Molecular cloning and characterization of IKKε gene from black carp Mylopharyngodon piceus

Molecular cloning and functional characterization of pigeon IKKε

Inhibitor of nuclear factor kappa-B kinase ε (IKKε), a member of the non-canonical IκB kinase family, plays a critical role in connecting various signaling pathways associated with the initiation of type I interferon (IFN) production. Although the importance of IKKε in innate immunity has been well established in mammals and fish, its characterization and function in pigeons have remained largely unexplored. In this study, we successfully cloned pigeon IKKε (piIKKε) from pigeon embryo fibroblasts (PEFs) for the first time. This gene encodes 722 amino acids and shares high amino acid similarity with its duck and goose counterparts. piIKKε showed a diffuse cytoplasmic distribution and broad expression in all tissues examined. Overexpression of piIKKε in PEFs significantly activated the IFN-β promoter, with both the kinase and CC domains of piIKKε playing key roles in initiating IFN-β expression. Knockdown of piIKKε using small interfering RNA significantly reduced the levels of IFN-β induced by NDV, AIV, poly (I:C), or SeV. Furthermore, the presence of piIKKε resulted in a remarkable reduction in the replication of both avian influenza virus (AIV) H9N2 and Newcastle disease virus (NDV) in PEFs. Our results demonstrate that piIKKε plays a critical role in mediating antiviral innate immunity in pigeons.

Identification and Characterization of C-Mos in Pearl Mussel Hyriopsis cumingii and Its Role in Gonadal Development

C-Mos, a proto-oncogene, regulates oocyte maturation by activating the classical MAPK pathway in cells. To examine the function of C-Mos in Hyriopsis cumingii, C-Mos was identified in this study. The full-length cDNA of C-Mos was 2213 bp, including 144 bp in the 5' UTR, 923 bp in 3' the UTR, and 1146 bp in the open reading frame (ORF) region. During early gonad development, the expression of C-Mos from 4 to 6 months of age in H. cumingii was significantly higher than that in other months, with the highest expression in 6-month-old H. cumingii, suggesting that C-Mos may be involved in early gonadal development in H. cumingii. Clear hybridization signals were found by in situ hybridization in the oocytes, oocyte nucleus and oogonium, and a small number of hybridization signals were found in the follicular wall of the male gonads. In addition, the C-Mos RNA interference (RNAi) assay results showed that the knockdown of C-Mos caused a down-regulation of ERK and P90rsk. In summary, these results indicate that C-Mos has a crucial part to play in gonadal development in H. cumingii.

Genome-wide identification and functional characterization of inhibitor of nuclear factor-κB (IκB) kinase (IKK) in turbot (Scophthalmus maximus)

The inhibitor of nuclear factor-κB (IκB) kinase (IKK) is involved in a variety of intracellular cell signaling pathways and is an important component of the NF-κB signaling pathway. IKK genes have been suggested to play important roles in the innate immune response to pathogen infection in both vertebrates and invertebrates. However, little information is available about IKK genes in turbot (Scophthalmus maximus). In this study, six IKK genes were identified including SmIKKα, SmIKKα2, SmIKKβ, SmIKKε, SmIKKγ, and SmTBK1. The IKK genes of turbot showed the highest identity and similarity with Cynoglossus semilaevis. Then, phylogenetic analysis showed that the IKK genes of turbot were most closely related to C. semilaevis. In addition, IKK genes were widely expressed in all the examined tissues. Meanwhile, the expression patterns of IKK genes were investigated by QRT-PCR after Vibrio anguillarum and Aeromonas salmonicida infection. The results showed that IKK genes had varying expression patterns in mucosal tissues after bacteria infection, indicating that they may play key roles in maintaining the integrity of the mucosal barrier. Subsequently, protein and protein interaction (PPI) network analysis showed that most proteins interacting with IKK genes were located in the NF-κB signaling pathway. Finally, the double luciferase report and overexpression experiments showed that SmIKKα/SmIKKα2/SmIKKβ involved in the activation of NF-κB in turbot. In summary, our results suggested that IKK genes of turbot played important roles in the innate immune response of teleost, and provide valuable information for further study of the function of IKK genes.

