Immune Response In Fish Research Articles

Cloning of Grass Carp Chemokine XC Receptor 1 (XCR1) Gene and Evaluation of Its Expression in Various Organs after GCRV Infection

Interaction between the chemokine receptor XCR1 and its ligand is closely related to the immune function in animals; however, there are only a few reports on role of XCR1 in the immune system of fish. We aimed to analyze the expression of XCR1 in various organs or tissues of grass carp before and after Grass Carp Reovirus (GCRV) infection to better understand the function of XCR1 in resistance to GCRV infection. We cloned and sequenced the cDNA of grass carp XCR1 and analyzed the molecular structure of XCR1 based its amino acid sequence. Further, we analyzed the relative expression levels of XCR1 in different organs or tissues of male parent grass carp with GCRV resistance (P1) and their first-generation offspring (F1) before and after GCRV infection. Our results show that the total length of cDNA of the grass carp XCR1 gene is 1659 bp and encodes 365 amino acids. XCR1 contains seven conserved transmembrane helical domains. The homologous tertiary structure of XCR1 is similar to its homologs in other species. After artificial GCRV infection, there were significant differences in the expression of the grass carp XCR1 gene in different tissues, at different time points, and between P1 and F1 fish. These results will contribute to our understanding of the role of XCR1 in fish immune responses and contribute to the development of GCRV-resistant grass carp.

Comparative Transcriptomic Immune Responses of Mullet (Mugil cephalus) Infected by Planktonic and Biofilm Lactococcus Garvieae.

Lactococcus garvieae is an important pathogen of fish, associated with high rates of mortality and infection recurrence in summer or stressful conditions. Chronic infection and disease recurrence have also been reported to be associated with biofilms. However, the impact of biofilm and planktonic bacterial infection on fish immune responses remains unclear. In this study, de novo sequencing was used to compare differences of the spleen transcriptome in planktonic- and biofilm-infected mullets. Among the 181,024 unigenes obtained, 3,392 unigenes were associated with immune response genes. Comparative analysis of the gene expression between infection with the L. garvieae planktonic type and biofilm type identified a total of 3,120 and 3,489 differentially expressed genes in response to planktonic and biofilm infection, respectively, of which 1,366 and 1,458 genes were upregulated, and 1,754 and 1,458 genes were downregulated, respectively. Gene ontology enrichment analysis of immune genes identified genes involved in the complement system, toll-like receptor signaling, and antigen processing, which were further verified by qPCR. Additionally, genes encoding TLR2, IL-1β, TNF-α, C7, and MHC class II peptides were downregulated in response to biofilm infection. Importantly, the results show that biofilm infection induces a different immune pathway response compared with planktonic bacterial infection and, furthermore, illustrates that the prevention of biofilm formation may be a necessary and new strategy for controlling bacterial infection in aquaculture.

Alternative Proteins for Fish Diets: Implications beyond Growth.

Simple SummaryAquaculture is now well-established as a provider of protein for human consumption, and its contribution will be paramount to providing food for a nine billion population in 2050. Protein is usually the major constituent of fish feeds and the most expensive ingredient. For years, fishmeal was the preferential protein source in fish diets, but environmental and economic concerns led to the search for more sustainable proteins. Hence, research on alternative protein sources to fishmeal was fruitful, being firstly directed to terrestrial plant ingredients. Recently, research on novel ingredients, such as insect meals, macroalgae, microalgae, and yeasts, has proliferated. However, the impacts of protein and its constituents (amino acids) go beyond fish growth. Thus, this review will provide knowledge on the impacts of alternative/novel protein sources on fish stress and immune responses, disease resistance, and health. Although some negative impacts of alternative ingredients, for instance, on gut integrity and immune responses have been observed, research results also point to the potential beneficial effects of novel ingredients, such as insect meals, on fish health. This information is essential to the development of innovative diets that guarantee the production of healthy fish with high quality standards and optimised welfare conditions.Aquaculture has been challenged to find alternative ingredients to develop innovative feed formulations that foster a sustainable future growth. Given the most recent trends in fish feed formulation on the use of alternative protein sources to decrease the dependency of fishmeal, it is fundamental to evaluate the implications of this new paradigm for fish health and welfare. This work intends to comprehensively review the impacts of alternative and novel dietary protein sources on fish gut microbiota and health, stress and immune responses, disease resistance, and antioxidant capacity. The research results indicate that alternative protein sources, such as terrestrial plant proteins, rendered animal by-products, insect meals, micro- and macroalgae, and single cell proteins (e.g., yeasts), may negatively impact gut microbiota and health, thus affecting immune and stress responses. Nevertheless, some of the novel protein sources, such as insects and algae meals, have functional properties and may exert an immunostimulatory activity. Further research on the effects of novel protein sources, beyond growth, is clearly needed. The information gathered here is of utmost importance, in order to develop innovative diets that guarantee the production of healthy fish with high quality standards and optimised welfare conditions, thus contributing to a sustainable growth of the aquaculture industry.

