Search

Dietary Astragalus polysaccharides (APS) get wide application in aquaculture due to their excellent immunoregulatory effects. However, little is known about the effects of dietary APS on vaccine potency in fish. In the present study, large yellow croakers (Larimichthys crocea) were injected with formalin-inactivated Pseudomonas plecoglossicida after APS feeding for 14 d and then challenged by live P. plecoglossicida on 28 d post-vaccination. The results showed that dietary APS combined with inactivated vaccine could improve the survival rate, and alleviate splenic lesions and bacteria load post-challenge, thus exhibiting a better protection in large yellow croaker against P. plecoglossicida infection than inactivated vaccine treatment alone. Fish in APS + P. plecoglossicida vaccine group expressed a better antioxidant status by possessing a relatively higher serum total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) activity and a significantly lower malondialdehyde (MDA) content than those in vaccine alone group. Serum lysozyme (LZM) and alkaline phosphatase (AKP) activities, and immunoglobulin M (IgM) titers were all improved in fish of APS + P. plecoglossicida vaccine group compared to fish in vaccine group. Furthermore, fish in APS + P. plecoglossicida vaccine group showed a lower down-regulation of pro-inflammatory cytokines interleukin-1β (IL-1β) and IL-6 , and a higher up-regulation of anti-inflammatory cytokine IL-10 , immunoglobulin (IgM) and T cell immunity-related cytokines, interferon-γ (IFN-γ), IL-4/13A , and IL-4/13B , when compared with those in fish of vaccine group. These results suggested that dietary APS could assist inactivated vaccine to trigger stronger innate and adaptive immune responses against P. plecoglossicida infection. These findings further uncover the immunoregulatory mechanism of dietary APS, and provide valuable information for prevention and control of bacteriosis in fish. • Dietary APS enhanced the potency of inactivated P. plecoglossicida vaccine. • Dietary APS assisted vaccine to produce a more potent antioxidant ability. • APS + vaccine triggered a stronger innate immune response than vaccine alone. • APS + vaccine triggered a stronger adaptive immune response than vaccine alone. [ABSTRACT FROM AUTHOR]

Clarias dussumieri , an air breathing catfish endemic to the Western Ghats in India, is categorized as 'Near Threatened' by the IUCN. This species is of high regional consumer demand and is one of the prioritized candidate species for aquaculture diversification and conservation. Despite its ecological and commercial significance, comprehensive studies on its immune system are lacking. This study elucidates the ontogenetic development and tissue-specific (brain, anterior kidney, gill, spleen, muscle, liver, hindgut and skin) expression profiles of key immune-related genes in C. dussumieri. Larvae were sampled at various developmental stages post-fertilization, and tissues from adult fish were analyzed for expression patterns of genes associated with inflammation (IL-1β , TNF-α , iNOS), antimicrobial defense (LYS , HAMP), stress response (HSP70), complement system (C3), cell-mediated immunity (MHC-IIβ, CD4-1), and adaptive immunity (IgM). The expression of IL-1β was highest at 60 days post-fertilization (60D), while TNF-α expression peaked at 25D before dropping notably by 60D. iNOS showed a peak at 7D, underscoring its importance in early immune defence. LYS exhibited a high expression at 10D, while HAMP peaked at 60D, highlighting their roles in antimicrobial defence. Stress marker HSP70 increased from 15D onwards and complement component C3 was consistently expressed at low levels throughout development. MHC-IIβ and CD4-1 showed significant increase since 10D and 7D respectively, suggesting the establishment of cell-mediated immunity. IgM expression increased notably from 15 days, indicating the development of adaptive immunity. In adult fish tissues, IL-1β, TNF-α, LYS and HSP70 showed highest expression in the hindgut, while C3 was predominantly expressed in the liver. MHC-IIβ and CD4-1 were highly expressed in the spleen and anterior kidney respectively. IgM was abundant in the anterior kidney and spleen. This study provides crucial baseline data on the immune competence of different developmental stages of C. dussumieri , informing strategies for effective vaccination and disease management in aquaculture, and enhancing our understanding of fish immunology for conservation efforts. • Clarias dussumieri , an endangered catfish species, holds significant ecological and aquaculture value. • The study investigated the expression of key immune genes during various developmental stages and in adult C. dussumieri. • A notable increase in IgM expression from 15 days post-fertilization suggests the onset of Ig mediated humoral immunity. [ABSTRACT FROM AUTHOR]

Streptococcosis is the leading bacterial disease impacting Nile tilapia (Oreochromis niloticus) and causes substantial economic losses in China. This study assessed the resistance and tolerance of three Nile tilapia (88, 99, and NG) to Streptococcus agalactiae infection. Survival rates were monitored, and samples were collected from blood, liver, and spleen at 0, 1, 2, 5, 7, and 14 days post-infection. Serum biochemical parameters, hepatic antioxidant enzymes, and the expression of related antioxidant and immune genes were measured. Results showed that strain 88 had superior resistance, with the highest survival rate, reduced liver damage, and lower alanine aminotransferase and alkaline phosphatase levels at 1 and 5 days post-infection. This strain also had higher serum cholesterol and triglyceride levels between days 5 and 14. Antioxidant activities increased in all strains post-infection, with strain 88 showing significantly higher superoxide dismutase (SOD) activity and elevated catalase (CAT) and SOD gene expressions; this indicated enhanced control of reactive oxygen species and reduced tissue damage. Additionally, strain 88 exhibited lower levels of inflammatory markers (TNF-α , IL-1β , IL-10) with higher IgM levels and superior MHC-II expression during early infection, which demonstrated a strong immune response. These results indicate that strain 88 is a promising candidate for selective breeding to improve streptococcosis resistance in tilapia. • Nile tilapia strain 88 shows highest survival rate and reduced liver damage. • Nile tilapia strain 88 exhibits enhanced antioxidant activity post-infection. • Nile tilapia strain 88 exhibits strong immune response and lower inflammation. • Nile tilapia strain 88 is a promising candidate for selective breeding. [ABSTRACT FROM AUTHOR]

Megalobrama amblycephala , a main herbivorous fish with notable economic benefits in China, often faces serious challenges to its survival and growth due to hypoxia and heat caused by factors such as global warming and intensive aquaculture. To evaluate the combined effects of these stressors, we performed a two-factor crossover test to assess the impacts of simultaneous exposure to hypoxia (2 mg/L) and heat (35 °C) on oxidative stress, immunity and apoptosis in M. amblycephala. These results showed that hypoxia and heat exposure significantly enhanced the expression of oxygen-sensing and heat shock protein (HSP) genes, hypoxia inducible factor 1α (Hif-1α), HIF-prolyl hydroxylase-2 (phd2) and factor inhibiting Hif-1 (fih-1) , as well as hsp70 and hsp90α. Furthermore, M. amblycephala suffering from hypoxia and heat exposure exhibited several changes in liver tissues, with the most severe lesions and up-regulation of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) observed in those subjected to simultaneous exposure. Moreover, the combined hypoxia and heat exposure initially triggered an increase in the activities of total antioxidant capacity (T-AOC), superoxide dismutase (SOD) and catalase (CAT), and glutathione (GSH) contents, followed by a reduction, and the accumulation of malondialdehyde (MDA), which induced oxidative stress. This was accompanied by an increase and subsequent reduction in the contents of alkaline phosphatase (AKP), acid phosphatase (ACP), complement component 3 (C3) and C4, immunoglobulin M (IgM), and interferon-γ (IFN-γ) leading to immunosuppression. Additionally, hypoxia and heat exposure up-regulated the expression of antioxidant enzyme genes (nrf2 , cu/zn-sod , mn-sod cat, ho-1 , pi3k and gpx-1a) , inflammatory genes (interleukin il-1β, il-8 and tnf-α), immunity effectors (igm and lyz), as well as apoptosis genes (casp3 , casp8 , casp9 and p53) and activated p-Akt/Akt , suggesting apoptosis may be linked with oxidative stress and inflammation and mediated through the PI3K/Akt signaling pathway. In short, the combined hypoxia and heat exposure disrupted homoeostasis in M. amblycephala , with a more pronounced detrimental effect than exposure to either stressor alone These results will contribute to understanding the mechanism of combined exposure to hypoxia and heat in fish and provide a fundamental base for fisheries management. • Simultaneous exposure can affect the survival rate and liver function of M. amblycephala. • Hypoxia and heat induces oxidative stress, immune response and apoptosis in M. amblycephala via the PI3K/Akt pathway. • Simultaneous exposure is more detrimental to biological responses than individual stressor. [ABSTRACT FROM AUTHOR]

The skin mucosa of fish is exposed to significant challenges from infectious disease agents due to continuous exposure to the aqueous environment. Interestingly, bony fish have evolved to express a unique IgT, which is absent in terrestrials, that appears to play a predominant role in the mucosal-associated lymphoid tissue of the rainbow trout. Nevertheless, in other IgT-producing fish, it is unclear whether IgM or IgT is primarily responsible for protection against infections of cutaneous tissue. Here, we show that grouper IgM appears quickly within the skin following challenge by the marine parasite, Crytopcaryon irritans. These IgM-class antibodies may arise from local proliferating antibody secreting cells or may infiltrate tissue from the serum in dimer polymer form. Based on details of IgM functional responses, we conclude that grouper IgM plays a predominant role in defense against C. irritans. • Immune fish rapidly increase skin-specific IgM against C. irritans. • C. irritans Challenged groupers exhibit local IgM + B cell expansion and infiltration. • Grouper skin IgM proves crucial in countering C. irritans. [ABSTRACT FROM AUTHOR]

Streptococcus agalactiae is a common pathogenic bacterium caused of streptococcosis, which has a negative impact on Nile tilapia aquaculture. Numerous vaccines have been developed recently to combat this disease, which are key components of global health efforts to prevent disease outbreaks. MONTANIDE™ IMS 1312 is a micro-emulsion recommended for immersion of fish. However, the data on the effectiveness of those immersion vaccines containing this aqueous adjuvant in fish are limited. The objective of this research was to explore the potential of MONTANIDE™ IMS 1312, an adjuvant for immersion vaccination, administered with an S. agalactiae inactivated whole-cell vaccine (SAIV) in Nile tilapia. Fish were separated into three groups: 1) fish were vaccinated by immersion vaccination with PBS (CTRL), 2) fish were vaccinated by immersion vaccination with SAIV vaccine alone (SAIV), and 3) fish were vaccinated by immersion vaccination with SAIV containing MONTANIDE™ IMS 1312. We found that the activity of several innate immunity parameters was increased significantly (P < 0.05) following the immunization. As expected, the levels of specific IgM antibody were significantly increased post-vaccination, and the highest IgM antibody levels were found in the fish vaccinated with SAIV containing MONTANIDE™ IMS 1312. Analysis of the transcriptional expression of major pro-inflammatory cytokines, as well as the presence of IgM+ B cells, revealed significant increases, suggesting that Nile tilapia were able to initiate cellular immune responses following vaccination. Taken together, our results indicate that using MONTANIDE™ IMS 1312 in combination with a SAIV can induce strong protection post S. agalactiae infection. Importantly, administration of an adjuvanted immersion vaccine is safe, no side effects were observed, and it does not negatively impact fish growth. In conclusion, MONTANIDE™ IMS 1312 has the potential to be used as adjuvants for immersion vaccines against streptococcosis in Nile tilapia. • An Streptococcus agalactiae inactivated whole-cell vaccine (SAIV) administered with MONTANIDE™ IMS 1312 was studied in Nile tilapia. • Immersion vaccination of SAIV with MONTANIDE™ IMS 1312 was safe, had no side effects, and did not negatively impact fish growth. • SAIV with MONTANIDE™ IMS 1312 increased innate and adaptive immunity post vaccination. • SAIV with MONTANIDE™ IMS 1312 gave high protection to S. agalactiae providing the RPS value was 50.0 %. [ABSTRACT FROM AUTHOR]

