Maternal transmission of immunity to white spot syndrome associated virus (WSSV) in shrimp (Penaeus monodon)

Beta-1,3-1,6-glucan, derived from bakers' yeast Saccharomyces cerevisiae, was used in the present study to investigate the extent to which glucan is able to protect spawners from white spot syndrome associated virus (WSSV), and whether this protection (if any) can be passed on to hatchlings via maternal transmission of immunity. Results showed that fewer spawners in the glucan-injected groups showed the clinical symptoms of red body coloration and white spots on the shell during the 15 days between eyestalk ablation and the end of repeated spawning. This suggests that the application of glucan might lead to a slight enhancement of disease resistance in spawners, although the differences were not statistically significant within the confidence limit chosen. Challenge results showed a significant increase in relative percent survival for larvae derived from groups of glucan-injected spawners compared to those derived from groups of untreated spawners. It therefore seems that a maternally transmitted disease resistance induced by glucan, protected the larvae against a WSSV infection. Glucan immersion was not only shown to be effective for nauplii derived from spawners that were not injected with glucan, it also provided additional, cumulative protection for nauplii which already had a maternally transmitted resistance to WSSV. This is the first documented demonstration of a maternal transmission of immunity in invertebrates.

Active immunisation of black tiger prawn (Penaeus monodon) against vibriosis in Thailand

Mechanisms of host defence in Crustaceae and vibriosis in shrimp and methods for its prevention are discussed as introduction. The own work deals with the development of a site-specific multivalent anti-vibrio vaccine and its application in Thailand. The vaccine was produced in a continuous bioreactor system from field strains of Vibrio alginolyticus, V. harveyi, V. parahaemolyticus and V. vulnificus, purified through ultrafiltration, and inactivated by formalin. It was applied to Penaeus monodon PL prior to release into the ponds via artemia larvae. As mean result from numerous trials carried out under commercial field conditions in Eastern Thailand it was shown that the PL tolerated the vaccine perfectly. Due to technical problems only few of the field trials could be monitored until harvest. The data available allow claiming an obvious protective effect of the vaccine.

Glucan-induced disease resistance in tiger shrimp (Penaeus monodon)

Non-specific disease resistance induced by yeast cell wall extract, beta-1,3-1,6-glucan, was demonstrated in the tiger shrimp. In this study beta-1,3-1,6-glucan was administered to shrimps by immersion before culturing and orally during the culturing period. Challenge of the treated shrimps with the virulent pathogens, Vibrio vulnificus and viral agents extracted from the white spot syndrome victims, yielded promising results. The tolerance of glucan-treated shrimps was slightly enhanced to stresses including catching, transport and ammonia. The growth and survival rates of treated and untreated shrimps were not significantly different. Therefore, we suggest that beta-1,3-1,6-glucan can be used as an immuno-stimulant of cultured shrimps and may benefit shrimp farmers.

[Preliminary studies of the immunization of shrimp (Penaeus monodon) against vibrio infections]

There is a great demand for an applicable vaccine against bacterial infections of prawns, especially Vibriosis. The results of the tests that had been carried out can be evaluated as promising and indicate that the vaccination of prawns against bacterial diseases is possible. Nevertheless it is still necessary to increase the scale of research on this subject, above all, the basics of the immuno-system of prawns. Adult prawns should be vaccinated to check if they are able to pass their immuno-protection to their progeny. If that is the case only a few breeding animals have to be vaccinated, instead of all the larvae. Actually the prophylactic application of antibiotics is the only method to prevent infections with Vibriosis. 100-150 mg of Oxytetracycline per kg of prawns are fed during one production period and these antibiotics are also used in humans. Assuming that the average amount of harvested prawns per production unit is 8-10 metric tons/pond (1 ha). 800-1500 g of antibiotics are used. Since different pathogenic strains have developed resistance to Oxytetracycline, also other kinds of antibiotics (for example oxolinic acid) are given today. Antibiotics are often fed until harvesting, however, there are laws which prohibit use to antibiotics during the last thirty days before harvesting, to prevent residues in the prawn body. A vaccine against bacterial diseases could decrease the production costs and reduce the amount of the applied antibiotics.

Antigenic analysis (IgE and monoclonal antibodies) of the major shrimp allergen Pen a 1 (Tropomyosin) from Penaeus aztecus

Pen a 1, the major shrimp allergen from the brown shrimp Penaeus aztecus was purified by preparative SDS-PAGE. Peptides were generated from Pen a 1 by CNBr cleavage and endoproteinase (Lys-C, Glu-C, trypsin, alkaline protease, Arg-C, chymotrypsin) digestion. The molecular weights of the resulting CNBr cleavage and enzymatic digestion products, separated by peptide SDS-PAGE, ranged from 1.5 to 20 kD. Following SDS-PAGE and semidry blotting, the analysis of monoclonal antibody (mAb) and subjects' IgE reactivities demonstrated that with the exception of alkaline protease, all cleavage procedures yielded IgE-binding peptides. However, since not all peptides of every digest bind IgE, it appears that IgE-binding epitopes are restricted to certain parts of the Pen a 1 molecule. mAbs bound to CNBr, Lys-C, trypsin, Glu-C and Arg-C peptides. Since mAbs reacted to several peptides from the same digest, Pen a 1 may have several similar epitopes. The comparison of IgE and mAb reactivities demonstrated similar but not identical binding patterns.

