Enhancement of disease resistance against penaeid acute viraemia and induction of virus-inactivating activity in haemolymph of kuruma shrimp, Penaeus japonicus, by oral administration of Pantoea agglomerans lipopolysaccharide (LPS)

Experimental Infection Models and Their Usefulness for White Spot Syndrome Virus (WSSV) Research in Shrimp

White spot syndrome virus (WSSV) is marked as one of the most economically devastating pathogens in shrimp aquaculture worldwide. Infection of cultured shrimp can lead to mass mortality (up to 100%). Although progress has been made, our understanding of WSSV's infection process and the virus-host-environment interaction is far from complete. This in turn hinders the development of effective mitigation strategies against WSSV. Infection models occupy a crucial first step in the research flow that tries to elucidate the infectious disease process to develop new antiviral treatments. Moreover, since the establishment of continuous shrimp cell lines is a work in progress, the development and use of standardized in vivo infection models that reflect the host-pathogen interaction in shrimp is a necessity. This review critically examines key aspects of in vivo WSSV infection model development that are often overlooked, such as standardization, (post)larval quality, inoculum type and choice of inoculation procedure, housing conditions, and shrimp welfare considerations. Furthermore, the usefulness of experimental infection models for different lines of WSSV research will be discussed with the aim to aid researchers when choosing a suitable model for their research needs.

RNAi-Based Therapy: Combating Shrimp Viral Diseases

Shrimp aquaculture has become a vital industry, meeting the growing global demand for seafood. Shrimp viral diseases have posed significant challenges to the aquaculture industry, causing major economic losses worldwide. Conventional treatment methods have proven to be ineffective in controlling these diseases. However, recent advances in RNA interference (RNAi) technology have opened new possibilities for combating shrimp viral diseases. This cutting-edge technology uses cellular machinery to silence specific viral genes, preventing viral replication and spread. Numerous studies have shown the effectiveness of RNAi-based therapies in various model organisms, paving the way for their use in shrimp health. By precisely targeting viral pathogens, RNAi has the potential to provide a sustainable and environmentally friendly solution to combat viral diseases in shrimp aquaculture. This review paper provides an overview of RNAi-based therapy and its potential as a game-changer for shrimp viral diseases. We discuss the principles of RNAi, its application in combating viral infections, and the current progress made in RNAi-based therapy for shrimp viral diseases. We also address the challenges and prospects of this innovative approach.

Preventing bacterial disease in poultry in the post-antibiotic era: a case for innate immunity modulation as an alternative to antibiotic use

The widespread use of antibiotics in the poultry industry has led to the emergence of antibiotic-resistant bacteria, which pose a significant health risk to humans and animals. These public health concerns, which have led to legislation limiting antibiotic use in animals, drive the need to find alternative strategies for controlling and treating bacterial infections. Modulation of the avian innate immune system using immunostimulatory compounds provides a promising solution to enhance poultry immune responses to a broad range of bacterial infections without the risk of generating antibiotic resistance. An array of immunomodulatory compounds have been investigated for their impact on poultry performance and immune responses. However, further research is required to identify compounds capable of controlling bacterial infections without detrimentally affecting bird performance. It is also crucial to determine the safety and effectiveness of these compounds in conjunction with poultry vaccines. This review provides an overview of the various immune modulators known to enhance innate immunity against avian bacterial pathogens in chickens, and describes the mechanisms involved.

Recent progress in the use of purple non-sulfur bacteria as probiotics in aquaculture

The use of probiotics in aquaculture is widely recognized as an ecological and cost-effective approach to raising healthy, pathogen-tolerant aquatic animals, including fish and shrimp. In particular for shrimp, probiotics are viewed as a promising countermeasure to the recent severe damage to the shrimp industry by bacterial and viral pathogens. Purple non-sulfur bacteria (PNSB) are Gram-negative, non-pathogenic bacteria with wide application potential in agriculture, wastewater treatment, and bioenergy/biomaterials production. In aquaculture, lactic bacteria and Bacillus are the major probiotic bacteria used, but PNSB, like Rhodopseudomonas and Rhodobacter, are also used. In this review, we summarize the previous work on the use of PNSB in aquaculture, overview the previous studies on the stimulation of innate immunity of shrimp by various probiotic microorganisms, and also share our results in the probiotic performance of Rhodovulum sulfidophilum KKMI01, a marine PNSB, which showed a superior effect in promotion of growth and stimulation of immunity in shrimp at a quite low concentration of 1 × 10³ cfu (colony forming unit)/ml in rearing water.

Comparative effects of different bacterial lipopolysaccharides on modulation of immune levels to improve survival of the black tiger shrimp

To prevent loss from disease, immunostimulants have been used as dietary supplements to improve immunity and survival of shrimps. Among the various types of immunostimulants, there is increasing evidence that a diet enriched with bacterial lipopolysaccharide can reduce the mortality rate of shrimp under exposure to pathogens. Here, the immunostimulatory effects of bacterial lipopolysaccharide (LPS) from various bacterial sources were explored. Bacterial LPS was extracted from a shrimp pathogen, Vibrio harveyi and its effects were compared with the commercially available LPS from the non-shrimp pathogen, Escherichia coli. Our results revealed that the LPS from V. harveyi was different in molecular size but contained similar functional groups to that from E. coli. To understand their molecular mechanisms, bacterial LPS from the two sources were applied as a supplementary diet and fed to juvenile shrimp for 4-week feeding period before tissue samples were collected for transcriptomic analysis by next generation sequencing. Gene expression profiling revealed that major immune-related genes such as pattern recognition proteins (PRPs), proteinases and proteinase inhibitors, prophenoloxidase systems (proPO system), antimicrobial peptides (AMPs), signaling transduction pathways, heat shock proteins (HSPs), oxidative stress responses, and other immune-related molecules such as mucins and peritrophins were modulated in the groups of shrimp fed with bacterial LPS from both sources, but at different levels. The results suggest that bacterial LPS could modulate shrimp immune system, and different LPS sources led to different activation of immune pathways. Additionally, metabolic-related genes were affected by LPS, suggesting that energy was required for immune stimulation. In the V. harveyi pathogen challenge trial, all shrimp groups fed with diets containing LPS from both bacterial sources showed better survival than the control group without LPS. When comparing groups fed with LPS supplemented diets, the higher concentration of LPS (8 μg/body weight) from E. coli resulted in a better survival rate than a lower concentration (4 μg/body weight). Conversely, shrimp fed with a diet containing LPS from V. harveyi showed a lower survival rate when a higher dose of LPS (8 μg/body weight) was administered than the group fed with a lower concentration of LPS (4 μg/body weight). This could be due to overstimulation of shrimp immune responses, especially by LPS derived from shrimp pathogens, resulting in a reverse effect. These results confirm that immunity in shrimp upon administration of bacterial LPS depends on the origin and dose of the LPS administered.

A review on molecular detection techniques of white spot syndrome virus: Perspectives of problems and solutions in shrimp farming

This review aims to provide an update on the current scientific understanding of various aspects of White Spot Syndrome Virus (WSSV) formation, diagnostic procedures, transmission, ecological effects, pathophysiology and management strategies. In terms of production and financial benefits, the WSSV has been the most virulent in shrimp and several other crustacean sectors around the globe. It spreads vertically from diseased broodstock to post-larvae and horizontally by cannibalism, invertebrate vectors, freshwater and sediments. In the transfer of white spot disease (WSD) in newly stocked ponds, the survivability of WSSV in sediment is the most important variable. In typical cultural conditions, it is a highly infectious pathogen capable of inflicting total death within 3-10 days after an outbreak. Some of the current biosecurity strategies used to keep diseases out of shrimp ponds such as pond water disinfection, quarantine of new stocks before stocking and broader usage of specific pathogen-free shrimp. The sequencing and characterisation of various WSSV strains have provided details about pathogen biology, pathogenicity and disease. To develop successful control methods, knowledge of these characteristics is essential. In several shrimp-producing countries in Asia and the Americas, the infections produced by the WSSV have had disastrous socio-economic consequences. As a result of international trade or migration of diseased species, the World Animal Health Organization recognised several illnesses as posing a substantial hazard to farmed shrimp. WSD is receiving much scientific research due to the potential economic effects of the virus. Research is now being done to understand better the molecular biology and pathophysiology of WSSV, as well as how to treat and prevent the virus. However, further study should be conducted in countries with more resilient host species to understand their role in mitigating disease impacts since these revelations may aid in developing a WSD treatment.

