Characterization of a Kunitz-type protease inhibitor (MjKuPI) reveals the involvement of MjKuPI positive hemocytes in the immune responses of kuruma shrimp Marsupenaeus japonicus

Serine proteases and their inhibitors play vital roles in biological processes. Serine protease inhibitors, including Kunitz-type protease inhibitors play important roles not only in physiological process (i.e. blood clotting and fibrinolysis) but also in immune responses. In this study, we characterized a Kunitz-type protease inhibitor, designated MjKuPI, from kuruma shrimp Marsupenaeus japonicus. An expression profile showed that MjKuPI was mainly expressed in hemocytes. Immunostaining revealed that some hemocytes expressed MjKuPI (MjKuPI(+) hemocytes) and others did not (MjKuPI(-) hemocytes). Injection of shrimp with Vibrio penaeicida and white spot syndrome virus (WSSV) upregulated the mRNA level of MjKuPI, and a flow cytometry analysis revealed that the proportion of MjKuPI(+) hemocytes increased significantly 24 h after injection. Together, these results suggest that MjKuPI and MjKuPI(+) hemocytes have a role in the innate immune system of kuruma shrimp.

Evaluation of ToxA and Vibrio parahaemolyticus lysate on humoral immune response and immune-related genes in Pacific red snapper

Immunogenicity of ToxA and Vibrio parahaemolyticus lysate was evaluated in a double immunostimulation scheme in Pacific red snapper after V. parahaemolyticus infection. Three groups of Pacific red snapper were intraperitonealy (i.p.) injected with phosphate-buffered saline (PBS group), ToxA of V. parahaemolyticus (ToxA-Vp group) or V. parahaemolyticus lysate (lysate-Vp group) (first injection, day 1; second injection, day 7). Fish were subsequently infected with live V. parahaemolyticus. Humoral immune parameters in skin mucus and serum were evaluated on days 1, 7, 8 and 14 days post-immunostimulation and 7 days post-infection. Moreover expression of immune-related genes was quantified by real time PCR in head-kidney leukocytes, spleen, liver, and intestine. The ToxA-Vp-treated group showed a higher anti-protease and catalase activity in skin mucus when compared with the PBS group. Measurements of SOD and CAT activities showed an increment in both activities a day after the second boost with ToxA-Vp or lysate-Vp. Interestingly, IgM levels in mucus and transcripts were enhanced followed the ToxA-Vp treatment even after challenge. Furthermore, IL-1β was strongly expressed in all analyzed cell or tissues followed ToxA-Vp or Vp-lysate treatments. Finally, SOD and CAT gene expression was up-regulated in fish immunostimulated with either treatment ToxA-Vp or lysate-Vp, mainly after infection in head-kidney leukocytes and intestine. This is the first study where the effects of ToxA from V. parahaemolyticus in the immune system of Pacific red snapper was evaluated. These results suggest that ToxA-Vp would positively affect humoral immune response and up-regulate expression of genes involved in the immune system function; and could help in the control of V. parahaemolyticus infection in Pacific red snapper Lutjanus peru, an economic important fish in Mexico.

TLR21's agonists in combination with Aeromonas antigens synergistically up-regulate functional TLR21 and cytokine gene expression in yellowtail leucocytes

The purpose of this study was to characterize the TLR21 gene from yellowtail (Seriola lalandi) and its functional activity using TLR agonist stimulation and Aeromonas antigens. The TLR21 nucleotide sequence from yellowtail was obtained using the whole-genome shotgun sequencing method and bioinformatics tools. Basal TLR21 gene expression was analyzed in several tissues. Subsequently, the gene expression of TLR21 and cytokines IL-1β and TNF-α was evaluated in TLR agonist (CpG-ODN2006, LPS, and Poly I:C) exposing head kidney leucocytes, which were then subjected to Aeromonas antigen stimulation. The yellowtail full-length cDNA sequence of SlTLR21 was 3615 bp (980 aa) showing a high degree of similarity with the counterparts of other fish species and sharing the common structural architecture of the TLR family, including LRR domains, one C-terminal LRR region, and a TIR domain. Gene expression studies revealed the constitutive expression of TLR21 mRNA in all the analyzed tissues; the highest levels were observed in spleen and head kidney where they play an important role in the fish immune system. Transcripts of TLR21 and the downstream IL-1β and TNF-α cytokine genes were most strongly up-regulated after exposure to the TLR agonists following Aeromonas antigen stimulation, suggesting they are involved in immune response. The results indicated that TLR agonists, in combination with Aeromonas antigens in head kidney leucocytes, synergistically enhance TLR21 and cytokines in yellowtail.