Dietary fish oil levels modulated lipid metabolism, immune response, intestinal health and salinity stress resistance of juvenile Penaeus monodon fed a low fish-meal diet

Dietary fish meal (FM) and fish oil (FO) replacement are crucial for the sustainable development of aquaculture. An eight weeks feeding trial was conducted to evaluate the potential replacing FM with soy protein concentrate, and the suitable FO level for a low FM diet of Penaeus monodon. A diet containing 25% FM was used as the control (C diet), and three other diets were formulated to contain 15% FM, and supplemented with 3%, 2%, 1% FO [high FO (HF), medium FO (MF) and low FO (LF), respectively]. The experiment was conducted in quadruplicates (30 shrimp per replicate, average weight 1.00 ± 0.01 g). The results indicated that besides the final body weight, there were no differences in weight gain, feed efficiency and survival rate observed among the four groups. The results of the acute salinity stress showed that shrimp fed the C and MF diets showed a similar survival rate, which was significantly higher than those fed a LF diet. Shrimp that were fed HF, MF and LF diets showed a lower level of fatty acid transport-related mRNA expression in the hepatopancreas, compared with those fed the C diet. Shrimp fed HF, MF and LF diets showed lower expression levels of superoxide dismutase, endoplasmic reticulum protein 57 and immune deficiency (IMD) in the hepatopancreas than those fed the C diet. Shrimp that were fed a LF diet showed the lowest expression levels of inhibitor of apoptosis proteins, Toll and tumor necrosis factor receptor associated factor 6 (TRAF6) in the hepatopancreas, as well as the highest expression levels of Toll, extracellular signal-regulated kinase, Relish and TRAF6 in the intestine among four groups. Intestinal microstructure damage was observed in shrimp that were fed a LF diet, and intestinal endoplasmic reticulum (ER) swelling was observed in shrimp fed MF and LF diets. In conclusion, these results indicated that the growth performance of shrimp was not affected when the FM and FO contents decreased, whereas a low content of FM negatively influenced the immune response in shrimp by modulating IMD and ER stress related gene expression. Under low FM conditions, a suitable dietary FO level would benefit to the lipid transport, hepatopancreas and intestine health, as well as the immune response of shrimp.

Research progress in molecular biology of fish immunoglobulin D

Immunoglobulins are the primary mediators of the humoral immune response in fish. Studies of immunoglobulins in fish are particularly important for the immunological control of fish diseases. While immunoglobulin D (IgD) was first discovered in 1965, it remains the least understood member of the antibody family. During evolutionary development from fish to humans, IgD has developed critical immunological functions. However, these immunological functions are not well understood. There are two forms of IgD, membrane IgD (mIgD) and secreted IgD (sIgD). sIgD and mIgD are formed by B lymphocytes through different splicing modes. In this paper, IgD’s structure and formation process in fish, the distribution characteristics of IgD on B cells, the mediated signaling pathways, and the functions of IgD are reviewed.

Interactive effects of dietary betaine and chromium picolinate on the immunomodulation, antioxidative response and disease resistance of Nile tilapia ( Oreochromis niloticus )