The Japanese eel (Anguilla japonica) experiences dramatic internal and external environmental changes during its transoceanic reproductive migrations. Here, we assess immune function changes in the primary and secondary immune organs (head kidney and spleen) of A. japonica during artificial ovarian maturation at the previtellogenic (PV), midvitellogenic (MV), and ovulating (OV) stages by transcriptome analyses. Stress responses were also assessed by determining the serum concentrations of lysozyme, alkaline phosphatase, acid phosphatase, total antioxidant capacity, and superoxide dismutase. Our results showed that together with increased serum 17β-estrogen and testosterone, lysozyme activity and antioxidant capacity were suppressed during artificial ovarian maturation. Comparisons across these developmental stages identified 60 (head kidney) and 36 (spleen) differentially expressed genes associated with the immune system. Genes related to the key activation markers of innate immune function, such as CXCL10 , CXCL11 , CCL20 , HSP90B , MMP9 , and MMP13 , were upregulated and significantly enriched in the interleukin-17 signaling pathway. Adaptive immune function-related genes (IGM and MHC1) were upregulated in the head kidney from PV to MV, and their levels increased thereafter in the spleen. Moreover, a correlation between Pax5 expression and IGM expression in the spleen of MV (IGM +/ Pax 5+) and OV (IGM ++/ Pax5 −) stage suggests that adaptive immune function was enhanced during ovarian maturation. To our knowledge, the present study is the first to describe transcriptome profiling of immune organs during ovarian maturation in teleost. Our findings suggest that the interleukin-17 pathway and IgM may play important roles in spawning. • IL-17 signaling pathway-related genes upregulated and enriched in the head kidney. • IGM and MHC1 upregulated successively in the head kidney and spleen. • A correlation between IGM and Pax 5 expression from MV to OV stage in the spleen. • Lysozyme and antioxidant capacity were suppressed during artificial maturation. [ABSTRACT FROM AUTHOR]

Nocardia seriolae , a Gram-positive facultative intercellular pathogen, has been identified as the causative agent of fish nocardiosis, causing substantial mortality and morbidity of a wide range of fish species. Looking into that fact, the effective vaccine against this pathogen is urgently needed to control the significant losses in aquaculture practices. In order to induct attenuated strains for developing the potential live vaccines, the mutagenic N. seriolae strain S-250 and U-20 were obtained from wild-type strain ZJ0503 through continuous passaging and ultraviolet (UV) irradiation, respectively. Additionally, the biological characteristic, virulence, stability, mediating immune response and supplying protective efficacy to hybrid snakehead of the S-250 and U-20 strains were determined in the present study. The results showed that U-20 strain displayed dramatic changes in morphological characteristic and significant decreased in the virulence to hybrid snakehead, while that of S-250 strain had no obvious different in comparison to ZJ0503 strain. When hybrid snakehead were intraperitoneally injected with ZJ0503, S-250 and U-20 strains at their respective sub-clinical dosage, the non-specific immunity parameters (serum LYZ, POD, ACP, AKP and SOD activities), specific antibody (IgM) titers production and immune-related genes (CC1 , CC2 , IL-1β , IL-8 , TNFα , IFNγ , MHCIα , MHCIIα , CD4 , CD8α , TCRα and TCRβ) expression were up-regulated, indicating that they were able to trigger humoral and cell-mediated immune responses. Furthermore, the protective efficacy in hybrid snakehead after vaccination with ZJ0503, S-250 and U-20 strains, in terms of relative percentage survival (RPS), were 28.85%, 56.89% and 89.65% respectively. Taken together, two attenuated N. seriolae strains S-250 and U-20 were obtained successfully and they could elicit strong immune response and supply protective efficacy to hybrid snakehead against N. seriolae , which suggested that these two attenuated strains were the potential candidates for live vaccine development to control fish nocardiosis in aquaculture. • N. seriolae strain S-250 and U-20 were attenuated from wild-type strain ZJ0503. • These two attenuated strains used as live vaccine could boost strong immune response. • Live vaccine trials of S-250 and U-20 strain could supply 56.89% and 89.65% RPS, respectively. [ABSTRACT FROM AUTHOR]

This study compared the N protein sequences of genotype J with other genotypes of IHNV to select amino acid residues that may be related to the change in viral virulence. The recombinant viruses containing different mutation sites were rescued by alanine scanning mutagenesis and the reverse genetic system. The nine recombinant virus strains obtained in this work were named rIHNV-N 85 , rIHNV-N 102 , rIHNV-N 146 , rIHNV-N 380 , rIHNV-N 85-102-146 , rIHNV-N 85-102-380 , rIHNV-N 85-146-380 , rIHNV-N 102-146-380 , and rIHNV-N 85-102-146-380. Pathogenicity and immunity assays were performed to determine the role of virulence sites. The result of the pathogenicity test showed that the survival rates of rIHNV-N 85 , rIHNV-N 102 , rIHNV-N 85-102-146 , and rIHNV-N 85-102-380 groups were 52.5%, 55%, 67.5%, and 57.5%, while the survival rate of wild-type (wt) IHNV HLJ-09 group was only 10%. The replication ability of recombinant viruses with substitutions at positions 85 and 102 was significantly inhibited in vivo and in vitro. The qRT-PCR result indicated that the cytokines of IFN1 , IL-8 , and IL-1β expression levels were increased in rIHNV-N 85 , rIHNV-N 102 , rIHNV-N 85-102-146 , and rIHNV-N 85-102-380 groups. In addition, these four recombinant viruses could cause the rainbow trout to produce anti-IHNV-specific antibodies immunoglobulin M (IgM) earlier, confirming that 85 and 102 amino acid residues of N protein affected the virulence and immunogenicity of IHNV. All these results suggest that mutations of the N protein virulence sites reduce virulence while retaining immunogenicity. This also provides a new idea for studying the virulence mechanism of rhabdoviruses and preparing attenuated vaccines. • Nine rIHNVs with N protein site mutations were rescued by reverse genetics. • Mutants in N protein attenuated IHNV replication. • Amino acid residues 85 and 102 in N protein were important sites affecting the virulence and immunogenicity of IHNV. • This study provides a new idea for studying the virulence mechanism of rhabdoviruses and preparing attenuated vaccines. [ABSTRACT FROM AUTHOR]

This study aimed to assess the effects of dietary addition with Chlorella sorokiniana on fish growth, gut histology, antioxidant capacity, immune response, and disease resistance in rainbow trout. Three diets with similar proximate composition and different Chlorella meal levels were formulated. The control diet, 5% Chlorella diet, and 10% Chlorella diet contained 0%, 5% Chlorella meal, and 10% Chlorella meal, respectively. Each diet was assigned to triplicate tanks containing 30 fish (165.3 ± 0.6 g) in each tank. Fish were fed experimental diets for ninety days. The results showed that the addition of 5% Chlorella in the diet significantly increased feed intake by 19.3% and weight gain rate by 17.3% (P < 0.05) without affecting feed efficiency and gut histology. Diets containing Chlorella meal significantly decreased malonaldehyde contents in the plasma after the lipopolysaccharide (LPS) challenge (P < 0.05). Dietary supplementation with Chlorella meal significantly increased lysozyme (LZM) activity levels (in the head kidney) and immunoglobulin M (IgM) (in the head kidney) and complement component 3 (C3) (in the spleen) contents before the LPS challenge, and simultaneously increased LZM activity levels (in the plasma) and C3 contents (in the plasma and head kidney) after the LPS challenge (P < 0.05). Furthermore, dietary administration of Chlorella meal significantly increased the survival rate of fish infected with Aeromonas salmonicida (P < 0.05). In conclusion, C. sorokiniana can be used to improve fish growth, antioxidant capacity, and immunity. • Chlorella sorokiniana meal increases feed intake and growth of Oncorhynchus mykiss. • C. sorokiniana reduced oxidative stress of O. mykiss. • C. sorokiniana enhanced the immune response and disease resistance of O. mykiss. [ABSTRACT FROM AUTHOR]

The glutamyl endopeptidase homolog of Nocardia seriolae (GluNS) has been proved to be a potential virulence factor in our previous study. Present investigation was carried out to construct an attenuated N. seriolae strain by deletion with GluNS gene and evaluate its protective immunity in head snakehead. A deletion strain (NS-Δ GluNS) was established by knockout of gene GluNS from wild strain N. seriolae ZJ0503 via homologous recombination. The LD50 of NS-Δ GluNS in 3.41 × 106 cfu/mL was significantly increased than that of wild strain in 4.75 × 105 cfu/mL, indicating that the virulence of N. seriolae has been attenuated with the knockout of GluNS. Meanwhile, applying NS-Δ GluNS as an attenuated live vaccine to immune hybrid snakehead, the non-specific immunity parameters (serum LYZ, POD, ACP, and AKP activities), specific antibody (IgM) titers production and immune-related genes (MHCIα , CD4 , and IL-8) expression were up-regulated in different tissues, which indicated that they were able to trigger humoral and cell-mediated immune responses. Furthermore, the protective efficacy in hybrid snakehead after vaccination with NS-Δ GluNS shown 73.53% relative percentage survival (RPS). Taken together, the attenuated NS-Δ GluNS was obtained successfully and it could elicit strong immune response and supply protective efficacy to hybrid snakehead against N. seriolae wild strain. • A deletion strain (NS-Δ GluNS) was established from wild strain N. seriolae ZJ0503. • The virulence of N. seriolae has been attenuated with the knockout of gene GluNS. • Attenuated deletion strain as live vaccines would be an effective strategy to control N. seriolae infection. [ABSTRACT FROM AUTHOR]

The teleost mucosal immune system consists mainly of the skin, gills and gut, which play crucial roles in local immune responses against invading organisms. Immunoglobulins are essential molecules in adaptive immunity that perform crucial biological functions. In our study, a mucosal immunity model was constructed in Epinephelus coioides groupers after Cryptocaryon irritans infection, according to previous experience. Total IgM and IgT in the groupers increased in the serum and mucus in the immune group, whereas only pathogen-specific IgM were detected existence. More critically, pathogen-specific IgM was detected in the head kidney, gill and skin supernatants, thus suggesting that the systematic immune and mucosal immune system secreted immunoglobulins. Furthermore, an early response in the skin was observed, on the basis of the detection of pathogen-specific IgM in the skin supernatant. In conclusion, this research characterized the grouper IgM and IgT in mucosal immune responses to pathogens in the gills and skin, thus providing a theoretical basis for future studies on vaccines against C. irritans. • A mucosal immune model was constructed in Epinephelus coioides after Cryptocaryon irritans infection. • Only pathogen-specific IgM was detected in the serum and mucus of multiply immunized groupers. • Mucosal tissues (gill and skin) secreted pathogen-specific IgM independently after C. irritans infection. [ABSTRACT FROM AUTHOR]

Disease prevention by vaccination is, on economic, environmental and ethical grounds the most appropriate method for pathogen control currently available to the aquaculture sector. However, vaccine administration in aquatic animals faces obvious technical problems not encountered in other land animals. Thus, oral vaccines are highly demanded by the aquaculture sector that requests alternatives to the labor-intensive injectable vaccines that require individual handling of fish, provoking stress-related immunosuppression and handling mortalities. Despite this, most previous attempts to obtain effective oral vaccines have failed both in fish and mammals. This could be a consequence of very restricted tolerance mechanisms in the intestine given the fact that this mucosa is at the frontline upon antigen encounter and has to balance the delicate equilibrium between tolerance and immunity in a microbe rich aquatic environment. In this context, the search for an optimal combination of antigen and adjuvant that can trigger an adequate immune response able to circumvent intestinal tolerance is needed for each pathogen. To this aim, we have explored potential of molecules such as β-glucans, flagellin, CpG and bacterial lipopolysacharide (LPS) as oral adjuvants. For this, we have determined the effects of these adjuvants ex vivo in rainbow trout intestine tissue sections, and in vitro in leucocytes isolated from rainbow trout spleen and intestine. The effects were evaluated by analyzing the levels of transcription of different genes related to the innate and adaptive immune response, as well as evaluating the number of IgM-secreting cells. LPS seems to be the molecule with stronger immunostimulatory potential, and could safely be used as a mucosal adjuvant in rainbow trout. Moreover, the designed strategy provides a fast methodology to screen adjuvants that are suitable for oral vaccination, providing us with valuable information about how the intestinal mucosa is regulated in fish. • Two simple methodologies to evaluate the potential of mucosal adjuvants were designed. • CpGs increase the amount of IgM-secreting cells in splenic and not in gut cultures. • LPS has the stronger transcriptional effects on gut explants among the tested molecules. • LPS increases the amount of IgM-secreting cells in gut cultures. [ABSTRACT FROM AUTHOR]