Shrimp miRNAs regulate innate immune response against white spot syndrome virus infection

MicroRNAs are short noncoding RNAs of RNA interference pathways that regulate gene expression through partial complementary base-pairing to target mRNAs. In this study, miRNAs that are expressed in white spot syndrome virus (WSSV)-infected Penaeus monodon, were identified using next generation sequencing. Forty-six miRNA homologs were identified from WSSV-infected shrimp hemocyte. Stem-loop real-time RT-PCR analysis showed that 11 out of 16 selected miRNAs were differentially expressed upon WSSV infection. Of those, pmo-miR-315 and pmo-miR-750 were highly responsive miRNAs. miRNA target prediction revealed that the miRNAs were targeted at 5'UTR, ORF, and 3'UTR of several immune-related genes such as genes encoding antimicrobial peptides, signaling transduction proteins, heat shock proteins, oxidative stress proteins, proteinases or proteinase inhibitors, proteins in blood clotting system, apoptosis-related proteins, proteins in prophenoloxidase system, pattern recognition proteins and other immune molecules. The highly conserved miRNA homolog, pmo-bantam, was characterized for its function in shrimp. The pmo-bantam was predicted to target the 3'UTR of Kunitz-type serine protease inhibitor (KuSPI). Binding of pmo-bantam to the target sequence of KuSPI gene was analyzed by luciferase reporter assay. Correlation of pmo-bantam and KuSPI expression was observed in lymphoid organ of WSSV-infected shrimp. These results implied that miRNAs might play roles as immune gene regulators in shrimp antiviral response.

WSV399, a viral tegument protein, interacts with the shrimp protein PmVRP15 to facilitate viral trafficking and assembly

Viral responsive protein 15 (PmVRP15) has been identified as a highly up-regulated gene in the hemocyte of white spot syndrome virus (WSSV)-infected shrimp Penaeus monodon. However, the function of PmVRP15 in host-viral interaction was still unclear. To elucidate PmVRP15 function, the interacting partner of PmVRP15 from WSSV was screened by yeast two-hybrid assay and then confirmed by co-immunoprecipitation (Co-IP). Only WSV399 protein was identified as a PmVRP15 binding protein; however, the function of WSV399 has not been characterized. Localization of WSV399 on the WSSV virion was revealed by immunoblotting analysis (in vitro) and immunoelectron microscopy (in vivo). The results showed that WSV399 is a structural protein of the WSSV virion and is particularly located on the tegument. Gene silencing of wsv399 in WSSV-infected shrimp reduced the percentage of cumulative mortality by 74%, although the expression level of a viral replication marker gene, vp28, was not changed suggesting that WSV399 might not involved in viral replication but viral assembly. Because it has already been known that tegument proteins function in capsid transport during viral trafficking and assembly, interaction between PmVRP15 on hemocyte nuclear membrane and the WSV399 viral tegument protein suggests that PmVRP15 might be required for trafficking and assembly of WSSV during infection.

Extracellular trap formation in kuruma shrimp (Marsupenaeus japonicus) hemocytes is coupled with c-type lysozyme

In invertebrates, hemocytes play an important role in immune responses. Recently, a novel form of innate immune mechanism called extracellular traps (ETs) was identified in shrimps, where DNA and antimicrobial peptides form complex structure to entrap the invading microbes. In this study, we detected the formation of ETs from hemocytes of kuruma shrimp in response to various stimulations, including phorbol myristate acetate (PMA), lipopolysaccharide (LPS), peptidoglycan (PGN) and Escherichia coli. E. coli cells were also found to be trapped by ET fibers. Fluorescence imaging revealed that c-type lysozyme proteins were released around the ET complex after E. coli stimulation, suggesting the presence of a coupled antimicrobial immune response involving ET formation and AMP release.