The enhancement effect of low-dose dietary lipopolysaccharide on the growth and immunity of Litopenaeus vannamei, and transcriptome analysis

In this study, the effects of dietary lipopolysaccharide (LPS) on Litopenaeus vannamei were investigated to determine whether LPS could play a role as a potential immunostimulant in shrimp. L. vannamei with an initial body weight of 0.30 ± 0.02 g were fed a diet containing LPS at doses of 0, 0.2, 1, 5, 25 or 125 mg kg^-1 for eight weeks (groups LPS0, LPS0.2, LPS1, LPS5, LPS25 and LPS125, respectively). After eight weeks of feeding, the growth performance, immunity and transcriptome response of L. vannamei were analysed. Only dietary LPS at 0.2 and 1 mg kg^-1 resulted in a significant increase in the growth of L. vannamei (P < 0.05). According to the weight gain rate (WGR) and specific growth rate (SGR), the optimum dietary LPS level was 2.462 and 2.455 mg kg^-1, respectively. When compared with the control group, the survival rate (SR) of L. vannamei in the LPS0.2 group was significantly increased after white spot syndrome virus (WSSV) infection and the SR of L. vannamei in the LPS1 group was significantly increased after Vibrio parahaemolyticus infection (both P < 0.05). Compared with the LPS0 group, immune enzyme activity in the serum of L. vannamei could be significantly increased and the content of maleic dialdehyde (MDA) significantly decreased by dietary LPS. Transcriptome analysis of the haemocytes of L. vannamei identified 399 up-regulated differentially expressed genes (DEGs) and 5000 down-regulated DEGs in the LPS0.2 compared to the control group. Most of the DEGs were significantly enriched in the following pathways: phosphatidylinositol signalling, Wnt signalling, Jak-STAT signalling and inositol phosphate metabolism. In conclusion, this study revealed that diets supplemented with low-dose LPS had positive effects on the growth and immunity of L. vannamei.

Probiotic Effects of a Marine Purple Non-Sulfur Bacterium, Rhodovulum sulfidophilum KKMI01, on Kuruma Shrimp (Marsupenaeus japonicus)

Purple non-sulfur bacteria (PNSB) are used as probiotics in shrimp aquaculture; however, no studies have examined the probiotic effects of PNSB in shrimp at the gene expression level. In this study, we examined the effects of a marine PNSB, Rhodovulum sulfidophilum KKMI01, on the gene expression of kuruma shrimp (Marsupenaeus japonicus). Short-term (3 days) effects of R. sulfidophilum KKMI01 on the gene expression in shrimp were examined using small-scale laboratory aquaria experiments, while long-term (145 days) effects of R. sulfidophilum KKMI01 on the growth performance and gene expression were examined using 200-ton outdoor aquaria experiments. Gene expression levels were examined using qRT-PCR. Results of the short-term experiments showed the upregulation of several molting-related genes, including cuticle proteins, calcification proteins, and cuticle pigment protein, suggesting that PNSB stimulated the growth of shrimp. The upregulation of several immune genes, such as prophenoloxidase, antimicrobial peptides, and superoxide dismutase, was also observed. In the 145-day outdoor experiments, the average body weight at harvest time, survival rate, and feed conversion ratio were significantly improved in PNSB-treated shrimp, and upregulation of molting and immune-related genes were also observed. When PNSB cells were added to the rearing water, the effective dosage of PNSB was as low as 10³ cfu/mL, which was more than a million times dilution of the original PNSB culture (2–3 × 10⁹ cfu/mL), indicating that R. sulfidophilum KKMI01 provides a feasible and cost-effective application as a probiotic candidate in shrimp aquaculture.

Immune toxicity of phenanthrene and its combined effects of white spot syndrome virus on the survival of kuruma shrimp (Penaeus Japonicus)

Shrimp inhabiting coasts that are frequented by humans are exposed to various pollutants. Additionally, viral infections that cause serious damage to shrimp populations have been observed in these environments. The present study sought to evaluate the immunotoxic effects of phenanthrene (Phe), a pollutant detected in coastal environments, on kuruma shrimp (Penaeus japonicus). We further examined the survival of shrimp following combined exposure to Phe (30 or 300 μg/L) and white spot syndrome virus (WSSV). Results show that exposure to Phe for seven days decreased immune system-related parameters, including total hemocyte count and phenoloxidase activity in hemolymph (p < 0.05). However, these effects were not detected after three days of exposure. Moreover, a combined exposure assay revealed that shrimp mortality increased following exposure to 300 μg/L Phe and infection with WSSV. The number of WSSV gene copies was also observed to increase in these co-exposed shrimp. Taken together, these results indicate that long-term Phe exposure impairs the immune system of P. japonicus, resulting in fatal proliferation of WSSV. Hence, considering that combined exposure to Phe and WSSV leads to increased mortality of shrimp, it is imperative that the detrimental effects elicited by multiple stresses be considered, and controlled, in areas inhabited by kuruma shrimp.

BALOs Improved Gut Microbiota Health in Postlarval Shrimp (Litopenaeus vannamei) After Being Subjected to Salinity Reduction Treatment

White shrimp, Litopenaeus vannamei, is a widely farmed species. In China, shrimp postlarvae (PL) are frequently subjected to salinity reduction treatment to meet end growers' needs. However, although this treatment effectively reduces vibrio counts, its impact on gut microbiota health is still unknown. In this study, we applied a euryhaline strain of BALOs, BDN-1F2 (BD), and Bacillus subtilis (SD) to the rearing of second-generation shrimp PL after salinity reduction treatment so as to determine if they could impact PL gut microbiota by using high-throughput sequencing analysis. Results show that PL gut microbiota, both compositionally and functionally, have been badly wrecked after salinity reduction treatment with the generally recognized as opportunistic pathogens Gammaproteobacteria being the only dominant class at day 1 of test, viz., 99.43, 85.61, and 83.28% in BD, SD, and control (CD) groups, respectively. At day 7, Gammaproteobacteria was still the only dominant class in the SD and CD groups with relative abundance of 99.77 and 99.87% correspondingly, whereas in the BD group, its value dropped to 8.44%. Regarding biodiversity parameter the Shannon index, over the 7-day test period, while the SD group was unchanged (0.98-0.93), the CD group dropped to 0.94 from 2.94, and the BD group was raised to 7.14 from 0.93. Functionally, compared to control, the SD group displayed similar strength of various predicted community functions, but the BD group had hugely enhanced its various capabilities (p < 0.05). These results demonstrated that the addition of BDN-1F2 had exceedingly improved PL gut microbiota health by raising its biodiversities and strengthening its functionalities. On reviewing data derived from this as well as relevant studies, a Shannon index cutoff value was tentatively suggested so as to differentiate microbiota-healthy PL7-15 from the unhealthy ones. Furthermore, a conceptual mechanism of BALOs in the rectification/improvement of the microbial community health has also been proposed.

