Aeromonas Salmonicida Infection Research Articles

A bacterial ghost vaccine against Aeromonas salmonicida infection in turbot (Scophthalmus maximus)

Aeromonas salmonicida is one of the most prevalent pathogens that causes huge economic losses to aquaculture. Effective vaccination is the first choice for preventing infection. Bacterial ghost (BG), an empty bacterial shell devoid of cytoplasm, is a promising vaccine antigen with distinct advantages. Herein, we established strategies for producing a substantial yield of A. salmonicida ghost (ASG) and investigated the immune-protective properties of it. As a result, 2.84 mg/ml NaOH was discovered to be capable of inducing considerable amounts of ASG. Furthermore, the ASG vaccine elicited adaptive immunity in turbots after rapid activation of innate immunity. Even though formalin-killed cells (FKC) produced a few more antibodies than ASG, ASG ultimately provided a much stronger immune protection effect because it strengthened cellular immunity, with a relative percentage survival (RPS) of 50.1 % compared to FKC. These findings demonstrated that ASG effectively activated cell-mediated immunity, which helped get rid of microorganisms inside cells. Therefore, this study presented novel perspectives for future research on furunculosis vaccine products based on ASG as an antigen.

Mechanism of Ligilactobacillus salivarius GX118 in Regulating the Growth of Rainbow Trout (Oncorhynchus mykiss) and Resistance to Aeromonas salmonicida Infection

Lactic acid bacteria Ligilactobacillus salivarius has been shown to be a substitute for antibiotics in the treatment of bacterial disease in high animals. However, its beneficial mechanism in fish farming is still unclear. This study evaluated the antagonistic effects of the Ligilactobacillus salivarius GX118 strain on Aeromonas salmonicida and its regulation of rainbow trout growth in vivo and in vitro. The results found that GX118 produces an antibacterial substance that can directly destroy the cell wall of A. salmonicida. Whole-genome sequencing of GX118 revealed that Enterolysin A is a type III bacteriocin with antibacterial properties. An in vivo experiment showed that the supplementation of GX118 in diet competitively inhibited the colonization of A. salmonicida in the intestine. In addition, it was able to improve the growth performance of rainbow trout within a 21-day feeding experiment. The supplementation of GX118 increased the diversity of gut microbiota, in which the abundance of Bacteroidota, Blautia, and Rhodobacteraceae increased. In addition, the use of GX118 activated the expression of IFN-γ and NF-κB genes and reduced the expression level of IL-6 and IL-8, thus exhibiting a certain effect on activating the immunity of rainbow trout. This study provides a scientific basis for the development of antibacterial probiotics in the healthy farming of rainbow trout.

Season affects the estrogen system and the immune response of common carp.

The physiology of ectothermic animals, including fish, is strictly regulated by season-related external factors such as temperature or photoperiod. The immune response and the production of hormones, such as estrogens, are therefore also subject to seasonal changes.This study in common carp aimed to determine how the season affects the estrogen system and the immune response, including the antibacterial response during Aeromonas salmonicida infection. We compared the immune reaction in spring and autumn in the head kidney and liver and found that carp have higher levels of blood 17β-estradiol in autumn, while in the liver of these fish there is a higher constitutive expression of genes encoding vitellogenin, estrogen receptors and Cyp19 aromatase than in spring. Fish sampled in autumn also exhibited higher expression of immune-related genes in the liver. In contrast, in the head kidney from fish sampled in the autumn, the expression of genes encoding estrogen receptors and aromatase was lower than in spring, and a similar profile of expression was also measured in the head kidney for inos, arginases and il-10. In turn, during bacterial infection, we observed higher upregulation of the expression of inos, il-12p35, ifnγ-2, arginase 2 and il-10 in the liver of carp sampled in spring. In the liver of carp infected in spring a higher upregulation of the expression of the genes encoding CRPs was observed compared to fish infected during autumn. The opposite trend occurred in the head kidney, where the upregulation of the expression of the genes involved in the immune response was higher in fish infected in autumn than in those infected in spring. During the infection, also season-dependent changes occurred in the estrogen system.In conclusion, we demonstrated that season differentially affects the estrogenic and immune activity of the head kidney and liver. These results reinforce our previous findings that the endocrine and immune systems cooperate in maintaining homeostasis and fighting infection.