Identification of endonuclease domain-containing 1 gene in Japanese flounder Paralichthys olivaceus

The mRNA level of the endonuclease domain-containing 1 gene (Jf_ENDOD1) in Japanese flounder Paralichthys olivaceus kidney was significantly increased after injection of formalin-killed bacteria cells (FKC) in the previous microarray study. ENDOD1 is a member of the DNA/RNA non-specific nucleases family, and its role in fish immunity has not been reported. The open reading frame of Jf_ENDOD1 cDNA was 912 bp, encoding 303 amino acids. The first 27 amino acids were predicted to be a signal peptide and the mature Jf_ENDOD1 was calculated as 32 kDa. The amino acid sequence of Jf_ENDOD1 showed 76% identity to that of large yellow croaker Larimichthys crocea. Transcripts of Jf_ENDOD1 were marginally detected in all sampled tissues from healthy fish, while they were significantly detected in brain, kidney, spleen and intestine at 6 h post FKC injection. Jf_ENDOD1 recombinant protein produced in Escherichia coli showed DNase activity. Furthermore, to evaluate the DNase activities in vivo, total proteins from Japanese flounder kidney and spleen were extracted at 12, 24 and 72 h post Edwardsiella tarda FKC injection. The DNase activity of extracted protein was higher in treated fish than in untreated fish. Since the mRNA levels were significantly up-regulated after the FKC treatment, Jf_ENDOD1 might be responsible for the activities.

Ichthyobacterium seriolicida gen. nov., sp. nov., a member of the phylum 'Bacteroidetes', isolated from yellowtail fish (Seriola quinqueradiata) affected by bacterial haemolytic jaundice, and proposal of a new family, Ichthyobacteriaceae fam. nov

A novel Gram-stain-negative, rod-shaped (0.3 × 4-6 μm), non-flagellated, aerobic strain with gliding motility, designated JBKA-6T, was isolated in 1991 from a yellowtail fish, Seriola quinqueradiata, showing symptoms of bacterial haemolytic jaundice. 16S rRNA gene sequence analysis showed that strain JBKA-6T was related most closely to members of the family Flavobacteriaceae in the phylum 'Bacteroidetes'. Furthermore, based on gyrB gene sequence analysis, JBKA-6T was classified into a single clade within the order Flavobacteriales, which was distinct from the known clades of the families Flavobacteriaceae, Blattabacteriaceae and Cryomorphaceae. The predominant isoprenoid quinone was identified as MK-6 (97.9 %), and the major cellular fatty acids (>10 %) were C14 : 0 and iso-C15 : 0. The main polar lipids were phosphatidylethanolamine, three unidentified phospholipids, two unidentified aminophospholipids and two unidentified polar lipids. The DNA G+C content of JBKA-6T, as derived from its whole genome, was 33.4 mol%. The distinct phylogenetic position and phenotypic traits of strain JBKA-6T distinguish it from all other described species of the phylum 'Bacteroidetes', and therefore it was concluded that strain JBKA-6T represents a new member of the phylum 'Bacteroidetes', and the name Ichthyobacterium seriolicida gen. nov., sp. nov. is proposed. The type strain of Ichthyobacterium seriolicida is JBKA-6T ( = ATCC BAA-2465T = JCM 18228T). We also propose that Icthyobacterium gen. nov. is the type genus of a novel family, Ichthyobacteriaceae fam. nov.

YHV-responsive gene expression under the influence of PmRelish regulation

In animals, infection by Gram-negative bacteria and certain viruses activates the Imd signaling pathway wherein the a NF-κB transcription factor, Relish, is a key regulatory protein for the synthesis of antimicrobial proteins. Infection by yellow head virus (YHV) activates the Imd pathway. To investigate the expression of genes involved in YHV infection and under the influence of PmRelish regulation, RNA interference and suppression subtractive hybridization (SSH) are employed. The genes in forward library expressed in shrimp after YHV infection and under the activity of PmRelish were obtained by subtracting the cDNAs from YHV-infected and PmRelish-knockdown shrimp with cDNAs from YHV-infected shrimp. Opposite subtraction gave a reverse library whereby an alternative set of genes under YHV infection and no PmRelish expression were obtained. Nucleotide sequences of 252 and 99 cDNA clones from the forward and reverse libraries, respectively, were obtained and annotated through blast search against the GenBank sequences. Genes involved in defense and homeostasis were abundant in both libraries, 31% and 23% in the forward and reverse libraries, respectively. They were predominantly antimicrobial proteins, proteinases and proteinase inhibitors. The expression of antimicrobial protein genes, ALFPm3, crustinPm1, penaeidin3 and penaeidin5 were tested under PmRelish silencing and Gram-negative bacterium Vibrio harveyi infection. Together with the results using YHV infection previously reported, the expression of penaeidin5 and also penaeidin3 but not ALFPm3 and crustinPm1 were under the regulation of PmRelish in the Imd pathway.