TmIKKε Is Required to Confer Protection Against Gram-Negative Bacteria, E. coli by the Regulation of Antimicrobial Peptide Production in the Tenebrio molitor Fat Body

The inhibitor of nuclear factor-kappa B (NF-κB) kinase (IKK) is the core regulator of the NF-κB pathway against pathogenic invasion in vertebrates or invertebrates. IKKβ, -ε and -γ have pivotal roles in the Toll and immune deficiency (IMD) pathways. In this study, a homolog of IKKε (TmIKKε) was identified from Tenebrio molitor RNA sequence database and functionally characterized for its role in regulating immune signaling pathways in insects. The TmIKKε gene is characterized by two exons and one intron comprising an open reading frame (ORF) of 2,196 bp that putatively encodes a polypeptide of 731 amino acid residues. TmIKKε contains a serine/threonine protein kinases catalytic domain. Phylogenetic analysis established the close homology of TmIKKε to Tribolium castaneum IKKε (TcIKKε) and its proximity with other IKK-related kinases. The expression of TmIKKε mRNA was elevated in the gut, integument, and hemocytes of the last-instar larva and the fat body, Malpighian tubules, and testis of 5-day-old adults. TmIKKε expression was significantly induced by Escherichia coli, Staphylococcus aureus, and Candida albicans challenge in whole larvae and tissues, such as hemocytes, gut, and fat body. The knockdown of the TmIKKε messenger RNA (mRNA) expression significantly reduced the survival of the larvae against microbial challenges. Further, we investigated the induction patterns of 14 T. molitor antimicrobial peptides (AMPs) genes in TmIKKε gene-silencing model after microbial challenges. While in hemocytes, the transcriptional regulation of most AMPs was negatively regulated in the gut and fat body tissue of T. molitor, AMPs, such as TmTenecin 1, TmTenecin 4, TmDefensin, TmColeoptericin A, TmColeoptericin B, TmAttacin 1a, and TmAttacin 2, were positively regulated in TmIKKε-silenced individuals after microbial challenge. Collectively, the results implicate TmIKKε as an important factor in antimicrobial innate immune responses in T. molitor.

Administration of a recombinant ALDH7A1 (rA7) indicates potential regulation of the metabolite and immunology pathways in Atlantic salmon infected with Aeromonas salmonicida

The bacterium Aeromonas salmonicida is the pathogen responsible for furunculosis, which is a serious disease of salmonids. This disease has a significant economic impact on the economic benefits of the global salmon farming industry. However, the pathogenesis of this disease in fish is still unknown. Members of the aldehyde dehydrogenase gene (ALDH) superfamily play a key role in the enzyme detoxification of endogenous and exogenous aldehydes. In this study, we obtained a recombinant aldehyde dehydrogenase 7A1 (ALDH7A1) protein to find its functions on Atlantic salmon infected by A. salmonicida. The transcriptional response in the liver of Atlantic salmon (Salmo salar) with differing levels of A. salmonicida infection was analysed and compared in order to reveal mechanisms by which ALDH7A1 may confer infection resistance. With the addition of ALDH7A1 protein, it was found that a total of 13,369 genes were annotated with one or more KEGG and localized to 360 KEGG pathways in the high concentration infection group. The differential expression genes were more enriched in immune signalling pathways such as the Toll-like receptor signalling pathway, NF-kappa B signalling pathway and TNF signalling pathway. On the other hand, at low concentrations of infection, KEGG enriched a smaller number of differential expression genes. However, these differential genes were more concentrated in immune signalling pathways such as the PI3K-Akt signalling pathway, JAK-STAT signalling pathway and complement and coagulation cascades. In addition, several known immune-related genes including HSP90α, HSP70, DNA damage-inducible transcript 4, integrin alpha 5 and microtubule-associated protein 2 were among the differentially expressed transcripts. These data provide the first insights into the host-ALDH7A1 vaccine interactome. The results of this study contribute to identifying the potential resistance mechanisms of Atlantic salmon to A. salmonicida infection and determining future treatment strategies.