Fish feed additives are recently encouraged to improve cultured fish health and production. Dietary supplementation with betaine (Bet) and chromium picolinate (Cr-Pic) is known for its high quality for the benefit of aquaculture. A total of 180 healthy and equal-sized O. niloticus were fed on a non-supplemented basal diet, or a basal diet supplemented with Bet (10g/kg dry feed) (Bet group) or Cr-Pic (800 μg/kg dry feed) (Cr-Pic group) or their combination at the same dosing regimens (Bet + Cr-Pic group) for 6 weeks feeding trial. Our findings revealed that dietary supplementation with Bet and/or Cr-Pic enhanced the non-specific immune parameters of O. niloticus in different manners in all supplemented groups compared to the control group. Bet + Cr-Pic group came over the other two groups and recorded the more pronounced highest level of these immune-relevant parameters. In addition, the antioxidative activity of the serum and tissue homogenates of all the supplemented fish was enhanced. The muscular malondialdehyde (MDA) was significantly decreased, with a nominal decrease in the hepatic one; whereas antioxidant enzyme activities (catalase/CAT), reduced glutathione/GSH), glutathione peroxidase/GPx) and superoxide dismutase/SOD) were all increased significantly in the muscular and hepatic tissues of the supplemented fish groups compared to the control group. The serum cortisol level was significantly decreased in all supplemented groups compared to the control group. Therefore, dietary supplementation with Bet and Cr-Pic combination is a promising feed additive for their additive effects improving fish immune response and antioxidative status and aquaculture sustainability.

Zinc Oxide Nanoparticles Boost the Immune Responses in Oreochromis niloticus and Improve Disease Resistance to Aeromonas hydrophila Infection.

Zinc is an essential element affecting immune responses in aquatic organisms. In the present research, the immunomodulating effect of zinc oxide nanoparticles (ZnO NPs) was studied in Nile tilapia (Oreochromis niloticus). The minimum inhibitory concentration of zinc oxide nanoparticles (ZnO NPs) for Aeromonas hydrophila was estimated at 60µg/mL. To evaluate the efficacy of ZnO NPs for improving disease resistance against A. hydrophila, three hundred fish were divided into 5 groups. Fish in the group T1 maintained on the control feed, T2 and T3 feed on ZnO at 60 and 30µg/g, while T4 and T5 received ZnO NPs at 60 and 30µg/g, respectively for 8weeks. Immune responses were evaluated by determining the phagocytic activity, serum antibacterial activity, lysozymes, respiratory burst activity, and also gene expression of immunoglobin M-2, tumor necrosis factor-α, interleukin (IL)-1β, heat shock proteins, IL-10, insulin growth factor 1, transforming growth factor-β2, superoxide dismutase enzyme, and catalase enzyme genes. Results indicated that groups that received ZnO NPs have exaggerated immune response and upregulation in the most of expressed immune-related genes. After the feeding trial, all groups were experimentally infected with A. hydrophila, and the mortality rate was monitored. Among all the treated groups, a higher survival rate and disease resistance were observed for fish that received ZnO NPs at 30 and 60µg/g. The inclusion of ZnO NPs in O. niloticus feed improves both fish immune response and disease resistance against A. hydrophila.

Atlantic Salmon (Salmo salar) bacterial and viral innate immune responses are not impaired by florfenicol or tetracycline administration

Antibiotics are used to treat bacterial infections in fish aquaculture, and these drugs can interact with immune cells/the immune system and potentially leave fish vulnerable to viral, fungal, parasitic, or other bacterial infections. However, the effects of antibiotics on fish immunity have largely been overlooked by the aquaculture industry. We tested, at 12 and 20 °C, whether tetracycline and florfenicol (the most commonly used antibiotics in commercial aquaculture), affected the Atlantic salmon's capacity to respond to bacterial or viral stimulation. Atlantic salmon were acclimated to 12 or 20 °C and fed with tetracycline or florfenicol (100 and 10 mg kg of body weight−1 day−1, respectively) medicated feed for 15 or 10 days, respectively. Thereafter, we evaluated their immune function prior to, and after, an intraperitoneal injection of Forte Micro (containing inactivated cultures of Aeromonas salmonicida, Vibrio anguillarum, Vibrio ordalii and Vibrio salmonicida) or the viral mimic polyriboinosinic polyribocytidylic acid (pIC). We measured the transcript expression levels of 8 anti-bacterial and 8 anti-viral putative biomarker genes, and the innate (leukocyte respiratory burst, plasma lysozyme activity and hemolytic activity of the alternative complement pathway) and cellular (relative number of erythrocytes, lymphocytes and thrombocytes, and granulocytes such as monocytes and neutrophils) responses to these challenges. Overall, we only found a few minor effects of either tetracycline or florfenicol on immune gene expression or function at either temperature. Although several studies have reported that antibiotics may negatively affect fish immune responses, our results show that industry-relevant dietary tetracycline and florfenicol treatments do not substantially impact the salmon's innate immune responses. Currently, this is the most comprehensive study on the effects of antibiotics administrated according to industry protocols on immune function in Atlantic salmon.