Genomic comparison between pathogenic Streptococcus agalactiae isolated from Nile tilapia in Thailand and fish-derived ST7 strains

Streptococcus agalactiae, or Group B streptococcus (GBS), is a highly virulent pathogen in aquatic animals, causing huge mortalities worldwide. In Thailand, the serotype Ia, β-hemolytic GBS, belonging to sequence type (ST) 7 of clonal complex (CC) 7, was found to be the major cause of streptococcosis outbreaks in fish farms. In this study, we performed an in silico genomic comparison, aiming to investigate the phylogenetic relationship between the pathogenic fish strains of Thai ST7 and other ST7 from different hosts and geographical origins. In general, the genomes of Thai ST7 strains are closely related to other fish ST7s, as the core genome is shared by 92-95% of any individual fish ST7 genome. Among the fish ST7 genomes, we observed only small dissimilarities, based on the analysis of clustered regularly interspaced short palindromic repeats (CRISPRs), surface protein markers, insertions sequence (IS) elements and putative virulence genes. The phylogenetic tree based on single nucleotide polymorphisms (SNPs) of the core genome sequences clearly categorized the ST7 strains according to their geographical and host origins, with the human ST7 being genetically distant from other fish ST7 strains. A pan-genome analysis of ST7 strains detected a 48-kb gene island specifically in the Thai ST7 isolates. The orientations and predicted amino acid sequences of the genes in the island closely matched those of Tn5252, a streptococcal conjugative transposon, in GBS 2603V/R serotype V, Streptococcus pneumoniae and Streptococcus suis. Thus, it was presumed that Thai ST7 acquired this Tn5252 homologue from related streptococci. The close phylogenetic relationship between the fish ST7 strains suggests that these strains were derived from a common ancestor and have diverged in different geographical regions and in different hosts.

Molecular cloning and comparative responses of Toll-like receptor 22 following ligands stimulation and parasitic infection in yellowtail (Seriola lalandi)

TLR22 is exclusively present in teleosts and amphibians and is expected to play the distinctive role in innate immunity. In this study, we cloned the full-length cDNA sequence of yellowtail (Seriola lalandi) TLR22 (SlTLR22). The complete cDNA sequence of SlTLR22 was 4208 bp and encodes a polypeptide of 961 amino acids. Analysis of the deduced amino acid sequence indicated that SlTLR22 has typical structural features of proteins belonging to the TLR family. These included 17 LRR domains (residues 91-633) and one C-terminal LRR domain (LRR-CT, residues 693-744) in the extracellular region, and a TIR domain (residues 800-943) in the cytoplasmic region. Comparison with homologous proteins showed that the deduced SlTLR22 has the highest sequence identity to turbot TLR22 (76%). Quantitative real-time PCR (qPCR) analysis demonstrated the constitutive expression of SlTLR22 mRNA in all examined tissues with higher levels in the head kidney, intestine, skin and spleen. Further, SlTLR22 expression was significantly up-regulated following TLR ligands injection with lipopolysaccharide (LPS), CpG ODN2006 and polyinosinic: polycytidylic acid (poly I:C) in spleen and liver. Amyloodinium ocellatum infection also induced a high expression of SlTLR22 in spleen, intestine, muscle, skin and gill, with maximum increases ranging from 1000 to 100 fold upon different ligands and organs. Finally, histological examination in gill tissue confirmed infection by the parasite and histopathological lesion was observed also in spleen and skin. These findings suggest a possible role of SlTLR22 in the immune responses to the infections of a broad range of pathogens that include DNA and RNA viruses and parasites.

