Vibrio Harveyi Infection Research Articles

A novel C-type lectin, perlucin, from the small abalone, Haliotis diversicolor involved in the innate immune defense against Vibrio harveyi infection

A novel C-type lectin, perlucin, from the small abalone, Haliotis diversicolor involved in the innate immune defense against Vibrio harveyi infection

Three hepcidins from the spotted knifejaw (Oplegnathus punctatus) promote antimicrobial activity via TLR/NFκB pathway

Hepcidin belongs to a class of small cationic antimicrobial peptides rich in cysteine. It is synthesized by liver and is widely involved in host antimicrobial, antiviral and other immune responses. We identified and characterized three hepcidin genes (OpHep1, OpHep2 and OpHep3) in spotted knifejaw. All the OpHeps shared high identities with hepcidins in other teleost, containing alpha helix and β-sheets. Three OpHeps were all detected in healthy tissues, with the abundant expression in liver. They were significantly increased after Vibrio harveyi infection in the six immune-relevant tissues (liver, kidney, spleen, gill, skin and intestine). OpHeps knockdown in spotted knifejaw liver cells affected the mRNA levels of inflammation-related genes, including il1β, il6, il8, and nfκb. Further, the recombinant hepcidin proteins were effective in suppressing the growth of both Gram-negative and Gram-positive bacteria. To identify the function of OpHeps in vivo, we performed the overexpression of three OpHeps in zebrafish, and found OpHeps could significantly induce immune-related genes expression in transgenic zebrafish, including myd88, il10, il21, il16, tlr1, tlr3 and lysozyme. When infected with V. harveyi, OpHeps transgenic zebrafishes had a higher survival rate than wild-type zebrafishes. The expression of myd88, il10, il8, il1β, nfκb and lysozyme were all significantly up-regulated in transgenic fishes during bacterial infection. In summary, these results indicated that hepcidin could protect fish fight against pathogen through TLR/NFκB signaling cascade and Lysozyme. Three OpHeps would be potential targets for prevention of bacterial infections in aquaculture industry of spotted knifejaw, which provided a new idea for the molecular breeding of fish disease resistance.

Transcriptome signature of juvenile Litopenaeus vannamei cultured under different salinity levels in response to Vibrio harveyi infection

Although the widely cultured Litopenaeus vannamei is highly tolerant to varying salinity levels, the rapid fluctuation of abiotic and biotic factors due to climatic changes may become stressors to the shrimp's physiology, resulting in impaired immunity and increased disease susceptibility. This study aimed to investigate the combined effects of both factors towards L. vannamei at transcriptomic level. L. vannamei were cultured at three different salinity levels (5 ppt, 20 ppt and 30 ppt) for 60 days and were challenged with Vibrio harveyi. RNA-seq analysis was conducted on the hepatopancreas to assess the differential expressed genes (DEGs) in both control and V. harveyi infected groups. Our results revealed 5,725 DEGs was observed in shrimp reared at 5 ppt, 3,643 DEGs at 20 ppt and 1,560 DEGs at 30 ppt. Most DEGs were identified to be associated with osmoregulation and transport activities, immune and stress regulation, nutrient metabolism, growth, chitin binding, gonadal development, and metal ion binding and toxicity. We identified that shrimp cultured at intermediate salinity of 20 ppt exhibits the greatest immunity level after infection by V. harveyi, given that low salinity (5 ppt) may augment the free ion metal toxicity, resulting in higher disease susceptibility. Both V. harveyi and salinity stress function together or separately to activate a wide range of immune and stress regulatory genes, which could be potential candidate markers for future RNAi and knockdown research in developing efficient prophylactic management strategies for L. vannamei.