Construction and analysis of competing endogenous RNA ceRNA networks in the liver of black rockfish (Sebastes schlegelii) following Aeromonas salmonicida infection

Given the dual roles in immune function and metabolism, the liver emerge as a compelling candidate to bridge host defense and metabolic adjustments during pathogen infections in teleosts. In order to dissect the roles of the liver in the immune response of Sebastes schlegelii, we conducted an investigation into the activities of SOD, CAT and GPX4, performed a systematic analysis of circRNA, miRNA and mRNA expression profiles, as well as constructed circRNA-miRNA-mRNA regulatory networks in the liver of S. schlegelii following Aeromonas salmonicida infection were performed in the present study. The present results demonstrated the content of SOD, CAT and GPX4 increased significantly at early infection stage to protect the liver tissue from excessive damage. Additionally, 622 circRNA-miRNAs pairs, 78 miRNA-mRNA pairs and 327 circRNA-miRNA-mRNA pairs were identified in our study. These differently expressed circRNAs and miRNAs were found to be associated with the regulation of LMNB1, DMBT1, NAMPT, IFIT1, CELSRs, PYGL. GO and KEGG enrichment analysis revealed that these differently expressed genes were involved in TLR signal pathway, RLRs signal pathway, PPAR signal pathway, shedding light on antibacterial ceRNA networks within the liver of S. schlegelii post A. hydrophila post infection, which provides new insights into the immune mechanisms of teleost.

The potential of bitter melon extract on cellular non-specific immunity of koi fish (Cyprinus carpio) after Aeromonas salmonicida infection

Abstract. Andayani S, Fadjar M, Suprastyani H, Rahmawati A, Nurhalisa, Nadiro VN. 2023. The potential of bitter melon extract on cellular non-specific immunity of koi fish (Cyprinus carpio) after Aeromonas salmonicida infection. Biodiversitas 24: 5215-5222. Indonesia has rich and potential fisheries resources both in freshwater (inland), coastal, and ocean. Potential fishery resources in freshwater include the diversity of fish species (germplasm) and fishery land. Utilization of freshwater fisheries potential can be realized by conducting fish farming, especially for economically valuable fish commodities, such as koi fish (Cyprinus carpio). Improving koi fish farming can be done by using bitter melon extract as an immunity enhancer. This study was conducted with the aim to determine the effect of bitter melon extract on cellular non-specific immune response. This study used a completely randomized design (CRD) method, with 4 treatments and 3 replicates, consisting of treatment K = not given bitter melon extract and not infected, A = dose of bitter melon extract 100 ppm, B = bitter melon extract 150 ppm, C = bitter melon extract 200 ppm. Before being given the treatment, the test fish were acclimatized with the aim of ensuring that the fish were healthy, not stressed and did not experience death. In addition, the dose of extract treatment and soaking time have been through the LD50 test as well as the density of bacterial infection and the length of time of infection have been through the LC50 test so that it has been confirmed that it does not cause stress and death in fish, with results SR 100%. A total of 10 fish were immersed into each treatment container (15 liters of water mixed with the extract) for 60 hours. Infection of Aeromonas salmonicida bacteria by immersion was carried out 5 days after immersion in bitter melon extract with a bacterial density of 107 cells.mL-1 for 1 hour. The results showed that lymphocytes increased after being given bitter melon extract and infected with A. salmonicida bacteria with a value of 63-83%. Monocytes increased from 3% to 8%, and Neutrophils increased from 4% to 9%. Phagocytosis activity increased from 18.4% to 28.9%, indicating that bitter melon extract can enhance non-specific immunity.