Structural and functional analysis of three Iκb kinases (IKK) in disk abalone (Haliotis discus discus): Investigating their role in the innate immune responses

The IκB kinases (IKK) are large multiprotein complexes that regulate the activation of the transcription factor NF-κB and are involved in a diverse range of biological processes, including innate immunity, inflammation, and development. To explore the potential roles of invertebrate IKKs on immunity, three IKK encoding genes have been identified from molluscan species disk abalone and designed as AbIKK1, AbIKK2 and AbIKK3 at the transcriptional level. Coding sequences of AbIKK1, AbIKK2 and AbIKK3 encode the peptides of 746, 751 and 713 amino acids with the predicted molecular mass of 86.16, 86.12 and 81.88 kDa respectively. All three AbIKKs were found to share conserved IKK family features including the kinase superfamily domain (KD), ubiquitin-like domain (ULD), and α-helical scaffold/dimerization domain (SDD), similar to their mammalian counterparts. Under normal physiological conditions, AbIKKs were ubiquitously detected in six different tissues, with the highest abundance in the digestive tract and gills. Temporal transcriptional profiles in abalone hemocytes revealed the induction of AbIKK1, AbIKK2, and AbIKK3 expression following exposure to Gram-negative (Vibrio parahemolyticus) and Gram-positive (Listeria monocytogenes) bacteria, viruses (viral hemorrhagic septicemia virus, VHSV), LPS, or poly I:C. The overexpression of AbIKKs in HEK293T or RAW264.7 murine macrophage cells induced NF-κB promoter activation independent of stimulation by TNF-α or LPS. Moreover, iNOS and COX2 expression was induced in AbIKK transfected RAW264.7 murine macrophage cells and the induced state was maintained post-LPS treatment. Furthermore, mRNA levels of three selected cytokine-encoding genes (IL-1β, IL-6, and TNF-α) were found to be elevated in abalone IKK overexpressed RAW264.7 murine macrophage cells, both with and without LPS exposure. Overall, our findings demonstrated that AbIKKs identified in this study were positively involved in eliciting innate immune responses in abalone. In addition, the data revealed the presence of an evolutionarily conserved signaling mechanism for IKK mediated NF-κB activation in mollusks.

Molecular characterization and functional analysis of IKKα in orange-spotted grouper (Epinephelus coioides)

Inhibitor of nuclear factor kappa-B kinase subunit alpha (IKKα) plays crucial roles in regulating activation of nuclear factor kappa-B (NF-κB) in response to pathogens infections. Here, we cloned and identified IKKα gene of orange-spotted grouper (Epinephelus coioides), named as EcIKKα. The gene transcript contained a 2262 bp open reading frame, which encoded 753 amino acids. The typically conserved IKKα structure, including serine kinase domain (KD), leucine chain (LZ) structure, helix-loop-helix (HLH) motif and IKKβ-NEMO-binding domain, was identified in EcIKKα. Phylogenetic analysis suggested that EcIKKα had the closest relationship with large yellow croaker (Larimichthy crocea) IKKα. Ecikkα was ubiquitously expressed in all tissues tested and the highest expression level was in ovary. After lipopolysaccharide (LPS), flagellin, polyinosinic-polycytidylic acid (poly I:C), polyadenylic-polyuridylic acid (poly A:U), and Vibrio parahaemolyticus stimulation, the expression of Ecikkα increased in grouper spleen (GS) cells. In the luciferase assay, NF-κB-luc activity was significantly up-regulated when human embryonic kidney 293T (HEK 293T) cells were transfected with EcIKKα plasmid. Moreover, overexpression of EcIKKα significantly increased LPS- and flagellin-induced proinflammatory cytokines (interleukin-6 (il-6) and tumor necrosis factor-α (tnf-α)) expression, but did not significantly affect poly I:C- and poly A:U-induced cytokines (il-6 and tnf-α) expression. Overall, these results suggested that EcIKKα functions like that of mammals to activate NF-κB, and it could be involved in host defense against invading pathogens.