Fish skin, the mucosal site most exposed to external antigens, requires protection by an efficient local mucosal immune system. The mucosal reserve of IgM is recognized as an immune strategy that blocks pathogen invasion to maintain homeostasis, whereas the mechanism of skin-associated local IgM production induced by mucosal antigens is not well know. In this study, we found that the skin of flounder (Paralichthys olivaceus) was equipped with the immune cellular and molecular basis for processing mucosal antigens and triggering local specific responses, i.e., CD4+ Zap-70+ T cells, CD4− Zap-70+ T/NK cells, IgM+ MHCII+ B cells, PNA+ MHCII+ antigen-presenting cells, UEA-1+ WGA+ and UEA-1+ WGA− antigen-sampling cells, as well as secreted IgM and pIgR, as demonstrated by indirect immunofluorescence assay using different antibodies and lectins. After immersion immunization with inactivated Edwardsiella tarda , qPCR assay displayed up-regulation of immune-related genes in flounder skin. Flow cytometry analysis and EdU labeling demonstrated that the mucosal inactivated vaccine induced local proliferation and increased amounts of cutaneous IgM+ B cells. Skin explant culture proved the local production of specific IgM in the skin, which could bind to the surface of E. tarda. ELISA, laser scanning confocal microscopy, and Western blot revealed that, in addition to the elevated IgM levels, pIgR protein level was significantly up-regulated in skin tissue and surface mucus containing the pIgR (secretory component, SC)-tetrameric IgM complex, indicating that mucosal vaccine stimulated up-regulation of IgM and pIgR, which were secreted as a complex into skin mucus to exert the protective effects as secretory IgM. These findings deepen the understanding of IgM-based local responses in the mucosal immunity of teleosts, which will be critical for subsequent investigation into the protective mechanism of mucosal vaccines for fish health. • Teleost skin possessed the cellular and molecular basis for triggering mucosal immune response. • Immersion immunization induced local proliferation and increased amounts of IgM + B cells in the skin. • Immersion immunization induced local production of vaccine-specific IgM in skin and mucus. • IgM and pIgR were distributed in the epidermis in individual or co-localized forms. • IgM and pIgR could be secreted into skin mucus as pIgR (SC)-tetrameric IgM complexes. [ABSTRACT FROM AUTHOR]

Probiotic Bacillus pumilus SE5, heat-inactivated (HSE5) or active (ASE5), were supplemented to high soybean meal (HSM) (36 %) diet at whole term (0–56 days) and middle term (29–56 days) to investigate the preventing and repairing effects of B. pumilus SE5 in ameliorating the adverse effects of HSM in Epinephelus coioides. The results suggested that the HSM significantly decreased the weight gain rate (WGR), specific growth rate (SGR), and increased the feed conversion rate (FCR) at day 56 (P < 0.05), while HSE5 and ASE5 promoted the growth performance. The HSE5 and ASE5 showed preventive and reparative functions on the antioxidant capacity and serum immunity, with significantly increased the total antioxidant capacity (T-AOC), superoxide dismutase (SOD), glutathione (GSH), glutathione peroxidase (GSH-PX) activities, and reduced malondialdehyde (MDA) level, and increased acid phosphatase (ACP), alkaline phosphatase (AKP), immunoglobulin M (IgM) and complement 3 (C3). The HSM impaired the intestinal health (destroyed the intestinal structure, significantly increased the contents of serum D-lactic acid and diamine oxidase, and reduced the expressions of claudin-3 and occludin), while HSE5 and ASE5 improved them at whole term and middle term. The HSM impaired the intestinal microbiota and reduced its diversity, and the HSE5 or ASE5 improved the intestinal microbiota (especially at whole term). HSE5 and ASE5 improved the intestinal mRNA expressions of anti-inflammatory genes (il-10 and tgf-β1) and reduced the expressions of pro-inflammatory genes (il-1β , il-8 , il-12), and promoted the expressions of humoral immune factor-related genes (cd4 , igm , mhcII-α) and antimicrobial peptide genes (β-defensin , epinecidin-1 and hepcidin-1), and decreased the expressions of NF-κB/MAPK signaling pathway-related genes (ikk-α , nf-κb, erk-1), and improved the expressions of MAPK signaling pathway-related gene p38-α (P < 0.05). In conclusion, the heat-inactivated and active B. pumilus SE5 effectively prevented and repaired the suppressive effects of soybean meal in E. coioides , which underscored the potential of B. pumilus SE5 as a nutritional intervention agent in HSM diet in aquaculture. • High soybean meal impaired growth, immunity and intestinal health. • Heat-inactivated and active B. pumilus SE5 relieved the adverse effects of high soybean meal. • The preventive effects of B. pumilus SE5 were better than the reparative effects. [ABSTRACT FROM AUTHOR]

The Asian seabass (Lates calcarifer) faces significant disease threats, which are exacerbated by intensive farming practices and environmental changes. Therefore, understanding its immune system is crucial. The current study presents a comprehensive analysis of immune-related genes in Asian seabass peripheral blood leukocytes (PBLs) using Iso-seq technology, identifying 16 key pathways associated with 7857 immune-related genes, comprising 634 unique immune-related genes. The research marks the first comprehensive report on the entire immunoglobulin repertoire in Asian seabass, revealing specific characteristics of immunoglobulin heavy chain constant region transcripts, including IgM (Cμ, ighm), IgT (Cτ, ight), and IgD (Cδ, ighd). The study confirms the presence of membrane-bound form, ighm mb , ight mb , ighd mb of IgM, IgT and IgD and secreted form, ighm sc and ight sc of IgM and IgT, respectively, with similar structural patterns and conserved features in amino acids across immunoglobulin molecules, including cysteine residues crucial for structural integrity observed in other teleost species. In response to bacterial infections by Flavobacterium covae (formerly F. columnare genomovar II) and Streptococcus iniae , both secreted and membrane-bound forms of IgM (ighm mb and ighm sc) and IgT (ight mb and ight sc) show significant expression, indicating their roles in systemic and mucosal immunity. The expression of membrane-bound form IgD gene, ighd mb , predominantly exhibits targeted upregulation in PBLs, suggesting a regulatory role in B cell-mediated immunity. The findings underscore the dynamic and tissue-specific expression of immunoglobulin repertoires, ighm mb , ighm sc , ight mb , ight sc and ighd mb in Asian seabass, indicating a sophisticated immune response to bacterial pathogens. These findings have practical implications for fish aquaculture, and disease control strategies, serving as a valuable resource for advancing research in Asian seabass immunology. • The full immunoglobulin repertoire in Asian seabass was obtained using the Iso-seq technique. • Full-length cDNAs encoding membrane-bound and secreted forms of IgM, IgT, and IgD were characterized. • IgM, IgT, and IgD each exhibited specific expression patterns under healthy and infection conditions. • Both secreted and membrane-bound forms of IgM and IgT show significant expression in response to bacterial infections. • IgD, predominantly in its membrane-bound form, exhibits upregulation in PBLs, suggesting a regulatory role in immunity. [ABSTRACT FROM AUTHOR]

Francisella noatunensis subsp. orientalis (Fno) is one of the infectious diseases that causes economic losses associated with tilapia mortality. Even though direct immersion administration of vaccines is more practicable for small fish and fry compared with oral and injection vaccination in the fields, the efficacy is still insufficient due to lower potency of antigen uptake. Herein, we accomplished the development of a mucoadhesive nanovaccine platform using cetyltrimethylammonium bromide (CTAB), a cationic surfactant, to improve the efficiency of immersion vaccination against Fno in tilapia. Cationic Fno nanovaccine (CAT- Fno -NV) was prepared though emulsification using an ultrasonic method. In our investigation, the CAT- Fno -NV increased the opportunity of Fno vaccine uptake by extending the contact time between vaccine and mucosal surface of fish gills and enhancing the protective efficacy against Fno infection. Fish were vaccinated with the CAT- Fno -NV by a direct immersion protocol. The challenge trial by Fno injection revealed that CAT- Fno -NV at the concentration 1:100 ratio (approximately 1 × 106 cfu/mL) had the highest efficacy to protect fish from Fno infection at day 30 after post challenge period according to the total number of Fno detected in head kidney, spleen and liver. A significant upregulation of IgM gene was observed in gills, skin, head kidney, serum and peripheral blood lymphocytes (PBLs) and spleen tissues treated with WC and CAT- Fno -NV (1:100) vaccines, while IgT gene was highly expressed in only gills and skin tissues for treated WC and CAT- Fno -NV (1:100) groups. We anticipate that the cationic surfactant-based nanovaccine developed in this study could become an efficient alternative for direct immersion vaccination to induce humoral immune responses against Fno in vaccinated tilapia. • The mucoadhesive nanovaccine was constructed from cationic surfactant, cetyltrimethylammonium bromide (CTAB), for direct immersion vaccination. • The mucoadhesive nanovaccine production platform can minimize batch-to-batch variation experienced when using other mucoadhesive agents such as chitosan. • The developed nanovaccine for direct immersion vaccination can efficiently induce humoral and specific immune responses against Fno in vaccinated tilapia. [ABSTRACT FROM AUTHOR]

Aeromonas caviae is a zoonotic pathogen that can cause disease in aquatic organisms and mammals, including humans, and it is widespread in nature, especially in freshwater environments. Previous research has reported that extracellular products (ECPs) secreted by pathogens during growth are effective protective antigens that can induce the host immune response and protect the host from pathogens. However, little is known about how ECPs enhance immunity. Here, we prepared extracellular products by the cellophane plate method, determined the total protein concentration, and analysed the protein composition of the extracellular products by SDS–PAGE. Subsequently, their enzyme activity and pathogenicity were evaluated separately. Crucian carp were randomly divided into four groups to receive formalin-inactivated A. caviae vaccine (FKC), ECPs mixed with the same amount of Freund's complete adjuvant, the same amount of ECPs mixed with an equal volume of A. caviae inactivated vaccine (FKC + ECPs), sterile PBS alone via intraperitoneal injection. On Days 7, 14, 21, and 28 after immunization, the expression levels of IgM, SOD, and CAT and the lysozyme (LYS) activity in the serum were detected by ELISA, and the relative expression levels of the TNF-α, IFN-γ, IL-1β, and IL-10 genes in the liver, kidney, spleen, intestine, and gills were measured by qPCR. The extracellular products generated five clearly visible protein bands and exhibited lipase, protease, amylase, DNase and lysozyme but no urease or lecithinase activities. In addition, the median lethal doses of A. caviae and ECPs to crucian carp were 411.64 μg/fish and 1.6 × 105 CFU/mL, respectively. Compared with those of the control group, the IgM, SOD, and CAT contents and serum LYS activity were significantly increased in the experimental groups, and the qRT–PCR results showed that the relative expression levels of TNF-α, IFN-γ, IL-1β, and IL-10 genes in the liver, kidney, spleen, and intestine were significantly increased after injection immunization. In addition, the relative immune protection rates of the three experimental groups were 60%, 65%, and 45%, all of which were significantly higher than those of the control group. Collectively, our findings show that the extracellular products of A. caviae can be used as a vaccine to significantly improve the immune level of crucian carp and have obvious anti-infection ability. This may represent a promising approach to prevent and control infection by A. caviae and provides strong theoretical support for the development of new inactivated vaccines. • The extracellular products of Aeromonas caviae AC-CY strain were successfully extracted and detected to have relevant biological characteristics. • Extracellular products have certain toxicity to crucian carp and good immunogenicity. • The immune enhancement effect of protein vaccine is better than that of inactivated vaccine and mixed vaccine, and the study is helpful to develop new aquatic immune agents. [ABSTRACT FROM AUTHOR]

The structures of fish serum immunoglobulin differ among different fish species. In this study, we accidently isolated a rabbit immunoglobulin (Ig) light chain bound to serum immunoglobulin from different marine fish species using phage display. Fish Ig was separated using a protein A column. The phage library was generated from variable regions of rabbit spleen B cells immunized with bluefin tuna Thunnus orientalis Ig. Fish Ig–specific phages were enriched using two rounds of bio-panning with yellowtail Seriola quinqueradiata serum Ig, followed by two rounds of bio-panning with red seabream Pagrus major serum Ig. The enriched phages demonstrated an increase in binding specificity to the tuna, yellowtail, and red seabream Igs compared to the phages listed in the unpanned library. A recombinant protein of a single clonal phage, which encodes the rabbit Ig light chain, was produced, and the binding specificities to fish Igs were analyzed using enzyme-linked immunosorbent assay (ELISA) and western blotting. The recombinant protein exhibited binding properties to fish Igs in the ELISA. However, the recombinant protein that bound to serum protein(s), but not IgM, was detected via western blotting. The recombinant protein may provide a novel information on the common structural feature in the fish immunoglobulins. • A phage display library was generated from rabbit spleen immunized with fish Ig. • Fish Ig-specific phages were enriched by bio-panning. • A clone of recombinant single chain variable fragment bound to various fish Ig. [ABSTRACT FROM AUTHOR]