Silica nanoparticles acute toxicity alters ethology, neuro-stress indices, and physiological status of African catfish (Clarias gariepinus)

Silica nanoparticles (SiNPs) are a new class of nanomaterials with unique properties due to their nanoscale size. Currently, SiNPs constitute a potential value in aquaculture; nonetheless, misuse induces toxicity to fisheries and ecosystems. Hence, the present prospective is a pioneer study that illustrates the acute toxicity of SiNPs to African catfish, Clarias gariepinus (B.) and the behavioral response in a renewal static system. Moreover, the influence of SiNPs on neuro-related, stress, immune-related, and oxidative stress indices was investigated. Fish groups of average body weights (73.09 ± 2.20 g) were exposed to 96-h of various concentrations of SiNPs including 0, 50, 100, 150, 200, 250, and 300 mg L−1 without water exchange. The value of 96-h LC50 of SiNPs was computed using Finney's probit analysis. Here we show that the exposure of fish to SiNPs resulted in remarkable ethological alterations such as lethargic, surfacing, inactive, slow swimming manner, and nervousness. By increasing the SiNPs concentration, the behavior scores and mortalities reached the upper limit of top values. The comparison with the control revealed a significant dose-dependent effect by increasing in the activity of 8-hydroxy-2-deoxyguanosine (8-OHdG) and malondialdehyde (MDA) with a concomitant elevation in the stress-controlled parameters (cortisol and nor-epinephrin) of all the fish groups undergone the SiNPs exposure. In contrast, there was a clear reduction in the acetylcholine esterase (AChE) level, immunological biomarkers (lysozymes and nitric oxide), and antioxidant enzymes (glutathione peroxidase (GPX) and superoxide dismutase (SOD)) of the exposed groups and the reduction elevated by increasing the SiNPs exposure concentration in comparison to the control group. Based on the study outcomes, the 96-h LC50 of SiNPs recorded 144.54 mg L−1 in C. gariepinus. We anticipate our assay to be a starting point for further applying the one-tenth of 96-h LC50- as an alternative safe treatment in therapy after considering the acute toxicity to preserve the aquaculture production and sustain human health. Additionally, it was approved that, the toxicity by the exposure to SiNPs observed clear alterations in fish behavior, neurological activity, immune and oxidative responses reflecting physiological disturbance.

Short-Term Immune Responses of Gilthead Seabream (Sparus aurata) Juveniles against Photobacterium damselae subsp. piscicida.

Photobacteriosis is a septicaemic bacterial disease affecting several marine species around the globe, resulting in significant economic losses. Although many studies have been performed related to the pathogen virulence and resistance factors, information regarding the host defence mechanisms activated once an infection takes place is still scarce. The present study was designed to understand innate immune responses of farmed juvenile gilthead seabream (Sparus aurata) after Photobacterium damselae subsp. piscicida (Phdp) infection. Therefore, two groups of seabream juveniles were intraperitoneally injected with 100 µL of PBS (placebo) or 100 µL of exponentially growing Phdp (1 × 106 CFU/mL; infected). The blood, plasma, liver, and head kidney of six fish from each treatment were sampled immediately before infection and 3, 6, 9, 24 and 48 h after infection for the broad screening of fish immune and oxidative stress responses. Infected animals presented marked anaemia, neutrophilia and monocytosis, conditions that are correlated with an increased expression of genes related to inflammation and phagocytic activity. Similar studies with different fish species and bacteria can be useful for the definition of health biomarkers that might help fish farmers to prevent the occurrence of such diseases.

Modulation of fish immune response by interferon regulatory factor 4 in redlip mullet (Liza haematocheilus): Delineation through expression profiling, antiviral assay, and macrophage polarization analysis

Interferon regulatory factor 4 (IRF4) is a crucial member of IRF family, which acts as an imperative transcription factor in the development and maturation of multiple lineages of blood cells and also plays a pivotal role in host defense against microbial infections. In the present study, we aimed to investigate the detailed structural and functional aspects of a redlip mullet IRF4 homolog (LhIRF4). The LhIRF4 open reading frame consists of 1347 base pairs encoding 449 amino acids, with the DNA-binding domain sharing significant homology with that of other vertebrate IRF4 homologs. The highest transcription levels of LhIRF4 were observed in the mullet intestine and spleen under normal physiological conditions. Furthermore, a time-dependent upregulation of LhIRF4 transcription was observed in the spleen and head kidney tissues upon pathogenic challenges. When overexpressed in mullet cells, LhIRF4 was localized to the nucleus and significantly stimulated the transcription of several host antiviral genes. Moreover, the overexpression of LhIRF4 strongly inhibited the replication of viral hemorrhagic septicemia virus (VHSV) in vitro. The function of LhIRF4 in regulation of macrophage M2 polarization has also been evidently demonstrated in RAW 264.7 cells. Taken together, our findings indicate the profound role of LhIRF4 in modulating immune responses against microbial infections in redlip mullet.

