Construction of a recombinant plasmid containing multi-copy CpG motifs and its effects on the innate immune responses of aquatic animals

Effectiveness of dietary heat-killed Bacillus subtilis harboring plasmid containing 60 copies of CpG-ODN 1668 against Vibrio harveyi in Penaeus vannamei

The cost of the purification process hinders the extensive use of cytosine phosphate guanosine-oligodeoxynucleotides (CpG-ODNs) for shrimp culture. Therefore, this study used a shuttle vector plasmid to carry 60 copies of CpG-ODN 1668 (pAD43-25_60CpG), which can replicate in Escherichia coli and Bacillus subtilis strain RIK1285. The first experiment used a reverse gavage procedure to deliver a substance (PBS [CK], pAD43-25 [P0], and pAD43-25_60CpG [P60], respectively) directly into the anterior midgut of Penaeus vannamei and transcriptome sequence analysis with a reference genome was performed to examine the expression of well-known immune-related genes. The results showed that the expression levels of immune-related genes in P60 group were significantly increased, particularly those associated with AMPs. In addition, using RT‒qPCR, the expression levels of AMP genes (LvALF, LvPEN-2, and LvPEN-3) in the P60 group may vary depending on the tissue and time point. The second experiment used dietary supplementation with three kinds of heat-killed B. subtilis (HKBS, HKBS-P0, and HKBS-P60) in 28 days of feeding experiments. The results showed that dietary supplementation with HKBS-P60 did not significantly improve shrimp growth performance and survival. However, on days 14 and 28 of the feeding regimens, alkaline phosphatase (AKP) and acid phosphatase (ACP) activity were considerably higher than in other treatments. In addition, following infection with Vibrio harveyi, AKP and ACP activity in the HKBS-P60 group was significantly higher than in other treatments, particularly at the early stage of bacterial infection. Moreover, HKBS-P60 was found to be better protected against V. harveyi infection with lower cumulative mortality (60%) compared to HKBS (90%) and HKBS-P0 (100%) at 7 days after infection. Overall, these findings confirmed that P60 could increase immunological responses in the shrimp midgut, and HKBS-P60 could be used as an effective tool to enhance the immune response and disease resistance in shrimp.

Protective immunity against CyHV-3 infection via different prime-boost vaccination regimens using CyHV-3 ORF131-based DNA/protein subunit vaccines in carp Cyprinus carpio var. Jian

Cyprinid Herpesvirus 3 (CyHV-3), also known as Koi Herpesvirus (KHV), causes Koi Herpesvirus Disease (KHVD) which leads to serious economic losses worldwide. To exploit DNA/subunit vaccine candidates, CyHV-3 ORF131 gene and cDNA was cloned and analyzed in the present study. Major B cell epitopes of deduced CyHV-3 pORF131 was also predicted. Then the complete CDS of CyHV-3 ORF131 was inserted into pEGFP-N1 vector and a modified pYD1/EBY100 system to construct the DNA and subunit vaccine, respectively. Subsequently, carp were immunized with homologous and heterologous prime-boost regimens relying on the constructed DNA and oral subunit vaccines. Then the protective immunity generated from different vaccines and regimens as well as the capacity of yeast (Saccharomyces cerevisiae) as an oral vaccine vehicle was evaluated. Our study confirmed that CyHV-3 ORF131 gene consisted of 2 introns and 3 exons encoding a 428 amino acids peptide. Further analysis indicated that four fragments of CyHV-3 pORF131 contained the major B cell epitopes (Cys20~Val140, Ser169~Tyr245, Thr258~Pro390, Phe414~Gln428), which could be linked and expressed in E. coli (BL21) as a truncated pORF131. The expression of full-length CyHV-3 pORF131 by pEGFP-N1 and yeast surface display was verified by In vitro assays before vaccination. Immunization of carp with CyHV-3 ORF131 DNA and subunit vaccines could evoke the activation of immune-related genes such as CXCa, CXCR1, IL-1β, TNF-α, INF-a1, Mx-1, IgM, IgT1 and production of specific serum IgM measured by ELISA. RPS (relative percent of survival) ranging from 53.33% to 66.67% was acquired post challenge test. Moreover, flow cytometry analysis illustrated the delivery of surface-displayed CyHV-3 pORF131 to midgut after oral gavage. Thus, our findings suggest that CyHV-3 ORF131 can serve as DNA/subunit vaccines candidate and the yeast as an ideal oral vaccine vehicle.