Chemotaxis Assay for Marsupenaeus japonicas Hemocytes and Application for the Development of an Oral Immunostimulant Against White Spot Syndrome Virus

The chemotactic activity of vertebrate leukocytes is an important host-defense mechanism. However, chemotaxis of invertebrate immune cells, particularly those of shrimp species, is incompletely understood and critically understudied. In this study, we aimed to optimize the conditions for a Boyden chamber chemotaxis assay using hemocytes (granulocytes) from cultured kuruma shrimp, Marsupenaeus japonicas (Mj) and the optimal conditions were: 5 μm-pore-size Polyvinylpyrrolidone membrane; culture buffer at pH 7.0; and chemotactic factor N-formyl-methionyl-leucyl-phenylalanine (fMLP) 10^-8 mol/L; 4 h incubation time. We then applied the chemotaxis assay to develop an oral immunostimulant against white spot syndrome virus (WSSV), which results in high mortality rates in several shrimp species worldwide. We focused on the kelp Laminaria japonica, as this species contains immunostimulative molecules such as β-glucan. We prepared Heat Extracts (HE) and Crude Laminarans (CL) from kelp using hot water and hydrochloric acid extraction methods, respectively. HE and CL ware mixed with normal shrimp feed. Kelp extracts were orally administered for 7 days, and hematocyte chemotaxis toward fMLP was compared. No difference was detected between control and kelp extracts on day 3, but HE stimulated chemotaxis 2-fold and CL stimulated chemotaxis 3-fold relative to control on day 7 after initiating administration. Kelp extract administration protected against WSSV exposure. Finally, we identified that Kelp extracts stimulated hematocyte superoxide production on days 3 and 7, and increased hematocyte phagocytosis and phenol oxidase activity on day 7 after administration. We concluded that the chemotaxis assay is informative in assessment of shrimp hemocyte immunological activity, and is applicable to the development of immunostimulants against shrimp infectious diseases.

Microbiome of Pacific Whiteleg shrimp reveals differential bacterial community composition between Wild, Aquacultured and AHPND/EMS outbreak conditions

Crustaceans form the second largest subphylum on Earth, which includes Litopeneaus vannamei (Pacific whiteleg shrimp), one of the most cultured shrimp worldwide. Despite efforts to study the shrimp microbiota, little is known about it from shrimp obtained from the open sea and the role that aquaculture plays in microbiota remodeling. Here, the microbiota from the hepatopancreas and intestine of wild type (wt) and aquacultured whiteleg shrimp and pond sediment from hatcheries were characterized using sequencing of seven hypervariable regions of the 16S rRNA gene. Cultured shrimp with AHPND/EMS disease symptoms were also included. We found that (i) microbiota and their predicted metagenomic functions were different between wt and cultured shrimp; (ii) independent of the shrimp source, the microbiota of the hepatopancreas and intestine was different; (iii) the microbial diversity between the sediment and intestines of cultured shrimp was similar; and (iv) associated to an early development of AHPND/EMS disease, we found changes in the microbiome and the appearance of disease-specific bacteria. Notably, under cultured conditions, we identified bacterial taxa enriched in healthy shrimp, such as Faecalibacterium prausnitzii and Pantoea agglomerans, and communities enriched in diseased shrimp, such as Aeromonas taiwanensis, Simiduia agarivorans and Photobacterium angustum.

A probiotic Bacillus strain containing amorphous poly-beta-hydroxybutyrate (PHB) stimulates the innate immune response of Penaeus monodon postlarvae

In this study, the PHB-accumulating Bacillus sp. JL47 strain (capable of accumulating 55% PHB on cell dry weight) was investigated for its effects on the immune response of giant tiger shrimp (Penaeus monodon) postlarvae (PL) before and after the Vibrio campbellii challenge. Briefly, shrimp PL were cultured and fed with Artemia nauplii enriched with Bacillus sp. JL47. Shrimp receiving the Artemia nauplii without JL47 enrichment were used as control. After 15 days of feeding, the shrimp were challenged with pathogenic V. campbellii LMG 21363 at 10⁶ cells mL^-1 by immersion. Relative expression of the immune related genes encoding for prophenoloxidase (proPO), transglutaminase (TGase) and heat shock protein 70 (Hsp70) in the shrimp were measured before (0 h) and after (3, 6, 9, 12, 24 h) the Vibrio challenge by quantitative real-time PCR using β-actin as the reference gene. The expressions of TGase and proPO were significantly up-regulated (p < 0.05) within 9 h and 12 h, respectively after challenge in shrimp receiving the Bacillus sp. JL47 as compared to the challenged and non-challenged controls. Hsp70 expression was significantly increased (p < 0.05) at 3 h post-challenge in all challenged shrimp. Interestingly, proPO and TGase genes were significantly up-regulated (p < 0.05) in Bacillus sp. JL47 treated shrimp even before the Vibrio challenge was applied. No up-regulation in the Hsp70 gene, however, was observed under these conditions. The data suggest that the protective effect of the PHB-accumulating Bacillus sp. JL47 in shrimp was due to its capacity to stimulate the innate immune related genes of the shrimp, specifically the proPO and TGase genes. The application of probiotic Bacillus species, capable of accumulating a significant amount of PHB, is suggested as potential immunostimulatory strategy for aquaculture.

Immunity enhancement with administration of Gracilaria corticata and Saccharomyces cerevisiae compared to gamma irradiation in expose to WSSV in shrimp, in juvenile Litopenaeus vannamei: A comparative study

This paper investigates the efficacy of Gracilaria corticata, Saccharomyces cerevisiae and gamma irradiation WSSV as immunostimulants to white shrimp Litopenaeus vannamei. Seven hundred and twenty healthy shrimp SPF L. vannamei subadult with average weight of 10 ± 1.02 g were collected and divided into 8 groups. The first group (T1) was fed with commercial pellet, the second group (T2) fed with S. cerevisiae (2 g/kg), the third group (T3) fed with G. corticata powder mixed with shrimp feed (2 g/kg) and, finally, the fourth group (T4) was fed with commercial pellet and injected intramuscularly gamma irradiant WSSV (1 μl/gbw) for 10 days. The shrimps were then injected with WSSV and maintained for 25 days. The positive control group for each treatment was maintained in the same manner but without injection with WSSV. Moreover, survival rate and immune parameters such as total hemocyte count (THC), total protein plasma (TPP), superoxide dismutase (SOD) activity, peroxidase (POD) activity and phenoloxidase activity (PO) were determined. Results indicated that the survival rates for groups T4, T3 T2 and T1 were 57.05 ± 3.52%, 22.5 ± 0.5%, 15 ± 1.05% and 00.0 ± 0%, respectively. Ultimately, at the end of the study the shrimp group T4 showed higher hematological data: THC, TPP, SOD, POD and PO. The study concluded that gamma irradiant WSSV is effective immunostimulants in shrimp L. vannamei and the immunity has better performances than those of the G. corticata and S. cerevisiae.

