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Interleukin (IL)-22 is an IL-10 family cytokine secreted by CD4+ T cells and plays an important role in regulating inflammation and infection elimination. IL-22 homologues have been reported in the teleost, but the functions of IL-22 are still unclear. In this study, we identified two duplicated IL-22 genes in common carp (Cyprinus carpio L.), termed Cc _IL-22A and Cc _IL-22B. Sequence analysis showed that Cc _IL-22A and Cc _IL-22B had four conserved cysteine residues, which could form two intra-chain disulfide bridges. The Cc _ IL-22A and Cc _ IL-22B were constitutively expressed in various tissues, with the highest expression in the gill. The mRNA expression levels of Cc _ IL-22A and Cc _ IL-22B were significantly up-regulated in the gill, intestine, head kidney, and spleen of common carp challenged with Aeromonas. hydrophila. In vivo study showed that the expression levels of pro-inflammatory cytokines were significantly up-regulated in the head kidney and spleen when Cc _IL-22A or Cc _IL-22B were over-expressed. Furthermore, the over-expression of Cc _IL-22A and Cc _IL-22B indicated a protective effect on tissues, with only lymphocytic infiltration observed in comparison to the control and pcN3 groups, without obvious change in tissue morphology. Similar stimulatory effects of rIL-22A and rIL-22B were observed in vitro. When HKLs were stimulated with rIL-22A or rIL-22B, the expression levels of critical signaling molecules in the Janus kinase (JAK) and signal transducer and activator of transcription (STAT) pathway were significantly induced, including JAK1 , JAK3 , STAT1 , and STAT3 , as well as pro-inflammatory cytokines (IL-1β and TNF-α). Together, these results suggest that Cc _IL-22A and Cc _IL-22B may regulate inflammatory responses through the JAK-STAT signaling pathway and have a significant impact on the immune defense of common carp against bacterial infection. Therefore, our study provides a new perspective on the functions of Cc _IL-22A and Cc _IL-22B in the immune defense mechanism of fish. • Common carp IL-22A and IL-22B (Cc _IL-22A and Cc _IL-22B) were identified and characterized. • Cc_IL-22s widely expressed in all tested tissues and responded to bacterial infection. • In vivo , Cc _IL-22s over-expression affected the expression of inflammatory cytokines. • Recombinant Cc _IL-22s induced the expression of genes in JAK–STAT pathway. [ABSTRACT FROM AUTHOR]

Parasitic dinoflagellates in genus Hematodinium have caused substantial economic losses to multiple commercially valuable marine crustaceans around the world. Recent efforts to better understand the life cycle and biology of the parasite have improved our understanding of the disease ecology. However, studies on the host-parasite interaction, especially how Hematodinium parasites evade the host immune response are lacking. To address this shortfall, we used the comprehensive omics approaches (miRNA transcriptomics, iTRAQ-based proteomics) to get insights into the host-parasite interaction between hemocytes from Portunus trituberculatus and Hematodinium perezi in the present study. The parasitic dinoflagellate H. perezi remodeled the miRNome and proteome of hemocytes from challenged hosts, modulated the host immune response at both post-transcriptional and translational levels and caused post-transcriptional regulation to the host immune response. Multiple important cellular and humoral immune-related pathways (ex. Apoptosis, Endocytosis, ECM-receptor interaction, proPO activation pathway, Toll-like signaling pathway, Jak-STAT signaling pathway) were significantly affected by Hematodinium parasites. Through modulation of the host miRNome, the host immune responses of nodulation, proPO activation and antimicrobial peptides were significantly suppressed. Cellular homeostasis was imbalanced via post-transcriptional dysregulation of the phagosome and peroxisome pathways. Cellular structure and communication was seriously impacted by post-transcriptional downregulation of ECM-receptor interaction and focal adhesion pathways. In conclusion, H. perezi parasites could trigger striking changes in the miRNome and proteome of crustacean hemocytes, and this parasite exhibited multifaceted immunomodulatory effects and potential immune-suppressive mechanisms in crustacean hosts. • Hematodinium perezi triggered striking changes in miRNome and proteome of Portunus trituberculatus hemocytes. • A total of 44 miRNAs and 523 proteins were differentially expressed in P. trituberculatus after H. perezi challenge. • H. perezi exhibited multifaceted immunomodulatory effects and potential immune-suppressive mechanisms in crustacean hosts. [ABSTRACT FROM AUTHOR]