Effectiveness of formalin-killed vaccines containing CpG oligodeoxynucleotide 1668 adjuvants against Vibrio harveyi in orange-spotted grouper

Vibrio harveyi is a major bacterial pathogen that causes serious vibriosis in cultured groupers, leading to massive deaths. In this study, we evaluated the immune responses and protective efficacy of vaccines containing V. harveyi formalin-killed cells (FKC) formulated with CpG ODN 1668-enriched plasmids (p30CpG and p60CpG) in the orange-spotted grouper. Results indicated that antibody titres were remarkably increased in vaccinated fish 2 weeks post-immunisation. Expression level of major histocompatibility complex (MHC) class II, CD 8, and toll-like receptor 9 was significantly upregulated in the spleen of fish immunised with CpG ODN 1668-adjuvanted vaccines, as recorded at 6 weeks after immunisation. Additionally, the FKC + p60CpG-vaccinated fish displayed greater mRNA levels of MHC I and tumor necrosis factor-alpha. Of note, the relative percent survival after V. harveyi challenge was significantly higher in FKC + p60CpG-vaccinated fish (96.2%) than in FKC + p30CpG-vaccinated (79.8%) and FKC-vaccinated fish (59.9%). These results demonstrate that the FKC + CpG ODN 1668 vaccines are promising candidates that could enhance both innate and adaptive immune responses, conferred remarkable protection, and CpG ODN 1668 is a potential adjuvant for vaccines against V. harveyi.

Mobilisation and dysfunction of haematopoietic stem/progenitor cells after Listonella anguillarum infection in ayu, Plecoglossus altivelis

Haematopoietic stem/progenitor cells (HSPCs) can mobilise into blood and produce immune cell lineages following stress. However, the homeostasis and function of HSPCs after infection in teleosts are less well known. Here, we report that Listonella anguillarum infection enhances HSPC mobilisation and reduces their differentiation into myeloid cells in ayu (Plecoglossus altivelis), an aquacultured teleost in East Asia. We established a colony-forming unit culture (CFU-C) assay to measure HSPCs using conditioned medium from peripheral blood mononuclear cells stimulated with phytohaemagglutinin. The number of CFU-Cs decreased in the head kidney and increased in the blood and spleen of ayu infected with L. anguillarum. HSPC mobilisation after L. anguillarum infection was mediated by norepinephrine. Furthermore, HSPCs from ayu treated with L. anguillarum lipopolysaccharide (LPS) showed defective myeloid differentiation and could no longer rescue L. anguillarum-infected ayu. HSPC expansion was suppressed after L. anguillarum infection or its LPS treatment in vitro. These results reveal a link between HSPC regulation and pathogen infection in teleosts.

Combinations of various CpG motifs cloned into plasmid backbone modulate and enhance protective immunity of viral replicon DNA anthrax vaccines

DNA vaccines are generally weak stimulators of the immune system. Fortunately, their efficacy can be improved using a viral replicon vector or by the addition of immunostimulatory CpG motifs, although the design of these engineered DNA vectors requires optimization. Our results clearly suggest that multiple copies of three types of CpG motifs or combinations of various types of CpG motifs cloned into a viral replicon vector backbone with strong immunostimulatory activities on human PBMC are efficient adjuvants for these DNA vaccines to modulate and enhance protective immunity against anthrax, although modifications with these different CpG forms in vivo elicited inconsistent immune response profiles. Modification with more copies of CpG motifs elicited more potent adjuvant effects leading to the generation of enhanced immunity, which indicated a CpG motif dose-dependent enhancement of antigen-specific immune responses. Notably, the enhanced and/or synchronous adjuvant effects were observed in modification with combinations of two different types of CpG motifs, which provides not only a contribution to the knowledge base on the adjuvant activities of CpG motifs combinations but also implications for the rational design of optimal DNA vaccines with combinations of CpG motifs as "built-in" adjuvants. We describe an efficient strategy to design and optimize DNA vaccines by the addition of combined immunostimulatory CpG motifs in a viral replicon DNA plasmid to produce strong immune responses, which indicates that the CpG-modified viral replicon DNA plasmid may be desirable for use as vector of DNA vaccines.