Lipopolysaccharide and β-1,3-glucan-binding protein (LGBP) bind to seaweed polysaccharides and activate the prophenoloxidase system in white shrimp Litopenaeus vannamei

Lipopolysaccharide and β-1,3-glucan-binding protein (LGBP), important pattern recognition proteins (PRPs), recognize lipopolysaccharide (LPS) and β-1,3-glucan (βG), known as pathogen-associated molecular patterns (PAMPs), and subsequently trigger innate immunity. Several seaweed polysaccharides and seaweed extracts increase immune parameters and resistance to pathogens. Here, we constructed the expression vector pET28b-LvLGBP and transferred it into Escherichia coli BL21 (DE3) for protein expression and to produce the recombinant protein LGBP (rLvLGBP) in white shrimp Litopenaeus vannamei. We examined the binding of rLvLGBP with seaweed-derived polysaccharides including alginate, carrageenan, fucoidan, laminarin, Gracilaria tenuistipitata extract (GTE), and Sargassum duplicatum extract (SDE), and examined the phenoloxidase activity of shrimp haemocytes incubated with a mixture of rLvLGBP and each polysaccharide. We also examined the binding of rLvLGBP with LPS and βG, and the phenoloxidase activity of shrimp haemocytes incubated with a mixture of rLvLGBP and LPS (rLvLGBP-LPS) or a mixture of rLvLGBP and βG (rLvLGBP-βG). An ELISA binding assay indicated that rLvLGBP binds to LPS, βG, alginate, carrageenan, fucoidan, laminarin, GTE, and SDE with dissociation constants of 0.1138-0.1770 μM. Furthermore, our results also indicated that the phenoloxidase activity of shrimp haemocytes incubated with a mixture of rLvLGBP and LPS, βG, alginate, carrageenan, fucoidan, laminarin, GTE, and SDE significantly increased by 328%, 172%, 200%, 213%, 197%, 194%, 191%, and 197%, respectively compared to controls (cacodylate buffer). We conclude that LvLGBP functions as a PRP, recognizes and binds to LPS, βG, alginate, carrageenan, fucoidan, laminarin, GTE, and SDE, and subsequently leads to activating innate immunity in shrimp.

A Lipopolysaccharide from Pantoea Agglomerans Is a Promising Adjuvant for Sublingual Vaccines to Induce Systemic and Mucosal Immune Responses in Mice via TLR4 Pathway

A lipopolysaccharide from Pantoea agglomerans (LPSpa) has been applied to various fields for human use as a Toll-like receptor 4 ligand and its safety has been confirmed. Here, we showed for the first time the application of LPSpa as an effective mucosal adjuvant for activating vaccine-induced antigen specific immune responses. Mice sublingually immunized with influenza vaccine (HA split vaccine) with LPSpa induced both HA-specific IgG (systemic) and IgA (mucosal) antibody responses, which led to a significant increase in survival rate against lethal influenza virus challenge compared with subcutaneous vaccination. After sublingual administration of ovalbumin with LPSpa, ovalbumin-specific mucosal IgA responses were induced at both mucosal surfaces close to the immunized site and at remote mucosal surfaces. Sublingual administration of LPSpa evoked local antigen-uptake by dendritic cells in cervical lymph nodes. LPSpa induced cytokine production and the maturation and proliferation of innate immune cells via Toll-like receptor 4 in dendritic cells. Collectively, these results suggest that LPSpa can be used as an effective mucosal adjuvant to stimulate and activate local innate immune cells to improve and enhance mucosal vaccine potency against various pathogens.

Immune responses of whiteleg shrimp, Litopenaeus vannamei (Boone, 1931), to bacterially expressed dsRNA specific to VP28 gene of white spot syndrome virus

In this study, dsRNA specific to VP28 gene of white spot syndrome virus (WSSV) of shrimp was synthesized in Escherichia coli in large scale and studied the immune response of shrimp to dsRNA-VP28. The haematological parameters such as clotting time and total haemocytes counts, and immunological parameters such as prophenoloxidase (proPO), superoxide dismutase (SOD), superoxide anion (SOA) and malondialdehyde content, as well as the mRNA expression of ten immune-related genes were examined to estimate the effect of dsRNA-VP28 on the innate immunity of Litopenaeus vannamei. The activities of proPO, SOA and SOD significantly increased in haemocyte after dsRNA-VP28 treatment, whereas MDA content did not change significantly. Among the ten immune-related genes examined, only the mRNA expression of proPO, cMnSOD, haemocyanin, crustin, BGBP, lipopolysaccharides (LPs), lectin and lysozyme in haemocytes, gill and hepatopancreas of L. vannamei, was significantly upregulated at 12 h after dsRNA-VP28 treatment, while no significant expression changes were observed in Toll receptor and tumour receptor genes. The increase of proPO and SOD activities, and SOA level and mRNA expression level of proPO, cMnSOD, haemocyanin, crustin, BGBP, LPs, lectin and lysozyme after dsRNA-VP28 stimulation indicate that these immune-related genes were involved in dsRNA-VP28-induced innate immunity in shrimp.

Immune gene expression profile of Penaeus monodon in response to marine yeast glucan application and white spot syndrome virus challenge

Immunostimulant potential of eight marine yeast glucans (YG) from Candida parapsilosis R20, Hortaea werneckii R23, Candida spencermartinsiae R28, Candida haemulonii R63, Candida oceani R89, Debaryomyces fabryi R100, Debaryomyces nepalensis R305 and Meyerozyma guilliermondii R340 were tested against WSSV challenge in Penaeus monodon post larvae (PL). Structural characterization of these marine yeast glucans by proton nuclear magnetic resonance (NMR) indicated structures containing (1-6)-branched (1-3)-β-D-glucan. PL were fed 0.2% glucan incorporated diet once in seven days for a period of 45 days and the animals were challenged with white spot syndrome virus (WSSV). The immunostimulatory activity of yeast glucans were assessed pre- and post-challenge WSSV by analysing the expression profile of six antimicrobial peptide (AMP) genes viz., anti-lipopolysaccharide factor (ALF), crustin-1, crustin-2, crustin-3, penaeidin-3 and penaeidin-5 and 13 immune genes viz., alpha-2-macroglobulin (α-2-M), astakine, caspase, catalase, glutathione peroxidase, glutathione-s-transferase, haemocyanin, peroxinectin, pmCathepsinC, prophenol oxidase (proPO), Rab-7, superoxide dismutase and transglutaminase. Expression of seven WSSV genes viz., DNA polymerase, endonuclease, protein kinase, immediate early gene, latency related gene, thymidine kinase and VP28 were also analysed to detect the presence and intensity of viral infection in the experimental animals post-challenge. The study revealed that yeast glucans (YG) do possess immunostimulatory activity against WSSV and also supported higher survival (40-70 %) post-challenge WSSV. Among the various glucans tested, YG23 showed maximum survival (70.27%), followed by YG20 (66.66%), YG28 (60.97%), YG89 (58.53%), YG100 (54.05%), YG63 (48.64%), YG305 (45.7%) and YG340 (43.24%).

Screening, isolation and optimization of anti-white spot syndrome virus drug derived from marine plants

OBJECTIVE

To screen, isolate and optimize anti-white spot syndrome virus (WSSV) drug derived from various marine floral ecosystems and to evaluate the efficacy of the same in host-pathogen interaction model.

METHODS

Thirty species of marine plants were subjected to Soxhlet extraction using water, ethanol, methanol and hexane as solvents. The 120 plant isolates thus obtained were screened for their in vivo anti-WSSV property in Litopenaeus vannamei. By means of chemical processes, the purified anti-WSSV plant isolate, MP07X was derived. The drug was optimized at various concentrations. Viral and immune genes were analysed using reverse transcriptase PCR to confirm the potency of the drug.

RESULTS

Nine plant isolates exhibited significant survivability in host. The drug MP07X thus formulated showing 85% survivability in host. The surviving shrimps were nested PCR negative at the end of the 15 d experimentation. The lowest concentration of MP07X required intramuscularly for virucidal property was 10 mg/mL. The oral dosage of 1 000 mg/kg body weight/day survived at the rate of 85%. Neither VP28 nor ie 1 was expressed in the test samples at 42nd hour and 84th hour post viral infection.

CONCLUSIONS

The drug MP07X derived from Rhizophora mucronata is a potent anti-WSSV drug.