Black carp IRF5 interacts with TBK1 to trigger cell death following viral infection

Interferon regulated factor 5 (IRF5) is a key regulator of inflammatory responses in human and mammals; however, its role in teleost remains largely unknown. In this study, IRF5 homologue of black carp (Mylopharyngodon piceus) has been cloned and characterized, which possesses conservation in structure and sequence to its mammalian counterparts. Black carp IRF5 (bcIRF5) was characterized as a predominantly cytosolic protein by immunofluorescent staining and showed little IFN promoter-inducing ability in reporter assay. The direct association between bcIRF5 and black carp TBK1 (bcTBK1) were identified through co-immunoprecipitation assay, and co-expressed bcIRF5 in EPC cells suppressed bcTBK1-mediated IFN promoter transcription in reporter assay. Surprisingly, the titer of grass carp reovirus (GCRV) in the media of EPC cells co-expressing bcIRF5 and bcTBK1 was obviously lower than that of EPC cells expressing bcTBK1 alone. It was interesting that expression of bcIRF5 and/or bcTBK1 in EPC cells showed little effect on cell growth; however, the survival ratio of EPC cells co-expressing bcTBK1 and bcIRF5 post GCRV infection was much lower than that of EPC cells expressing bcIRF5 or bcTBK1 alone. These results indicate that bcIRF5 negatively regulates bcTBK1-mediated IFN signaling in healthy cells; however, it correlates with bcTBK1 and triggers cell death to inhibit the virus replication during the innate immune activation.

TAK1 of black carp positively regulates IRF7-mediated antiviral signaling in innate immune activation

Transforming growth factor β-activated kinase 1 (TAK1) plays a vital role in IL-1-mediated NF-κB, JNK, and p38 activation in human and mammals. However, the function of TAK1 in teleost fish still remains largely unknown. To explore the role of TAK1 during the antiviral innate immune response of teleost fish, TAK1 of black carp (Mylopharyngodon piceus) was cloned and characterized in this paper. The open reading frame (ORF) of black carp TAK1 (bcTAK1) consists of 1626 nucleotides and the predicted bcTAK1 protein contains 541 amino acids, which includes a N-terminal Serine/Threonine protein kinases (S/TKc) and a C-terminal coiled-coil region. bcTAK1 migrated around 75 kDa in immunoblotting assay and was identified as a cytosolic protein by immunofluorescence staining. bcTAK1 transcription in Mylopharyngodon piceus kidney (MPK) cells varied in response to the stimulation of poly (I:C), LPS, grass carp reovirus (GCRV), and spring viremia of carp virus (SVCV). bcTAK1 showed deficient IFN-inducing ability in reporter assay and feeble antiviral activity against GCRV and SVCV in plaque assay. However, when co-expressed with bcIRF7 in EPC cells, bcTAK1 obviously enhanced bcIRF7-mediated IFN promoter induction in reporter assay. Accordingly, the data of plaque assay demonstrated that the antiviral activity of bcIRF7 against both GCRV and SVCV was unregulated by bcTAK1. Thus, the data generated in this study support the conclusion that bcTAK1 up-regulates bcIRF7-mediated antiviral signaling during host innate immune activation, which is reported for the first time in vertebrates.