The immune responses triggered by CpG ODNs in shrimp Litopenaeus vannamei are associated with LvTolls

CpG oligodeoxynucleotides (ODNs) represent a kind of pathogen-associated molecular patterns (PAMPs) as well as a novel adjuvant that activate the innate immune system through interaction with Toll-like receptor 9 (TLR9) in mammals. In the present study, the synthetic oligodeoxynucleotides, CpG ODN 2395, was employed to investigate the interactive mode of CpG ODNs with three known Tolls (LvToll1-3) from shrimp Litopenaeus vannamei. The mature peptides of extracellular domains of LvTolls (LvToll-ECDs) were recombinant expressed and their binding activities to CpG ODN 2395 were further examined by ELISA. rLvToll1-ECD and rLvToll3-ECD exhibited affinity to CpG ODN 2395 in a dose-dependent manner when their concentrations ranged from 0.25 to 2.00 μmol/L, while rLvToll2-ECD did not show any binding activities to CpG ODN 2395 in tested concentrations. Additionally, after the stimulation of CpG ODN 2395, the luciferase activities of HEK293T cells transfected with LvToll1-mosaic or LvToll3-mosaic were significantly increased to 2.38-fold (p<0.01) and 1.56-fold (p<0.01), while that in the HEK293T cells transfected with LvToll2-mosaic declined to 0.41-fold. The TNF-α activities were significantly enhanced (p<0.01), and a significant increase (p<0.05) of the NO production was observed at 12h post CpG ODN 2395 stimulation. Moreover, the induced TNF-α activities and increased NO production triggered by CpG ODN 2395 were abolished after the treatment of chloroquine (CQ). The uptake of CpG ODN 2395 by shrimp haemocytes was investigated using the laser scanning confocal microscope, and CpG ODN 2395 was observed to be internalized by the haemocytes and distributed in the cytoplasm with aggregated signals around the nucleuses. It suggested that the interactions of CpG ODNs with LvToll1 and LvToll3 as well as the mature of endosomes in the haemocytes of shrimp L. vannamei were indispensable for the triggering of immune responses by CpG ODNs, and the results provided a foundation for the application of CpG ODNs as the novel immunostimulants in aquaculture.

G-protein coupled receptor 18 (GPR18) in channel catfish: expression analysis and efficacy as immunostimulant against Aeromonas hydrophila infection

The objectives of this study were: 1) to determine the transcriptional profiles of G-protein coupled receptor 18 (GPR18) in channel catfish after infection with Aeromonas hydrophila compared to that in healthy catfish; 2) to determine whether over-expression of GPR18 in catfish gill cells will offer protection against infection of A. hydrophila; 3) to determine whether recombinant pcDNA-GPR18 could be used as an immunostimulant to protect channel catfish against A. hydrophila infection. Quantitative PCR revealed that the transcription levels of GPR18 in all tissues of infected catfish were significantly (P < 0.05) induced except in the intestine. When pcDNA3.2-vectored recombinant GPR18 was transfected in catfish gill cells G1B, the over-expression of pcDNA-GPR18 offered significant (P < 0.05) protection to G1B cells against A. hydrophila infection. When channel catfish were intraperitoneally injected with QCDCR adjuvant formulated pcDNA-GPR18 and challenged with a highly virulent A. hydrophila strain at 1-, 2-, 14-, and 28-days post treatment, pcDNA-GPR18 offered 50%, 100%, 57%, and 55% protection to channel catfish, respectively. Macrophages of fish treated with pcDNA-GPR18 produced significantly (P < 0.05) higher amounts of reactive oxygen species and nitric oxide than that of fish treated with pcDNA vector alone. In addition, serum lysozyme activity of catfish injected with pcDNA-GPR18 was significantly (P < 0.08) increased. Taken together, our results suggest that pcDNA-GPR18 could be used as a novel immunostimulant to provide immediate protection to channel catfish against A. hydrophila infection.