Comparative analysis of two types of CXCL8 from Japanese flounder (Paralichthys olivaceus)

A new type of CXCL8, named CXCL8_L1b, was identified in this research. Comparison of amino acid sequences of Japanese flounder CXCL8_L1b and CXCL8_L1a (BAB86884.1) showed only 41.2% identity. Transcripts of CXCL8_L1a were highly detected in spleen, kidney, gill and liver, while transcripts of CXCL8_L1b only were detected highly in spleen and kidney of apparently healthy fish. In fish challenged with E. tarda, transcripts of CXCL8_L1a were significantly increased at day 6, while no significant increase was detected in the mRNA level of CXCL8_L1b. On the other hand, fish infected by S. iniae significantly increased both transcripts of CXCL8_L1a and CXCL8_L1b at days 1 and 3. In VHSV-infected fish, only the transcripts of CXCL8_L1b were significantly induced at day 6. LPS and poly I:C stimulation of PBLs induced a high level of CXCL8_L1a transcripts, while CXCL8_L1b transcripts were significantly increased only post poly I:C treatment. To evaluate the chemotactic activity of CXCL8_L1a and CXCL8_L1b, Japanese flounder were intramuscularly injected with recombinant plasmids pCI-CXCL8_L1a and pCI-CXCL8_L1b. H & E staining showed that injections of both pCI-CXCL8_L1a and pCI-CXCL8_L1b caused strong immune responses in the form of intermuscular cell infiltration and capillary congestion. Injection of pCI-CXCL8_L1a and pCI-CXCL8_L1b significantly induced the expressions of genes related to inflammatory response such as IL-6 and CD8α on day 1 post-injection. The transcripts of IgM only significantly increased on day 7 post-injection of pCI-CXCL8_L1b.

Microarray Analysis of Immunity Against WSSV in Response to Injection of Non-specific Long dsRNA in Kuruma Shrimp, Marsupenaeus japonicus

Injection of shrimp with non-specific double-stranded RNA (dsRNA) of diverse lengths, sequences, and base compositions is known to induce non-specific immunity and protect against lethal disease, although the mechanisms are unclear. Previous shrimp studies examined the effects of non-specific RNA on particular pathways, while their global effects have not been examined. To understand the global effects of non-specific RNA in shrimp, we injected kuruma shrimp (Marsupenaeus japonicus) with a dsRNA and a small interfering RNA (siRNA) that is not specific to any gene in the shrimp genome and then examined global gene expression at 24 and 48 h with a microarray. For the non-specific RNA, we chose double-stranded green fluorescent protein (dsGFP) and siGFP because they are commonly used as mock controls and their effects on shrimp have not yet been studied. Injection of PBS was used as a control. The microarray results showed that many genes were up-regulated and some were down-regulated by dsGFP. In addition, dsGFP injection increased survival following WSSV challenge. The changes in expression for several genes were confirmed by quantitative PCR. The up-regulated genes included genes for eight immune-related proteins: c-type lectin 2, hemocyte homeostasis-associated protein, viral responsive protein, fibrinogen-related protein 1, sid-1 like protein, argonaute 2, Dicer 2, and heat shock protein 90. These results show that injection of shrimp with non-specific dsRNA hinders viral accumulation and prevents significant mortalities.

Temperature-dependent regulation of gene expression in poly (I:C)-treated Japanese flounder, Paralichthys olivaceus

Gene expression profiling of poly (I:C)-treated Japanese flounder, Paralichthys olivaceus, under different temperatures was investigated using microarray analysis. The response was analyzed in spleen tissue at 3 and 24 h post injection (hpi) at 15 °C and 25 °C. A large number of genes in fish treated with poly (I:C) at 25 °C were expressed at 3 hpi, whereas the expression profiles at 24 hpi appeared to be similar to those of the controls. Cluster analysis of the different expression profiles showed three distinct groups of up-regulated genes in fish reared at 15 °C. These were early (3 hpi), early-to-late (3 and 24 hpi), and late (24 hpi) up-regulated genes. These genes included type I IFN-related genes and inflammatory genes. Among the up-regulated genes, most of the type I IFN-related genes played early-to-late- and late-responding genes at 15 °C but early-responding genes at 25 °C. Thus, several up-regulated genes in these groups from the microarray result were further verified by qPCR. These results indicate that the type I IFN gene expressions of P. olivaceus treated with poly (I:C) can be regulated in a temperature-dependent manner.

