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Grass carp reovirus (GCRV) is the most virulent agent to Grass carp, Ctenopharyngodon idella , and causes a severe infectious disease called hemorrhagic disease of grass carp. Generally, barbel chub, Squaliobarbus curriculus , a genetically closely related species to grass carp, exhibits significant resistance against GCRV infection compared to grass carp. To investigate whether the Toll-like receptor 22 ( tlr22 ) has got a vital role against the GCRV infection, the full cDNA sequence of tlr22 from barbel chub ( Sctlr22 ) was cloned by RACE-PCR, and the structure and expression feature were studied. The complete cDNA sequence of Sctlr22 has a size of 3504 bp, encoding for 960 amino acid residues. Sctlr22 possesses typical structural features of the tlrs family, including 19 leucine rich repeats (LRRs), a transmembrane (TM) and a Toll/interleukin-1 receptor (TIR) domain. Phylogenetic analysis revealed that barbel chub Tlr22 was clustered together with the Tlr22 of grass carp ( Citlr22 ). Structurally, barbel chub Tlr22 have two different structure in LRRs domain and TIR domain with grass carp (Susceptible to GCRV), but was similar to that of Danio rerio and Cyprinus carpio (Resistance to GCRV). Quantitative RT-PCR analysis has shown that Sctlr22 is prominently expressed in immune relevant tissues such as head kidney and spleen. After GCRV infection, Sctlr22 expression level was up-regulated in four tested tissues and the highest expression of Sctlr22 appeared fast and higher than Citlr22 . The interferon-β ( ifn-β ) expression level in CIK cells over-expressing fused cDNA encoding the LRR domain of Sctlr22 to the transmembrane and TIR domain of Citlr22 was significantly higher than that cells overexpressing Citlr22 after GCRV infection. The virus titer was significantly reduced compared to Citlr22 over-expressing cells. These results suggested that Sctlr22 seems to play a vital role in the immune response against GCRV. [ABSTRACT FROM AUTHOR]

Diseases caused by Vibrio harveyi in shrimps have gradually become one group of the most serious threats to shrimp production, while related molecular mechanisms of infections with Vibrio harveyi are still not known well in shrimps. Here, we performed proteomic sequencing of hepatopancreas in whiteleg shrimps (Litopenaeus vannamei) infected with exogenous Vibrio harveyi , and subsequent functional annotation and calculation of differentially expressed proteins (DEPs) in this study. A total of 145 DEPs were obtained, among them 36 were up-regulated and 109 were down-regulated after the infection. Meanwhile, our results showed that after the infection of Vibrio harveyi , expression levels of a variety of C-type lectins (CTLs) were changed significantly. In-depth functional domain analysis and spatial structure prediction of these CTLs revealed that amino acid sequences and spatial structures of the C-type lectin domain (CTLD) shared by the CTL-S and IML proteins were variant, suggesting differential functions between the two CTLs. In summary, various members of the CTL family have different epidemic responses to Vibrio harveyi infection, which provides a theoretical guidance for deep-going investigations on practical immunity reactions and pathogen infections in shrimps. • We build a proteomics dataset of whiteleg shrimp. • First systematic study (Including structure and function) of C type lectin in whiteleg shrimp. • This study is helpful for in-depth understanding on pathogen infections in whiteleg shrimp. [ABSTRACT FROM AUTHOR]

Complement component 4 (C4) has critical immunological functions in vertebrates. In the current study, a C4 homolog (gcC4) was identified in grass carp (Ctenopharyngodon idella). The full-length 5458 bp gcC4 cDNA contained a 5148 bp open reading frame (ORF) encoding a protein of 1715 amino acids with a signal peptide and eight conservative domains. The gcC4 protein has a high level of identity with other fish C4 counterparts and is phylogenetically clustered with cyprinid fish C4. The gcC4 transcript shows wide tissue distribution and is inducible by Aeromonas hydrophila in vivo and in vitro. Furthermore, its expression also fluctuates upon lipopolysaccharide or flagellin stimulation in vitro. During infection, the gcC4 protein level decreases or increases to varying degrees, and the intrahepatic C4 expression location changes. With gcC4 overexpression, interleukin 1 beta, tumor necrosis factor alpha, and interferon transcripts are all upregulated by A. hydrophila infection. Meanwhile, overexpression of gcC4 reduces bacterial invasion or proliferation. Moreover, gcC4 may activate the NF-κB signaling pathway. These findings demonstrate the vital role of gcC4 in the innate immunity of grass carp. • A C4 homolog (gcC4) is identified in grass carp (Ctenopharyngodon idella). • gcC4 mRNA or protein expression is induced by A. hydrophila or PAMPs. • Overexpression of gcC4 inhibits the invasion and proliferation of A. hydrophila. • Overexpression of gcC4 induces the expression of immune-related genes. • Overexpression of gcC4 activates the NF-κB signaling pathway. [ABSTRACT FROM AUTHOR]

Aeromonas hydrophila is the causative agent of bacterial septicemia that is frequently observed in grass carp, Ctenopharyngodon idellus . In this study, we evaluated the biological parameters and immune enzymes in the liver of grass carp following A. hydrophila infection and quantified the alterations in liver histology using a semi-quantitative system. For the biological parameters, we found that the liver somatic index (LSI) was more sensitive than Fulton's condition factor (CF) and was significantly decreased at three days post-injection (DPI). At the immune enzyme level, the level of peroxidase (POD) in the liver significantly increased at 1 and 3 DPI. The activity of alkaline phosphatase (ALP) significantly increased at 3 DPI. Similarly, acid phosphatase (ACP) activity significantly increased at 1, 3, and 5 DPI. Histologically, the results indicated that the liver index at 3, 5, and 7 DPI was significantly higher than that of control groups. The regressive alterations as the highly variable reactions patterns and its index at 5 DPI was significantly higher than that of 1, 21 DPI, and the control groups. Based on our results, we suggest that grass carp resist A. hydrophila infection via an innate immune mechanism in the liver. The findings of this study will help elucidate the underlying mechanisms of resistance to A. hydrophila infection. [ABSTRACT FROM AUTHOR]

The mannan-binding lectin-associated serine protease-1 ( MASP-1 ) gene is a crucial component of the lectin pathway in the complement and coagulation cascade. Although MASP-1 has been found in the immune system of teleosts, its immune functions in response to bacterial infection are unclear. In this study, we identified a MASP-1 homolog ( gcMASP-1 ) in the grass carp ( Ctenopharyngodon idella ). The full-length 3308-bp gcMASP-1 cDNA includes a 2160-bp open reading frame encoding a protein composed of 719 amino acids with epidermal growth factor-like, complement control protein, and trypsin-like domains. gcMASP-1 shares a high similarity with MASP-1 counterparts in other species, and it is most closely related to Cyprinus carpio MASP-1 and Sinocyclocheilus anshuiensis MASP-1. Transcription of gcMASP-1 was widely distributed in different tissues and induced by Aeromonas hydrophila in vivo and in vitro . Expression of gcMASP-1 was also affected by lipopolysaccharide and flagellin stimulation in vitro . In cells over-expressing gcMASP-1 , transcript levels of almost all components, except gcMBL and gcC5 , were significantly enhanced, and gcIL1β , gcTNF-α , gcIFN , gcCD59 , gcC5aR1 , and gcITGβ-2 were significantly upregulated after exposure to A. hydrophila ; gcMASP-1 interference downregulated the transcript levels after A. hydrophila challenge. In addition, gcMASP-1 activated NF-κB signaling. These findings indicate the vital role of gcMASP-1 in innate immunity in C. idella . [ABSTRACT FROM AUTHOR]