Immune Response In Fish Research Articles

Beyond 2020

Beyond 2020

Immune Response of VNN (Viral Nervous Necrosis) Infected Grouper Utilizing Chlorella vulgaris Extract as an Anti-Virus Candidate

The quality and health of fish guarantee the success of aquaculture. However, grouper aquaculture are susceptible to diseases such as VNN (Viral Nervous Necrosis). It is necessary to determine the fish immune response system by observing the changes in the number of blood cells. Utilizing alternative substances, Chlorella vulgaris for instance, may minimize infection. This study aims to determine the effect of C. vulgaris extract treatment, as a candidate of VNN anti-virus, through hematological observations. The research method used qualitative experimental design by describing the fish immune response based on the number of blood cells. Fish blood was collected from each treated fish in the following treatments: (A) healthy fish, (B) VNN-infected fish, (C) VNN-infected fish treated with 17 µg / mL C. vulgaris extract, (D) VNN-infected fish treated with 33 µg / mL C. vulgaris extract, and (E) VNN-infected fish treated with 50 µg / mL C. vulgaris extract. The blood cells are observed using a light microscope. The water quality parameters analyzed were Temperature, pH, Salinity, and Dissolved Oxygen (DO) as supporting data. The research results showed that healthy fish has a high number of erythrocytes (28 cells/field of view). Treatment (D) shows a value close to healthy conditions, namely 22 cells/field of view. C. vulgaris extract treatment on VNN-infected groupers improves the immune system as indicated by an increased number of erythrocytes and decreased number of basophils cells (11 cells/field of view) and neutrophils (16 cells/field of view). Examination of water quality parameters shows tolerable conditions for the growth of groupers based on quality standards.

Experimental infection model with the bivalvulid Enteromyxum leei (Myxidiidae) in the sharpsnout seabream, Diplodus puntazzo (Sparidae), and evaluation of the antiparasitic efficacy of a functional diet.

An infection model for sharpsnout seabream Diplodus puntazzo (Walbaum) challenged with the myxosporean Enteromyxum leei (Diamant, Lom et Dyková, 1994), resembling the natural infection conditions, was used to evaluate the antiparasitic efficacy of a functional diet. Fish of an average weight of 12.5 ± 1.2 g were delivered either a functional (included as feed supplement at 0.3% levels) or a control extruded diet. After four weeks of administration of the experimental diets, fish were challenged with the parasites (cohabitation with infected donors; donor: recipient ratio 1 : 1). The experiment was terminated four weeks after the start of the challenge. At the end of the experiment, growth and feeding (specific growth rate and feed efficiency), as well as immunological parameters (respiratory burst activity, antibacterial activities, hemoglobin concentration, anti-protease activity and ceruloplasmin activity) were measured along with cumulative mortality and total parasitic count in the gut. No significant difference was evident with regard to growth and feeding performance, mortality, gut parasitic load or immunological parameters as the parasitical challenge significantly affected both the performance of the control and functional diet fed fish. However, there was a less prominent impact on antibacterial, anti-protease and ceruloplasmin activity in fish fed with the functional diet. Overall, the present study validated the experimental cohabitation infection model and evaluated the efficacy of a functional ingredient as an antiparasitic agent, showing some potential effects on the fish immune response.

Large yellow croaker peroxiredoxin IV protect cells against oxidative damage and apoptosis

Oxidative stress and inflammation lead to cell damage and are implicated in many disease states. High concentrations of hydrogen peroxide (H2O2) may mediate cells apoptosis by increasing intracellular reactive oxygen species (ROS) levels. In this study, we established a LYCK-PrxIV cell line (large yellow croaker head kidney cell line stably expressing peroxiredoxin IV). The level of nitric oxide (NO), superoxide anion and hydrogen peroxide (H2O2) in this LYCK-PrxIV cells were significantly lower than those in control cells of LYCK-pcDNA3.1 (LYCK cell line stably transfected by pcDNA3.1 vector). Additionally, when exposed to H2O2, cell apoptosis was significantly alleviated in LYCK-PrxIV than in control cells. Meanwhile, the ROS level and ATP content were maintained more stable in LYCK-PrxIV than in LYCK-pcDNA3.1. The over-expression of LcPrxIV in LYCK-PrxIV cells induced a declined mRNA expression of LcCXC, LcCC, LcIL-8 and LcTNF-α2, as well as an increase of LcIL-10 mRNA expression, when compared to LYCK-pcDNA3.1. On the other hand, the expression of chemokine LcCXC, LcCC and LcTNF-a2 increased in LYCK-pcDNA3.1 after H2O2 stimulation, while that of LcIL-8 and LcIL-10 decreased. The regualtion of gene expression in LYCK-PrxIV cells was almost the same as that in LYCK-pcDNA3.1, but the change fold was much more moderate. These results suggest that LcPrxIV may be an indispensable ROS scavenger protecting LYCK cells against oxidative damage as well as the subsequent apoptosis and inflammatory response, which provides a clue that LcPrxIV may be an assist in fish immune response.