Effects of Vibrio harveyi infection on the biochemistry, histology and transcriptome in the hepatopancreas of ivory shell (Babylonia areolata)

The ivory shell (Babylonia areolata) is one of the most promising high quality marine products. However, ivory shell is susceptible to Vibrio harveyi infection during the culture period. In this study, we investigated the biochemical indicators, histological changes and transcriptomic response in the hepatopancreas of ivory shells from the PBS control group (PC) and infection group (A3) with 1 × 109 CFU/mL V. harveyi after 24 h. Results showed that compared to the PC group, biochemical indicators, including malondialdehyde (MDA), reactive oxygen species (ROS), acid phosphatase (ACP), and Caspase 3 (Casp-3) were significantly increased (p < 0.05) in A3 group after V. harveyi infection for 24 h. Compared with the PC group, the hepatopancreas of A3 group were seriously damaged, the columnar epithelial cells of the tissue were enlarged, the space of digestive cells was increased, and vacuolar cavities appeared. A total of 95,581 unigenes were obtained and 2949 (1787 up-regulated and 1162 down-regulated) differential expressed genes (DEGs) were identified in the A3 group. GO and KEGG enrichment analysis showed that DEGs were mainly enriched in immune system process (GO:0002376), antioxidant activity (GO:0016209), lysosome (ko04142), toll and IMD signaling pathway (ko04624), and etc. These biological functions and pathways are associated with immune and inflammatory responses and apoptosis. 12 DEGs were randomly selected for real-time quantitative PCR (RT-qPCR) validation, and the expression profiles of these DEGs were consistent with the transcriptome data, confirming the accuracy and reliability of the transcriptome results. In summary, V. harveyi infection of ivory shells inducing oxidative stress, leading to severe hepatopancreatic damage, stimulating glutathione production to neutralize excessive ROS, and stimulating antimicrobial peptides production to counteract the deleterious effects of bacterial infection, which in turn modifying the immune and inflammatory response, ultimately resulting in apoptosis. This study provided valuable information to explore the immune regulation mechanism after V. harveyi infection and established molecular basis to support the prevention of V. harveyi infection.

Fermentation and fortification of Sargassum linearifolium with multi-strain probiotics improves mucosal barrier status, inflammatory response and resistance to Vibrio harveyi infection in barramundi Lates calcarifer

While aquaculture intensification increases productivity and profitability, it can lead to increased susceptibility of fish to disease outbreaks. As such, the production of aquafeeds with immunomodulatory properties is currently of significant interest to the aquaculture sector with a view of improving on-farm welfare. This study aimed to assess the effectiveness of the brown seaweed Sargassum linearifolium fortified with the probiotics Lactobacillus casei and Saccharomyces cerevisiae through submerged fermentation in improving growth, overall health and the ability to resist Vibrio harveyi infection in barramundi, Lates calcarifer. Two seaweed-based diets, probiotic-fortified S. linearifolium (referred to as PF-SL) and S. linearifolium without probiotic fortification (referred to as SL), were compared with a standard barramundi diet (control). Barramundi juveniles weighing 4.25 ± 0.09 g were fed the test diets three times daily to satiety for 56 days. The results demonstrated a significantly higher growth performance in fish fed the PF-SL diet when compared to the control. However, there were no notable differences in the apparent digestibility coefficient (ADC) of dry matter, protein, and lipid between PF-SL and control. Fish fed the PF-SL diet showed improved mucosal barrier function in both the skin and intestine, as indicated by the increased density of mucous cells. Similarly, fish fed the PF-SL diet exhibited higher glutathione peroxidase and total antioxidant activity than the control. The qRT-PCR revealed significant upregulation in the expression of anti-inflammatory genes (occludin, claudin1 and nrf2) and downregulation in the expression of proinflammatory genes (hsp70 and tnf-α) in fish fed the PF-SL diet. Furthermore, the PF-SL diet resulted in a 27% mortality in a 14-day challenge trial with V. harveyi, which was lower than the mortality rates of the SL (46%) and control (67%). Overall, this study demonstrates that feeding juvenile barramundi with probiotic-fortified brown seaweed S. linearifolium was able to improve growth, immunity, and resistance against Vibrio harveyi infection, suggesting significant potential for application across the aquaculture industry for improved fish welfare.