Molecular cloning and characterization of Mj-mov-10, a putative RNA helicase involved in RNAi of kuruma shrimp

Identification and characterization of the RNAi-related genes is the key to understanding RNAi mechanism in shrimp. In this study, we have identified and characterized a novel putative RNA helicase gene, Mj-mov-10 from the kuruma shrimp, Marsupenaeus japonicus and its implication in shrimp RNAi was demonstrated. The full-length Mj-mov-10 gene contained 3536bp, including 239 bp of 5'UTR, 2895 bp of the open reading frame (ORF) and 402bp of 3'UTR, respectively. An ORF of Mj-mov-10 could be translated to a 109-kDa protein which consists of a single helicase core domain containing seven signature motifs of the RNA helicase superfamily-1. Mj-MOV-10 protein shared 47% and 40% identity with mammalian MOV-10 and plant SDE3, respectively. Expression of Mj-mov-10 gene was significantly up-regulated upon dsRNA and white spot syndrome virus (WSSV) challenge. In vivo gene knockdown of Mj-mov-10 resulted in an increase of a susceptibility of shrimp to WSSV infection. Our results implied the functional significance of Mj-MOV-10 in dsRNA-mediated gene silencing and antiviral defense mechanism in shrimp.

Activation of PmRelish from Penaeus monodon by yellow head virus

Humoral innate immune response against pathogenic infection is partly responsible by the Imd pathway in which a transcription factor Relish relays the infection signals to the nuclei for the expression of antimicrobial proteins. A PmRelish gene which encoded a protein of 1195 amino acids was cloned. The PmRelish was constitutively expressed in all tissues tested and mostly up-regulated upon YHV infection. In hemocytes, the PmRelish expression was up-regulated upon Vibrio harveyi, yellow head virus (YHV) and white spot syndrome virus (WSSV) challenges. Using dsRNA silencing of PmRelish gene, it was shown that the expression of penaeidin5 but not anti-lipopolysaccharide factor ALFPm3, crustinPm1 and penaeidin3 was under the regulation of Imd pathway. Under PmRelish silencing, the shrimp were more susceptible to infection by YHV with the 50% survival rate reduced from about 72 h to 42 h. The PmRelish was detected in the cytoplasm of all the hemocytes from both uninfected and YHV-infected shrimp. The accumulation of activated PmRelish in the nuclei was not clearly observed but the activated PmRelish was detected in the YHV-infected hemocytes by Western blot analysis. Thus, the PmRelish and, hence, the Imd pathway respond to the YHV infection.

Successful yellow head virus infection of Penaeus monodon requires clathrin heavy chain

Viral disease caused by the Yellow head virus (YHV) had great impact on economic loss in the aquaculture industry. Prevention or curing YHV disease is still not possible due to the lack of understanding of the basic mechanisms of YHV infection. In this report, the endocytosis inhibitors (chlorpromazine (CPZ), amiloride and methyl-β-cyclodextrin (MβCD)) were used to identify the cellular entry pathway of YHV. Pretreating shrimp with CPZ but not amiloride or MβCD followed by YHV challenge resulted in a significant reduction of YHV levels, suggesting that YHV entered the shrimp cells via clathrin-mediated endocytosis. Next, the major component of the clathrin-coated vesicle, Penaeus monodon clathrin heavy chain (PmCHC) was cloned and characterized. The complete coding sequence of PmCHC is 5055 bp encoding a putative protein of 1684 amino acids. Specific silencing of PmCHC mRNA by dsRNA-PmCHC showed an inhibition of YHV replication for 48 h post YHV injection as well as exhibiting a delay in shrimp mortality. These results indicated that PmCHC was an essential component for YHV infection of shrimp cells.

Comprehensive gene expression profiling in Japanese flounder kidney after injection with two different formalin-killed pathogenic bacteria

Pathogenic bacteria possess some components, that are recognized by the host immune receptors. Different components are recognized by distinct receptors, and thus it is speculated that these components may regulate different gene sets. To investigate the gene expression profiles regulated by different bacterial components in Japanese flounder Paralichthys olivaceus, Japanese flounder were intraperitoneally injected with formalin-killed bacterial cells (FKC) of Edwardsiella tarda and Streptococcus iniae. The numbers of differentially regulated genes were much larger in the fish injected with E. tarda than those with S. iniae. Comprehensive gene expression profiling showed that almost all of the genes differentially regulated by injections of E. tarda FKC were also differentially regulated by injections of S. iniae FKC. mRNA levels of inflammatory cytokines, including interleukin (IL)-1β, IL-8, interferon γ and tumor necrosis factor were upregulated in both of the injected groups. Each of these mRNAs except for IL-8 mRNA were also much higher in the E. tarda FKC injected group than in the S. iniae FKC injected group. Furthermore, mRNA levels of IL-6 were strongly up-regulated in the E. tarda FKC injected group. The E. tarda FKC might induce higher inflammatory responses than S. iniae FKC.