Characterization of caspase gene family in Sebastes schlegelii and their expression profiles under Aeromonas salmonicida and Vibrio anguillarum infection

The caspase, functioning as a proteinase, plays a crucial role in eukaryotic cell apoptosis, regulation of apoptosis, cellular growth, differentiation, and immunity. The identification of caspase gene family in Sebastes schlegelii is of great help to understand its antimicrobial research. In S. schlegelii, we totally identified nine caspase genes, including four apoptosis initiator caspases (caspase 2, caspase 8, caspase 9 and caspase 10), four apoptosis executioners (caspase 3a, caspase 3b, caspase 6, and caspase 7) and one inflammatory executioner (caspase 1). The duplication of caspase 3 genes on chr3 and chr8 may have been facilitated by whole genome duplication (WGD) events or other complex evolutionary processes. In general, the number of caspase genes relatively conserved in high vertebrates, while exhibiting variation in teleosts. Furthermore, syntenic analysis and phylogenetic relationships analysis supported the correct classification of these caspase gene family in S. schlegelii, especially for genes with duplicated copies. Additionally, the expression patterns of these caspase genes in different tissues of S. schlegelii under healthy conditions were assessed. The results revealed that the expression levels of most caspase genes were significantly elevated in the intestine, spleen, and liver. To further investigate the potential immune functions of these caspase genes in S. schlegelii, we challenged individuals with A. salmonicida and V. anguillarum, respectively. After infection with A. salmonicida, the expression levels of caspase 1 in the liver and spleen of S. schlegelii remained consistently elevated throughout the infection time points. The expression levels of most caspase family members in the intestine exhibited significant divergence following V. anguillarum infection. This study provides a comprehensive understanding of the caspase gene families in S. schlegelii, thereby establishing a solid foundation for further investigations into the functional roles of these caspase genes.

Efficacy of bivalent vaccine against Aeromonas salmonicida and Edwardsiella tarda infections in turbot.

In recent years, more than one pathogenic organism has usually been isolated from diseased turbot Scophthalmus maximus, creating a pressing need for the development of combination vaccines to prevent fish diseases brought on simultaneously by various infections. In this study, the inactivated bivalent vaccine of Aeromonas salmonicida and Edwardsiella tarda was prepared by the formalin inactivation method. After challenge with A. salmonicida and E. tarda at 4 weeks post-vaccination in turbot, the relative percentage survival (RPS) of the inactivated bivalent vaccine was 77.1%. In addition, we assessed the effects of the inactivated bivalent vaccine and evaluated the immunological processes after immunization in a turbot model. Serum antibody titer and lysozyme activity of the vaccinated group were both upregulated and higher than that in control group after vaccination. The expression levels of genes (TLR2, IL-1β, CD4, MHCI, MHCⅡ) that related to antigen recognition, processing and presentation were also studied in the liver, spleen and kidney tissues of vaccinated turbot. All the detected genes in the vaccinated group had a significant upward trend, and most of them reached the maximum value at 3-4 weeks, which had significant differences from the control group, suggesting that antigen recognition, processing and presentation pathway was activated by the inactivated bivalent vaccine. Our study provides a basis for further application of the killed bivalent vaccine against A. salmonicida and E. tarda in turbot, making it good potential that can be applied in aquaculture.

Identification, characterization, and transcription of serotonin receptors in rainbow trout (Oncorhynchus mykiss) in response to bacterial infection and salinity changes

Serotonergic system is involved in the regulation of physiological functions and behavioral traits including cognition, memory, aggression, stress coping, appetite and immunomodulation. Serotonin exerts its functions via binding distinct serotonin receptors which are classified into 7 groups. Salmonid exhibits expanded functional gene copies due to salmonid-specific whole genome duplication. However, serotonin receptor (htr) repertoire is not fully identified in rainbow trout (Oncorhynchus mykiss). In this study, we identified 39 htr genes, including 14 htr1, 4 htr2, 4 htr2 like, 3 htr3, 4 htr4, 2 htr5, 2 htr6, and 6 htr7 subtypes. We investigated physiological functions of serotonin receptors in response to bacterial pathogens exposure and salinity changes. We showed htr1, htr2, htr4 and htr7 subtypes were associated with immunomodulation in response to Vibrio anguillarum or Aeromonas salmonicida infection. Saltwater (salinity of 15) transfer significantly altered htr1, htr2, htr4, and htr7 subtypes, suggesting trout Htr was associated with osmoregulation. We further showed residues interacted with inverse agonist (methiothepin) and serotonin analogue (5-Carboxamidotryptamine) were conserved between trout and human, suggesting exogenous ligands targeting human HTRs might have a role in aquaculture. This study showed duplicated trout Htrs might be physiologically neofunctionalized and potentially exhibit pleiotropic effects in regulating immunomodulation and osmoregulation.