Cloning, expression, and primary structure of Metapenaeus ensis tropomyosin, the major heat-stable shrimp allergen

Shrimp is a common cause of seafood hypersensitivity. To study the mechanism of seafood hypersensitivity at the molecular level, we have determined the primary structure of the major heat-stable allergen of shrimp by cloning, expression, nucleotide sequencing, and amino acid sequence determination of an IgE-reactive cDNA clone, Met e I, isolated from a Metapenaeus ensis expression library in lambda gt 11. We first constructed a cDNA library from the shrimp M. ensis in lambda gt 11. We then screened the library with sera from patients with hypersensitivity reactions to shrimp and identified a positive IgE-reactive clone, designated as Met e I. This cDNA was purified to homogeneity and subsequently expressed in the plasmid pGEX. Serum antibodies from patients with shrimp allergy demonstrated positive IgE reactivity by immunoblotting to a protein encoded by the clone Met e I; sera from nonallergic control subjects were not reactive. The nucleotide sequence of this cDNA clone revealed an open reading frame of 281 amino acid residues, coding for a protein of 34 kd. Comparison of the Met e I amino acid sequence with the Genbank database showed that Met e I is highly homologous to multiple isoforms of tropomyosin.

Identification of the major brown shrimp (Penaeus aztecus) allergen as the muscle protein tropomyosin

Shrimp, a major seafood allergen, was investigated as a model food allergen. Extracts from both shrimp (Penaeus aztecus) meat and cooking fluid contain a substantial and similar amount of allergenic activity. A 36-kD allergen, demonstrated in both extracts by SDS-PAGE/Western blot analysis, reacted with 28/34 (82%) sera from shrimp-sensitive, skin test and RAST-positive, individuals. This allergen, named Pen a I, was isolated by SDS-PAGE; its amino acid composition was rich in aspartic and glutamic acids. A 21-residue peptide, obtained from endoproteinase Lys-C digested Pen a I by high-performance liquid chromatography, demonstrated significant homology (60-87%) with the muscle protein tropomyosin from various species and origins. The greatest homology (87%) was noted with tropomyosin of the fruit fly (Drosophila melanogaster) reflecting the phylogenic relationship between these two arthropods. These studies demonstrate that tropomyosin is the major shrimp allergen. Although the amino acid sequence of this shrimp muscle protein shares considerable homology with tropomyosins of other species including man, significant differences remain in allergenic activity.

Immunostimulation of tiger shrimp (Penaeus monodon) hemocytes for generation of microbicidal substances: analysis of reactive oxygen species

NBT staining was used to determine the presence of superoxide anions (O2-) produced by tiger shrimp (Penaeus monodon) hemocytes attached to a coverslip. When cells were treated with beta-glucan, blue granules were observed in 41% of studied hemocyte cytoplasm. For zymosan-treated, PMA-treated, and control cells, the percentages of hemocytes showing similar blue granules were 31, 9, and 5%, respectively. A comparison of stimulative effects on 15 hemocyte suspensions, each collected from a single tiger shrimp, showed that beta-glucan had the strongest effect on intracellular O2- generation, followed by zymosan and PMA (2.5, 2, and 1.3 times greater than the O2- generated by the control group, respectively). After oxidizing phenol red to measure the amounts of hydrogen peroxide (H2O2) produced by the hemocytes, we found that beta-glucan had the strongest stimulative effect (12.2 nmol/mg protein), followed by zymosan and PMA (7.2 and 2.6 nmol/mg, respectively). However, a luminol-enhanced chemiluminescence analysis of hypochlorites (OCl-) produced by the experimental hemocytes showed that neither zymosan nor beta-glucan had a stimulative effect on OCl- production. However, following PMA stimulation, hemocyte chemiluminescence was detected although only at 1.7 mV. Using H2O2 as substrate and guaiacol as an electron acceptor, the enzyme activity of crude enzyme extract derived from broken hemocytes was analyzed; enzyme activity similar to that of human myeloperoxidase (MPO) (0.104 U/mg protein) was observed. The data showed that only PMA had any stimulative effect on MPO-like enzyme activity (2.23 times that of the control group); zymosan and beta-glucan did not have any observable effects on this specific enzyme activity. This is the first documented demonstration of a respiratory burst in shrimp hemocytes.

Isolation and characterization of heat-stable allergens from shrimp (Penaeus indicus)

Shrimp are among the more common causes of immediate hypersensitivity reactions to food. To characterize better the allergenic substances within shrimp, extracts from heated shrimp were systematically examined with solid-phase radioimmunoassay and sera from patients clinically sensitive to shrimp. Two heat-stable protein allergens, designated as Sa-I and Sa-II, were identified from boiled shrimp (Penaeus indicus) extracts. Sa-I was isolated by ultrafiltration, Sephadex G-25, and diethylaminoethyl-Sephacel chromatography, whereas, Sa-II, the major allergen, was purified by successive chromatography on diethylaminoethyl-Sephacel, Bio-Gel P-200, and Sepharose 4B columns. Sa-I, was homogeneous by polyacrylamide gel electrophoresis (PAGE), elicited a single band on sodium dodecyl sulfate-PAGE corresponding to a molecular weight of 8.2 kd. Sa-II was also found to be homogeneous by PAGE, crossed immunoelectrophoresis, and immunoblotting. On sodium dodecyl sulfate- PAGE, it elicited a single band with a molecular weight of 34 kd. Sa-II was found to contain 301 amino acid residues and was particularly rich in glutamate/glutamate and aspartate/asparagine. Solid-phase radioimmunoassay-inhibition studies revealed that Sa-I and Sa-II share 54% of the allergenic epitopes, suggesting that Sa-I may be a fragment of Sa-II.