Dietary Use of Monoglycerides Blend in Plant-Based Diets Influences Growth Performance, Hepatopancreatic Histology, Immunity and Disease Resistance of Pacific White Shrimp Penaeus vannamei Against Vibrio harveyi

Feeding trials were conducted to evaluate the efficacy of commercially available optimized mixtures of monoglyceride blend (MG, as BalanGut® AQ L supplied by BASF, Germany) on growth performance and health condition of Pacific white shrimp Penaeus vannamei. A basal diet was formulated without MG, and four other diets were prepared by supplementing the powder forms of MG at inclusion levels of 0.5, 0.75, 1,0, and 1,5%. In a growth trial, eight replicate groups of shrimps were hand-fed with one of the diets four times daily for 60 days and observed for growth, total hemocyte count (THC), lysozyme activity, and histomorphological conditions of the hepatopancreas of the shrimp. In a challenge test, diseases challenged with Vibrio harveyi infection at a dose of 1 × 105 CFU mL-1 intramuscularly were conducted and then followed with the observation of the cumulative survival rate after 96 h postchallenge, phenoloxidase, the mean percentage of phagocytic activity and phagocytic index on the blood of the shrimp. In the growth trial, shrimps with inclusion levels of 0,75 up to 1,5% of MG showed significantly higher growth performance than the control treatment. The number of THC and lysozyme activity showed an increasing trend with the inclusion of MG at 0.5 up to 1.0% and then declined with the inclusion of 1.5%. The inclusion of MG did not cause any significant changes in the histomorphology of the shrimp's hepatopancreas. In the challenge test, the lowest survival rate after being infected with Vibrio harveyi was found in the control treatment, and the highest survival rate was found in the group of shrimps fed with 1 MG. The phenoloxidase (PO) activity, phagocytic activity, and index were higher in the group of shrimps fed with MG compared to the control treatment. The results of these studies indicate that the dietary supplementation of 0.75 – 1.0 % of MG can improve the growth, health condition, and disease resistance of P. vannamei.

Pufferfish gasdermin Ea is a significant player in the defense against bacterial pathogens

Gasdermins (GSDMs) are proteins cleaved by caspase (CASP) to trigger pyroptosis. In teleosts, pyroptosis is mediated by gasdermin E (GSDME). The Pufferfish, Takifugu rubripes, possesses two GSDME orthologs: named TrGSDMEa and TrGSDMEb. TrGSDMEa is cleaved by CASP3/7 to liberate the N-terminal (NT) domain that can trigger pyroptosis in mammalian cells. However, the biological function of TrGSDMEa in pufferfish is unknown, and TrGSDMEb is poorly studied. We found that TrGSDMEb was cleaved by CASP1/3/6/7/8, but the resulting NT domain, despite its similarity to TrGSDMEa-NT domain in sequence and structure, failed to induce pyroptosis. TrGSDMEa and TrGSDMEb exhibited similar expression patterns in pufferfish under normal physiological conditions but were up- and downregulated, respectively, in expression during Vibrio harveyi and Edwardsiella tarda infection. Bacterial infection induced the activation of TrGSDMEa and CASP3/7 in pufferfish cells, resulting in pyroptosis accompanied with IL-1β production and maturation. Inhibition of TrGSDMEa-mediated pyroptosis via TrCASP3/7 reduced the death of pufferfish cells and augmented bacterial dissemination in fish tissues. Structure-oriented mutagenesis identified 16 conserved residues in teleost GSDMEa that were required for the pore formation or auto-inhibition of GSDMEa. This study illustrates the role of GSDMEa-mediated pyroptosis in teleost defense against bacterial pathogens and provides new insights into the structure-based function of vertebrate GSDME.