The present study was conducted to assess the protective efficacy of a trivalent oral vaccine containing chitosan–PLGA encapsulated inactivated viral haemorrhagic septicemia virus (VHSV), Streptococcus parauberis serotype I and Miamiensis avidus antigens, followed by its oral (incorporated in feed) administration to olive flounder (Paralichthys olivaceus) fingerlings for a period of 15-consecutive days. After 35 days of initial vaccination, three separate challenge studies were conducted at the optimal temperature of the targeted pathogens using an intraperitoneal injection route. RPS analysis revealed moderate protection in the immunized group against all the three pathogens viz., VHSV (53.30% RPS), S. parauberis serotype-I (33.30% RPS), and M. avidus (66.75% RPS), as compared to the respective non-vaccinated challenge (NVC) control group. In addition, the immunized fish demonstrated significantly (p < 0.05) higher specific antibody titres in serum and significant (p < 0.05) upregulation in the transcript levels of immune genes of Igs (IgM, IgT, pIgR), TLRs (TLR 2, TLR 7), cytokines (IL-1β, IL-8) and complement pathway (C3) in the mucosal and systemic tissues than those of NVC control fish, suggesting orchestration of pathogen-specific host immune responses thereby favouring its combativeness against the three pathogens. The expression dynamics of IFN-γ, Mx, caspase 3 genes post VHSV challenge; IFN-γ, TLR 2, caspase 1 genes post S. parauberis serotype I challenge and CD-8α, IL-10, TNF-α genes post M. avidus challenge further substantiates the efficacy of the vaccine in stimulating antiviral, antibacterial and antiparasitic immune responses in the host resulting in their better survival. The findings from the present study reflect that the formulated trivalent oral vaccine incorporating VHSV, S. parauberis serotype I and M. avidus antigens can be a promising prophylactic strategy to prevent the associated disease outbreaks in olive flounder. • An oral vaccine (Chi/PNPs-IV + Sp + Sc) against VHSV, S. parauberis serotype I and M. avidus was formulated for olive flounder. • Encapsulation of the inactivated antigens in chitosan coated PLGA nanoparticles resulted in efficient vaccine delivery. • Vaccinated fish showed significantly (p < 0.05) higher serum antibody responses and immune gene transcripts both in systemic and mucosal tissues. • RPS of 53.30%, 33.30% and 66.75% against VHSV, S. parauberis serotype I, and M. avidus , respectively, highlights the protective efficacy of the formulated vaccine. [ABSTRACT FROM AUTHOR]

Combination of antimicrobial proteins and nanomaterials provides a platform for the development of immunopotentiators. Oral administration of immunopotentiators can significantly enhance the immunity of organisms, which provides ideas for disease prevention. In this study, we confirmed that nanoparticles CMCS-20a can efficiently prevent grass carp reovirus (GCRV) infection. Firstly, we verified that CiCXCL20a is involved in the immune responses post GCRV challenge in vivo and alleviates the cell death post GCRV challenge in CIK cells. Then, we prepared nanoparticles CMCS-20a using carboxymethyl chitosan (CMCS) loaded with grass carp (Ctenopharyngodon idella) CXCL20a (CiCXCL20a). Meanwhile, we confirmed nanoparticles CMCS-20a can alleviate the degradation in intestine. Subsequently, we added it to the feed by low temperature vacuum drying method and high temperature spray drying method, respectively. Grass carp were oral administration for 28 days and challenged by GCRV. Low temperature vacuum drying group (LD-CMCS-20a) significantly improve grass carp survival rate, but not high temperature spray drying group (HD-CMCS-20a). To reveal the mechanisms, we investigated the serum biochemical indexes, intestinal mucus barrier, immune gene regulation and tissue damage. The complement component 3 content, lysozyme and total superoxide dismutase activities are highest in LD-CMCS-20a group. LD-CMCS-20a effectively attenuates the damage of GCRV to the number of intestinal villous goblet cells and mucin thickness. LD-CMCS-20a effectively regulates mRNA expressions of immune genes (IFN1, Mx2, Gig1 and IgM) in spleen and head kidney tissues. In addition, LD-CMCS-20a obviously alleviate tissue lesions and viral load in spleen. These results indicated that the nanoparticles CMCS-20a can enhance the disease resistance of fish by improving their immunity, which provides a new perspective for fish to prevent viral infections. • The nanoparticle CMCS-20a has good tolerance in intestine. • Oral LD-CMCS-20a improves the innate immunity in grass carp. • LD-CMCS-20a improves mucin thickness and survival rate post GCRV infection. [ABSTRACT FROM AUTHOR]

Interleukin-17 (IL-17), as a pro-inflammatory cytokine family, mediates different pro-inflammatory mediators in various cell types (e.g., epithelial cells, macrophages, endothelial cells, and fibroblasts), which play an important role in defending against pathogens. The IL-17A/F1 genes have recently been reported in fish. However, the functions of these genes are still unclear. In this study, we identified two duplicated IL-17A/F1 genes in common carp (Cyprinus carpio L.), namely, CcIL-17A/F1a and CcIL-17A/F1b. Sequence analysis showed that Cc IL-17A/F1a and Cc IL-17A/F1b proteins had four conserved cysteine residues, which could form two intra-chain disulfide bridges. Homology comparison displayed that the deduced amino acid sequences of Cc IL-17A/F1a and Cc IL-17A/F1b shared 31.1%–77.3% and 32.5%–75.7% of sequence similarity to IL-17A/F1 homologues from other fish species, respectively. The mRNA expression levels of CcIL-17A/F1a and CcIL-17A/F1b were obviously increased in gill and head–kidney of fish challenged with A. hydrophila. The recombinant protein r Cc IL-17A/F1a and r Cc IL-17A/F1b could enhance the expression levels of pro-inflammatory cytokines (IL-1β , IL-6 , IFN-γ , and TNF-α) and chemokines (CXCL8 and CXCL20). The 3 × Flag eukaryotic expression vectors to express protein r Cc IL-17A/F1a (or r Cc IL-17A/F1b) were constructed and intramuscularly injected in common carp. The r Cc IL-17A/F1a (or r Cc IL-17A/F1b) could be successfully expressed in vivo. Four immune-related genes, namely, CD4 , CD8 , TNF-α , and IgM , were also significantly induced to be expressed at higher mRNA levels compared with the control. The pretreatment with Cc IL-17A/F1a or Cc IL-17A/F1b could markedly increase the survival rate of common carp challenged with A. hydrophila. Our results demonstrated that Cc IL-17A/F1a or Cc IL-17A/F1b plays an important role in immune responses and immune defense against bacteria. Cc IL-17A/F1a or Cc IL-17A/F1b could also be potentially used as an immunopotentiator to prevent diseases in common carp. • CcIL-17A/F1a and CcIL-17A/F1b were cloned and characterized in common carp. • Prokaryotic expression rCcIL-17A/F1s could up-regulate pro-inflammatory cytokines in cells. • Eukaryotic expression rCcIL-17A/F1s could induce the expression levels of immune-related genes in vivo. • Pretreatment with CcIL-17A/F1s could increase antibacterial ability and fish survival rate. [ABSTRACT FROM AUTHOR]

Columnaris is a bacterial disease, found in freshwater fish, caused by Flavobacterium oreochromis. The disease has a devastating impact on a range of cultured and wild freshwater fish species e.g. Lates calcarifer (Asian sea bass), which is a serious economic losses to the freshwater aquaculture in Thailand. The disease can be prevented by an efficacious vaccine, however, no licensed effective vaccine is available to date. Current study was based on the development of a novel mucoadhesive nano-encapsulated vaccine (EncapFlavoNP++), where, cationic lipid-based nanoparticles were combined with an antigen obtained from F. oreochromis. Various parameters including transmission electron microscopy (TEM), physiochemical properties; zeta potential, and polydispersity index were determined. The TEM results depicted well-formed circular-shaped nano-encapsulates complexed with cationic lipid surfactants. The average diameter of the molecules was 200 nm, having a zeta potential of 31.82 mV, while, the polydispersity index (PDI) was 0.31. The in vivo study lasted for 8 weeks, the immunologic and protective potentials of the prepared molecules were determined by challenging the fish for 8 weeks. The most effective dilutions of EncapFlavoNP++ solution were 1:100 and 1:200, which significantly improved the efficacy of the immunity by increasing the level of antibody specific to F. oreochromis. A trend of upregulation was found in the immune-related genes including immunoglobulin M heavy chain (IgM), major histocompatibility complex class IIα molecules (MHC-IIα), and dendritic cell specific transcript (DCs) in gills, skin, liver, peripheral blood lymphocytes (PBLs), head kidneys, and spleen as compared to the control group (P < 0.05 and P < 0.01). Upon immunization with EncapFlavoNP++ solution at the dilution of 1:100 and 1:200, the significant increase in survival rate (SR) and relative percent survival (RPS) were found in fish challenged with virulent F. oreochromis bacterium (SR 72.50% and RPS 62.07) and (SR 65.83% and RPS 52.87), respectively as compared to the control group (P < 0.05). It can be concluded that immunization with EncapFlavoNP++ solution has significant immunologic and protective effects against Columnaris disease. Furthermore, the prepared vaccine candidate has more potential as compared to whole-cell immersion vaccination (FK-WC). It can be used on a large scale in the freshwater aquaculture industry to boost immunity against Columnaris disease. • Mucoadhesive cationic lipid-based F. oreochromis nanoencapsulation (EncapFlavoNP++) was constructed from Cetyltrimethylammonium bromide (CTAB) lipid surfactant. • Physiochemical characteristics of EncapFlavoNP++ are approximately 200 nm in size, 31.82 mV of zeta potential and 0.31 of polydispersity index (PDI). • EncapFlavoNP++ was significantly increased serum antibody and upregulated in the immune-related genes (i.e. IgM, MHC-IIα, and DCs) in Asian sea bass. • EncapFlavoNP++ exhibited a significant increase in RPS and survival rate after challenged with F. oreochromis. [ABSTRACT FROM AUTHOR]

The current perspective is a pioneer to assess the efficacy of Salvia officinalis leave powder (SOLP) on growth, intestinal enzymes, physiological and antioxidant status, immunological response, and gene expression of Common carp (Cyprinus carpio). We also looked into fish resistance after being challenged with Aeromonas sobria , a pathogenic zoonotic bacteria. Fish (N = 120) were fed four different experimental diets in triplicate for 8 weeks. The control diet (SOLP0 - without SOLP); meanwhile, the other three diets included SOLP of 2, 4, and 8 g kg−1 concentrations (SOLP2, SOLP4, and SOLP8), respectively. Findings demonstrated that fish fed SOLP4 and SOLP8 diets had better growth performance and improved digestion by noticeable enhancing lipase and amylase enzymes activity than other groups. Additionally, the antioxidant (superoxide dismutase and glutathione peroxidase) and immune activities (immunoglobulin M, nitric oxide, and antiprotease) clarified a significant increase (p < 0.05) in SOLP4 and SOLP8 groups. Enriched diets with SOLP4 and SOLP8 exhibited better expression of splenic genes (IL-1β, IL-6 , IL-10 , TLR-2 , and SOD), intestinal genes (Slc26a6) and (PepT1 or Slc15a1), and muscular genes (IGF-1 and SOD), while MSTN was down-regulated. After 8 weeks of the experimental trial, C. carpio challenged by A. sobria exhibited the highest cumulative mortality (66.67%), while SOLP8-dietary intervention showed the best results in enhancing the fish resistance against A. sobria by lessening mortalities to 13.33% followed by SOLP4 diet (20%). The outcomes indicate that the expression of splenic, muscular, and intestinal genes confirm the efficacy of SOLP on enhancing growth, digestion, and immune-antioxidant status, and recommend the potential use of SOLP especially at 4 g kg−1 level as a valuable natural economic diet additive in C. carpio culture for sustaining aquaculture. • Dietary Salvia officinalis leaves powder (SOLP) enhances growth and digestion in Cyprinus carpio. • Diet supplement with SOLP modulates antioxidant-immune-capacity. • Dietary intervention of SOLP enhances resistance against Aeromonas sobria infection. • A supplemented diet with SOLP up-regulates the expression of different genes. [ABSTRACT FROM AUTHOR]