Apolipoprotein A1 in channel catfish: transcriptional analysis, antimicrobial activity, and efficacy as plasmid DNA immunostimulant against Aeromonas hydrophila infection

The objectives of this study were to: 1) determine transcriptional profiles of apolipoprotein A1 (ApoA1) in collected channel catfish tissues after infection with Aeromonas hydrophila by bath immersion; 2) investigate whether recombinant channel catfish apolipoprotein A1 produced in Escherichia coli expression system possesses any antimicrobial activity against A. hydrophila; 3) evaulate whether recombinant channel catfish apolipoprotein A1 plasmid DNA could be used as immunostimulant to protect fish against A. hydrophila infection. Quantitative PCR revealed that the transcription levels of ApoA1 in infected catfish were significantly (P < 0.05) more induced in the anterior kidney. Recombinant apoA1 produced in E. coli expression system exhibited lytic activity against Gram-positive Micrococcus lysodeikticus and Gram-negative A. hydrophila. When pcDNA3.2-vectored recombinant apoA1 was transfected in channel catfish gill cells G1B, the over-expression of pcDNA-ApoA1 offered significant (P < 0.05) protection to G1B cells against A. hydrophila infection. When channel catfish were intraperitoneally injected with QCDCR adjuvant formulated pcDNA-ApoA1 and challenged with a highly virulent A. hydrophila strain AL-09-71 at two days post injection, pcDNA-ApoA1 injection offered 100% protection to channel catfish. Macrophages of fish injected with pcDNA-ApoA1 produced significantly (P < 0.05) higher amounts of reactive oxygen species and nitric oxide than that of fish injected with pcDNA vector alone. Our results suggest that pcDNA-ApoA1 could be used as a novel immunostimulant to offer immediate protection to catfish against A. hydrophila infection.

Recombinant goose-type lysozyme in channel catfish: lysozyme activity and efficacy as plasmid DNA immunostimulant against Aeromonas hydrophila infection

The objectives of this study were: 1) to investigate whether recombinant channel catfish lysozyme-g (CC-Lys-g) produced in Escherichia coli expression system possesses any lysozyme activity; and 2) to evaluate whether channel catfish lysozyme-g plasmid DNA could be used as an immunostimulant to protect channel catfish against Aeromonas hydrophila infection. Recombinant CC-Lys-g produced in E. coli expression system exhibited significant (P < 0.05) lytic activity against Gram-positive Micrococcus lysodeikticus and Gram-negative A. hydrophila. When pcDNA3.2-vectored recombinant channel catfish lysozyme-g (pcDNA-Lys-g) was transfected in channel catfish gill cells G1B, the over-expression of pcDNA-Lys-g offered significant (P < 0.05) protection to G1B cells against A. hydrophila infection. When channel catfish were intraperitoneally injected with pcDNA-Lys-g along with an adjuvant QCDCR, the transcriptional level of Lys-g was significantly (P < 0.05) increased. When pcDNA-Lys-g injected fish was challenged with a highly virulent A. hydrophila strain AL-09-71, pcDNA-Lys-g offered 100% protection to channel catfish at two days post DNA injection. Macrophages of fish injected with pcDNA-Lys-g produced significantly (P < 0.05) higher amounts of reactive oxygen species and nitric oxide than that of fish injected with pcDNA vector alone at two days post DNA injection. Taken together, our results suggest that pcDNA-Lys-g could be used as a novel immunostimulant to offer immediate protection to channel catfish against A. hydrophila infection.

Chicken-type lysozyme in channel catfish: expression analysis, lysozyme activity, and efficacy as immunostimulant against Aeromonas hydrophila infection

To understand whether chicken-type lysozyme (Lys-c) in channel catfish was induced by infection of Aeromonas hydrophila, the transcriptional levels of Lys-c in skin, gut, liver, spleen, posterior kidney, and blood cells in healthy channel catfish was compared to that in channel catfish infected with A. hydrophila by bath immersion. Quantitative PCR revealed that the transcription levels of Lys-c in infected catfish were significantly (P < 0.05) induced in all five tissues tested as well as in blood cells. Recombinant CC-Lys-c produced in Escherichia coli expression system (R-CC-Lys-c) exhibited significant (P < 0.05) lytic activity to Gram-positive Micrococcus lysodeikticus and Gram-negative A. hydrophila. When pcDNA3.2-vectored recombinant channel catfish lysozyme-c (pcDNA-Lys-c) was transfected in channel catfish gill cells G1B, the over-expression of pcDNA-Lys-c offered significant (P < 0.05) protection to G1B against A. hydrophila infection. When channel catfish were intraperitoneally injected with QCDCR adjuvant formulated pcDNA-Lys-c and challenged with a highly virulent A. hydrophila strain AL-09-71 at 1-, 2-, 14-, and 28-days post treatment, pcDNA-Lys-c offered 75%, 100%, 60%, and 77% protection to channel catfish, respectively. Macrophages of fish treated with pcDNA-Lys-c produced significantly (P < 0.05) higher amounts of reactive oxygen species and nitric oxide than that of fish treated with pcDNA vector alone. Taken together, our results suggest that pcDNA-Lys-c could be used as a novel immunostimulant to protect channel catfish against A. hydrophila infection.