Lysine 39 of IKKε of black carp is crucial for its regulation on IRF7-mediated antiviral signaling

Interferon regulatory factor 7 (IRF7) plays a crucial role in the interferon (IFN) signaling in mammals, in which it is activated by the TBK1/IKKε complex during host antiviral innate immune response. There are few reports about the relation between IRF7 and IKKε in teleost fishes. In this study, the IRF7 homologue (bcIRF7) of black carp (Mylopharyngodon Piceus) has been cloned and characterized. The transcription of bcIRF7 gene increased in host cells in response to the stimulation of LPS, poly (I:C) and viral infection. bcIRF7 migrated around 56 KDa in immunoblot assay and was identified as a predominantly cytosolic protein by immunofluorescent staining. bcIRF7 showed IFN-inducing ability in reporter assay and EPC cells expressing bcIRF7 showed enhanced antiviral ability against both grass carp reovirus (GCRV) and spring viremia of carp virus (SVCV). IKKε of black carp (bcIKKε) was found to be recruited into host innate immune response initiated by SVCV and GCRV in the previous work; in this paper, the kinase dead mutant of bcIKKε, bcIKKε-K39A was constructed and showed no IFN-inducing activity. The data of reporter assay and plaque assay demonstrated that bcIKKε but not bcIKKε-K39A obviously enhanced bcIRF7-mediated IFN production and antiviral activity. Our data support the conclusion that bcIKKε upregulates bcIRF7-mediated antiviral signaling, which most likely depends on its kinase activity.

TRAF2 of black carp upregulates MAVS-mediated antiviral signaling during innate immune response

Tumor necrosis factor receptor-associated factor 2 (TRAF2) is a crucial component of the tumor necrosis factor (TNF) mediated signaling of higher vertebrates. To elucidate its function in teleost fish, TRAF2 homologue of black carp (Mylopharyngodon piceus) has been cloned and characterized in this study. The open reading frame (ORF) of black carp TRAF2 (bcTRAF2) consists of 1611 nucleotides and bcTRAF2 contains 536 amino acids. bcTRAF2 protein migrated around 65 KDa in immunoblot analysis of both EPC and HEK293T cells. bcTRAF2 was identified as a cytosolic protein and suggested to be associated with vesicles scattering in the cytoplasm. NF-κB transcription instead of IFN transcription was activated by bcTRAF2 in reporter assay. It was interesting that bcMAVS-mediated IFN production was up-regulated by bcTRAF2 in a dose dependent manner in reporter assay. Accordingly, EPC cells transfected with both bcMAVS and bcTRAF2 showed enhanced antiviral activity comparing EPC cells only expressing bcMAVS. When co-expressed with bcMAVS, bcTRAF2 was redistributed in the cytoplasm and its subcellular location overlapped with the subcellular location of bcMAVS, which suggested the association between these two molecules. Taken together, the data generated in this paper supported the conclusion that bcTRAF2 was recruited into host innate immune response and positively regulated bcMAVS-mediated antiviral signaling.

TBK1 of black carp plays an important role in host innate immune response against SVCV and GCRV

Tank-binding kinase 1 (TBK1) plays a pivotal role in the induction of type I IFNs in higher vertebrates. To explore the function of TBK1 in teleost, TBK1 of black carp (Mylopharyngodon Piceus) was cloned and characterized in this paper. The full-length cDNA of black carp TBK1 (bcTBK1) consists of 2857 nucleotides and the predicted bcTBK1 protein contains 727 amino acids, which includes an N-terminal kinase domain (KD), an ubiquitin-like domain (ULD) and two C-terminal coiled-coils. The transcription of bcTBK1 was constitutively detected in all the selected tissues and bcTBK1 mRNA level was increased in all selected tissues in response to SVCV or GCRV infection except that in muscle post GCRV invasion. The transcription of bcTBK1 in Mylopharyngodon Piceus fin (MPF) cells was up-regulated by the stimulation of SVCV, GCRV or poly (I:C) but not by LPS treatment. bcTBK1 migrated around 80 kDa in immunoblot assay and was identified as a cytosolic protein by immunofluorescence staining. bcTBK1 showed strong IFN-inducing ability in reporter assay and presented strong antiviral activity against both GCRV and SVCV in EPC cells. The reporter assay demonstrated that TRAF6 of black carp (bcTRAF6) up-regulated bcTBK1-induced IFN expression and the subcellular distribution of bcTBK1 overlapped with that of bcTRAF6 when these two proteins were co-expressed in EPC cells. Taken together, our study support the conclusion that bcTBK1 plays an important role in the antiviral innate immune response of black carp against SVCV and GCRV, in which its activity was positively regulated by bcTRAF6.