IFN-γ (interferon gamma) is a critical cytokine in the immune system involved both directly and indirectly in antiviral activity, stimulation of bactericidal activity, antigen presentation and activation of macrophages via the Janus kinase/signal transducer and activator of transcription (JAK-STAT) pathway. The IFN-γ function is best described in cell defense against intracellular pathogens in mammals, but IFN-γ cytokine-induced metabolic change and its role in anti-infection remain unknown in teleost fish. In this study, a novel IFN-γ (SsIFN-γ) was identified from black rockfish (Sebastes schlegeli) by rapid amplification of cDNA ends (RACE). The open reading frame (ORF) of SsIFN-γ encoded a putative protein of 215 amino acids and shares 60.2%–93.5% overall sequence identities with other teleost IFN-γ. SsIFN-γ was distributed ubiquitously in all the detected tissues and immune cells, which was highly expressed in the spleen, gills, head kidney by quantitative real-time PCR. The mRNA expression of SsIFN-γ was significantly upregulated in the spleen, head kidney, head kidney (HK) macrophages and peripheral blood lymphocytes (PBLs) during pathogen infection. Meanwhile, the recombinant protein (rSsIFN-γ) exhibited an immunomodulatory function to enhance respiratory burst activity and nitric oxide response of HK macrophages. Furthermore, rSsIFN-γ could effectively upregulate the expression of macrophage proinflammatory cytokine, the expression of JAK-STAT signaling pathway related genes and interferon-related downstream genes in the head kidney and spleen. Luciferase assays showed ISRE and GAS activity were obviously enhanced after rSsIFN-γ treatment. These results indicated that SsIFN-γ possessed apparent immunoregulatory properties and played a role in fighting pathogen infection which will be helpful to further understanding of the immunologic mechanism of teleosts IFN-γ in innate immunity. • A novel IFN-γ from black rockfish, Sebastes schlegeli (named SsIFN-γ) was characterized. • The relative expression of SsIFN-γ was significantly upregulated in immune-related tissues (spleen and head kidney) after treatment in vivo with Vibrio anguillarum , Edwardsiella tarda or polyI:C. • The recombinant protein (rSsIFN-γ) exhibited an immunomodulatory function to enhance respiratory burst activity and nitric oxide response of HK macrophages. • rSsIFN-γ could effectively upregulate the expression of macrophage proinflammatory cytokines, JAK-STAT signaling pathway related and antiviral genes. [ABSTRACT FROM AUTHOR]

In shrimp, the JAK-STAT pathway is essentially implicated in both antiviral and antibacterial responses. However, few regulatory target genes of the JAK-STAT pathway in shrimp have been reported so far. In this study, a novel single WAP domain-containing peptide (LvSWD4) was identified from Pacific white shrimp Litopenaeus vannamei. The promoter of LvSWD4 was predicted to harbor multiple STAT-binding DNA motifs. Over-expression of the JAK-STAT pathway components STAT, JAK and Domeless in vitro significantly enhanced the transcriptional activity of the LvSWD4 promoter, and in vivo silencing of STAT and the the JAK-STAT pathway upstream regulator IRF down-regulated the expression of LvSWD4, suggesting that LvSWD4 could be a target gene of the JAK-STAT pathway. The expression of LvSWD4 was significantly increased after infection with Gram-negative and positive bacteria, fungi and virus, and silencing of LvSWD4 increased the susceptibility of shrimp to V. parahaemolyticus and WSSV infections. In vitro experiments also demonstrated that the recombinant LvSWD4 protein had significant inhibitory activities against Gram negative bacteria V. parahaemolyticus and E. coli and Gram positive bacteria S. aureus and B. subtilis. Furthermore, silencing of LvSWD4 in vivo significantly affected expression of various immune functional genes and attenuated the phagocytic activity of hemocytes. These suggested that as a target gene of STAT, LvSWD4 was essentially implicated in shrimp immunity, which could constitute part of the mechanism underlying the immune function of the shrimp JAK-STAT pathway. • Identification of a novel SWD gene (LvSWD4) from Litopenaeus vannamei. • Expression of LvSWD4 is regulated by the JAK-STAT pathway. • Recombinant LvSWD4 protein has antibacterial activity. • LvSWD4 is involved in antibacterial and antiviral responses and immune regulation. [ABSTRACT FROM AUTHOR]