Genome-wide identification and functional characterization of inhibitor of nuclear factor-κB (IκB) kinase (IKK) in turbot (Scophthalmus maximus)

The inhibitor of nuclear factor-κB (IκB) kinase (IKK) is involved in a variety of intracellular cell signaling pathways and is an important component of the NF-κB signaling pathway. IKK genes have been suggested to play important roles in the innate immune response to pathogen infection in both vertebrates and invertebrates. However, little information is available about IKK genes in turbot (Scophthalmus maximus). In this study, six IKK genes were identified including SmIKKα, SmIKKα2, SmIKKβ, SmIKKε, SmIKKγ, and SmTBK1. The IKK genes of turbot showed the highest identity and similarity with Cynoglossus semilaevis. Then, phylogenetic analysis showed that the IKK genes of turbot were most closely related to C. semilaevis. In addition, IKK genes were widely expressed in all the examined tissues. Meanwhile, the expression patterns of IKK genes were investigated by QRT-PCR after Vibrio anguillarum and Aeromonas salmonicida infection. The results showed that IKK genes had varying expression patterns in mucosal tissues after bacteria infection, indicating that they may play key roles in maintaining the integrity of the mucosal barrier. Subsequently, protein and protein interaction (PPI) network analysis showed that most proteins interacting with IKK genes were located in the NF-κB signaling pathway. Finally, the double luciferase report and overexpression experiments showed that SmIKKα/SmIKKα2/SmIKKβ involved in the activation of NF-κB in turbot. In summary, our results suggested that IKK genes of turbot played important roles in the innate immune response of teleost, and provide valuable information for further study of the function of IKK genes.

Integrative transcriptomic profiling reveals the key pathways in the regulation mechanism of fish intestine-spleen immunity during the bacterial challenges

In teleost, the immune roles of the gut-associated lymphoid tissue (GALT) have been well recognized. The antibacterial functions of the spleen have been also documented in various fish species. However, the mechanism of fish intestine-spleen immunity during bacterial infection still remains largely unknown. In this study, an integrative analysis was conducted in the black rockfish intestine and spleen after Aeromonas salmonicida and Edwardsiella tarda infection on the transcriptomic level. The immune gene libraries were constructed in the intestine and spleen. A total of 211 and 253 differentially expressed genes were observed in the immune gene library of spleen and intestine, respectively. One more category of immune genes was found in the intestine (9 categories) than in the spleen (8 categories). Potential evidence of the cooperation in the intestine-spleen axis was obtained based on the functional annotation and enrichment analyses of joint immune genes between intestine and spleen. In addition, bioinformatic and ceRNA analyses for transcriptomic data were performed. Finally, two key immune genes (CO3 and MRC1) and their related non-coding RNAs were observed in the functions of bacterial recognition and binding. According to the pathway “intestinal immune network for IgA production” predicted in the splenic transcriptome by functional enrichment, a novel regulatory pathway of the immunity of the intestine-spleen axis was hypothesized in black rockfish during bacterial infection. Moreover, the regulatory relationships between the immune transcripts in this pathway were verified preliminarily by RT-qPCR. Dual-luciferase reporter assays were performed to determine the regulations between the ceRNAs of MRC1/miR-23b-5p/LNC_00057980 and CO3/miR-214/LNC_00096415 axis. Overall, our findings demonstrate the key pathways of MRC1/miR-23b-5p/LNC_00057980 and CO3/miR-214/LNC_00096415 in the regulation mechanism of intestine-spleen axis during two different Gram-negative bacteria infection in black rockfish.