Comparative effects of dietary micro- and nano-scale chitosan on the growth performance, non-specific immunity, and resistance of silver carp Hypophthalmichthys molitrix against Staphylococcus aureus infection

Globally, with the expansion of aquaculture, the demand for functional feeds is continuously increasing, and effort is in progress to improve the efficiency of the feed additives. Herein, nano-scale chitosan (CNP) with an average size 0.001). Our results indicate the improved efficiency of CNPs and recommend it as a feed additive to enhance fish productivity and fish immune response towards the invading pathogens.

수산양식에서 친환경성 약제개발을 위한 항병성 생약소재의 검토

This study is examination about herb medicines that counters the effects of a fish pathogens, and is for eco-pharmaceutical development in aquaculture industry. 13 kinds of herb medicines were selected, and the hot water extracts and ethanol extracts were tested for antibacterial, antiparasitic, antifungal and antiviral effects. Minimal inhibitory concentration (MIC) of 13 kinds of candidate herb medicines were measured, above all, hot water and ethanol extracts of In-jin (1/10 and 1/10² dilution) showed antibacterial activities against 14 kinds of fish pathogenic bacteria. Hot water extract and ethanol extract of Dang-gwi showed antiparasitic and antifungal activities, and the extract had strong antifungal activity especially (~1/10³ dilution). In antiviral activity against VHSV (Viral hemorrhagic septicemia virus), hot-water and ethanol extract of In-jin and Dang-gwi were effective down to 1/10³ dilution. From these results, In-jin and Dang-gwi were selected as effective herbs among 13 kinds of herb medicines and further study on the synergy effect using combination with in-jin and dang-gwi against fish pathogens will be applied to fish immune response.

Atlantic salmon kidney (ASK) cells are an effective model to characterise interferon (IFN) and IFN-induced gene expression following salmonid alphavirus infection

Salmonid alphavirus (SAV), the causative agent of pancreas disease, is a serious pathogen of farmed Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss). Given the economic impact of SAV outbreaks, much effort is focussed upon understanding the fish immune response following infection and the exploitation of this knowledge to reduce disease impact. Herein we examine the utility of the long-term Atlantic salmon kidney (ASK) cell line as a tool to study antiviral responses upon infection with SAV. Following infection with SAV subtype 1 (isolate V4640) we examined the kinetics and magnitude of induction of IFNa, IFN-regulatory factor (IRF) genes IRF1, IRF3, and IRF7b, as well as the antiviral effector Mx by RT-qPCR. SAV-1 non-structural protein (nsp1) transcript levels increased continuously over the experimental period, indicating viral replication, but cytopathic effect (CPE) was not observed. All the immune genes studied showed an increase in transcript levels over the 96-h study period following SAV infection, with strongest induction of Mx. Our data confirm that ASK cells are a suitable model to study the virus-associated immune responses of salmonids and may be a useful tool when assaying the effectiveness of potential prophylactic or antiviral treatments.

Toll-Like Receptor 5 of Golden Pompano Trachinotus ovatus (Linnaeus 1758): Characterization, Promoter Activity and Functional Analysis.