Influence of temperature on Mx gene expression profiles and the protection of sevenband grouper, Epinephelus septemfasciatus, against red-spotted grouper nervous necrosis virus (RGNNV) infection after poly (I:C) injection

Influence of temperature on the susceptibility of fish against virus infection has been studied for a decade. Recent reports have been shown the effects of rearing temperatures on the fish immune system against virus infection. However, the roles of temperature in regulation of type I interferon (IFN) system has not yet been investigated. Thus, the effects of temperature on type I IFN response were investigated in this study using poly (I:C) injection in sevenband grouper and Mx gene was used as a marker for type I IFN expression. Quantitative real-time PCR (qPCR) result showed that Mx expression profiles were moderately different between temperatures. The highly up-regulated Mx transcripts at 3 h post injection (hpi) were observed in high temperatures (25 °C and 30 °C) but not in low temperatures (15 °C and 20 °C). Meanwhile, low temperatures (15 °C and 20 °C) could detect the highly up-regulated Mx transcripts at 24 hpi. Expression of Mx transcripts was also observed at 72 hpi at 15 °C. Poly (I:C)-injected fish were challenged with RGNNV after 72 and 168 hpi. At 72 hpi, 100% of fish survived at all temperatures, whereas 95% survival rate was observed at 168 hpi at 25 °C during 14 days of observation. To further verify the duration period of an antiviral state at different temperatures, qPCR and endpoint dilution assay were used to quantify the number of virus in fish challenged with RGNNV. The reduction of viral copy numbers and viral titers could be observed at 72 and 168 hpi. However, high viral copy numbers and viral titers could be detected at 168 hpi at 30 °C. These results demonstrate that temperatures influenced on the Mx expression profiles and the duration period of an antiviral state efficiently interfered with virus replication at different temperatures.

Cloning and expression analysis of three novel CC chemokine genes from Japanese flounder (Paralichthys olivaceus)

Chemokines are small cytokines secreted by various cell types. They not only function in cell activation, differentiation and trafficking, but they also have influences on many biological processes. In this study, three novel CC chemokine genes Paol-SCYA105, 106 and 107 in Japanese flounder (Paralichthys olivaceus) were cloned and characterized. Paol-SCYA105 was mainly detected in gill, kidney and spleen, Paol-SCYA106 was detected in all tissues examined and Paol-SCYA107 was mainly detected in the spleen and kidney. Paol-SCYA105 and Paol-SCYA106 gene expressions peaked in kidney at day 3 after viral hemorrhagic septicemia virus infection and decreased at day 6, but Paol-SCYA106 still remained at a high level at day 6. Paol-SCYA107 gene expression was significantly up-regulated in kidney at day 6 after viral hemorrhagic septicemia virus infection. In response to infection by Gram-negative Edwardsiella tarda and Gram-positive Streptococcus iniae in kidney, only Paol-SCYA106 gene expression significantly increased. Together, these results indicate that these three novel CC chemokines are involved in the immune response against pathogen infections.

Identification of novel copper/zinc superoxide dismutase (Cu/ZnSOD) genes in kuruma shrimp Marsupenaeus japonicus

Superoxide dismutases (SODs) protect cells from superoxides, but in invertebrates, they also have role in the innate immune system. In this study, the genes for five isoforms of copper/zinc superoxide dismutase (MjCu/ZnSOD) gene were identified and sequenced in kuruma shrimp, Marsupenaeus japonicus. The coding parts of the genes ranged from 516 to 585 bp in length and encoded from 172 to 194 amino acids. Structure, phylogenetic and BLAST analyses indicated that MjCu/ZnSOD isoform_3 and _5 belonged to extracellular Cu/ZnSOD (ecSOD) group while the other three isoforms belong to the intracellular Cu/ZnSOD family. In healthy shrimp, the highest expressions of isoform 2, 3 and 4 were in the gills, whereas the expression of isoform 5 was highest in hemocytes. Challenging the shrimp with WSSV and Vibrio penaeicida up-regulated the mRNA expressions of isoforms 3 and 5, suggesting that these isoforms have roles in the innate immune system of kuruma shrimp.