CARD and TM of MAVS of black carp play the key role in its self-association and antiviral ability

Mitochondrial antiviral signaling protein (MAVS) is an adaptor protein of the innate immune system of higher vertebrate. In this paper, the transcription profile of black carp MAVS (bcMAVS) in host cells in response to spring viremia of carp virus (SVCV) and grass carp reovirus (GCRV) infection was identified. EPC cells expressing bcMAVS possessed obviously enhanced antiviral activity against both SVCV and GCRV. Immunofluorescence (IF) staining data demonstrated that bcMAVS molecules were redistributed and formed aggregates on the mitochondria of EPC cells after virus infection. Co-immunoprecipitation (co-IP) assay in HEK293T cells demonstrated that bcMAVS proteins bound to each other, which suggested that this fish protein owned self-association in vivo. IF assay identified that the transmembrane (TM) domain of bcMAVS was crucial for its mitochondrial localization. Co-IP assays among bcMAVS mutants demonstrated that both N-terminal caspase recruitment domain (CARD) and TM domain were indispensible for dimerization of bcMAVS. It was interesting that Truncated-bcMAVS possessed much enhanced interferon-inducing activity and antiviral ability than wild type bcMAVS, which only contains CARD and TM. All the data generated in this study support the idea that oligomerization of bcMAVS on mitochondrion is crucial for the antiviral ability of bcMAVS, which is depend on both CARD and TM domain of this fish MAVS orthologue.

IFNa2 of triploid hybrid of gold fish and allotetraploid is an intracellular antiviral cytokine against SVCV and GCRV

Sterile triploid hybrids (3n = 150) of gold fish (Carassius auratus red var., ♀, 2n = 100) and allotetroploid (♂, 2n = 100) display obviously improved disease resistance and much enhanced growth rate than their parents, which have been cultured widely in China. In this paper, one of the type I IFNs of triploid hybrid (3nIFNa2) has been cloned and characterized. The full-length cDNA of 3nIFNa2 gene consists of 715 nucleotides and the predicted 3nIFNa2 contains 183 amino acids. The transcription of 3nIFNa2 gene was detected in all the examined tissues of triploid hybrid and the mRNA level of 3nIFNa2 was obviously enhanced in response to SVCV and GCRV infection. 3nIFNa2 has been detected in the whole cell lysate of HEK293T cells transfected with plasmids expressing 3nIFNa2 but not in the supernatant media. EPC cells transfected with plasmid expressing 3nIFNa2 at 24 h before SVCV and GCRV infection showed obviously decreased cytopathic effect; and the virus titers in the supernatant media were much lower than those of the control cells. Glycosidase digestion analysis demonstrates that 3nIFNa2 is modified with N-linked glycosylation, which occurs on the asparagine (N) of residue 177 of this cytokine. The un-glycosylated mutant 3nIFNa2-N177Q shows the similar antiviral ability as that of 3nIFNa2, which suggests that the N-linked glycosylation does not contribute directly to its antiviral property. All the above data support the conclusion that 3nIFNa2 is an intracellular cytokine functioning importantly in host antiviral innate immunity.