Toll-like receptors (TLRs), as important pattern recognition receptors, represent a significant component of fish immune systems and play an important role in resisting the invasion of pathogenic microorganisms. The TLR5 subfamily contains two types of TLR5, the membrane form of TLR5 (TLR5M) and the soluble form of TLR5 (TLR5S), whose detailed functions have not been completely elucidated. In the present study, we first identified two genes, TLR5M (ToTLR5M) and TLR5S (ToTLR5S), from golden pompano (Trachinotus ovatus). The full-length ToTLR5M and ToTLR5S cDNA are 3644 bp and 2329 bp, respectively, comprising an open reading frame (ORF) of 2673 bp, encoding 890 amino acids, and an ORF of 1935 bp, encoding 644 amino acids. Both the ToTLR5s possess representative TLR domains; however, only ToTLR5M has transmembrane and intracellular TIR domains. Moreover, the transcription of two ToTLR5s was significantly upregulated after stimulation by polyinosinic:polycytidylic acid (poly (I:C)), lipopolysaccharide (LPS), and flagellin in both immune-related tissues (liver, intestine, blood, kidney, and skin) and nonimmune-related tissue (muscle). Furthermore, the results of bioinformatic and promoter analysis show that the transcription factors GATA-1 (GATA Binding Protein 1), C/EBPalpha (CCAAT Enhancer Binding Protein Alpha), and ICSBP (Interferon (IFN) consensus sequence binding protein) may play a positive role in moderating the expression of two ToTLR5s. Overexpression of ToTLR5M and ToTLR5S notably increases NF-κB (nuclear factor kappa-B) activity. Additionally, the binding assay revealed that two rToTLR5s can bind specifically to bacteria and pathogen-associated molecular patterns (PAMPs) containing Vibrio harveyi, Vibrio anguillarum, Vibrio vulnificus, Escherichia coli, Photobacterium damselae, Staphylococcus aureus, Aeromonas hydrophila, LPS, poly(I:C), flagellin, and peptidoglycan (PGN). In conclusion, the present study may help to elucidate the function of ToTLR5M/S and clarify their possible roles in the fish immune response to bacterial infection.

A live attenuated Edwardsiella tarda vaccine induces immunological expression pattern in Japanese flounder (Paralichthys olivaceus) in the early phase of immunization

A previous study showed that an attenuated Edwardsiella tarda strain, TXhfq, as a live vaccine could elicit protective immune effects in fish against E. tarda infection. In the current study, in order to clarify the molecular mechanism of fish immune response at the early stage after TXhfq vaccination, RNA-Seq technology was used to compare the transcriptomes of skin, intestine, and spleen between bath-vaccinated and unvaccinated Japanese flounder (Paralichthys olivaceus). An average of 46.6 million clean reads per library was obtained, ~88.04% of which were successfully mapped to the reference genome, and approximately 24,600 genes were detected in each sample. A total of 565, 878, and 1258 differential expression genes (DEGs) were found in skin, intestine, and spleen, respectively, including 1263 up-regulated genes and 1438 down-regulated genes. The DEGs exhibited different characteristics in each tissue. One hundred and sixteen DEGs belonging to six immune related categories were scrutinized, i.e., inflammatory factors, cytokines, complement and coagulation system, mucins, phagocytosis, and antigen processing and presentation. A protein-protein interaction network was constructed to get the interaction network between immune genes during the early stage of immunization. The top six hub genes highly regulated by TXhfq formed complicated interaction relationship with each other, which were involved in immune processes, notably inflammation and phagocytosis. Our results provide valuable information for the understanding of the immune mechanism underlying the protection of live attenuated vaccines in fish.

Patterns of monogenean abundance in native and invasive populations of Planiliza haematocheila (Teleostei: Mugilidae): interactions between climate and host defence mechanisms explain parasite release

One of the most intriguing questions in invasive biology is how an introduced species changes its population parameters in a new environment. Translocation of free-living species commonly results in co-introduction of their parasites. The current study focuses on the abundance pattern of the monogenean parasite Ligophorus llewellyni of the pacific so-iuy mullet, Planiliza haematocheila, across the native and introduced distribution ranges. We evaluated parasite release by the so-iuy mullet by comparing abundance patterns of L. llewellyni under effects of the host length, water temperature and month of the year in the Sea of Japan and the Sea of Azov. Generalised additive models applied to analysis of parasite abundance data showed that relationships between the mean number of L. llewellyni and the three tested independent variables were not linear. Our results suggest that the introduced host lost a large amount of parasite abundance due to the effect of warm climate in a new region, which is mediated by host defence mechanisms. The abundance of L. llewellyni rapidly rose in autumn, as fish activity and immune response decrease, reached the maximum in winter and began to fall in spring as a warm temperature facilitates the fish immune defence. The abundance of L. llewellyni showed an initial increase in response to fish growth and reached an asymptote. The response curves built for native and introduced regions reached an asymptote at different fish body lengths, reflecting the fish growth rate, which is higher in the introduced range of P. haematocheila. We found that the carried parasite species holds the same trend in relationships compared with its native area, between the mean number of monogeneans per host and independent variables increasing abundance with fish length, low temperature and cold months. Our results open new perspectives for future research on statistical modelling of parasite abundance across native and introduced distribution ranges in order to provide deeper insight into host-parasite interactions of invasive populations.