Influences of indigenous isolates Pantoea agglomerans RCS2 on growth, proximate analysis, haematological parameters, digestive enzyme activities, serum biochemical parameters, antioxidants activities, intestinal morphology, disease resistance, and molecular immune response in juvenile's cobia fish (Rachycentron canadum)

The fast expansion and high intensity of cobia culture or, better still, farming has resulted in diseases infestation and has been recognised as a significant evolving problem for cobia culture throughout its production cycle. This study explored the possible effects of dietary additives of indigenous Pantoea agglomerans RCS2 on growth, haematological parameters, biochemical blood indices, antioxidant enzyme activities, disease resistance, digestive enzyme activities, and molecular immune response in juvenile's cobia fish. After 70 days, the growth parameters (i.e., specific growth rate, weight gain, and final weight) and feed conversion ratio significantly improved (P < 0.05) compared to those fed diets without supplementation. Also, haematological parameters such as red blood cells, white blood cells, corpuscular haemoglobin concentration, mean corpuscular volume, haemoglobin, and Mean corpuscular haemoglobin were high significantly (P < 0.05) in supplemented groups. The serum blood biochemical indices aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, triglyceride, cholesterol, and glucose recorded no significant difference (P > 0.05) while globulin, total protein, and albumin were high significantly (P < 0.05) in supplemented groups as compared to the group without supplement. The current results displayed that the activities of superoxide dismutase, glutathione peroxidase, and catalase in the liver and head kidney were affected by dietary supplements of indigenous isolated microorganisms. An exceptionally low mortality rate was observed in the treatment groups than the group without supplemented diets when challenged with pathogenic bacteria. Similarly, light microscopy revealed an increase in the intestinal villus length in fish fed with the supplemented diet compared to those without supplements. In this study, the higher digestive enzyme activities show that supplemented bacteria isolates have impacted digestive enzyme secretion in juvenile cobia. Regarding the gene expression, Interleukin-1 Beta (IL-1β), Tumour necrosis factor α (TNFα), and Interleukin-8 (IL-8) were all up-regulated by indigenous isolates. The current results show that the dietary additive of indigenous P. agglomerans RCS2 could constitute a treasured nutritional approach in the path of a sustainable cobia aquaculture. The fish immune responses enhancement and the gut morphology are vital in enhancing growth, absorption of nutrients, and disease resistance; hence the results in the present study are essential outcomes for the development and competitive aquaculture sector.

The transcription factor RFX5 positively regulates expression of MHCIa in the red‐spotted grouper (Epinephelus akaara)

Regulatory factor X 5 (RFX 5) is a member of the RFX family, and it forms the transcription factor complex RFX with RFXANK/B and RFXAP. The RFX complex can activate MHC expression by binding to the MHC promoter. However, the regulate mechanism of RFX in fish species is not been fully elucidated. In this study, we investigated the transcriptional regulation of Epinephelus akaara RFX5 (EaRFX5) on EaMHCI, and its effect on immune pathways. The genomic sequence of EaRFX5 was 35,774 bp and consisted of ten exons and nine introns. The length of EaRFX5 ORF sequence is 2,160 bp, encoding 719 amino acids. By qRT-PCR, EaRFX5 was detected constitutively expressed in twelve selected tissues, showing a wide range of expression. EaRFX5 expression parttern in response to poly (I:C), LPS, Zymosan A, SGIV, and NNV challenges showed that EaRFX5 plays a differentiated immunomodulatory role in response to various stimuli in different tissues, and EaRFX5 was most significantly upregulated in the kidney after challenge with SGIV. Subcellular localization assays showed that EaRFX5 is a typical nuclear protein. Based on the in vitro overexpression experiments, EaRFX5 appeared to promote the expression of EaMHCIa gene, interferon signalling pathway and inflammatory cytokine. Luciferase reporter assay showed that the −267 bp to +82 bp region of EaMHCIa promoter was the core region where EaRFX5 modulated. Additionally, point mutations and electrophoretic mobility shift assays indicating M3 is the EaRFX5 binding sites in the EaMHCIa promoter. These results contribute to elucidating the function of EaRFX5 in fish immune response, and provide the first evidence of positive regulation of MHCIa expression by RFX5 in fish.