The CpG ODNs enriched diets enhance the immuno-protection efficiency and growth rate of Chinese mitten crab, Eriocheir sinensis

CpG oligodeoxynucleotides (ODNs), the well-known vaccine adjuvant in mammals, have been proved to mount innate immune responses in crustaceans. In the present study, CpG ODNs was employed as supplements in diets to fed crab Eriocheir sinensis, and the changes of immune parameters as well as weight gain were investigated to evaluate its possible application in crab farming. After the crabs were fed with 40 mg/kg and 100 mg/kg CpG ODNs containing diets (designated as C40 and C100 group) for four weeks, the lysozyme activities were significantly enhanced (p < 0.01) in both groups, while the catalase activity was only increased (p < 0.01) in the C40 group. When those crabs were subsequently challenged with Aeromonas hydrophila, the cumulative mortalities in C40 and C100 groups were declined by 10.4% and 10.8% (p < 0.05) compared with that of control group, respectively. Interestingly, the final weights of crabs were increased after four weeks' feeding of CpG ODNs, and the percentage of weight gain in C40 group reached 124.5 ± 14.2%, which was significantly higher (p < 0.05) than that of control group (78.1 ± 19.2%) and C100 group (107.3 ± 28.2%). The uptake of CpG ODNs by haemocytes and the possible mechanism of CpG ODNs to active the immune response were investigated by using the laser scanning confocal microscope. CpG ODNs (labeled with 5'-end-FAM) could be internalized by the haemocytes after incubation of 20 min, with strong signals detected at the cell membrane and in the cytoplasm. In the cytoplasm, most of the CpG ODNs were localized in lysosome, and some of them escaped from the lysosomal compartments and aggregated around the nuclear. The results clearly demonstrated that CpG ODNs could be internalized directly by crab haemocytes and mostly located in the late endosome. The enhancements of immuno-protection efficiency and growth rate from CpG ODNs as supplements in diets might depend on the uptaking and locating processes, and they could be used as a potential immunostimulant for the crab aquaculture.

Hemocytic immune responses triggered by CpG ODNs in shrimp Litopenaeus vannamei

CpG oligodeoxynucleotides (CpG ODNs), also called bacterial DNA or synthetic oligodeoxynucleotides, can induce apparent immunity protection against various pathogens, and they are widely used as functional immunostimulant or vaccine adjuvant in mammals. In the present study, CpG-rich plasmid pUC57-CpG was constructed and employed to stimulate the shrimp Litopenaeus vannamei, and the total hemocyte count, percentage of apoptotic hemocytes, regeneration of circulating hemocytes, the ability of phagocytosis and generation of reactive oxygen species (ROS) were measured to reveal the possible protection mechanism of CpG ODNs. After the injection of pUC57-CpG, the total hemocyte count significantly decreased (p < 0.01) to 2.56 × 10(7) cell/mL at the first day post stimulation, while the apoptosis increased (p < 0.01), which was 1.72-fold of that in control group. At the same time, the regeneration of circulating hemocytes fluctuated in a similar trend, and a significant increase was observed at the first day post stimulation. The phagocytotic activity including the percentage of phagocytosis and phagocytotic index, experienced an upward tend during the whole experimental period and the ROS level increased by 22% (p < 0.05) compared to that in the control group at first day post stimulation. These results together suggested that pUC57-CpG could promote the apoptosis and regeneration of circulating hemocytes, and enhance the phagocytosis and ROS production, which might contribute to the boosted immunity against the infection of pathogens.