Dietary effect of Sargassum wightii fucoidan to enhance growth, prophenoloxidase gene expression of Penaeus monodon and immune resistance to Vibrio parahaemolyticus

The polysaccharide fucoidan from brown seaweed Sargassum wightii was extracted and it was incorporated with pellet diets at three concentrations (0.1, 0.2 & 0.3%). The fucoidan incorporated diets were fed to shrimp Penaeus monodon for 60 days and the growth performance was assessed. The weight gain and SGR of control group was 6.83 g and 9.72%, respectively, but the weight gain and SGR of various concentrations (0.1-0.3%) of fucoidan incorporated diets fed groups of shrimp was increased from 7.30 to 8.20 g and 9.83 to 10.03%, respectively. After 60 days of feeding experiment, the relative quantification of prophenoloxidase gene of experimental groups over control group was analysed by RT-PCR and it was ranged between 2.13 and 7.95 fold increase within 33.52-34.61 threshold cycles, respectively at 0.1-0.3% concentrations of fucoidan. After 60 days of feeding experiment, the P. monodon were challenged with shrimp pathogen Vibrio parahaemolyticus and the mortality percentage was recorded daily up to 21 days. The reduction in mortality percentage of experimental groups over control group was recorded from 44.56 to 72.79%, respectively in 0.1-0.3% of fucoidan incorporated diets fed groups. During challenge experiment, all the immunological parameters such as THC, prophenoloxidase activity, respiratory burst activity, superoxide dismutase activity, phagocytic activity, bactericidal activity and bacterial clearance ability of experimental groups were significantly (P < 0.05) increased than control group. The V. parahaemolyticus load was enumerated from the infected shrimp at every 10 days intervals during challenge experiment. In control group, the Vibrio load was increased in hepatopancreas and muscle tissues from 10th to 21st days of challenge test. But in the experimental groups, the Vibrio load in both the tissues decreased positively from 10th to 21st days of challenge duration. It is concluded that the S. wightii fucoidan had enhanced the innate immunity and increased resistance to V. parahaemolyticus infection in P. monodon.

Screening, isolation and optimization of anti-white spot syndrome virus drug derived from terrestrial plants

OBJECTIVE

To screen, isolate and optimize anti-white spot syndrome virus (WSSV) drug derived from various terrestrial plants and to evaluate the efficacy of the same in host-pathogen interaction model.

METHODS

Thirty plants were subjected to Soxhlet extraction using water, ethanol, methanol and hexane as solvents. The 120 plant isolates thus obtained were screened for their in vivo anti-WSSV property in Litopenaeus vannamei. The best anti-WSSV plant isolate, TP22C was isolated and further analyzed. The drug was optimized at various concentrations. Viral and immune genes were analysed using reverse transcriptase PCR to confirm the potency of the drug.

RESULTS

Seven plant isolates exhibited significant survivability in host. The drug TP22C thus formulated showed 86% survivability in host. The surviving shrimps were nested PCR negative at the end of the 15 d experimentation. The lowest concentration of TP22C required intramuscularly for virucidal property was 10 mg/mL. The oral dosage of 750 mg/kg body weight/day survived at the rate of 86%. Neither VP28 nor ie 1 was expressed in the test samples at 42nd hour and 84th hour post viral infection.

CONCLUSIONS

The drug TP22C derived from Momordica charantia is a potent anti-white spot syndrome virus drug.

Immunostimulatory activity of sulfated galactans isolated from the red seaweed Gracilaria fisheri and development of resistance against white spot syndrome virus (WSSV) in shrimp

Sulfated galactans (SG) were isolated from the red seaweed Gracilaria fisheri (G. fisheri). Chemical analysis revealed SG contains sulfate (12.7%) and total carbohydrate (42.2%) with an estimated molecular mass of 100 kDa. Structure analysis by NMR and FT-IR spectroscopy revealed that SG is a complex structure with a linear backbone of alternating 3-linked β-D-galactopyranose and 4-linked 3,6-anhydrogalactose units with partial 6-O-methylate-β-D-galactopyranose and with sulfation occurring on C4 of D-galactopyranose and C6 of L-galactopyranose units. SG treatment enhanced immune parameters including total haemocytes, phenoloxidase activity, superoxide anions and superoxide dismutase in shrimp Penaeus monodon. Shrimp fed with Artemia salina enriched with SG (100 and 200 μg ml(-1)) and inoculated with white spot syndrome virus (WSSV) showed a significantly lower mortality rate and lower viral VP 28 amplification and expression than control. The results suggest that SG from G. fisheri exhibits immune stimulatory and antiviral activities that could protect P. monodon from WSSV infection.

Application of bacterial lipopolysaccharide to improve survival of the black tiger shrimp after Vibrio harveyi exposure

This study investigates an effect of bacterial lipopolysaccharide (LPS) as feed supplement to improve immunity of the black tiger shrimp (Penaeus monodon). LPS was coated to commercial feed pellets and given to the shrimp once or twice a day for 10 days before an exposure with shrimp pathogenic bacterium Vibrio harveyi. The growth rates, percent weight gains, total hemocyte and granulocyte counts and survival rates of shrimp between the LPS-coated pellet fed groups and a control group where shrimp fed with commercial feed pellets were compared. After 10 days of the feeding trials, growth rates were not significantly different in all groups, suggesting no toxicity from LPS supplement. To determine beneficial effect of LPS diets, each group was subsequently exposed to V. harveyi by immersion method and the survival rates were recorded for seven days after the immersion. Regardless of the dosages of LPS, the shrimp groups fed with LPS-coated pellets showed higher survival rates than the control group. There was no significant difference in survival rates between the two LPS dosages groups. In addition to survival under pathogen challenge, we also determine effect of LPS on immune-related genes after 10-day feeding trial. Gene expression analysis in the P. monodon intestines revealed that antilipopolysaccharide factor isoform 3 (ALF3), C-type lectin, and mucine-like peritrophin (mucin-like PM) were expressed significantly higher in a group fed with LPS supplemental diet once or twice a day than in a control group. The transcript levels of C-type lectin and mucin-like PM had increased significantly when LPS was given once a day, while significant induction of ALF3 transcripts was observed when shrimp were fed with LPS twice a day. The up-regulation of the immune gene levels in intestines and higher resistance to V. harveyi of the shrimp fed with LPS provide the evidence for potential application of LPS as an immunostimulant in P. monodon farming.

Sodium alginate from Sargassum wightii retards mortalities in Penaeus monodon postlarvae challenged with white spot syndrome virus

Sodium alginate extracted from brown seaweed Sargassum wightii (16.35 ± 1.42%, mean [±SD] yield from 5 extractions) was prepared as a powder or beads and used to enrich Artemia nauplii at concentrations of 100, 200, 300 and 400 mg l-1. The alginate-enriched nauplii were fed to Penaeus monodon shrimp postlarvae (PL) stage 15 (PL15, i.e. 15 d old) for 20 d. Mean weight gain and specific growth rate over this period were 0.24 g and 15.8%, respectively, in PL groups not fed alginate, and 0.20-0.28 g and 14.7-16.5%, respectively, in PL groups fed alginate. Amongst PL35 then challenged with white spot syndrome virus (WSSV) by immersion, all PL not fed alginate died within 9 d. However, amongst PL fed the 4 concentrations of alginate powder or beads, mortality rates reduced with increasing alginate concentration, and between 25 and 32% PL remained alive when the bioassay was terminated on Day 21. Amongst alginate-fed PL groups compared with the control group, mortality was reduced by 26.5 to 58.4%. Nested PCR detection of WSSV revealed sodium alginate concentration-dependent reductions in infection loads. The data indicate that sodium alginate extracted from brown seaweed and fed to P. monodon can retard progression of WSSV disease.