The exosomal miRNAs involve in the inflammatory balance of Cynoglossus semilaevis by Vibrio harveyi infection

Cynoglossus semilaevis is infected by the main pathogenic Vibrio harveyi to induce inflammation response, resulting in epidermal ulceration. The exosomes are extracellular vesicles that play a crucial role on intercellular communication and transportation. In C. semilaevis, serum-derived exosomes regulate the production of inflammatory related cytokines, but the regulation mechanism remains unclear. In this study, the serum-derived exosomes from C. semilaevis were investigated the molecular mechanism on the inflammation response following V. harveyi infection. The results showed that V. harveyi infection induced the production of skin ulceration and inflammatory response in C. semilaevis. In vivo and in vitro, the serum-derived exosomes could internalize into the hemocytes and head kidney monocytes of C. semilaevis. The expression of six miRNAs could be detected in the serum-derived exosomes. In exosomes, the expressions level of miR-128-3p and miR-730 were decreased, whereas the expression level of miR-133-3p was increased following V. harveyi infection. The expression levels of pro-inflammatory cytokines were up-regulated at the early stage of V. harveyi infection, whereas the anti-inflammatory cytokines were increased the expression at the late stage of infection. Further study found that miR-128-3p, miR-730, and miR-133-3p could interact with the 3’UTR of their target genes. These results indicated that exosomal miRNAs are involved in anti-bacterial infection and played an important role in the inflammatory balance of C. semilaevis.

Study on the mechanism of miR-7562 regulating ATG5 and ATG12 genes in Penaeus monodon under Vibrio harveyi infection

MicroRNAs (miRNAs) play a fundamental role in the post-transcriptional regulation of genes and are pivotal in modulating immune responses in marine species, particularly during pathogen assaults. This study focused on the function of miR-7562 and its regulatory effects on autophagy against Vibrio harveyi infection in the black tiger shrimp (Penaeus monodon), an economically important aquatic species. We successfully cloned and characterized two essential autophagy-related genes (ATGs) from P. monodon, PmATG5 and PmATG12, and then identified the miRNAs potentially involved in co-regulating these genes, which were notably miR-7562, miR-8485, and miR-278. Subsequent bacterial challenge experiments and dual-luciferase reporter assays identified miR-7562 as the principal regulator of both genes, particularly by targeting the 3′UTR of each gene. By manipulating the in vivo levels of miR-7562 using mimics and antagomirs, we found significant differences in the expression of PmATG5 and PmATG12, which corresponded to alterations in autophagic activity. Notably, miR-7562 overexpression resulted in the downregulation of PmATG5 and PmATG12, leading to a subdued autophagic response. Conversely, miR-7562 knockdown elevated the expression levels of these genes, thereby enhancing autophagic activity. Our findings further revealed that during V. harveyi infection, miR-7562 continued to influence the autophagic pathway by specifically targeting the ATG5-ATG12 complex. This research not only sheds light on the miRNA-dependent mechanisms governing autophagic immunity in shrimp but also proposes miR-7562 as a promising target for therapeutic strategies intended to strengthen disease resistance within the crustacean aquaculture industry.

Impact of transport conditions and underlying disease on post-stocking survival of juvenile Lates calcarifer.

Diseases caused by pathogens commonly occurring in the aquatic environment or those that are non-host specific are prevalent and threaten the rapid growth of tropical aquaculture. This study investigates causes of mortality in 12 batches of newly stocked juvenile Lates calcarifer from three different hatcheries. Cytology based on Diff-Quik™-stained tissue and blood smears provides rapid diagnosis of possible causes of mortality, while histopathology and haematology provide a better understanding of how prolonged transport and fish with existing chronic disease are more likely to experience elevated mortality post-stocking. Our findings showed that accumulation of ammonia during prolonged transport causes extensive damage to epithelial barriers in gastrointestinal tracts and depressed immunity due to marked hypoglycaemia, predisposing fish to acute Streptococcosis. Lates calcarifer with chronic bacterial enteritis developed severe hypoglycaemia, had low circulating total plasma protein, and suffered high mortality within 24 hours post-stocking. Hypoglycaemia and low circulating blood proteins disrupt osmoregulation and exacerbate dehydration, which is fatal in fish in sea water. Dying L. calcarifer tested PCR positive for scale drop disease virus (SDDV) at 28 days post-stocking showed a 10-fold elevation of white blood cell counts, severe vasculitis, and obstruction of blood supply to major organs. Destruction of important immune organs such as spleen is a hallmark of SDDV infection that explains high incidences of opportunistic Vibrio harveyi infections in 61% of fish with SDDV. Overall, this study reiterates the importance of stocking disease-free fish and reducing transport stress.