Identification and functional characterization of CL-11 in black rockfish (Sebastes schlegelii)

CL-11 (Collectin-11, also known as Collectin kidney-1 or CL-K1) is a member of collectin family that works as a pattern recognition molecule (PRM) and participating in lectin-complement pathway in host defense against pathogens. We identified the CL-11 homologue SsCL-11 in black rockfish (Sebastes schlegelii) and investigated the functional characteristics in this study. The SsCL-11 has conserved protein modules, i.e. an N-terminal hydrophobic region, a collagen-like region, an α-helical neck region and a carbohydrate recognition domain (CRD). SsCL-11 has varying degrees of expressions in difference tissues, among which the highest expression is observed in liver. It also shows induced expressions in immune-related tissues following Aeromonas salmonicida (A. salmonicida) infection. In addition, SsCL-11 exhibits binding abilities to different kinds of carbohydrates, pathogen-associated molecular patterns (PAMPs) and bacteria. It exhibits comparatively strong binding to l-fucose, d-mannose, and d-glucose, which is consistent with the functional EPN motif in its CRD. SsCL-11 also shows agglutinating effects on various bacteria in the presence of Ca2+. Furthermore, SsCL-11 is confirmed to be a secretory lectin and can form multimers. These findings collectively demonstrate that SsCL-11 can function as a recognition molecule in pathogen resistance in black rockfish, which will promote our understanding of immunological roles of fish collectins.

Genome-Wide Identification, Evolutionary Analysis, and Expression Patterns of Cathepsin Superfamily in Black Rockfish (Sebastes schlegelii) following Aeromonas salmonicida Infection.

Cathepsins are lysosomal cysteine proteases belonging to the papain family and play crucial roles in intracellular protein degradation/turnover, hormone maturation, antigen processing, and immune responses. In the present study, 18 cathepsins were systematically identified from the fish S. schlegelii genome. Phylogenetic analysis indicated that cathepsin superfamilies are categorized into eleven major clusters. Synteny and genome organization analysis revealed that whole-genome duplication led to the expansion of S. schlegelii cathepsins. Evolutionary rate analyses indicated that the lowest Ka/Ks ratios were observed in CTSBa (0.13) and CTSBb (0.14), and the highest Ka/Ks ratios were observed in CTSZa (1.97) and CTSZb (1.75). In addition, cathepsins were ubiquitously expressed in all examined tissues, with high expression levels observed in the gill, intestine, head kidney, and spleen. Additionally, most cathepsins were differentially expressed in the head kidney, gill, spleen, and liver following Aeromonas salmonicida infection, and their expression signatures showed tissue-specific and time-dependent patterns. Finally, protein–protein interaction network (PPI) analyses revealed that cathepsins are closely related to a few immune-related genes, such as interleukins, chemokines, and TLR genes. These results are expected to be valuable for comparative immunological studies and provide insights for further functional characterization of cathepsins in fish species.

Effects of probiotics on growth, the toll-like receptor mediated immune response and susceptibility to Aeromonas salmonicida infection in rainbow trout Oncorhynchus mykiss