Effects of Dietary Doum Palm Fruit Powder on Growth, Antioxidant Capacity, Immune Response, and Disease Resistance of African Catfish, Clarias gariepinus (B.)

Simple SummaryIn aquaculture, medicinal plants and their by-products can be effectively used as natural immune-stimulants, growth promoters, anti-stress agents, and antimicrobials. However, very few studies have been conducted to evaluate the possible use of doum palm fruit powder (DPFP) in diets for African catfish. In this study, four experimental diets with four levels of DPFP (0, 5, 10, and 15 g kg−1 diet) in African catfish were evaluated. The findings suggested that DPFP is a good dietary supplement in the aquaculture, which can positively influence fish growth, intestinal histomorphology, hepatic antioxidant activity phagocytic percent and index, lysozyme activity, nitric oxide (NO) production, and disease resistance against A. hydrophila challenge.Application of herbal immune-stimulants for modulation of fish growth and immune response has received great interest during the past decades. With several pharmacological properties, Doum palm, Hyphaene thebaica (Mart.) is known to be a beneficial medicinal plant. The objective of this study was to investigate the effects of the dietary addition of doum palm fruit powder (DPFP) on growth performance, non-specific immune response, and antioxidant parameters of African catfish, Clarias gariepinus (B.). A total of 120 fish (average initial weight 60.50 ± 0.04 g) were randomly allocated to four groups (three replicates/group, 10 fish/aquarium); a basal diet without DPFP supplementation was used as a control, and three other diets were prepared by supplementing 5, 10, or 15 g kg−1 DPFP for a ten-week feeding period. Following ten weeks of feeding, the fish were challenged with Aeromonas hydrophila (as an immune challenge test), and mortalities were recorded. In comparison to the control diet, dietary DPFP significantly improved growth parameters, including final body weight, body weight gain (WG), specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio (PER), along with an increase in the content of dry matter of the whole body, in a concentration-dependent manner. Moreover, the heights of intestinal villi, numbers of goblet cells, and intraepithelial lymphocytes (IEL) exhibited marked escalation in all parts of the intestine by increasing the level of DPFP, except for numbers of IEL in the proximal part. The decline in serum glucose, cholesterol, and triglyceride levels was prominent in DPFP10 and DPFP15 groups respective to the DPFP0 group. Furthermore, DPFP boosted the hepatic level of catalase (CAT) in the fish, in a dose-dependent manner; meanwhile, the activity of superoxide dismutase (SOD) and reduced glutathione (GSH) content were also augmented in DPFP10 and DPFP15 groups respective to the DPFP0 group. Dietary DPFP (DPFP15 followed by DPFP10 then DPFP5) led to a pronounced enhancement in the innate immune response (phagocytic percent and index, lysozyme activity, nitric oxide (NO) production, and sialoglycans, namely α 2,3-sialyltransferase and α 2,6-sialyltransferase content); however, the myeloperoxidase (MPO) activity was reduced. Significantly higher relative percentage survival (RPS, 88.56%) of the fish, following the A. hydrophila challenge, was observed for the DPFP15 group. We can suggest that DPFP can beneficially influence fish growth, intestinal histomorphology, hepatic levels of catalase (CAT), superoxide dismutase (SOD) activity and glutathione (GSH) content, immune response, and disease resistance against A. hydrophila challenge.