Immune responses and acute inflammation in common carp Cyprinus carpio injected by E.coli lipopolysaccharide (LPS) as affected by dietary oils

Eicosanoids, resolvins, and lipoxins formed from long-chain polyunsaturated fatty acids (LC-PUFAs) are the main lipid mediators in the inflammatory processes explaining the influence of dietary lipid sources on the immune system. The current study aimed to determine the effects of dietary plant oils instead of fish oil or LC-PUFA supplementation in these oils on fish immune and inflammatory responses under normal and LPS-stimulated conditions. Six iso-nitrogenous (ranging from 30.4 to 31.1%) and iso-lipidic (from 11.2 to 11.6%) diets were formulated using three oil sources: cod liver oil (CLO, as fish oil control); linseed oil (LO, rich in α-linolenic acid, ALA); sesame oil (SO, rich in linoleic acid, LA); a blend of LO and SO (SLO, v:v 1:1); and two pure plant oil diets supplemented with docosahexaenoic acid, DHA (SO + DHA, SOD) or arachidonic acid, ARA (LO + ARA, LOA). Fish were fed the experimental diets to satiation for 42 days. On day 43, they were injected with E.coli lipopolysaccharide (LPS) at 100 μg/fish. Fish plasma and tissues such as head kidney and liver were collected on day 42 and one day after LPS injection (day 44) for humoral immune variables and gene expression analyses, respectively. After 42 days of feeding, no influences of dietary oils were found on fish survival, growth, feed utilization, and humoral immune responses. On the other hand, LPS injection significantly stimulated immune responses and induced an acute inflammation in common carp through an increase of the complement activity and the up-regulation of genes involved in the innate immune system (c2), pro-inflammatory response (tlr-4, tnf-α, il-1, il-6, il-8, and cxc), eicosanoid metabolism (pla2, cox-1, 5-lox, and pge2), and anti-inflammatory response (tgf-β1 and nf-fki). Further, the expression of hsp70 was stimulated by LPS injection. The effects of dietary oil sources were observed after LPS injection, with a significant modification in the expression of almost all candidate genes. The highest pro-inflammatory responses induced by LPS were observed in CLO-fed fish while the mixture of plant oils (SLO) and LC-PUFA-supplemented diets induced significantly higher modulations in anti-inflammatory responses (il-10 and nf-kbi), general stress status (hsp70), and cytoprotection (gpx-1) compared to fish oil control and other pure plant oil groups. In conclusion, the immune response of common carp has been modified by the dietary fat sources. The fish oil-based diet supported an increase of the pro-inflammatory responses while the mixture of plant oil or LC-PUFA supplemented diets improved the anti-inflammatory responses and cytoprotection.

Oral delivery of a dsRNA-Phytoglycogen nanoparticle complex enhances both local and systemic innate immune responses in rainbow trout

Salmonids are one of the most farmed fish species worldwide. These aquatic vertebrates rely heavily on their innate immune responses as the first line of defense to defend themselves against invading pathogens. Although commercial vaccines are available against some viral and bacterial pathogens affecting salmonids, their protective efficacy varies. Using a prophylactic inducer of local and systemic innate immune responses to limit infection could have significant implications in salmonid aquaculture. A potent inducer of innate immune responses in fish is double-stranded RNA (dsRNA), a molecule that all viruses make during their replicative cycle. Polyinosinic: polycytidylic acid (polyI:C) is a synthetic dsRNA commonly used to induce type I interferons (IFNs), interferon stimulated genes (ISGs) as well as an antiviral state in vertebrate species. Based on in vitro data it was hypothesized that both local and systemic innate immune responses, in salmonids, would be enhanced by orally delivering high molecular weight polyI:C (HMW polyI:C) using cationic phytoglycogen nanoparticles (NPs) as a delivery method. The present study investigates this hypothesis using two feed delivery methods. In the first in vivo study, to ensure an equal distribution of dose, individual rainbow trout (Oncorhynchus mykiss) were orally gavaged with feed moistened with a solution containing HMW-NP (polyI:C complexed with cationic phytoglycogen nanoparticles) or HMW polyI:C alone. In a second in vivo experiment, to better mimic a more realistic feeding scenario, rainbow trout were fed feed pellets to which HMW, or HMW-NP was added. The expression of IFN1 and ISGs (vig-3, Mx1) were quantified using real-time PCR in the intestine (local response) and head kidney (systemic response). The results of these studies indicate that HMW-NP induced a higher level of IFN1 and ISG expression in the intestine and head kidney compared to the HMW fed fish. The results of this study could lead to new advances in therapeutics for the aquaculture industry by utilizing the innate immune response against invading pathogens using an orally delivered stimulant.