This study evaluated the effects of probiotics on growth, survival, and toll-like receptors (TLRs)-mediated immune response and susceptibility to Aeromonas salmonicida infection in the rainbow trout (Oncorhynchus mykiss). Probiotic bacterium Bacillus velezensis MVCR2 strain isolated from turbot and Latilactobacillus sakei RDB2 strain isolated from rainbow trout were administered. A 30-day feeding experiment was conducted with three diet treatments: diet supplemented with B. velezensis (BV group), diet supplemented with L. sakei (LS group), and diet without probiotic supplementation as a control. Rainbow trout supplemented with probiotics benefitted by gaining body weight and resistance to A. salmonicida. The expression levels of TLRs (1, 2, 3, 4, 5, 7, 9, and 22) and the related signaling cascade pathways were determined. Upregulation of TLRs (1, 2, 3, 4, 7, 9, and 22) and the signaling cascade genes myd88 and irak4 was detected in different organs after ten days of feeding in the two groups. Interestingly, most of the upregulated TLRs on day ten recovered or even showed downward regulation after 30 days of feeding. Notably, the expression levels of all selected TLRs in the BV and LS groups were significantly upregulated in the kidneys and spleens after the A. salmonicida challenge. Our results suggest that different TLRs are involved in the recognition of exogenous and indigenous beneficial bacteria. Moreover, probiotics were capable of enhancing innate immune function in rainbow trout by training TLR-mediated MyD88-independent pathways, thus helping the host to respond rapidly to pathogen invasion. These findings lay the foundation for future studies on the mechanism by which probiotics regulate fish hosts and provide scientific basis for the use of probiotics in healthy rainbow trout culture.

CC and CXC chemokines in turbot (Scophthalmus maximus L.): Identification, evolutionary analyses, and expression profiling after Aeromonas salmonicida infection

Chemokines are a superfamily of structurally related cytokines, which exert essential roles in guiding cell migration in development, homeostasis, and immunity. CC and CXC chemokines are the two major subfamilies in teleost species. In this study, a total of seventeen CC and CXC chemokines, with inclusion of twelve CC and five CXC chemokines, were systematically identified from the turbot genome, making turbot the teleost harboring the least number of CC and CXC chemokines among all teleost species ever reported. Phylogeny, synteny, and genomic organization analyses were performed to annotate these genes, and multiple chemokine genes were identified in the turbot genome, due to the tandem duplications (CCL19 and CCL20), the whole genome duplications (CCL20, CCL25, and CXCL12), and the teleost-specific members (CCL34-36, CCL44, and CXCL18). In addition, chemokines were ubiquitously expressed in nine examined healthy tissues, with high expression levels observed in liver, gill, and spleen. Moreover, most chemokines were significantly differentially expressed in gill and spleen after Aeromonas salmonicida infection, and exhibited tissue-specific and time-dependent manner. Finally, protein-protein interaction network (PPI) analysis indicated that turbot chemokines interacted with a few immune-related genes such as interleukins, cathepsins, stats, and TLRs. These results should be valuable for comparative immunological studies and provide insights for further functional characterization of chemokines in teleost.

Preventive effect of starch hydrogel-based oral vaccine against Aeromonas salmonicida infection in rainbow trout (Oncorhynchus mykiss)

In rainbow trout aquaculture, furunculosis infection, caused by Aeromonas salmonicida, results in significant losses. Although vaccination is considered one of the most effective procedures against furunculosis, in Korea, there is no vaccine available for rainbow trout. Thus, the present study investigated the effect of a starch hydrogel-based oral (SHO) vaccine on antibody reactivity, immune-related genes expression, and protection against furunculosis infection in rainbow trout. In addition, the effect of booster vaccination was evaluated by comparing the immunostimulatory effect of a single vaccination with that of a booster vaccination. To determine the optimal SHO vaccination strategy, fish were individually orally administered the vaccine as follows: vaccinated only once (VT1), booster-vaccinated once 3 weeks after the initial vaccination (VT2), booster-vaccinated twice at 3-week intervals (VT3), or booster-vaccinated three times at 3-week intervals (VT4). Serum agglutination test showed that agglutination titers in booster-vaccinated groups were higher than those in the single-vaccinated group. The survival rate of rainbow trout was assessed after introduction of A. salmonicida at 11 weeks post vaccination. The relative survival rate was investigated as follows: 100% when challenged with 102 colony-forming units (CFU)/fish; 69.84 ± 2.75% when challenged with 103 CFU/fish; and 65.28 ± 2.41% when challenged with 104 CFU/fish. The results revealed that the expression of immune-related genes such as tumor necrosis factor α (TNFα), interleukins (IL-1β, IL-6, IL-8, and IL-10), IgM, IgDs, heat shock protein (HSP) 70, complement factor C3, serum amyloid protein A (SAA), MHC II, and transforming growth factor β (TGF-β) increased in SHO-vaccinated fish, whereas IgDm decreased. These results indicate that the SHO vaccine may be a promising oral vaccine for rainbow trout aquaculture.