Enzymatic fish protein hydrolysates in finfish aquaculture: a review

AbstractIn intensive farming systems, fish are held at high densities, which may increase stress, leading to susceptibility to diseases that result in economic losses. Therefore, effective feeding practices incorporating health‐promoting compounds such as proteins, hydrolysates and bioactive peptides that can stimulate the defence mechanisms of fish and achieve better growth are some of the priorities for sustainable aquaculture development. Globally, the fish processing industries generate and discard a large volume of waste every year, estimated at up to 60% of the harvested biomass. This waste can be converted to value‐added products such as fish protein hydrolysate (FPH) with the addition of various proteolytic enzymes. FPH from fish processing waste including skin, heads, muscle, viscera, liver and bones is a good source of protein, amino acids, peptides and antioxidants and has been found to possess desirable functional and bioactive peptides. A moderate inclusion of FPH in aquafeeds has the potential to improve growth, feed utilization, immune functions and disease resistance of fish. Production of FPH, targeted to more precise molecular weight ranges, has superior functionalities that are in high demand. With interest in FPH as an aquafeed supplement, this review aimed to summarize the source, production processes and functional properties of FPH and the reported impact of FPH in aquafeed supplement on fish growth, survival, feed utilization, immune response and disease resistance. Possible limitations of using FPH and future research potential as an opportunity for the use of processing fish waste are also discussed.

Molecular and functional characterization of a mitochondrial glutathione reductase homolog from redlip mullet (Liza haematocheila): Disclosing its antioxidant properties in the fish immune response mechanism

Glutathione reductase (GSHR) is a biologically important enzyme involved in the conversion of oxidized glutathione (GSSG) into its reduced form, reduced glutathione (GSH), with the catalytic activity of NADPH. Most animals and aquatic organisms, including fish, possess high levels of this enzyme system to neutralize oxidative stress in cells. The current study was conducted to broaden our knowledge of GSHR in fish by identifying a mitochondrial isoform of this enzyme (LhGSHRm) in redlip mullet, Liza haematocheila, and clarifying its structure and function. The complete open reading frame of LhGSHRm consists of 1527 base pairs, encoding 508 amino acids, with a predicted molecular weight of 55.43 kDa. Multiple sequence alignment revealed the conservation of important amino acids in this fish. Phylogenetic analysis demonstrated the closest evolutionary relationship between LhGSHRm and other fish GSHRm counterparts. In tissue distribution analysis, the highest mRNA expression of LhGSHRm was observed in the gill tissue under normal physiological conditions. Following pathogenic challenges, the LhGSHRm transcription level was upregulated in a time-dependent manner in the gill and liver tissues, which may modulate the immune reaction against pathogens. rLhGSHRm showed considerable glutathione reductase activity in an enzyme assay. Further, the biological activity of rLhGSHRm in balancing cellular oxidative stress was observed in both disk diffusion and DPPH assays. Collectively, these results support that LhGSHRm has profound effects on modulating the immune reaction in fish to sustain precise redox homeostasis.

Identification of an IgD/IgT chimera in the European sea bass (Dicentrarchus labrax L.)

Three classes of immunoglobulins have been identified in Teleosts: IgM, IgT/Z and IgD. They are fundamental for fish immune responses and, therefore, their functional activities are heavily investigated. In this paper, we describe the identification of a new IgD/IgT chimera in sea bass (Dicentrarchus labrax) from a gills transcriptome. This transcript joined the first six constant domains of the IgD chain with the two terminal constant domains of IgT, generating a long in-frame coding sequence with a junction between the canonical δ6 exon splicing donor site and the τ3 exon splicing acceptor site. Studies performed on genomic DNA confirmed the presence of the sequence and identifies and intronic region of 656 bp within this joining region. The basal expression of the IgD/IgT chimera was investigated both in silico and in vivo: high level of expression was found in gills, gut and head kidney. Moreover, IgD/IgT transcripts were up-regulated after in vitro stimulation of sea bass HK leukocytes with LPS. The IgD/IgT chimera was found also in two congener species, Morone saxatilis and Morone chrysops. It is not possible to have a precise idea on the evolutionary scenario that lead to the appearance of this sequence due to the lack of genomic information, but we could speculate that an ancestral duplication of the entire IgH locus was followed by the chimerization of Cδ/Cτ in one of the two loci. Finally, the IgD/IgT high basal expression in tissues and organs fundamental for sea bass immune response and its modulation after LPS stimulation provide a very preliminary indication that this unusual Ig variant could have a functional activity.