Mx1 of black carp functions importantly in the antiviral innate immune response

Mx (myxovirus resistance) is an important antiviral protein in the innate immune responses of vertebrates to microbial pathogens. In this study, we cloned and characterized Mx1 of black carp (Mylopharyngodon piceus). The full-length cDNA of black carp Mx1 (bcMx1) consists of 2781 nucleotides and the predicted bcMx1 protein contains 631 amino acids. bcMx1 contains a GTPase domain at the N-terminnus, a "central interactive domain" in the middle and a GTPase effector domain at the C-terminus. bcMx1 mRNA was constitutively transcribed in all tissues tested, including the heart, liver, spleen, kidney, intestine, muscle, skin and gill; and bcMx1 mRNA levels increased in all but the gill after grass carp reovirus (GCRV) or viraemia of carp virus (SVCV) infection. Quantitative PCR analysis of Mylopharyngodon piceus fin (MPF) cells indicated that bcMx1 mRNA levels increased after GCRV or SVCV infection at different multiplicities of infection (MOI). Western blotting demonstrated that the molecular weight of bcMx1 is ∼75 kDa and immunofluorescent staining data of both HeLa cells and EPC cells showed that bcMx1 is a cytosolic protein. EPC cells transfected with plasmid expressing bcMx1 showed increased antiviral activity against SVCV and GCRV. All our data suggest that bcMx1 is an antiviral protein in the innate immune response of the black carp.

LGP2 of black carp plays an important role in the innate immune response against SVCV and GCRV

RIG-I like receptors (RLRs) detect cytosolic RNA virus components and initiate antiviral innate immune response through downstream signaling in vertebrates. In this paper, LGP2 of black carp (Mylopharyngodon piceus) has been cloned and characterized, which is a key member of RLR family. The full-length cDNA of black carp LGP2 (bcLGP2) comprises 2941 nucleotides and the predicted bcLGP2 protein contains 682 amino acids. bcLGP2 shares core homologous structural domains of RLRs, including a N-terminnal DExD/H helicase domain, a helicase superfamily c-terminal domain, and a C-terminal regulatory domain (CTD). bcLGP2 mRNA was constitutively detected in all selected tissues including heart, liver, spleen, kidney, intestine, muscle, skin, gill; and bcLGP2 mRNA level was increased in all the tissues except gill in response to GCRV or SVCV infection. Q-PCR of Mylopharyngodon piceus fin (MPF) cells demonstrated that bcLGP2 transcription was up-regulated by Poly (I:C) treatment, GCRV or SVCV infection, but not by LPS or PMA treatment. Western blot analysis demonstrated that the molecular weight of bcLGP2 was around 80 KDa; and the immunofluorescence staining of both HeLa cells and EPC cells showed that bcLGP2 was a cytosolic protein. EPC cells transfected with plasmid expressing bcLGP2 showed obviously improved antiviral ability against SVCV and GCRV. In general, these data support the conclusion that bcLGP2 functions importantly in the host antiviral innate immune response.

IFNa of triploid hybrid of gold fish and allotetraploid is an antiviral cytokine against SVCV and GCRV

Triploid hybrid of gold fish (Carassius auratus red var., ♀, 2n = 100) and allotetroploid (♂, 2n = 100) displays much improved disease resistance than its parents. In this paper, one of the type I IFNs of triploid hybrid (3nIFNa) has been cloned and characterized. The full-length cDNA of 3nIFNa consists of 740 nucleotides and the predicted 3nIFNa protein contains 183 amino acids. The mRNA transcription of 3nIFNa was detected in all the selected tissues of triploid hybrid and was obviously enhanced after SVCV or GCRV infection. bcIFNa was detected in both whole cell lysate and supernatant media of HEK293T cells transfected with plasmids expressing bcIFNa. It is interesting that the pre-matured 3nIFNa is modified with N-linked glycosylation, which is located within the N-terminal signal peptide. EPC cells showed much-decreased cytopathic effect when treated with 3nIFNa-containing media or transfected with plasmid expressing 3nIFNa at 24 h before SVCV or GCRV infection; and the virus titers in these cells were much lower than those of the control EPC cells. All the above data support the conclusion that 3nIFNa is a secreted cytokine functioning in host innate immune response against virus invasion.