Transcriptional Signatures of Immune, Neural, and Endocrine Functions in the Brain and Kidney of Rainbow Trout (Oncorhynchus mykiss) in Response to Aeromonas salmonicida Infection.

Rainbow trout (Oncorhynchus mykiss) serves as one of the most important commercial fish with an annual production of around 800,000 tonnes. However, infectious diseases, such as furunculosis caused by Aeromonas salmonicida infection, results in great economic loss in trout culture. The brain and kidney are two important organs associated with “sickness behaviors” and immunomodulation in response to disease. Therefore, we worked with 60 trout and investigated transcriptional responses and enrichment pathways between healthy and infected trout. We observed that furunculosis resulted in the activation of toll-like receptors with neuroinflammation and neural dysfunction in the brain, which might cause the “sickness behaviors” of infected trout including anorexia and lethargy. We also showed the salmonid-specific whole genome duplication contributed to duplicated colony stimulating factor 1 (csf-1) paralogs, which play an important role in modulating brain immunomodulation. Enrichment analyses of kidneys showed up-regulated immunomodulation and down-regulated neural functions, suggesting an immune-neural interaction between the brain and kidney. Moreover, the kidney endocrine network was activated in response to A. salmonicida infection, further convincing the communications between endocrine and immune systems in regulating internal homeostasis. Our study provided a foundation for pathophysiological responses of the brain and kidney in response to furunculosis and potentially offered a reference for generating disease-resistant trout strains.

Characterization of IL-17/IL-17R gene family in Sebastes schlegelii and their expression profiles under Aeromonas salmonicida and Edwardsiella piscicida infections

Interleukin 17 (IL-17) is a hallmark inflammatory cytokine that can induce a variety of cells to produce immune-related factors, and plays a critical role in host defend itself against invasion by pathogens, which signals through a distinct receptor subclass- IL-17R. In our study, seven IL-17 and eight IL-17R family members were identified in black rockfish. Subsequently, phylogenetic relationships, gene structures and syntenic analysis were performed to confirm the annotation and homology of these genes during evolution. Except for eight positive selection sites were detected in IL-17RA1, IL-17RC1 and IL-17RD, most of gene sites were underwent purification selection. The mRNA levels of IL-17 and IL-17R genes were higher in immune-related tissues. Additionally, the expressions of IL-17RA1 and IL-17RE1 in spleen were dramatically induced by A. salmonicida treatment, as well as IL-17RA1, IL-17RB, IL-17RC1 and IL-17RE1 in liver, which indicated their important roles in antimicrobial infections. Furthermore, the expression patterns of IL-17 and IL-17R genes in mucosal tissues in response to E. piscicida infection were investigated, of which some members were dramatically induced, particularly for IL-17A/F1 and IL-17A/F3 in skin, IL-17A/F2 in gill, IL-17RB in intestine, IL-17RA1 and IL-17RC1 in skin and gill, suggests their potential essential roles in innate immune response. In summary, this study provides a systemic overview of the IL-17 and IL-17R gene families in black rockfish, which is of great importance to further study the functional characteristics of these genes.

Effect of ploidy status of juvenile turbot, Scophthalmus maximus, on innate immune response and disease susceptibility against Aeromonas salmonicida, Vibrio anguillarum and Viral hemorrhagic septicemia virus

Triploid induction is a promising tool for sterility and triploid turbot showed improvement in growth after sexual maturation. However, it is essential to characterise the response of triploids to pathogens to evaluate their suitability to aquaculture. The aim of the study was to investigate the ploidy status of turbot on the innate immune response and susceptibility against Vibrio anguillarum, Aeromonas salmonicida, and viral haemorrhagic septicaemia virus (VHSV) infection. Diploid and triploid turbot were subjected to experimental infection with these pathogens via intraperitoneal (IP) injection and immersion. Antibody response against V. anguillarum and A. salmonicida was assessed at 0, 7, 14, 21, and 30 days post injection. A. salmonicida did not cause any mortality in ploidy groups. However, ploidy had significant effects on susceptibility against V. anguillarum and VHSV infections. Triploids were significantly more susceptible to both V. anguillarum and VHSV. While there were no significant difference in antibody response against V. anguillarum in ploidy groups, antibody response of diploid turbot against VHSV was significantly higher.