The reduction of fishmeal in aquafeeds has been the concern of researchers. Replacing fishmeal with plant proteins affects intestinal function and inflammation, but the interaction between the intestinal responses and gut microbiota remains unclear. In this study, juvenile channel catfish (Ictalurus punctatus) was fed with four diets in which enzymatic rice protein (RP) replaced fishmeal at levels of 0 (FM), 2.5% (RP2.5), 5.0% (RP5.0), and 7.5% (RP7.5) for 8 weeks to solve the problem mentioned above. Quantification of intestinal morphology showed that 2.5% or 5.0% RP significantly increased villus length and goblet cell number, accompanied by higher activities of intestinal trypsin, alkaline phosphatase (AKP), and Na+/K+-ATPase (NKA) in RP2.5 group (P < 0.05). In contrast, 7.5% RP slightly damaged the intestinal mucosa and significantly reduced the activities of amylase, AKP, and NKA, as well as decreased serum complement 4 (C4) and immunoglobulin M (IgM). Noteworthy, RT-qPCR showed that 2.5% RP significantly down-regulated intestinal mRNA expression level of il8 , while up-regulated mif , tlr4 , tlr7 , tgfβ3 , and cldn2. In contrast, 7.5% RP up-regulated the mRNA expression levels of il1β , il8 , and mif , while down-regulated cldn3d. Analysis of gut microbiota showed that 2.5% RP increased the relative abundance of Bacteroidetes and significantly activated potential functions of gut microbiota involved in carbohydrate metabolism. The 7.5% RP increased the diversity of the gut microbiota, accompanied by a significant increase in the relative abundance of conditionally pathogenic bacteria such as Vibrio , Serratia , and Aeromonas (classified as Proteobacteria). Notably, Vibrio was the biomarker species with the greatest difference between the FM and RP7.5 groups (genus level). Correlation analysis indicated that Vibrio may affect immunity through the C4 pathway and further lead to gut inflammation and digestive impairment. Taken above, these results indicated that RP could affect intestinal morphology, digestion, and inflammation, and interact with the composition and potential function of gut microbiota. The low RP supplement (2.5%) improved intestinal morphology and digestion, while high supplement (7.5%) disrupted gut microbiota homeostasis, resulting in damage to intestinal mucosa and inflammatory response. • Replacing 2.5% of fishmeal with RP improved gut morphology and digestion. • The 7.5% RP supplement resulted in damaged intestinal mucosa, decreased digestion, and inflammatory responses. • The 7.5% RP induced gut inflammation by affecting the abundance and predicted function ofpathogenic bacteria. [ABSTRACT FROM AUTHOR]

Infectious pancreatic necrosis virus (IPNV), belonging to the genus Aquabirnavirus within the family Birnaviridae , causes huge economic loss to the global salmonid industry every year. Recently, outbreaks of disease caused by genogroup I IPNV were found in many rainbow trout (Oncorhynchus mykiss) farms worldwide. An inactivated vaccine was prepared using a genogroup I IPNV isolate with an optimized procedure as incubation with β-propanolactone (BPL) at the final concentration of 0.5% at room temperature for 48 h. The inactivated vaccine was used to immunize rainbow trout, and the protection efficiency was evaluated by viral loads determination, immune-related genes quantification, and neutralizing antibody tests. The viral loads in immunized rainbow trout were significantly decreased and the strongest antiviral effect was observed on 30 days post-immunization (d.p.i). The expression of innate immune-related genes IFN-1, and Mx-1 genes were significantly up-regulated on 3, 7, and 15 d.p.i (p < 0.05), and adaptive immune-related genes CD4, CD8, and IgM genes were significantly up-regulated on 15 and 30 d.p.i (p < 0.05). Neutralizing antibodies were firstly detected on 30 d.p.i and the highest titer was observed on 45 d.p.i, which began to decrease on 60 d.p.i, but was still significantly higher than that in negative control fish. The results indicated that the vaccine prepared in this study could stimulate the non-specific and specific immune response and provide significant immune protection to the vaccinated rainbow trout. • Genogroup I IPNV is causing huge economic loss to rainbow trout farming worldwide. • A promising inactivation scheme was established by using β-propanolactone (BPL). • An inactivated vaccine was prepared by using a genogroup I IPNV isolate. • The vaccine could provide immune protection to IPNV challenged rainbow trout. [ABSTRACT FROM AUTHOR]

The dinoflagellate Amyloodinium ocellatum is an important pathogenic parasite infecting cultured marine and brackish water fishes worldwide. This includes cultured Florida pompano (Trachinotus carolinus), which is one of the most desirable marine food fish with high economic value in the USA. A. ocellatum infects fish gills and causes tissue damage, increased respiratory rate, reduced appetite, and mortality, especially in closed aquaculture systems. This study mimicked the natural infection of A. ocellatum in cultured pompano and conducted a transcriptomic comparison of gene expression in the gills of control and A. ocellatum infected fish to explore the molecular mechanisms of infection. RNA-seq data revealed 604 differentially expressed genes in the infected fish gills. The immunoglobulin genes (including IgM/T) augmentation and IL1 inflammation suppression were detected after infection. Genes involved in reactive oxygen species mediating parasite killing were also highly induced. However, excessive oxidants have been linked to oxidative tissue damage and apoptosis. Correspondingly, widespread down-regulation of collagen genes and growth factor deprivation indicated impaired tissue repair, and meanwhile the key executor of apoptosis, caspase-3 was highly expressed (25.02-fold) in infected fish. The infection also influenced the respiratory gas sensing and transport genes and established hypoxic conditions in the gill tissue. Additionally, food intake and lipid metabolism were also affected. Our work provides the transcriptome sequencing of Florida pompano and provides key insights into the acute pathogenesis of A. ocellatum. This information can be utilized for designing optimal disease surveillance strategies, future selection for host resistance, and development of novel therapeutic measures. • Transcriptomes of Florida pompano gills after A. ocellatum infection. • IL1 suppression and antibody augmentation were detected in infected fish. • Infection caused oxidative stress, tissue damage and apoptosis in pompano gills. [ABSTRACT FROM AUTHOR]

The coastal aquaculture is characterized with environmental salinity fluctuation, and the effects of salinity stress on the immunity of cultured fish are needed to be further explored. Scatophagus argus is an important species in the wild fisheries and aquaculture industry, it would be of great value to reveal the impact of salinity change on the immune response in this species. Understanding the effects of salinity stress on immune response can provide valuable insights into salinity management in the aquacultural process. The head kidney, which is an organ unique for teleost fish, functions not only as a central immune organ but also as a crucial role in the stress response during which the secretion of immunoregulatory molecules i.e. cytokines is facilitated. In the present study, Individuals of S. argus acclimated to 3 different salinities [0‰ (FW), 10‰ (BW), and 25‰ (SW)] were injected intraperitoneally with A. hydrophila , and then monitored throughout one week. The effects of environmental salinity on the immune response in S. argus stimulated by A. hydrophila infection were investigated. mRNA expression profiles of cytokine genes IL-1β, IL-6, IL-10 and TNF-α in different salinity groups was quite different. mRNA expression of cytokine genes in BW group and SW group rose more quickly and significantly higher than FW group (p < 0.05) at early stages (6–24 hpi) after bacterial injection, and before 96 hpi, the highest value of cytokine expression at each time point was recorded in SW group. Immune parameters such as lysozyme level, complement C3 activity and IgM content in BW and FW groups were lower than SW group at each time point from 24 to 144 hpi after bacterial injection. In addition, leukocyte profiles in the head kidney and blood were also investigated. Although hypoosmotic acclimation could temporarily stimulate monocyte and neutrophil proliferation, it was observed that the number of monocytes, neutrophils and lymphocytes of the head kidney and blood in SW group increased more quickly than BW and FW groups after bacterial infection. Our results indicate that hypoosmotic stress due to the decrease of environmental salinity has suppressive immunoregulatory effects on the immune response of S. argus. • mRNA expression levels of cytokines in the head kidney of S. argus were impacted by environmental salinity change. • Salinity treatments affected immune parameters after bacterial injection. • Environmental salinity changes influenced leukocyte profiles in the head kidney and blood of S. argus. • Hypoosmotic stress has suppressive immunoregulatory effects on the immune response of S. argus. [ABSTRACT FROM AUTHOR]

Currently, the intervention of plant by-products in the fish diet has gained tremendous attention owing to the economic and high nutritious value. The current study is a pioneer attempt to incorporate the apricot, Prunus armeniaca kernel powder (PAKP) into the Common carp, Cyprinus carpio diets, and assess its efficacy on growth, digestion, intestinal morphology, immunity, antioxidant capacity, and splenic cytokines expression, besides the antibacterial role against Aeromonas veronii infection. Apparently healthy fish (N = 120) with an initial body weight of 24.76 ± 0.03g were allotted in 12 glass aquaria (60 L) and randomly distributed into four groups (triplicates, 10 fish/aquarium). The control group (PAKP0) was fed a basal diet without additives. The second, third, and fourth groups were provided PAKP diets with various concentrations (2.5 (PAKP2.5), 5 (PAKP5), and 10 g kg−1 (PAKP10)) respectively. After 60 days (feeding trial), sub-samples of the fish (12 fish/group) were intraperitoneally injected with 1 × 107 CFU mL−1 of A. veronii. Results revealed that body weight gain, feed conversion ratio, and specific growth rates were significantly augmented in the PAKP10 group in comparison to the other groups. The dietary inclusion of PAKP at all concentrations boosted the digestive capacity and maintained the intestinal morphology (average villus length, villus width, and goblet cells count) with a marked improvement in PAKP10. Moreover, fish fed on PAKP10 followed by PAKP5 then PAKP2.5 diets had noticeably elevated values of immunological biomarkers (IgM, antiprotease, and lysozyme activity) and antioxidant capabilities (the total antioxidant capacity, superoxide dismutase, and reduced glutathione) as well as significant up-regulation of immune and antioxidant-related genes (TGF-β2 , TLR-2 , TNF-α , IL-10 , SOD , GPx , and GSS). Fourteen days post-infection with A. veronii , the highest relative percentage survival of fish was observed in PAKP10 (83.33%), followed by PAKP5 (66.67%), and PAKP2.5 (50%). Our results indicated that a dietary intervention with PAKP could promise growth, digestion, immunity, and protect C. carpio against A. veronii infection in a dose-dependent manner. This offers a framework for future application of such seeds as a growth promotor, immune-stimulant, and antioxidant, besides an alternative cheap therapeutic antibacterial agent for sustaining the aquaculture industry. • Prunus armeniaca kernel powder (PAKP) diet inclusion improved growth performance of C. carpio. • Diet supplement with PAKP enhanced digestion and intestinal architecture. • Dietary PAKP induced an immune-antioxidant indices and genes expression augmentation. • PAKP enhanced the resistance against Aeromonas veronii infection in C. carpio. [ABSTRACT FROM AUTHOR]

The impact of dietary supplementation with silk fibroin (SF) microparticles on the wound healing process in gilthead seabream (Sparus aurata) skin was studied. A control diet was enriched with different SF levels: 0 (control), 50 (SF50 diet), and 100 (SF100 diet) mg Kg−1 to form three experimental diets and was fed to seabream for 30 days. Experimental wounds were performed and after 7 days post-wounding (dpw) skin mucus immunity, macroscopic wound closure, and skin regeneration were studied at a microscopic and genetic level. Results indicated that fish fed SF100 did not suffer the decreases in protease and IgM levels observed in the skin mucus of wounded fish fed with the control diet. Macroscopic findings illustrated that dietary SF100 significantly improved the wound closure ratio compared to those reared in the control group. At a microscopic level, changes in the shape of keratocyte cells were evident in the wounded fish. In addition, the intercellular spaces present between epidermal cells and their proliferation in the epidermis, as well as the presence of blood vessels in the dermis were significantly statistically higher in the skin of fish fed the SF100 diet and sampled at 7 dpw compared to those observed in the skin of fish fed the control or SF50 diets. Moreover, regarding the RNA: DNA ratio, statistically significant increases and decreases were observed in fish fed the control and SF100 diet, respectively, in non-wounded and wounded fish. Interestingly, dietary SF100 supplementation improved skin cell proliferation, enhanced the inflammatory phase, and increased the expression of important genes involved in tissue repair and extracellular matrix formation. In conclusion, the SF100 diet can be considered as an appropriate feed additive to improve wound healing in gilthead seabream. [Display omitted] • The impacts of dietary supplementation with silk fibroin microparticles (SF) on the skin wound healing process were studied. • The macroscopic wound closure and the skin regeneration at a microscopic and genetic level were studied. • At microscopic levels, changes in the keratocyte cells shape were evident in wounded fish. • Dietary SF100 supplementation improved the skin cell proliferation and enhanced the inflammatory phase. [ABSTRACT FROM AUTHOR]