Challenges in shrimp aquaculture due to viral diseases: distribution and biology of the five major penaeid viruses and interventions to avoid viral incidence and dispersion

Shrimp aquaculture has been dramatically affected by many pathogenic diseases, mainly caused by five viruses: IHHNV, YHV, TSV, WSSV, and IMNV. Here we provide a state-of-the-art overview of these shrimp viruses, with emphasis on distribution, pathology, morphology, and genomic organization, in addition to current diagnostic methods and intervention practices.

The effect of fucoidan from brown seaweed Sargassum wightii on WSSV resistance and immune activity in shrimp Penaeus monodon (Fab)

The polysaccharide-fucoidan was extracted from brown seaweed Sargassum wightii and characterized through FT-IR and (13)C &(1)H NMR analysis. The extracted fucoidan was supplemented with pellet diets at three different concentrations (0.1, 0.2 and 0.3%). The fucoidan supplemented diets were fed to Penaeus monodon for 45 days, then challenged with WSSV and the mortality percentage was recorded daily up to 21 days. During the challenge test, the control group showed 100% mortality within 10 days, but in the experimental groups, the mortality percentage (51-72% within 21 days) was decreased considerably (P < 0.05) with respect to the concentrations of fucoidan. The reduction in mortality percentage of experimental groups over control group was ranged from 50.81 to 68.06%. During challenge experiment, the immunological parameters such as THC, prophenoloxidase activity, respiratory burst activity, superoxide dismutase activity and phagocytic activity were measured before injection of WSSV (0 day) and after the injection of WSSV on 10th and 21st days, respectively. All the immunological parameters of experimental groups were significantly (P < 0.05) increased than control group. RT-PCR analysis confirmed the considerable reduction of WSSV DNA copy numbers with respect to the concentration of fucoidan. It was concluded that P. monodon fed with fucoidan of S. wightii supplemented diet had enhanced the innate immunity and increased resistance against WSSV infection.

Genome sequence of Pantoea agglomerans strain IG1

Pantoea agglomerans is a gram-negative bacterium that grows symbiotically with various plants. Here we report the 4.8-Mb genome sequence of P. agglomerans strain IG1. The lipopolysaccharides derived from P. agglomerans IG1 have been shown to be effective in the prevention of various diseases, such as bacterial or viral infection, lifestyle-related diseases. This genome sequence represents a substantial step toward the elucidation of pathways for production of lipopolysaccharides.

Immunomodulatory effect of Withania somnifera supplementation diet in the giant freshwater prawn Macrobrachium rosenbergii (de Man) against Aeromonas hydrophila

The effect of Withania somnifera extract supplementation diets on innate immune response in giant freshwater prawn Macrobrachium rosenbergii (de Man) against Aeromonas hydrophila was investigated. The bacterial clearance efficiency significantly increased in prawn fed with 0.1% and 1.0% doses of W. somnifera supplementation diet against pathogen from weeks 1-4 as compared to the control. The innate immune parameters such as, phenoloxidase activity, superoxide anion level, superoxide dismutase activity, nitrate, and nitrite concentrations were significantly enhanced in prawn fed with 0.1% and 1.0% doses of W. somnifera supplementation diet from weeks 1-4 against pathogen. The total hemocyte counts (THC) significantly increased in prawn fed with 0.1% and 1.0% doses diet from weeks 1-4 against pathogen as compared to the control. These results strongly suggested that administration of W. somnifera through supplementation diet positively enhances the innate immune system and enhanced survival rate in M. rosenbergii against A. hydrophila infection.

Microarray analyses of shrimp immune responses

Shrimp aquaculture is one of the major foodproducing industries in the world. However, it is being impacted by several problems including diseases, antibiotic use, and environmental factors. The extent of the effects of these problems in the immune system of the shrimp at the molecular level is just beginning to be understood. Here, we review the gene expression profile of shrimp in response to some of these problems using the high-throughput microarray analysis, including white spot syndrome virus, yellow head virus, Vibrio spp., peptidoglycan, oxytetracycline, oxolinic acid, salinity, and temperature.

The effect of dietary Panax ginseng polysaccharide extract on the immune responses in white shrimp, Litopenaeus vannamei

The immunostimulatory effects of orally administered Panax ginseng root or its polysaccharides (GSP) in white shrimp, Litopenaeus vannamei, were investigated in this study. Shrimp were fed a diet containing 0.4 g kg⁻¹ GSP over a period of 84 days, during which the activities of total superoxide dismutase (T-SOD), catalase (CAT), glutathione peroxidase (GSH-Px), acid phosphatase (ACP), and alkaline phosphatase (AKP), as well as malondialdehyde (MDA) content, and expressions of cytosolic superoxide dismutase (cyt-SOD), CAT, GSH-Px, and peroxiredoxin (Prx) genes were determined in various tissues of the shrimp. Results showed that the shrimp fed the GSP diet had significantly increased ACP and AKP activities in the gills. The GSP-fed shrimp also displayed significantly increased T-SOD and GSH-Px activities in the gills and hepatopancreas of the shrimp; meanwhile there was enhanced CAT activity in the gills, but decreased MDA content in the gills, hepatopancreas and muscle. The mRNA expressions of cyt-SOD, CAT, GSH-Px and Prx were significantly elevated in the gills and hepatopancreas of the shrimp fed the GSP diet for 84 days, compared with that of the control. Therefore, GSP can be used as an immunostimulant for shrimp through dietary administration to increase immune enzyme activity and modify expression of immune genes in shrimp.

Studies on the immunomodulatory effect of polysaccharide gel extracted from Durio zibethinus in Penaeus monodon shrimp against Vibrio harveyi and WSSV

Oral administration of polysaccharide gel (PG) in shrimp diets revealed immunostimulating potential and disease resistance in Penaeus monodon (black tiger shrimp). PG from the fruit-rind of Durio zibethinus has been characterized to be a pectic polysaccharide with immunomodulating and antibacterial activities. PG inhibited growth of the shrimp bacterial pathogen, Vibrio harveyi 1526, by agar diffusion and broth microdilution tests. Clear inhibition zones on agar plates were observed at the lowest PG concentration of 3.1 mg/ml, where minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values for PG were 6.3 and 12.5 mg/ml, respectively. Each group of juvenile shrimps, initial mean body weight 0.29 +/- 0.04 g, was housed in a closed-recirculating treated water system and was fed with PG-supplemented diets containing 1, 2 and 3% PG or shrimp basal diet in the control group for 8 and 12 weeks. PG-supplemented diets did not contribute to the overall growth of black tiger shrimp. The immune response was evaluated by analysis of prophenoloxidase activity and total hemocyte count in the shrimp fed PG-supplemented diets for 12 weeks. Prophenoloxidase activity in shrimp fed the 1, 2 and 3% PG-supplemented diet and total hemocyte count in shrimp fed the 1 and 2% PG-supplemented diet were higher (P < 0.05) than those of the control group. The percent survival was higher in groups fed the 1-3% PG-supplemented diets in challenge tests with either white spot syndrome virus (WSSV) or the bacterium V. harveyi 1526 than that of the control group. Relative percent survival (RPS) values in groups fed the 2% PG-supplemented diet showed the highest RPS value for disease resistance of 100% (at Day 6) and 36% (at Day 4) in treated shrimp against viral and bacterial infection, respectively. Mortality of PG-supplemented diets in treated shrimps against WSSV infection was also found to be much lower (P < 0.05) than that of the control group.

