2 and 4 microg g(-1) increased significantly its THC and respiratory burst after 2 days. L. vannamei received chitin at 6 microg g(-1) or chitosan at 2 and 4 microg g(-1) still maintained significantly higher phenoloxidase activity after 6 days. L. vannamei received chitin at 4 and 6 microg g(-1) or chitosan at 2 and 4 microg g(-1) increased its phagocytic activity against V. alginolyticus after 1 day, respectively. It is therefore concluded that L. vannamei that received chitin at 6 microg g(-1) or chitosan at 4 microg g(-1) or less increased its immune ability and resistance to V. alginolyticus infection.

The prophenoloxidase-activating system in invertebrates

A major innate defense system in invertebrates is the melanization of pathogens and damaged tissues. This important process is controlled by the enzyme phenoloxidase (PO) that in turn is regulated in a highly elaborate manner for avoiding unnecessary production of highly toxic and reactive compounds. Recent progress, especially in arthropods, in the elucidation of mechanisms controlling the activation of zymogenic proPO into active PO by a cascade of serine proteinases and other factors is reviewed. The proPO-activating system (proPO system) is triggered by the presence of minute amounts of compounds of microbial origins, such as beta-1,3-glucans, lipopolysaccharides, and peptidoglycans, which ensures that the system will become active in the presence of potential pathogens. The presence of specific proteinase inhibitors prevents superfluous activation. Concomitant with proPO activation, many other immune reactions will be produced, such as the generation of factors with anti-microbial, cytotoxic, opsonic, or encapsulation-promoting activities.

Vitamin E requirements of juvenile grass shrimp, Penaeus monodon, and effects on non-specific immune responses

A feeding trial was conducted to determine the dietary vitamin E (DL-alpha-tocopheryl acetate, dl-alpha-TOA) requirement and its effect on the non-specific immune responses of juvenile grass shrimp, Penaeus monodon. Purified diets with eight levels (0, 25, 50, 75, 100, 150, 200, 400 mg vitamin E kg diet-1) of supplemental dl-alpha-TOA were fed to P. monodon (mean initial weight 0.29 +/- 0.01 g) for eight weeks. Each diet was fed to three replicate groups of shrimp. Weight gains and total haemocyte count (THC) were higher (P < 0.05) in shrimp fed diets supplemented with 75 and 100 mg vitamin E kg diet-1 than in shrimp fed diets supplemented with </= 50 mg vitamin E kg diet-1. Superoxide dismutase (SOD) activity was higher in shrimp fed diets supplemented with 50-200 mg vitamin E kg diet-1 than in shrimp fed diets supplemented with </= 25 and 400 mg vitamin E kg diet-1. Vitamin E concentrations in the hepatopancreas and muscle of the shrimp were increased as the dietary vitamin E supplementation level was increased up to 200 mg vitamin E kg diet-1. Thiobarbituric acid (TBA) values in the hepatopancreas and muscle were generally decreased as the dietary vitamin E supplementation level increased. Analysis by polynomial regression of weight gain, THC and hepatopancreatic vitamin E concentration of the shrimp indicated that a level of 85-89 mg vitamin E kg diet-1 is required for maximal growth and non-specific immune responses of P. monodon and that 179 mg vitamin E kg diet-1 is required to maximise tissue vitamin E concentration.

Increase of dietary vitamin C improves haemocyte respiratory burst response and growth of juvenile grass shrimp, Penaeus monodon, fed with high dietary copper

Effects of dietary vitamin C (l-ascorbyl-2-monophosphate-Mg, C2MP-Mg) on growth, tissue copper (Cu) accumulation, and haemocyte superoxide anion production of juvenile grass shrimp, Penaeus monodon, fed with either adequate or high (8 x adequate) dietary Cu were studied. Three experimental diets were used: basal diet supplemented with adequate levels of both C2MP-Mg (40 mg kg diet(-1)) and Cu (20mg kg diet(-1)) (NC-NCu); basal diet supplemented with adequate C2MP-Mg and high Cu (8 x adequate) (NC-HCu); and basal diet supplemented with high C2MP-Mg (5 x adequate) and high Cu (HC-HCu). These were each fed to triplicate groups of shrimp (mean initial weight: 0.29+/-0.01 g) for 8 weeks. Highest (P< 0.01) weight gain, feed efficiency (FE) and protein efficiency ratio (PER) were observed in shrimp fed NC-NCu diet, intermediate in shrimp fed HC-HCu diet, and lowest in shrimp fed NC-HCu diet. Cu concentrations in hepatopancreas, muscle and haemolymph were highest in shrimp fed NC-HCu diet, followed by shrimp fed HC-HCu diet, and lowest for shrimp fed NC-NCu diet. Survival, total haemocyte count (THC) and intracellular superoxide anion (O-2) production were higher in shrimp fed NC-NCu diet than shrimp fed NC-HCu diet, whereas hepatosomatic index (HSI) was higher in shrimp fed NC-HCu diet than shrimp fed NC-NCu diet. However, all these parameters were similar in shrimp fed NC-NCu diet and shrimp fed HC-HCu diet. These data suggest that increase of dietary vitamin C improved haemocyte respiratory burst response and growth and prevented tissue Cu accumulation in P. monodon fed with high dietary Cu.

Processing of an antibacterial peptide from hemocyanin of the freshwater crayfish Pacifastacus leniusculus

An antibacterial peptide with 16 amino acid residues was found in plasma of the freshwater crayfish, Pacifastacus leniusculus. This peptide, designated astacidin 1, was purified by cation-exchange column chromatography and reverse-phase high performance liquid chromatography. Astacidin 1 has a broad range of antibacterial activity, and it inhibits growth of both Gram-positive and Gram-negative bacteria. The primary sequence of astacidin 1 was FKVQNQHGQVVKIFHH-COOH. The molecular mass was 1945.2 Da, and no carbohydrate-linked amino acid residues could be found by mass spectrometry. A synthetic astacidin 1 resulted in similar activity as the authentic astacidin 1 against Gram-positive bacteria, whereas it had less or no activity against Gram-negative bacteria. Three amino-terminal-truncated synthetic peptides were made; they all showed low activity, suggesting that the amino-terminal part of astacidin 1 contributes to the antibacterial activity. The structure of astacidin 1 based on the CD results showed that it has a beta-sheet structure in citric acid buffer at pH 4, 6, and 8. Cloning of astacidin 1 shows that it is the carboxyl-terminal part of crayfish hemocyanin and that astacidin 1 is produced by a proteolytic cleavage from hemocyanin under acidic conditions. The processing and release of astacidin 1 from hemocyanin is enhanced when crayfish are injected with lipopolysaccharide or glucan.