Bacillus spp. are well known for their probiotic properties. Hence, the long-term feeding of Bacillus spp. strains to different fish species has been proved to confer beneficial effects regarding growth or pathogen resistance, among others. However, whether these strains could function as mucosal adjuvants, up-regulating immune responses after a single administration, has not yet been investigated in fish. Thus, in the current work, we have performed a series of experiments in rainbow trout (Oncorhynchus mykiss) aimed at establishing the potential of two Bacillus subtilis spore-forming strains, designated as ABP1 and ABP2, as oral adjuvants/immunostimulants. As an initial step, we evaluated their transcriptional effects on the rainbow trout intestinal epithelial cell line RTgutGC, and in gut tissue explants incubated ex vivo with the two strains. Their capacity to adhere to RTgutGC cells was also evaluated by flow cytometry. Although both strains had the capacity to modulate the transcription of several genes related to innate and adaptive immune responses, it was the ABP1 strain that led to stronger transcriptional effects, also exerting a higher binding capacity to intestinal epithelial cells. Consequently, we selected this strain to establish its effects on splenic B cells upon in vitro exposure as well as to determine the transcriptional effects exerted in the spleen, kidney, and gut after a single oral administration of the bacteria. Our results showed that B. subtilis ABP1 had the capacity to modulate the proliferation, IgM secreting capacity and MHC II surface expression of splenic B cells. Finally, we confirmed that this strain also induced the transcription of genes involved in inflammation, antimicrobial genes, and genes involved in T cell responses upon a single oral administration. Our results provide valuable information regarding how B. subtilis modulates the immune response of rainbow trout, pointing to the usefulness of the ABP1 strain to design novel oral vaccination strategies for aquaculture. • Bacillus subtilis regulates the transcription of many immune genes in epithelial cells and gut explants. • B. subtilis ABP1 strain has a higher adhesive capacity to trout intestinal epithelial cells than the ABP2 strain. • B. subtilis ABP1 increased the proliferation, IgM secreting capacity and MHC II surface expression of splenic B cells. • A single oral administration of ABP1 affected the transcription of a wide range of immune genes locally and systematically. [ABSTRACT FROM AUTHOR]

The phagocytic actives of B cells in fish have been proven in recent years. In this study, five positive hybridomas secreting monoclonal antibodies (MAbs) against largemouth bass IgM were produced. Indirect immunofluorescence assay (IFA) demonstrated that five MAbs could specifically recognize membrane-bound IgM (mIgM) molecule of largemouth bass. Indirect ELISA and Western blotting analysis showed that all the five MAbs had no cross-reactions with the other two teleost IgMs. Flow cytometry analysis (FCM) revealed that the percentages of largemouth bass mIgM+ lymphocytes in head kidney, peripheral blood and spleen were 51.66 ± 0.608%, 16.5 ± 1.235% and 42.92 ± 1.091%, respectively. In addition, the phagocytosis rates of mIgM + lymphocytes ingesting Nocardia seriolae from head kidney, peripheral blood and spleen were calculated to be 5.413 ± 0.274%, 16.6 ± 0.289% and 26.3 ± 0.296%, respectively. The qPCR results of sorted cells indicated that most inflammatory cytokines (IFNγ, IL-1β, IL-2, IL-12β, IL-34, IL-10) , chemokine (CXCL12), chemokines receptors (CXCR2, CXCR4) and genes (FcγRⅠa, NCF1, CFL, ARP2/3, CD45, Syk, MARCKS) related to FcγR-mediated phagocytic signaling pathway in phagocytic mIgM+ lymphocytes were up-regulated significantly (P < 0.05). Taken together, the results suggested that the MAb (MM06H) produced in this paper could be used as a tool to study mIgM+ lymphocytes of largemouth bass, and FcγR may participate in the phagocytosis of mIgM+ lymphocytes, which is helpful to further study the role of mIgM+ lymphocytes in innate immunity. • Monoclonal antibodies against Micropterus salmoides were produced. • The phagocytosis of mIgM+ lymphocytes from largemouth bass was validated. • 33 immune-related genes of sorted phagocytic mIgM+ lymphocytes were up-regulated. • FcγR-mediated phagocytosis pathway may participate in the phagocytosis of mIgM+ lymphocytes. [ABSTRACT FROM AUTHOR]

Paeonol, a naturally occurring polyphenol isolated from medical plant, has been known to exhibit anti-oxidative and anti-inflammatory effects. In order to evaluate the effect of paeonol on Carassius auratus gibelio infected by pathogenic bacteria Aeromonas hydriphila. 750 fish were randomly divided into 5 groups, which separately treated with 0.85% sterile saline (blank), A. hydriphila (negative control), A. hydriphila with paeonol (4 mg/kg, 64 mg/kg), and A. hydriphila with enrofloxacin (12 mg/kg, positive control). Fish were anaesthetized with MS-222 (100 mg/L), and samples were collected at 6 and 72 h after A. hydriphila challenge. The results showed that compared with the negative group, the survival in paeonol groups marked increased by 14.75% and 18.94%. The plasma immunoglobulin M (IgM) was notably increased, and low density lipoprotein (LDL) was significantly decreased in paeonol groups at 6 h (P < 0.05). The antioxidative enzymes catalase (CAT), total antioxidant capacity (T-AOC) and glutathione peroxidase (GSH-Px) were significantly increased in paeonol groups at 6 h, while malondialdehyde (MDA) and myeloperoxidase (MPO) contents were lower (P < 0.05). The inflammatory related genes MyD88 and TLR-5 were significantly downregulated, and the TLR-3 was significantly increased in paeonol groups at 72 h (P < 0.05). In addition, histopathological analyses showed that the lesion in liver, spleen and caudal kidney were considerably attenuated in paeonol groups. In conclusion, paeonol could increase the survival rate, mitigate oxidative damage, inflammation, tissue lesions, and improve the immunity of gibel carp challenged with A. hydrophila. [Display omitted] • Paeonol enhanced antioxidant and anti-inflammatory ability challenged with A. hydrophila. • Paeonol attenuated liver, spleen and caudal kidney lesions challenged with A. hydrophila. • Paeonol increased the survival of Carassius auratus gibelio challenged with A. hydrophila. [ABSTRACT FROM AUTHOR]

In aquatic animals, dietary protein plays a crucial role in their growth and immunity. A feeding trial was conducted on soft-shelled turtles (Pelodiscus sinensis) to assess the effects of various levels of protein on the specific growth rate (SGR), ambient water quality (total ammonia nitrogen (TAN), total nitrogen (TN) and total phosphorus (TP)), hematological parameters (respiratory burst (RB), red blood cell count (RBC), albumin content (Alb), hemoglobin level (Hb) and osmolality), plasma immunoglobulin M (IgM) levels and lysozyme activity. Soft-shelled turtles weighing about 4.02 g were fed fish meal-based diets with 14.38%, 20.41%, 26.19%, 32.23%, 37.63% and 45.23% protein for 8 weeks. SGR, RBC, Hb, Alb, RB, IgM and lysozyme activity were enhanced as the dietary protein was increased from 14.38% to 26.19%, then reached a plateau. For identical feeding times, TAN and TN were increased with elevating dietary protein levels. While, no statistically significant differences were observed among the 26.19%, 32.23% and 37.63% groups. When the turtles were cultivated for 56 days and fed with 45.23% protein, the TP in the culturing water was higher than that in the other groups. An increase in dietary protein level up to 26.19% increased the RNA/DNA ratio, which subsequently plateaued at a steady level. The levels of dietary protein had no impact on osmolality or alkaline phosphatase (AKP) activity. On the basis of broken-line analyses derived from SGR, the optimum dietary protein level for soft-shelled turtles was found to be 27.11% protein. • Optimum dietary protein level for soft-shell turtles was 27.11% protein, based on broken-line analyses derived from SGR. • Optimum protein level improved the specific growth rate. • Optimum protein level enhanced hematological indicators (respiratory burst, red blood cells, albumin, and hemoglobin). • Optimum protein level increased Ig M, lysozyme activity, and the RNA/DNA ratio. • Total ammonia nitrogen and total nitrogen were elevated with increasing dietary protein levels. [ABSTRACT FROM AUTHOR]

Fish stress is a major concern in the aquaculture industry. Many stressors coming from routine practices can predispose fish to compromised growth, immunity and overall health. This study focuses on the characterization of the skin microbiota using next generation sequencing (NGS) platform by targeting a genomic marker 16S and to determine growth performance and immune status of gilthead seabream (Sparus aurata) during an episode of chronic stress. Two groups were established: control group and chronically stressed group. Stressed fish were subjected to 1 min air exposure twice a week for 4 weeks. Results showed that stress negatively affected fish growth performance. Cellular and humoral systemic immunity remained unaffected while local immunity in skin was positively stimulated (total IgM and peroxidase). Skin mucus microbial composition showed significant differences especially after 14 days. Stressed fish showed a decrease in the abundance of the genera Acinetobacter , NS3a_marine_group and Pseudomonas , while Pseudoalteromonas and Marinagarivorans increased significantly. In conclusion, air exposure stress was associated with alterations in skin mucosal immunity and microbial composition that may have been beneficial to the host favoring adaptation to stress. [Display omitted] • Gilthead seabream growth performance, immunity and skin mucus microbiota were studied during an episode of chronic stress. • A negative impact in growth performance was observed in stressed fish. • No statistically significant differences were observed in systemic immunity between control and stressed fish. • Significant differences were obtained in skin immunity and microbial communities especially after 14 days of trial. • The observed alterations in the skin immunity and microbiota may be beneficial for stress adaptation. [ABSTRACT FROM AUTHOR]

In response to the invasion of exogenous microorganisms, one of the defence strategies of the immune system is to produce antibodies. Cartilaginous fish is among those who evolved the earliest humoral immune system that utilizes immunoglobulin-type antibodies. The cartilaginous fish antibodies fall into three categories: IgW, IgM, and IgNAR. The shark Immunoglobulin Novel Antigen Receptor (IgNAR) constitutes disulfide-bonded dimers of two protein chains, similar to the heavy chain of mammalian IgGs. Shark IgNAR is the primary antibody of a shark's adaptive immune system with a serum concentration of 0.1–1.0 mg/mL. Its structure comprises of one variable (V) domain (VNAR) and five constant (C1 –C5) domains in the secretory form. VNARs are classified into several subclasses based on specific properties such as the quantity and position of additional non-canonical cysteine (Cys) residues in the VNAR. The VDJ recombination in IgNAR comprises various fragments; one variable component, three diverse sections, one joining portion, and a solitary arrangement of constant fragments framed in each IgNAR gene cluster. The re-arrangement happens just inside this gene cluster bringing about a VD1D2D3J segment. Therefore, four re-arrangement procedures create the entire VNAR space. IgNAR antibody can serve as an excellent diagnostic, therapeutic, and research tool because it has a smaller size, high specificity for antigen-binding, and perfect stability. The domain characterization, structural features, types, diversity and therapeutic applications of IgNAR molecules are highlighted in this review. It would be helpful for further research on IgNAR antibodies acting as an essential constituent of the adaptive immune system and a potential therapeutic agent. • Cartilaginous fish antibodies, namely IgW, IgM, IgNAR, are reviewed. • The molecular properties of VNARs, including domain organization, structural features are summarized. • VNAR shuttles are excellent candidates for therapeutic development against neurodegenerative diseases. • New therapeutic approaches have been aimed to design SARS-COV-2 neutralizing VNAR antibodies. [ABSTRACT FROM AUTHOR]

This study was conducted to investigate the effect of figwort on the growth and immunohematological parameters of common carp (14.20 ± 0.53 g). Four experimental diets were developed to feed fish for eight weeks: control, Figw10 (10 g/kg figwort), Figw20 (20 g/kg figwort), and Figw30 (30 g/kg figwort). The results showed that fish fed dietary Figw10 gained more weight (38.25 g) than control (P < 0.05). Regarding immunohematological parameters, fish fed dietary Figw30 had a higher level of white blood cells (31.2 103/mm3), hematocrit (35.82%), blood performance (14.63), total protein (1.96 g/dL), albumin (0.79 g/dL), globulin (1.17 g/dL), lymphocyte (70.53%), monocyte (3.03%), alternative hemolytic complement activity (ACH50) (147.76 u/mL), lysozyme (62.19 u/mL), and bactericidal activities (135.24) than the control group (P < 0.05). After 14 days of the challenge with Aeromonas hydrophila, the Figw30 treatment had the highest survival ratio (61.76%) compared to the control with 26.46%. Further, after the challenge, fish fed dietary Figw30 had a higher value of immunoglobulin M (42.00 μg/mL), antibody titer (19.23), complement component 3 (296.39 μg/mL), and complement component 4 (97.91 μg/mL) when compared with those fed control diet (P < 0.05). In conclusion, the optimum dosage for providing the best immune response was 30 g/kg in diet. • The first report of immunostimulatory and antibacterial effects of figwort. • Dietary Figw10 improved growth while Figw30 remarkably improved immunohematology. • In vivo and in vitro tests show that figwort has potent antibacterial properties. [ABSTRACT FROM AUTHOR]