Grass carp (Ctenopharyngodon idella) GPATCH3 initiates IFN 1 expression via the activation of STING-IRF7 signal axis

GPATCH3, a protein with G-patch domain, is known to participate in innate immune response and organ development in mammals. However, there are few reports on GPATCH3 in fish. Here the cDNA sequence of GPATCH3 was cloned from Ctenopharyngodon idella (CiGPATCH3, MN149902) and was determined its character. A cDNA sequence of CiGPATCH3 is 1646 bp and contains an ORF of 1221 bp translating a protein of 407 amino acids. Phylogenetic analysis uncovered that CiGPATCH3 possesses a relatively high degree of homology with Cyprinus carpio GPATCH3. The mRNA level of CiGPATCH3 was increased following the intracellular stimulation of poly (I:C) into CIK cells. In vivo, over-expression of CiGPATCH3 can significantly up-regulate IFN 1 and ISG15 expression at mRNA and protein levels. To investigate the molecular mechanism by which GPATCH3 initiates the innate immune response in fish, co-IP experiments were performed to analyze the substrates of CiGPATCH3. The results showed that CiGPATCH3 directly interacted with CiSTING, but not with CiIRF3, CiIRF7, CiTBK1 or CiIPS-1. As compared with the single transfection of CO cells with either CiGPATCH3 or CiSTING, the expression of IFN 1 was more significantly up-regulated in cells under treatment with dual transfection of CiGPATCH3 and CiSTING. Knockdown of CiGPATCH3 inhibited STING-mediated IFN 1 expression in fish cells. Over-expression of CiGPATCH3 and CiSTING facilitated the phosphorylation and cytoplasmic-to-nuclear translocation of CiIRF7. These results explicitly showed that CiGPATCH3 up-regulates IFN 1 and ISG15 expression via the activation of STING-IRF7 signal axis in vivo.

IMMUNE RELATED GENES EXPRESSION ANALYSIS IN KOI FISH AFTER VACCINATED WITH KOI HERPES VIRUS DNA VACCINES

Vaccination is a practical step in preventing diseases caused by koi herpes virus (KHV) in koi fish (Cyprinus carpio haematopterus). We have developed two DNA vaccines for KHV named as GP-25 and GP-11 from two local isolates coded as ORF25 and ORF81, respectively. Although both vaccines have been reported to increase survival rates, the evaluation of koi fish immune responses at the molecular level has not been done post-vaccinations. The aim of this research was to determine the effects of koi herpesvirus DNA vaccine on the immune-modulation of koi fish at mRNA level. This recent research used the best vaccine doses of both vaccines determined from our previous study: 7.5 and 12.5 µg per 100 g fish of GP-11, and 12.5 µg per 100 g fish of GP-25. The immune gene expression was analyzed using the RT-qPCR method from the fish liver at 0, 1, 7, 14, and 28 days post-vaccination (dpv). The results showed that, in the vaccinated fish, the immune genes viz. tumor necrosis factor a (TNFa), interleukin-1b (IL1b), interferon-g (IFNg), Mx1, immunoglobulin Mu chain (IgM), and major histocompatibility complex (MHC) class I and class II were induced to significant extents. The higher dose vaccination using the GP-11 vaccine showed higher immune gene expression than that of the lower dose. Furthermore, the GP-25 vaccine had induced lower immune responses than the GP-11 vaccine when using the same dose of vaccination, but relatively the same when the half-dose of GP-11 vaccine was used. In conclusion, the GP-11 and GP-25 vaccine provided the immune-modulatory effects on the koi fish immune response after vaccination.

Distribution of Mpeg1+ cells in healthy grouper (Epinephelus coioides) and after Cryptocaryon irritans infection

Cryptocaryon irritans is an extremely harmful ciliated obligate parasite that is responsible for large economic losses in aquaculture. C. irritans infection can cause an insect-resistant immune response in fish, and many immune cells can be observed in the local infection site. However, it is unclear whether macrophages are involved in the host defense against C. irritans infection. The Mpeg1 protein can form pores and destroy the cell membrane of invading pathogens, and is also used as a macrophage-specific marker in mammals. Therefore, a polyclonal antibody against grouper recombinant Mpeg1a was produced to mark macrophages in this study, which could recognize both isoforms of Mpeg1 (Mpeg1a/b). Immunofluorescence revealed that EcMpeg1 positive cells were mostly distributed in the head kidney and spleen in healthy grouper. Immunofluorescence and immunohistochemistry showed that the number of EcMpeg1 positive cells increased in the gills after infection with C. irritans, implying that EcMpeg1 positive cells may be involved in the process of grouper resistance against C. irritans infection.