Protection of blue shrimp (Litopenaeus stylirostris) against the White Spot Syndrome Virus (WSSV) when injected with shrimp lysozyme

In this study we found that a blue shrimp (Litopenaeus stylirostris) lysozyme gene (Lslzm) was up-regulated in WSSV-infected shrimp, suggesting that lysozyme is involved in the innate response of shrimp to this virus. Shrimp were intramuscularly injected with Lslzm protein to identify how this recombinant protein protects L. stylirostris from WSSV infection and to determine how this protein influences nonspecific cellular and humoral defense mechanisms. Higher survival rates and a lower viral load (compared with controls) were reported for shrimps that were first injected with the Lslzm protein and then infected with WSSV. In addition, the Lslzm expression level and the immunological parameters (including THC, phagocytic activity, respiratory burst activity, phenoloxidase activity and lysozyme activity) were all significantly higher in the WSSV-infected shrimp treated with the Lslzm protein, compared with the controls. These results indicate that lysozyme is effective at blocking WSSV infection in L. stylirostris and that lysozyme modulates the cellular and humoral defense mechanisms after they are suppressed by the WSSV virus.

Antiviral immunity in crustaceans

Viral diseases of shrimp have caused negative effects on the economy in several countries in Asia, South America and America, where they have numerous shrimp culture industries. The studies on the immunity of shrimp and other crustaceans have mainly focused on general aspects of immunity and as a consequence little is known about the antiviral responses in crustaceans. The aim of this review is to update recent knowledge of innate immunity against viral infections in crustaceans. Several antiviral molecules have been isolated and characterized recently from decapods. Characterization and identification of these molecules might provide a promising strategy for protection and treatment of these viral diseases. In addition dsRNA-induced antiviral immunity is also included.

Evaluation of the antibacterial activity of leaf and twig extracts of stout camphor tree, Cinnamomum kanehirae, and the effects on immunity and disease resistance of white shrimp, Litopenaeus vannamei

Effects of essential oils and hot-water extracts isolated from leaf and twig of stout camphor tree, Cinnamomum kanehirae on antibacterial activity to pathogen of fish, abalone, marine fish and freshwater prawn, and the white shrimp, Litopenaeus vannamei immunity and disease resistance to Vibrio alginolyticus were carried out in this study. A better antibacterial activity against nine selected pathogen bacteria was recorded in twig essential oil, and the selected pathogens of both Gram-positive bacteria and Gram-negative bacteria were sensitive to the leaf and twig essential oils in the present study. No antibacterial activity was recorded in the hot-water extracts of leaf and twig. In challenge trial, a significant decrease of sensitivity to V. alginolyticus (1 x 10(6) cfu shrimp(-1)) was found in that of shrimp received hot-water extract from twig at the levels of 2 microg g shrimp(-1) compared to control. In addition, the how-water extract of twig in vitro showed greater enhanced effects on phenoloxidase activity, respiratory burst and phagocytosis of white shrimp compared to the hot-water extract of leaf. It is considered that the extracts of stout camphor tree could be a candidate to replace the chemo-therapeutants through the inhibitory effects against the growth of pathogens, and enhanced effects on shrimp immunity and disease resistance.

Studies on the immunomodulatory effect of extract of Cyanodon dactylon in shrimp, Penaeus monodon, and its efficacy to protect the shrimp from white spot syndrome virus (WSSV)

The present study investigates the protection of shrimp Penaeus monodon against white spot syndrome virus (WSSV) using antiviral plant extract derived from Cyanodon dactylon and the modulation of the shrimp non-specific immunity. To determine the antiviral activity, the shrimp were treated by both in vitro (intramuscular injection) and in vivo (orally with feed) methods at the concentration of 2mg per animal and 2% of the plant extract incorporated with commercially available artificial pellet feed, respectively. The antiviral activity of C. dactylon plant extract was confirmed by PCR, bioassay and Western blot analysis. In the present study, anti-WSSV activity of C. dactylon plant extract by in vivo and in vitro methods showed strong antiviral activity and the immunological parameters such as proPO, O(2)(-), NO, THC and clotting time were all significantly (P<0.05) higher in the WSSV-infected shrimp treated with plant extract when compared to control groups. These results strongly indicate that in vivo and in vitro administration of C. dactylon plant extract enhances immunity of the shrimp. Based on the present data and the advantages of plant extract available at low price, we believe that oral administration of C. dactylon plant extract along with the pellet feed is a potential prophylactic agent against WSSV infection of shrimp.

Gene expression profile of hemocytes of kuruma shrimp, Marsupenaeus japonicus following peptidoglycan stimulation

Shrimps are believed to lack an adaptive immune system and therefore rely heavily on their innate immune mechanisms to ward off pathogens. Moreover, their innate defense reactions are triggered by bacterial and fungal cell wall components such as lipopolysaccharides, peptidoglycan and beta-glucans. In this study, we used microarray to examine the gene expression profile of kuruma shrimp, Marsupenaeus japonicus, after stimulation with peptidoglycan. Subsequent results show that the number of upregulated genes and percentage of differential expression (21%) was highest at day 1 poststimulation. Differentially expressed genes in day 7 and day 14, on the other hand, were 3.25% and 11.21%, respectively. Sixty-one (61) genes of unknown function were found to have responded outright to peptidoglycan (PG) stimulation. Administration of PG also caused increases in the expressions of crustin, lysozyme, and a few antibacterial peptides, all of which are known to be involved in crustacean immune response. Taken together, our results suggest that innate response in shrimp is triggered instantaneously upon exposure to a bacterial component.

Oral administration of bacterially expressed VP28dsRNA to protect Penaeus monodon from white spot syndrome virus

We explored the possibility of protecting Penaeus monodon against white spot syndrome virus (WSSV) infection via interference RNA technology by oral administration of bacterially expressed WSSV VP28dsRNA. Shrimp were given dsRNA orally via two methods. In the first method, pellet feed was coated with inactivated bacteria containing overexpressed dsRNA of the WSSV VP28 gene, and in the second method, pellet feed was coated with VP28dsRNA-chitosan complex nanoparticles. The treated shrimp were orally challenged with WSSV by feeding WSSV-infected tissue. The experiment was conducted for 30 days. The dsRNA-treated shrimp challenged with WSSV showed higher survival compared to control shrimp. Sixty-eight percent survival was observed in shrimp fed with feed coated with inactivated bacteria containing dsRNA of the WSSV VP28 gene whereas 37% survival was observed in shrimp fed with VP28dsRNA-chitosan complex nanoparticle-coated feed. The WSSV caused 100% mortality in shrimp fed with pellet feed coated with inactivated bacteria with empty LITMUS38i vector. At the end of the experiment, the tissue samples prepared from randomly selected shrimp that survived were analyzed via reverse transcriptase-polymerase chain reaction and Western blot analysis for WSSV. The samples were negative for WSSV. Based on the present data and the advantages of dsRNA, we believe that oral administration of crude extract of bacterially expressed VP28dsRNA is a potential therapeutic agent against WSSV infection of shrimp.

Differential time-series expression of immune-related genes of Pacific white shrimp Litopenaeus vannamei in response to dietary inclusion of beta-1,3-glucan

Time-series changes in transcript abundance of nine genes encoding important immune proteins in haemocytes or hepatopancreas of Pacific white shrimp Litopenaeus vannamei fed daily in a 1-week feeding trial diets containing three levels (0%, 0.2% or 1%) of beta-1,3-glucan from Schizophyllum commune were quantified by real-time PCR. As a whole, the immune modulation elicited by beta-glucan is bimodal, one swift reaction of up- or down-regulation occurred within 24h and a delayed regulation was commenced as late as 3-7days. Haemocyanin, crustin, prophenoloxidase (proPO) and transglutaminase (TGase) did not respond to the glucan treatment. While penaeidin 3 (Litvan PEN3) was swiftly down-regulated (0-24h), lysozyme and cytosolic manganese superoxide dismutase (cMnSOD) were swiftly up-regulated (0-24h). In contrast, the two pattern recognition proteins (PRPs), beta-glucan binding protein-high density lipoprotein (BGBP-HDL) and lipopolysaccharide/beta-glucan binding protein (LGBP), showed a delayed up-regulation. Their expressions were not maximized until as late as 72h or 7days, respectively, which coincide with the initiation of reported immune enhancement (6-24days) of PO and SOD activity, phagocytosis and superoxide anion production in penaeid shrimp receiving glucan-containing diet. These immune responses could be the downstream effects of the two PRP gene up-regulation that predispose the shrimp to a state of high immune responsiveness. Increased dosage of beta-glucan from 2 to 10gkg(-1) diet did not affect the expressions of the genes, indicating the sufficiency of beta-glucan supplementation at 2gkg(-1) diet.