Recently, nanotechnology has been greatly developed to provide the aquaculture industry with new beneficial nanomaterials to improve the health and welfare of aquatic animals. Herein, an eight-week experiment was designed to examine the dietary impacts of sodium butyrate nanoparticles (SB-NPs) on the hematological profile, blood proteins, immunological indices, antioxidant capacity, and expression analysis of cytokines and antioxidant-related genes in Oreochromis niloticus. Fish were randomly assigned into 5 experimental groups (3 replicates per group) and were fed diets supplemented with 5 levels of SB-NPs as 0.0 (control), 0.5, 1.0, 1.5, and 2.0 mg kg−1. The results revealed that supplementing diets with SB-NPs (1.0–2.0 mg kg−1) significantly elevated erythrocyte and leukocyte counts, hemoglobin concentrations, hematocrit values, total albumin, globulin, serum lysozyme activities, and total immunoglobulin M values compared with the control group. Notably, the highest levels of the parameters mentioned above were noticed in the group fed diet supplemented with 1.5 mg kg−1 SB-NPs. Moreover, dietary SB-NPs modulated the fish's antioxidant defense mechanisms, whereas there was a significant increase in hepatic superoxide dismutase, catalase, and glutathione peroxidase enzyme activities along with a significant decline in hepatic malondialdehyde concentrations in fish groups fed diets supplemented with SB-NPs (1.0–2.0 mg kg−1). A significant upregulation of antioxidant enzyme genes (gpx and sod), anti-inflammatory cytokine (il-10), and pro-inflammatory cytokines (il-1β and il-8) were noticed in liver tissues of SB-NPs groups (0.5–1.5 mg kg−1). The highest mRNA expression folds of the above genes were recorded in the fish group fed diet supplemented with 1.5 mg kg−1 SB-NPs. In this context, we hypothesized that dietary supplementation with SB-NPs can boost the antioxidant status and immunity of O. niloticus. However, further research studies are still recommended. • Several levels of sodium butyrate nanoparticles (SB-NPs) have been included in diets of Nile tilapia. • Dietary SB-NPs increased the serum lysozyme, total IgM, and hepatic antioxidant enzymes. • SB-NPs increased the expression of hepatic cytokines (il-1β , il-8 , and il-10) and antioxidant-related genes (gpx and sod). [ABSTRACT FROM AUTHOR]

Quantification of specific antibody responses is critical in determining activation of MHCII-dependent immune memory and is generally performed by enzyme-linked immunosorbent assay (ELISA). Antibody avidity for a particular antigen is also informative of the quality of the adaptive immune response following vaccination. Avidity can be determined by chaotropic elution ELISA, pre-absorption ELISA, or surface plasmon resonance (SPR), although multimeric antibodies such as IgM are problematic for SPR. ELISA-based assays are very time consuming, require secondary antibody reagents, and are poorly repeatable. Here we demonstrate that biolayer interferometry (BLI) using an Octet HTX instrument can robustly and reproducibly quantify and determine avidity of specific IgM for an antigen directly from fish serum in a single step. We collected sera from giant grouper (Epinephelus lanceolatus) that had been vaccinated with the hapten 2,4-dinitrophenol conjugated to keyhole limpet hemocyanin (DNP-KLH) and from control fish injected with phosphate buffered saline. The specific IgM in the serum and its avidity for DNP were quantified via ELISA and BLI. BLI was precise and highly repeatable for determination of the quantity and avidity of antibody in the serum compared to ELISA. The wet-lab preparation and machine running time for BLI was 3–5 times faster than ELISA to generate the same amount of data. The ELISA inter-plate variation significantly affected reproducibility while BLI was consistent and repeatable between samples and plates. Indeed, the consistency of BLI data indicated that technical triplicates were redundant. Biological replication alone was sufficient to elucidate the effect of treatments. However, BLI required a lower serum dilution than ELISA for similar sensitivity, and thus more serum was required to produce high resolution data. BLI is an extremely high-throughput assay, providing teleost serum IgM quantification and avidity data as a single-step, agile alternative to ELISA. • BLI measures fish serum IgM quantity and avidity in a single step assay. • Antibody data generated are comparable between BLI and ELISA. • BLI has much higher throughput than ELISA and data is remarkably consistent. • BLI can replace ELISA in determining fish serum IgM quantity and avidity. [ABSTRACT FROM AUTHOR]

Seven immune factors, lysozyme, hepcidin, heat-shock protein (HSP) 70, HSP90, immunoglobulin M, C-type lectin, and Lily-type lectin, were measured by PCR in the livers, spleens, and head kidneys of turbot infected with Vibrio anguillarum. Additive main effects and multiplicative interaction (AMMI) and genotype main effects and genotype × environment interaction (GGE) biplot analysis were used to analyze genotype × tissue interactions for immunological factors. The AMMI analysis revealed that immune factor expression was significantly affected by genotype, tissue, and genotype × tissue interactions. Genotype (65.85%) was the major contributor to the total variation in immune factor expression in comparison to tissue effects (7.54%) and genotype × tissue interactions (12.52%). GGE biplot analysis revealed differences in the ranking of the seven immune factors in the three tissues; head kidney possessed the strongest ability to distinguish the seven immune factors. The test tissue locations were divided into liver-spleen and head kidneys regions; HSP70 was expressed the highest in the liver-spleen regions, and lysozyme had the highest expression in the head kidney region. Overall, HSP70 and HSP90 had the best expression and stability in the three tissues. • Genotype was the major contributor to the total variation in immune factor expression. • HSP70 and lysozyme had the highest expression in the liver-spleen region and the head kidney region, respectively. • HSP70 and HSP90 would be the preferred breeding index. [ABSTRACT FROM AUTHOR]

The need for accurate assessments of in vitro generated antibody prompted examination of the effect of antigen on secreted antibody concentrations and affinities. It was found that the antigen concentrations commonly employed for in vitro stimulation were able to significantly compromise IgM titer and affinity estimates in rainbow trout. Specifically, IgM titers were underestimated with the high affinity antibodies being specifically blocked. To remedy this, pulsed antigen cultures were employed, and it was found to reveal more accurate IgM antibody titers and affinity estimates. Additionally, pulsed dose responses provided evidence that high antigen concentrations specifically suppressed high affinity B cell induction. Optimal expression of high affinity antibodies required exposure to lower concentrations of antigen. Each affinity subpopulation appeared to possess a graded sensitivity to each dose of antigen, revealing the complex dynamic for differential IgM-bearing B cell induction that is possible during a response. These results reveal not only the need for antigen removal prior to in vitro antibody secretion, but also the possible role of high zone immunological tolerance on IgM affinity maturation in rainbow trout. • Antigens commonly employed for in vitro stimulation significantly compromised IgM titer and affinity estimates in trout. • Employment of pulsed antigen in vitro cultures was found to reveal more accurate IgM titers and affinity estimates. • Differential antigen sensitivity of IgM affinity subpopulations indicated high zone immunological tolerance in trout. [ABSTRACT FROM AUTHOR]

Interleukin-1β is a key pro-inflammatory cytokine functioning in initiation of inflammatory responses against bacterial- and viral-infections. In the present study, a putative IL-1β counterpart was identified from Siberian sturgeon (Acipenser baeri) and designated as AbIL-1β. The Abil-1β cDNA sequence consists of 1130 bp with an open reading frame (ORF) of 585 bp, which encodes a 194 amino acid (aa) protein. Multiple amino acid sequence alignment revealed that a possible mature peptide could start at Leu18, although no cut site for ICE (IL-1β converting enzyme) enzyme was present in Siberian sturgeon IL-1β. Even if AbIL-1β shares a relative low identity (33.6%) with another sturgeon type II IL-1β gene from Acipenser dabryanus , they still clustered together in phylogenetic tree. Endogenous Abil-1β was highly expressed in brain, blood, head kidney and spleen of healthy Siberian sturgeon, and remarkably up regulated in head kidney, spleen, and liver upon Aeromonas hydrophila (A.h) challenge. Consistently, in vitro stimulation test using heat-killed A.h and LPS significantly increased Abil-1β transcripts of primary spleen cells. To investigate the bactericidal capability of AbIL-1β, recombinant AbIL-1β (rAbIL-1β) was generated by prokaryotes. Pre-injection of rAbIL-1β reduced the bacterial load in sturgeon spleen after A.h infection. Further, rAbIL-1β was served as feed additive and demonstrated to enhance hybrid sturgeon's defense against A.h infection by increased expressional levels of immune-related genes (IL-1β , IL-6 , IL-8 , IgM and MHCIIβ), elevated activities of serum lysosome, ACH50, and MPO, as well as higher percent survival. In summary, the current results suggested that AbIL-1β functions in immune regulation and could improve sturgeon's resistance to bacterial infection. • A novel sturgeon Interleukin-1β homologue was characterized and prokaryotically expressed from Siberian sturgeon. • Abil-1β was highly expressed in brain, blood, head kidney, spleen, and up-regulated by bacteria A. hydrophila infection. • Abil-1β in spleen cells responded to in vitro inactivated A.h and LPS stimulants. • Intraperitoneal injection of rAbIL-1β reduced the tissue bacterial loads of sturgeon from A.h infection. • Dietary rAbIL-1β additive enhanced hybrid sturgeon's defense against A.h infection. [ABSTRACT FROM AUTHOR]

The association of vaccines with immunostimulants such as β-glucan, promote the production of cytokines, competent immune cells and antibodies. However, differences between β-glucan types and trials make it difficult to understand β-glucan's mechanism of action. In this study, three trials were carried out with control and fish fed β-glucan, the first trial occurred at 15 days; the second trial occurred at 30 days when we associated β-glucan and vaccine; and the third trial occurred at 15 days post-challenge with Streptococcus agalactiae in tilapia (O. niloticus) in order to investigate immune-related gene expression in the head kidney and spleen using real-time qPCR. We found increases in HSP70, IL-6, IL-1β, TNF-α, IL-10, Lys and C3 predominantly in the head kidney, except for IgM expression, which prevailed in the spleen, under vaccinated + β-glucan action. This demonstrates the trade-off presented by the head kidney and spleen after immunostimulation in order to produce acquired immunity, as well as an increase in HSP70 expression in vaccinated + β-glucan fish. The results suggest that β-glucan stimulates the immune response through damage-associated molecular patterns (DAMPs) recognition. Therefore, these dynamics of the immune response promote a more robust defense against disease. • β-glucan stimulates the immune response through damage-associated molecular pattern (DAMPs) recognition. • β-glucan and vaccines generate a trade-off between head kidney and spleen to produce acquired immunity. • β-glucan and vaccine associations prompt more expressive and prolonged response in head kidney than in the spleen. • β-glucan prompts stronger responses for vaccine antigen recognition and consequently better response to immunization. • β-glucan prompts immune responses after at least 15 days of administration. [ABSTRACT FROM AUTHOR]