Mytilus galloprovincialis myticin C: a chemotactic molecule with antiviral activity and immunoregulatory properties

Previous research has shown that an antimicrobial peptide (AMP) of the myticin class C (Myt C) is the most abundantly expressed gene in cDNA and suppressive subtractive hybridization (SSH) libraries after immune stimulation of mussel Mytilus galloprovincialis. However, to date, the expression pattern, the antimicrobial activities and the immunomodulatory properties of the Myt C peptide have not been determined. In contrast, it is known that Myt C mRNA presents an unusual and high level of polymorphism of unidentified biological significance. Therefore, to provide a better understanding of the features of this interesting molecule, we have investigated its function using four different cloned and expressed variants of Myt C cDNA and polyclonal anti-Myt C sera. The in vivo results suggest that this AMP, mainly present in hemocytes, could be acting as an immune system modulator molecule because its overexpression was able to alter the expression of mussel immune-related genes (as the antimicrobial peptides Myticin B and Mytilin B, the C1q domain-containing protein MgC1q, and lysozyme). Moreover, the in vitro results indicate that Myt C peptides have antimicrobial and chemotactic properties. Their recombinant expression in a fish cell line conferred protection against two different fish viruses (enveloped and non-enveloped). Cell extracts from Myt C expressing fish cells were also able to attract hemocytes. All together, these results suggest that Myt C should be considered not only as an AMP but also as the first chemokine/cytokine-like molecule identified in bivalves and one of the few examples in all of the invertebrates.

The introduction of multi-copy CpG motifs into an antiviral DNA vaccine strongly up-regulates its immunogenicity in fish

The protection conferred by antiviral DNA vaccines in fish is known to rely greatly on innate immune responses. Since oligodeoxynucleotides (ODNs) containing unmethylated CpG dinucleotides (CpG motifs) have been shown to induce potential innate immune responses, we have introduced several copies (either two or four) of a fragment containing multiple CpG sequences of known immunostimulatory effects into a DNA vaccine against viral hemorrhagic septicemia virus (VHSV). We have determined the effects of this introduction on the vaccine immunogenicity, measured as immune gene induction, serum neutralizing activity and antigen-dependent proliferation. When comparing the effects of the vaccine containing 2 copies of this CpG fragment (pVHSV-2CpG) or that containing 4 copies of the fragment (pVHSV-4CpG) with the original VHSV DNA vaccine (pVHSV), we found that the levels of expression of type I interferon (IFN) were significantly up-regulated in muscle and spleen when the CpG fragments were introduced. An up-regulation in the levels of MHC-I expression in spleen were also observed in response to the modified vaccines, whereas, the levels of transcription of interleukin 1β (IL-1β) were strongly reduced in comparison to the original vaccine. Important but very variable differences were also observed concerning the vaccine induction of IFN-γ. Moreover, the serum neutralizing capacity was strongly increased as fish were vaccinated with plasmids containing more CpG fragments. Taken together, all these results demonstrate a strongly increased immunogenicity of the VHSV DNA vaccine, through the introduction of this multicopy CpG fragment.

Identification and analysis of a CpG motif that protects turbot (Scophthalmus maximus) against bacterial challenge and enhances vaccine-induced specific immunity

Oligodeoxynucleotides (ODNs) containing unmethylated CpG motifs in certain contexts are known to be immunostimulatory in vertebrate systems. CpG ODNs with immune effects have been identified for many fish species but, to our knowledge, not for turbot. In this study, a turbot-effective CpG ODN, ODN 205, was identified and a plasmid, pCN5, was constructed which contains the CpG motif of ODN 205. When administered into turbot via intraperitoneal (i.p.) injection, both ODN 205 and pCN5 could (i) inhibit bacterial dissemination in blood in dose and time dependent manners, and (ii) protect against lethal bacterial challenge. Immunological analyses showed that in vitro treatment with ODN 205 stimulated peripheral blood leukocyte proliferation, while i.p. injection with ODN 205 enhanced the respiratory burst activity, chemiluminescence response, and acid phosphatase activity of turbot head kidney macrophages. pCN5 treatment-induced immune responses similar to those induced by ODN 205 treatment except that pCN5 could also enhance serum bactericidal activity in a calcium-independent manner. To examine whether ODN 205 and pCN5 had any effect on specific immunity, ODN 205 and pCN5 were co-administered into turbot with a Vibrio harveyi subunit vaccine, DegQ. The results showed that pCN5, but not ODN 205, significantly increased the immunoprotective efficacy of DegQ and enhanced the production of specific serum antibodies in the vaccinated fish. Further analysis indicated that vaccination with DegQ in the presence of pCN5 upregulated the expression of the genes encoding MHC class IIalpha, IgM, Mx, and IL-8 receptor. Taken together, these results demonstrate that ODN 205 and pCN5 can stimulate the immune system of turbot and induce protection against bacterial challenge. In addition, pCN5 also possesses adjuvant property and can potentiate vaccine-induced specific immunity.