A review on the morphology, molecular characterization, morphogenesis and pathogenesis of white spot syndrome virus

Since it first appeared in 1992, white spot syndrome virus (WSSV) has become the most threatening infectious agent in shrimp aquaculture. Within a decade, this pathogen has spread to all the main shrimp farming areas and has caused enormous economic losses amounting to more than seven billion US dollars. At present, biosecurity methods used to exclude pathogens in shrimp farms include disinfecting ponds and water, preventing the entrance of animals that may carry infectious agents and stocking ponds with specific pathogen-free post-larvae. The combination of these practices increases biosecurity in shrimp farming facilities and may contribute to reduce the risk of a WSSV outbreak. Although several control methods have shown some efficacy against WSSV under experimental conditions, no therapeutic products or strategies are available to effectively control WSSV in the field. Furthermore, differences in virulence and clinical outcome of WSSV infections have been reported. The sequencing and characterization of different strains of WSSV has begun to determine aspects of its biology, virulence and pathogenesis. Knowledge on these aspects is critical for developing effective control methods. The aim of this review is to present an update of the knowledge generated so far on different aspects of WSSV organization, morphogenesis, pathology and pathogenesis.

Enhanced disease resistance in Artemia by application of commercial beta-glucans sources and chitin in a gnotobiotic Artemia challenge test

The anti-infectious potential of a selection of putative immunostimulants including six commercial beta-glucans (all extracted from baker's yeast Saccharomyces cerevisiae except for Laminarin) and chitin particles were verified in Artemia nauplii by challenging them under gnotobiotic conditions with the pathogen Vibrio campbellii. Under the described experimental conditions, no differential macroscopic nutritional effect (e.g. growth) was observed among the products. Significant increased survival was observed with beta-glucan (Sigma) and Zymosan and to a lesser extent with MacroGard in challenged nauplii. A poor correlation was found between survival values of the challenged Artemia and the product compositions (such as chitin, mannose and beta-glucan content) indicating that the quality of beta-glucans (e.g. the ratio of beta-1,3 and beta-1,6 glucan, the molecular weight, the dimensional structure, type and frequency of branches), eventually in combination with other unidentified compounds, is more important than the amount of product offered. This small-scale testing under gnotobiotic conditions using freshly hatched Artemia nauplii allows for a rapid and simultaneous screening of anti-infectious and/or putative immunostimulatory polymers, and should be combined with studies on cellular and humoral immune responses in order to gain more quantitative insight into their functional properties.

The protective effect against Vibrio campbellii in Artemia nauplii by pure beta-glucan and isogenic yeast cells differing in beta-glucan and chitin content operated with a source-dependent time lag

In invertebrates the defence system to fight infectious diseases depends mainly on a non-specific or innate immune response, contrary to the vertebrate immune system. The use of natural immunostimulants that enhance the defence mechanism or the immune response of target organisms may be an excellent preventive tool against pathogens. Several strains of baker's yeast Saccharomyces cerevisiae have been found to be good immune enhancers. Previously, it was shown that small quantities of the mnn9 yeast cells and/or glucan particles could protect Artemia nauplii against the pathogenic bacterium Vibrio campbellii in the gnotobiotic Artemia challenge test. Apparently, the higher amount and/or availability of beta-glucans and/or chitin present in mnn9 yeast strain might play an essential role in such protection. The present study reveals that these compounds could only provide protection against the pathogen when they were supplied to Artemia well in advance of the challenge (8-48 h depending on the source). Also the putative immunostimulant did not have a curative action. Moreover, short-time exposure of Artemia to mnn9 strain (priming) did not provide protection against the pathogen longer than two days. Hence, it is hypothesized that the mere stimulation of known biochemical pathways, e.g. prophenoloxidase is not sufficient to explain the mechanisms involved in the observed immunostimulation obtained by beta-glucans and/or mnn9 yeast in Artemia nauplii.

Antiviral activity of bis(2-methylheptyl)phthalate isolated from Pongamia pinnata leaves against White Spot Syndrome Virus of Penaeus monodon Fabricius

White Spot Syndrome Virus (WSSV) is an extremely virulent, contagious, causative agent of the White spot syndrome of shrimp and causes high mortality and affects most of the commercially important cultured marine crustacean species globally. Oral administration of ethanolic extract and purified compound from the leaves of Pongamia pinnata, an indigenious Indian "medicinal plant" "has increased the survival of WSSV infected Penaeus monodon". Pelletized feed impregnated with ethanolic extract of the leaves of P. pinnata was fed to shrimp prior and after WSSV infection at 200 and 300 microg/g of body weight of shrimp/day. The survival rate for the WSSV-infected shrimp that were fed with 200 and 300 microg extract/g were 40% and 80%, respectively. The active WSSV antiviral compound 1 that was isolated from the leaves of P. pinnata was identified as bis(2-methylheptyl)phthalate. Thus, the present work revealed that oral administration of the crude and purified compound from the leaves of P. pinnata effectively inhibited WSSV pathogenesis and reduced the mortality of infected shrimp.

The immunostimulatory effects of hot-water extract of Gelidium amansii via immersion, injection and dietary administrations on white shrimp Litopenaeus vannamei and its resistance against Vibrio alginolyticus

The total haemocyte count (THC), phenoloxidase activity, and respiratory burst were examined when white shrimp Litopenaeus vannamei were immersed in seawater (34 per thousand) containing hot-water extract of red alga Gelidium amansii at 200, 400 and 600 mg l(-1), injected with hot-water extract at 4 and 6 microg g(-1) shrimp, and fed diets containing hot-water extract at 0, 0.5, 1.0 and 2.0 g kg(-1). These parameters increased significantly when shrimp were immersed in seawater containing hot-water extract at 400 and 600 mg l(-1) after 1h, when shrimp were injected with hot-water extract at 6 microg g(-1) shrimp after one day, and when shrimp were fed diets containing hot-water extract at 1.0 and 2.0 g kg(-1) after 14 days. Phagocytic activity and clearance efficiency were significantly higher for the shrimp that were fed diets containing hot-water extract at 1.0 and 2.0 g kg(-1) than those of shrimp that were fed diets containing hot-water extract at 0 and 0.5 g kg(-1) after 14 and 28 days. In a separate experiment, L. vannamei which had received hot-water extract via injection, or fed diets containing hot-water extract, were challenged after 3h or 28 days with V. alginolyticus at 2 x 10(6) cfu shrimp(-1) and 1 x 10(6) cfu shrimp(-1), respectively, and then placed in seawater. The survival of shrimp that were injected with hot-water extract at 6 microg g(-1) was significantly higher than that of control shrimp after 1 day, and the survival of shrimp fed diets containing hot-water extract at 0.5, 1.0 and 2.0 g kg(-1) increased significantly after 3 days as well as at the end of the experiment (6 days after the challenge), respectively. It was concluded that L. vannamei that were immersed in hot-water extract at 400 mg l(-1), injected with hot-water extract at 6 microg g(-1) shrimp, and fed hot-water extract of G. amansii at 2.0 g kg(-1) or less showed increased immune ability as well as resistance to V. alginolyticus infection.