The effect of cinnamaldehyde (CM) enriched diet on immunity and cytokine gene expression in Channa striatus against Aphanomyces invadans is reported. C. striatus was uniformly divided into eight groups (n = 25 fish each) and fed with formulated diets with 0, 5, 10, and 15 mg kg−1 CM enriched diet. In healthy and infected groups fed with 5 mg kg−1 diet the leukocytes count increased significantly after 4th week; with 10 mg kg−1 CM diet the increase manifested after 6th week, but with 15 mg kg−1 not even after 8th week. In both groups, 5 mg kg−1 CM diet resulted in a significant increase in the serum total protein, albumin, and globulin levels after 4th week, whereas with other diets this effect was observed only after 6th week. Similarly, with any enriched diet the lysozyme activity increased significantly, but with 15 mg kg−1 CM diet only after 6th week. In both groups the complement activity and lymphocyte production increased significantly when fed with 5 mg kg−1 CM diet after 4th week while with other enriched diets only after 6th week. The phagocytic activity increased significantly in both groups fed with 5 mg kg−1 CM diet after 6th week, whereas the SOD activity increased after 4th week. The IgM production increased significantly in both groups fed with 5 mg kg−1 CM diet after 2nd week, while with 5 and 10 mg kg−1 CM diet after 4th week. In both groups, the expression of CXCR3α was significant on 4th week when fed with 10 mg kg−1 CM diet, while in the healthy group fed with 15 mg kg−1 CM diet the expression manifested earlier than 4th week. However, when fed with 10 and 15 mg kg−1 CM diets the increase was observed on 6th week; whereas, the expression of MHC-I reached the maximum on 6th week with any enriched diet. The results indicate that in C. striatus the innate immunity and expression of cytokine and immune related genes were significantly modulated when fed with 5 mg kg−1 CM diet on 4th week against A. invadans. • Cinnamaldehyde (CM) 5 mg kg−1 significantly enhanced haematological and biological parameters. • Supplementation of 5 mg kg−1 CM significantly improved innate immune of C. striatus. • Chemokine genes were up-regulation in fish fed 5 mg kg−1 CM. [ABSTRACT FROM AUTHOR]

This study was designed to evaluate the impacts of dietary supplementation with Ginkgo biloba leaf extract (GBL) on the growth, intestinal histomorphometry, immunity, antioxidant status, and expression of cytokine genes in Nile tilapia reared in the hapas. A control diet was enriched with different GBL levels (0.0, 5.0, 7.0, and 9.0 g/kg) to form 4 experimental diets and were fed to Nile tilapia for 8 weeks. The findings illustrated that dietary GBL significantly enhanced the growth and feed utilization indices compared to those reared in the control group. A dose-dependent increase of hepatic catalase, superoxide dismutase, and glutathione peroxidase activities alongside a decline of hepatic malondialdehyde levels were recorded in GBL groups compared with the control. Serum lysozyme activity, complement C3, and immunoglobulin M levels were significantly increased in GBL groups compared with the control group. Moreover, dietary GBL maintained the normal intestinal and hepatopancreatic histological structures with a significant increase of some histomorphometric measurements of proximal, middle, and distal intestinal parts of the treated fish. Interestingly, dietary GBL supplementation significantly increased the mRNA expression of interleukin-1 beta (IL-1β), IL-6 , IL-10 , tumor necrosis factor alpha (TNF-α) and interferon gamma (INF-γ) genes in the splenic tissues of treated fish over the control group. To conclude, it could be recommended to use GBL as a functional phytogenic feed additive to improve the growth, hepatic and intestinal health status, hepatic antioxidant status, and immunity of treated Nile tilapia. Besides, the second order polynomial regression revealed that 7.50 g GBL/kg diet is the optimal inclusion level to improve growth with no negative impacts on the overall health condition of treated Nile tilapia. • Ginkgo biloba leaf extract (GBL) improved the growth and feed utilization in hapa-reared Nile tilapia. • The optimal dietary supplementation of GBL was 7.5 g/kg diet for maximum growth rates. • Dietary GBL enhanced the immunity and hepatic antioxidant capacity. • GBL upregulated expression of splenic IL-1β , IL-6 , IL-10 , TNF-α , and INF-γ genes. • GBL maintained normal hepatopancreatic and intestinal histology, and improved intestinal morphometry. [ABSTRACT FROM AUTHOR]

The polymeric immunoglobulin receptor (pIgR) plays an important role in mediating the transcytosis of polymeric immunoglobulins (pIgs) to protect organisms against pathogen invasion. Here, a polyclonal antibody against grass carp (Ctenopharyngodon idellus) recombinant pIgR was developed by immunizing New Zealand white rabbit, and the responses of pIgR, IgM and IgZ were analyzed after bath immunization and intraperitoneal administration with Flavobacterium columnare. The results showed that pIgR transcription level was similar to IgM and IgZ, but pIgR rose much faster and peaked earlier than IgM and IgZ ; the pIgR mRNA levels were higher in the skin and spleen for both immunized groups, while IgM and IgZ mRNA expression were higher in skin, gills, and intestines in bath immersion group, or spleen and head kidney in intraperitoneal immunization group. ELISA revealed that the IgM, IgZ and pIgR protein levels were up-regulated in skin mucus, gill mucus, gut mucus and bile, reaching a higher peak level earlier in skin mucus and gill mucus in bath immersion group, but a higher peak level in bile in injection group. Moreover, secretory component molecules were detected in grass carp's skin, gill and intestine mucus and bile, but not in serum, which molecular mass was near the theoretical mass obtained from the sequence of grass carp pIgR. These results demonstrated that bath and intraperitoneal immunization up-regulated pIgR and secretory Ig expression in secretions, which provided more insights into the role of pIgR in immunity and offer insight into ways of protecting teleost against pathogen invasion. • The polyclonal antibody specifically reacting with rpIgR was developed. • The pIgR transcription level rose much faster and peaked earlier than IgM and IgZ. • The IgM, IgZ and pIgR protein levels were up-regulated in skin, gill and gut mucus and bile. • SC molecules were detected in mucus and bile but not in serum. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effects of dietary bile acids (BAs) on intestinal healthy status of tongue sole in terms of immunity, antioxidant status, digestive ability, mucosal barrier-related genes expression and microbiota. Three experimental diets were prepared with BA levels at 0 mg/kg (CT), 300 mg/kg (BA1) and 900 mg/kg (BA2) in a commercial basal diet. Each diet was fed to three replicates with 120 fish (10.87 ± 0.32 g) in each tank. After an 8-week feeding trial, growth parameters were significantly enhanced in both BAs supplementary groups (P < 0.05), and compared with CT group, survival rate in BA2 group was significantly improved (P < 0.05). Intestinal lysozyme activity and contents of immunoglobulin M and complement 3 were significantly increased in both BAs supplementary groups (P < 0.05), suggesting an enhancement effect on the non-specific immune response. BAs inclusion also significantly improved intestinal antioxidant capabilities by increasing antioxidase activities and decreasing malondialdehyde levels. In addition, compared with CT group, intestinal digestive ability was substantially enhanced as indicated by the significantly increased lipase activity in BA2 group (P < 0.05) and significantly increased amylase activity in BA1 and BA2 groups (P < 0.05). Coincidentally, BAs inclusion significantly upregulated the relative expression of intestinal mucosal barrier-related genes (P < 0.05). Further, dietary BAs distinctly remodeled intestinal microbiota by decreased the abundance of some potential pathogenic bacteria. In conclusion, dietary BAs supplementation is an effective way to improve the intestinal healthy status of tongue sole. • Dietary bile acid (BA) can significantly improve the growth performance and survival of tongue sole. • BA inclusion can significantly enhance intestinal non-specific immune response, antioxidant capability and digestive ability. • BA inclusion significantly upregulated the relative expression of intestinal mucosal barrier-related genes. • Dietary BA distinctly remodeled intestinal microbiota by decreased the abundance of some potential pathogenic bacteria. [ABSTRACT FROM AUTHOR]

Streptococcus agalactiae is one of the most important pathogens infecting tilapia worldwide and causes meningoencephalitis, septicemia and high mortalities with considerable losses. Various types of vaccines have been developed against S. agalactiae infection, such as inactivated vaccines, live attenuated vaccines and subunit vaccines. Bacterial ghosts (BGs) are nonliving, empty cell envelopes and have been reported as novel vaccine candidates. Therefore, the main aims of this study were to develop an S. agalactiae ghost vaccine (SAGV) and to evaluate the immune response and protective effect of SAGV against S. agalactiae with two novel adjuvants, Montanide™ ISA 763B VG and Montanide™ GEL02. Nile tilapia, mean weight 50 g, were divided into four groups as follows; 1) fish injected with PBS as control, 2) fish injected with the SAGV alone; 3) fish injected with the SAGV+Montanide™ ISA 763B VG; and 4) fish injected with SAGV+Montanide™ GEL02. Following vaccination, innate immunity parameters including serum lysozyme, myeloperoxidase, catalase, and bactericidal activity were all significantly enhanced. Moreover, specific serum IgM antibodies were induced and reached their highest level 2–8 weeks post vaccination. Importantly, the relative percent survival of tilapia vaccinated against the SAGV formulated with both adjuvants was 80–93%. Furthermore, the transcription of immune-related genes (IgM, TCRβ, IL-1β, IL-8 and TNFα) were up-regulated in tilapia after vaccination, indicating that both cellular and humoral immune responses were induced by these adjuvanted vaccines. In summary, Montanide™ ISA 763B VG and Montanide™ GEL02 can enhance immunoprotection induced by the SAGV vaccine against streptococcosis, demonstrating that both have value as potential adjuvants of fish vaccines. • A Streptococcus agalactiae Ghost Vaccine (SAGV) was made to vaccinate Nile tilapia. • Tilapia were injected with SAGV plus Montanide™ ISA 763 B VG and Montanide™ GEL02. • SAGV with Montanide™ ISA 763 B VG or GEL02 increased innate immunity. • SAGV with Montanide™ ISA 763B VG or GEL02 induced specific IgM and IgM/TCR expression. • SAGV with Montanide™ ISA 763B VG or GEL02 gave excellent protection to S. agalactiae. [ABSTRACT FROM AUTHOR]

Rainbow trout is an important fish species for Peruvian artisanal aquaculture, comprising over 60 % of the total aquaculture production. However, their industry has been highly affected by several bacterial agents such as Yersinia ruckeri. This pathogen is the causative agent of Enteric Redmouth Disease, and causes high mortality in fingerlings and chronic infection in adult rainbow trout. To date, the immune response of rainbow trout against Y. ruckeri has been well studied in laboratory-controlled infection studies (i.e. intraperitoneal infection, bath immersion), however, the immune response during natural infection has not been explored. To address this, in this study, 35 clinically healthy O. mykiss without evidence of lesions or changes in behavior and 32 rainbow trout naturally infected by Y. ruckeri , were collected from semi-intensive fish farms located in the Central Highlands of Peru. To evaluate the effect on the immune response, RT-qPCR, western blotting, and ELISA were conducted using head kidney, spleen, and skin tissues to evaluate the relative gene expression and protein levels. Our results show a significant increase in the expression of the pro-inflammatory cytokines il1b , tnfa , and il6 , as well as ifng in all three tissues, as well as increases in IL-1β and IFN-γ protein levels. The endogenous pathway of antigen presentation showed to play a key role in defense against Y. ruckeri , due to the upregulation of mhc-I , tapasin , and b2m transcripts, and the significant increase of Tapasin protein levels in infected rainbow trout. None of the genes associated with the exogenous pathway of antigen presentation showed a significant increase in infected fish, suggesting that this pathway is not involved in the response against this intracellular pathogen. Finally, the transcripts of immunoglobulins IgM and IgT did not show a modulation, nor were the protein levels evaluated in this study. • Natural Y. ruckeri infection initially induced proinflammatory cytokines in head kidney, spleen, and skin. • The MHC-I receptor and its chaperones played a key role. • The exogenous pathway of antigen presentation was not activated during Y. ruckeri natural infection. • Y. ruckeri specific IgM and IgT protein levels did not increase over the course of natural infection in rainbow trout. [ABSTRACT FROM AUTHOR]

The thymus of fishes is located as a dual organ in a rostrodorsal projection within the gill chamber and is covered by the operculum. The histological organization of the teleost fish thymus displays considerable diversity, particularly in salmonids where a clear distinction between the thymus cortex and medulla is yet to be defined. Recent interest has focused on the role of B cells in thymic function, but the presence of these cells within the salmon thymus remains poorly understood. In this morphological study, we applied in situ hybridization to investigate developing Atlantic salmon thymi for the expression of recombination activating (Rag) genes 1 and 2. We identified the location of the cortex, aligning with the previously described inner zone. Expression of IgM and IgD transcripts was predominantly observed in cells within the outer and subcapsular zones, with lesser expression in the cortex and inner zone. IgT expression was confined to a limited number of cells in the inner zone and capsule. The location of the thymus medulla could not be established. Our results are discussed in the context of the recently identified lymphoid organs, namely the intrabranchial lymphoid tissue (ILT) and the salmon bursa. • The organization into cortex and medulla of the salmonid thymus has not been established. • We utilize the expression of Rag-1 and Rag-2 to determine the location of the salmonid thymus cortex. • The cortex corresponds to the inner zone of the salmonid thymus. • Immunoglobulin-expressing cells are present in the thymus. [ABSTRACT FROM AUTHOR]