DDX43 recruits TRIF or IPS-1 as an adaptor and activates the IFN-β pathway in Nile tilapia (Oreochromis niloticus)

DDX43 is one of the members of the DExD/H-box protein family, and emerging data suggest that it may play an important role in antiviral immunity across mammals. However, little is known about DDX43 in the fish immune response. In this study, we isolated the cDNA sequence of ddx43 in Nile tilapia (Oreochromis niloticus). The ddx43 gene was 2338 bp in length, contained an open reading frame (ORF) of 2064 bp and encoded a polypeptide of 687 amino acids. The predicted protein of OnDDX43 has three conserved domains, including the RNA binding domain KH, DEAD-like helicase superfamily DEXDc and C-terminal HELICc domain. In healthy Nile tilapia, the Onddx43 transcript was broadly expressed in all examined tissues, with the highest expression levels in the muscle and brain and the lowest in the liver. After challenge with Streptococcus agalactiae, lipopolysaccharides (LPS) and polyinosinic polycytidylic acid (Poly I:C), the expression level of Onddx43 mRNA was upregulated or downregulated in all of the tissues tested. Overexpression of OnDDX43 in 293 T cells showed that it has a positive regulatory effect on IFN-β. The subcellular localization showed that OnDDX43 was expressed in the cytoplasm. We performed further pull-down assays and found that OnDDX43 interacted with both interferon-β promoter stimulator1 (IPS-1) and TIR domain-containing adaptor inducing interferon-β (TRIF).

Evaluation of potential applications of dietary probiotic (Bacillus licheniformis SB3086): Effect on growth, digestive enzyme activity, hematological, biochemical, and immune response of Tilapia (Oreochromis mossambicus)

The present study was designed to evaluate the dietary effect of dietary supplementation of Bacillus licheniformis on growth, hematological and immune parameters of Oreochromis mossambicus fingerlings. A feeding trial of 8 weeks was carried out, in which fish were fed at a rate of 2% body weight with four experimental diets, including a control diet and three supplemented diets such as, 105, 107 and 109 CFUg-1 respectively. At the termination of feeding experiment, growth related parameters, hematological and immune response of fish were evaluated. Feed conversion ratio (FCR) was significantly decreased, inferring high efficiency in utilizing feed. In similar groups, hematological parameters such as total erythrocyte count, total leukocyte, total serum protein, blood glucose level and hemoglobin count were significantly increased (P&lt;0.05), with higher probiotic concentration. Similarly, digestive enzyme activity of protease, lipase and amylase was also higher in fish fed with increased concentration of probiotic. Diet groups having 109 CFUg-1 of probiotic was observed with elevated immune response, as levels of lysozyme activity, respiratory burst activity and phagocytic activity were significantly higher (P&lt;0.05) in this group as compared to control group. In conclusion, supplementation of diet with Bacillus licheniformis can enhance growth performance, and health status of O. mossambicus.

Effects of Moringa oleifera, Allium sativum, Zingiber officinale on the haematological parameters and histopathological changes in visceral organs of Clarias gariepinus infected with Pseudomonas aeruginosa

Bacterial resistance to synthetic antibiotics is been a worrisome issue globally resulting in the search for alternative medicament for the treatment of bacterial infection in man, fish and other livestock. The study investigated the histological changes caused by selected medicinal plant extracts on sub-adults of the sharp tooth African catfish Clarias gariepinus experimentally infected with Pseudomonas aeruginosa. Phytochemical screening of test plants was done using standard methods. Agar well diffusion method was used to screen susceptibility of P. aeruginosa; ATCC 27853 to extracts of Moringa oleifera, Allium sativum, Zingiber officinale and oxytetracycline at 1000 mg/ml, 750 mg/ml and 500 mg/ml. Three fish samples from each group were tested for immune response and histopathological alterations. Saponins, terpenoids, flavonoids, cardiac glycoside, anthraquinone and alkaloids were present in test plants. Values of packed cell volume was 29.33%, 30.67%, 34.33%, 25.33% and 22.33% in fish exposed to oxytetracycline, Z. officinale, M. oleifera, A. sativum and untreated fish respectively. Similar trend was observed in the levels of red blood cell, haemoglobin and lymphocyte. White blood cell and neutrophil values were comparatively high in the untreated than treated fish. Organs of untreated fish showed degenerations in gill lamellae, gastric glands and hepatocytes while treated fish organs showed slight regeneration. The studied medicinal plant extracts showed significant antibacterial activity and compared with oxytetracycline in the treatment of P. aeruginosa diseases in fish. Use of these medicinal plants enhanced cultured fish immune responses.