Viral infection-induced changes in the expression profile of non-RLR DExD/H-box RNA helicases (DDX1, DDX3, DHX9, DDX21 and DHX36) in zebrafish and common carp

In mammals, several non-RLR DExD/H-box RNA helicases are involve in sensing of viral nucleic acids and activation of antiviral immune response, however their role in the immune defense of fish is much less known. In this study, the expression profile of non-RLR DExD/H-box RNA helicase genes: ddx1, ddx3, dhx9, ddx21 and dhx36, was studied in zebrafish (Danio rerio) and common carp (Cyprinus carpio L.) during infection with two RNA viruses: spring viremia of carp virus (SVCV) and Chum salmon reovirus (CSV). Bioinformatic analysis of the amino acid sequences of the core helicase of DDX1, DDX3, DHX9, DDX21 and DHX36 in zebrafish and common carp revealed presence of all conserved motifs found amongst all other species, with the exception of common carp DHX9 which do not possess motif V. The transcripts of studied DExD/H-box RNA helicases were found in zebrafish ZF4 cell line as well as in all studied organs from zebrafish and common carp. The expression study demonstrated the up-regulation of the expression of selected non-RLR DExD/H-box RNA helicases during viral infections in ZF4 cell line (in vitro study) and in zebrafish and common carp organs (in vivo study). DDX1 was the only DExD/H-box RNA helicase which expression was repetitively up-regulated during in vivo infections with SVCV and CSV in zebrafish and SVCV in common carp. In ZF4 cells and kidney of common carp, viral infection-induced up-regulation of DExD/H-box RNA helicases preceded the up-regulation of type I IFN gene. Our results suggest that studied non-RLR DExD/H-box RNA helicases might be involved in antiviral immune response in fish.

Characterization of miRNAs in Cultured Atlantic Salmon Head Kidney Monocyte-Like and Macrophage-Like Cells.

Macrophages are among the first cells to respond to infection and disease. While microRNAs (miRNAs) are involved in the process of monocyte-to-macrophage differentiation in mammals, less is known in teleost fish. Here, Atlantic salmon head kidney leukocytes (HKLs) were used to study the expression of miRNAs in response to in vitro culture. The morphological analysis of cultures showed predominantly monocyte-like cells on Day 1 and macrophage-like cells on Day 5, suggesting that the HKLs had differentiated from monocytes to macrophages. Day 5 HKLs also contained a higher percentage of phagocytic cells. Small RNA sequencing and qPCR analysis were applied to examine the miRNA diversity and expression. There were 370 known mature Atlantic salmon miRNAs in HKLs. Twenty-two miRNAs (15 families) were downregulated while 44 miRNAs (25 families) were upregulated on Day 5 vs. Day 1. Mammalian orthologs of many of the differentially expressed (DE) miRNAs are known to regulate macrophage activation and differentiation, while the teleost-specific miR-2188, miR-462 and miR-731 were also DE and are associated with immune responses in fish. In silico predictions identified several putative target genes of qPCR-validated miRNAs associated with vertebrate macrophage differentiation. This study identified Atlantic salmon miRNAs likely to influence macrophage differentiation, providing important knowledge for future functional studies.

A portrait of the immune response to proliferative kidney disease (PKD) in rainbow trout.

Proliferative kidney disease (PKD), caused by the myxozoan Tetracapsuloides bryosalmonae, is one of the most serious parasitic diseases of salmonids in which outbreaks cause severe economic constraints for the aquaculture industry and declines of wild species throughout Europe and North America. Given that rainbow trout (Oncorhynchus mykiss) is one of the most widely farmed freshwater fish and an important model species for fish immunology, most of the knowledge on how the fish immune response is affected during PKD is from this organism. Once rainbow trout are infected, PKD pathogenesis results in a chronic kidney immunopathology mediated by decreasing myeloid cells and increasing lymphocytes. Transcriptional studies have revealed the regulation of essential genes related to T‐helper (Th)‐like functions and a dysregulated B‐cell antibody type response. Recent reports have discovered unique details of teleost B‐cell differentiation and functionality and characterized the differential immunoglobulin (Ig)‐mediated response. These studies have solidified the rainbow trout T. bryosalmonae system as a sophisticated disease model capable of feeding key advances into mainstream immunology and have contributed essential information to design novel parasite disease prevention strategies. In our following perspective, we summarize these efforts to evaluate the immune mechanisms of rainbow trout during PKD pathogenesis.