CC chemokines and their receptors in black rockfish (Sebastes schlegelii): Characterization, evolutionary analysis, and expression patterns after Aeromonas Salmonicida infection

Chemokines are a superfamily of structurally related cytokines, which could interact with chemokine receptors, a superfamily of seven-transmembrane domain G-coupled receptors, to play crucial roles in guiding cell mobilization in development, homeostasis, and immunity. Among them, the CC subfamily is the largest subfamily with several members. In the present study, 24 CC chemokine ligands and 12 CC chemokine receptors were systematically identified from Black rockfish (Sebastes schlegelii). Sequence analyses indicated that most CC chemokine ligands, located in extracellular region, possess SCY domain, and CC chemokine receptors, located in plasma membrane, harbored the seven-transmembrane-region domain. Subsequently, the phylogeny, synteny, genome organization, and evolutionary analyses were performed to annotate these genes, and revealed that the tandem duplications (CCL19, CCL20a, CCL32, CCL33, CCL36, CCL38, CCR2, and CCR8), the whole genome duplications (CCL20, CCL25, CCR6, CCR9, and CCR12), and the teleost-specific members (CCL32–36, CCL38, CCL39, CCL44, and CCR12) led to the expansion of CCLs and CCRs in S. schlegelii. In addition, CCLs and CCRs were ubiquitously expressed in nine examined healthy tissues, with high expression levels in gill, head kidney, and spleen. Moreover, most CCLs and CCRs were significantly differentially expressed in head kidney, liver, and gill after A. salmonicida infection, and their expression patterns exhibited tissue-specific and time-dependent manner. Finally, the protein-protein interaction network (PPI) analysis indicated that CCLs and CCRs interacted with a few immune-related genes such as interleukins, CD genes, and TLR genes, etc. These results should be valuable for comparative immunological studies and provide insights for further functional characterization of chemokines and receptors in teleost.

CXC chemokines and their receptors in black rockfish (Sebastes schlegelii): Characterization, evolution analyses, and expression pattern after Aeromonas salmonicida infection

Chemokines are crucial regulators of cell mobilization for development, homeostasis, and immunity. Chemokines signal through binding to chemokine receptors, a superfamily of seven-transmembrane domain G-coupled receptors. In the present study, seventeen CXC chemokine ligands (SsCXCLs) and nine CXC chemokine receptors (SsCXCRs) were systematically identified from Sebastes schlegelii genome. Phylogeny, synteny, and evolutionary analyses were performed to annotate these genes, indicating that the tandem duplications (CXCL8, CXCL11, CXCL32, CXCR2, and CXCR3), the whole genome duplications (CXCL8, CXCL12, CXCL18, and CXCR4), and the teleost-specific members (CXCL18, CXCL19, and CXCL32) led to the expansion of SsCXCLs and SsCXCRs. In addition, SsCXCLs and SsCXCRs were ubiquitously expressed in nine examined healthy tissues, with high expression levels observed in head kidney, liver, gill and spleen. Moreover, most SsCXCLs and SsCXCRs were significantly differentially expressed in head kidney, liver, and gill after Aeromonas salmonicida infection, and exhibited tissue-specific and time-dependent manner. Finally, protein-protein interaction network (PPI) analysis indicated that SsCXCLs and SsCXCRs interacted with a few immune-related genes such as interleukins, cathepsins, CD genes, and TLRs, etc. These results should be valuable for comparative immunological studies and provide insights for further functional characterization of chemokines and receptors in teleost.