Influence of quercetin loaded mesoporous silica nanoparticles (QMSNs) on immunity and diseases resistance in Nile tilapia (Oreochromis niloticus)

ABSTRACT The aim of the present study is to scrutinize the potentiality of Quercetin loaded mesoporous silica nanoparticles (QMSNs) to improve the disease resistance and immune response in Nile tilapia (Oreochromis niloticus). The study used five experimental groups of fish with a mean weight of 0.69 ± 0.31 g; three groups were fed quercetin loaded mesoporous silica nanoparticles (QMSNs) incorporated diets (0.25 g kg−1 – QMSNs 0.25, 0.50 g kg−1 – QMSNs 0.50, 1 g kg−1 – QMSNs 1), while the control group was fed an additive-free basal diet. The fifth group was a strict quercetin-only diet (0.25 g kg−1 – QMD). Feeding trial was done for 90 days prior to the experimental challenge with Klebsiella pneumoniae and Streptococcus agalactiae. Dietary quercetin loaded mesoporous silica nanoparticles (QMSNs) especially at 0.50 g kg−1 significantly increased digestive enzymes, phagocytic index, potential killing activity, respiratory burst activity, and Serum antibacterial activity. Furthermore, antioxidant-related genes [superoxide dismutase (SOD) and catalase (CAT)] and metabolic enzymes [serum glutamic oxaloacetic transaminase (AST) and serum glutamic pyruvic transaminase (ALT)] were found to be upregulated in the muscle and hepatopancreases of fish fed with 0.50 g kg−1 QMSNs. Survival rates were significantly higher in the 0.50 g kg−1 QMSNs group at the end of the 15th day challenge period compared to all other treatment groups. As a result, feeding Nile tilapia with 0.50 g kg−1 QMSNs for 90 days may be sufficient to improve fish immune response, antioxidant status, and survival rate against Klebsiella pneumoniae and Streptococcus agalactiae. As a result, quercetin loaded mesoporous silica nanoparticles (QMSNs) can be recommended as a dietary substitute against K.pneumoniae and S. agalactiae in Nile tilapia.

Innate response of rainbow trout gill epithelial (RTgill-W1) cell line to ultraviolet-inactivated VHSV and FliC and rhabdovirus infection

Gills reportedly play a crucial role in induction of an antiviral immune response in fish. We investigated the expression of innate response genes in the rainbow trout gill epithelial cell line RTgill-W1 36 h after pretreatment with ultraviolet-inactivated viral hemorrhagic septicemia virus (UV-VHSV), flagellin C protein from Edwardsiella tarda (FliC), VHSV and SVCV using an Agilent 4 × 44k cGRASP salmonid microarray. RTgill-W1 cells pretreated with UV-VHSV, triggered an independent gene expression profile from those treated with a recombinant flagellin C protein from Edwardsiella tarda. In addition, exposure of RTgill-W1 cells to live viruses spring viremia of carp virus and viral hemorrhagic septicemia virus induced a less robust transcriptional change of 24 and 22 gene probes, respectively, when compared to 123 genes for UV-VHSV. Further the pretreatment of RTgill-W1 cells with (UV-VHSV) significantly reduced VHSV genome copy number at 6 d post infection (dpi) relative to the FliC-treated and untreated control. A quantitative PCR was used to study the transcriptional modulation of a set of 25 innate immune-related genes highlighted by the microarray data and a panel of 7 established antiviral genes in the protected cells. Notably, the expression of ifn1, ifn2, mx1 and mx3 were expressed more in untreated cells than in UV-VHSV-treated cells where virus replication was inhibited. The results from this study shed light on the mechanisms and pathways used by teleost gill epithelium innate immunity in combating viral and bacterial infection.