Protective immunity induced by CpG ODNs against white spot syndrome virus (WSSV) via intermediation of virus replication indirectly in Litopenaeus vannamei

The worldwide shrimp culture is beset with diseases mainly caused by white spot syndrome virus (WSSV) and suffered huge economic losses, which bring out an urgent need to develop the novel strategies to better protect shrimps against WSSV. In the present study, CpG-rich plasmid pUC57-CpG, plasmid pUC57 and PBS were employed to pretreat shrimps comparatively to evaluate the protective effects of CpG ODNs on shrimps against WSSV. The survival rates, WSSV copy numbers, and antiviral associated factors (Dicer, Argonaute, STAT and ROS) were detected in Litopenaeus vannamei. There were higher survival proportion, lower WSSV copy numbers, and higher mRNA expression of Dicer and STAT in pUC57-CpG-pretreatment shrimps than those in pUC57- and PBS-pretreatment shrimps after WSSV infection. The Argonaute mRNA expression in pUC57-CpG-, pUC57- and PBS-pretreatment shrimps after WSSV infection was significantly higher than that of shrimps post PBS stimulation on the first day. The ROS levels in pUC57-CpG-pretreatment shrimps post secondary stimulation of PBS were significantly higher than those post WSSV infection on the first day. These results together demonstrated that pUC57-CpG induced partial protective immunity in shrimps against WSSV via intermediation of virus replication indirectly and could be used as a potential candidate in the development of therapeutic agents for disease control of WSSV in L. vannamei.

Inhibitor of REL/NF-KappaB is regulated in Sydney rock oysters in response to specific double-stranded RNA and Vibrio alginolyticus, but the major immune anti-oxidants EcSOD and Prx6 are non-inducible

Invertebrates, such as oysters have mechanisms to recognize different microbial associated molecular patterns (MAMPs) and recognition of these antigens triggers signaling pathways for the transcription of immune-related proteins. Components of the Rel/NF-(capital KA, Cyrillic)B pathway have been identified in mollusks but the role of different MAMPs in the activation of this pathway is poorly understood. In the current study, the Sydney rock oyster (Saccostrea glomerata) was injected intramuscularly with a range of different MAMPs. Oysters were sampled over a 24 h period and the difference in expression of genes associated with immunity was determined by quantitative reverse transcription polymerase chain reaction (qRT-PCR) using RNA extracted from hemocytes. The results showed that oysters can discriminate between different nucleic acids and double-stranded RNA sequences for activation of the Rel/NF-(capital KA, Cyrillic)B pathway in S. glomerata. Polyinosinic-polycytidylic acid (poly I:C) up-regulated expression of inhibitor of Rel/NF-(capital KA, Cyrillic)B (I(capital KA, Cyrillic)B) by 26-fold and interferon-inhibiting cytokine (IK) by 2.2-fold, whereas polycytidylic acid-polyguanylic acid (poly G:C) and double stranded Vibrio alginolyticus genomic DNA (dsDNA) did not. I(capital KA, Cyrillic)B was also up-regulated 3.8-fold higher for oysters stimulated with V. alginolyticus bacterial cells suggesting that lipopolysaccharide (LPS) also activates the Rel/NF-(capital KA, Cyrillic)B pathway. The expressions of extracellular superoxide dismutase (EcSOD) and peroxiredoxin 6 (Prx6) were not significantly affected by dsRNA, dsDNA or V. alginolyticus bacterial cells suggesting that these two genes, previously demonstrated to be important in the resistance of S. glomerata to disease are not directly inducible by these MAMPs. This is the first study investigating differences in expression kinetics of immune genes in response to challenge from different MAMPs in this economically important bivalve species.