Identification and functional characterization of interleukin-22 (IL-22) in orange-spotted grouper (Epinephelus coioides)

In mammals, IL-22 is considered as a critical cytokine regulating of immunity and homeostasis at barrier surfaces. Although IL-22 have been functional characterization in different species of fish, the studies about distinct responses of IL-22 in different organs/tissues/cell types is rather limited. Here, we identified and cloned IL-22 gene (named as Ec-IL-22) from grouper (Epinephelus coioides). Ec-IL-22 gene was detected in all orangs/tissues examined, and was induced in intestine, gill, spleen, head kidney, and primary head kidney/intestine leukocytes following the stimulation of LPS and poly (I:C), as well as Vibrio harveyi and Singapore grouper iridovirus infection (SGIV). In addition, the stimulation of DSS could induce the expression of Ec-IL-22 in intestine and primary leukocytes from intestine. Importantly, the treatment of recombinant Ec-IL-22 induced the mRNA level of proinflammatory cytokines in primary intestine/head kidney leukocytes. The present results improve the understanding of expression patterns and functional characteristics of fish IL-22 in different organs/tissues/cell types.

A novel vaccination strategy against Vibrio harveyi infection in Asian seabass (Lates calcarifer) with the aid of oxygen nanobubbles and chitosan

Immersion vaccination, albeit easier to administer than immunization by injection, sometimes has challenges with antigen uptake, resulting in sub-optimal protection. In this research, a new strategy to enhance antigen uptake of a heat-inactivated Vibrio harveyi vaccine in Asian seabass (Lates calcarifer) using oxygen nanobubble-enriched water (ONB) and positively charged chitosan (CS) was explored. Antigen uptake in fish gills was assessed, as was the antibody response and vaccine efficacy of four different combinations of vaccine with ONB and CS, and two control groups. Pre-mixing of ONB and CS before introducing the vaccine, referred to as (ONB + CS) + Vac, resulted in superior antigen uptake and anti-V. harveyi antibody (IgM) production in both serum and mucus compared to other formulas. The integration of an oral booster (4.22 × 108 CFU/g, at day 21–25) within a vaccine trial experiment set out to further evaluate how survival rates post exposure to V. harveyi might be improved. Antibody responses were measured over 42 days, and vaccine efficacy was assessed through an experimental challenge with V. harveyi. The expression of immune-related genes IL1β, TNFα, CD4, CD8, IgT and antibody levels were assessed at 1, 3, and 7-day(s) post challenge (dpc). The results revealed that antibody levels in the group (ONB + CS) + Vac were consistently higher than the other groups post immersion immunization and oral booster, along with elevated expression of immune-related genes after challenge with V. harveyi. Ultimately, this group demonstrated a significantly higher relative percent survival (RPS) of 63 % ± 10.5 %, showcasing the potential of the ONB-CS-Vac complex as a promising immersion vaccination strategy for enhancing antigen uptake, stimulating immunological responses, and improving survival of Asian seabass against vibriosis.

Strain-Specific Benefits of Bacillus Probiotics in Hybrid Grouper: Growth Enhancement, Metabolic Health, Immune Modulation, and Vibrio harveyi Resistance.

In the realm of modern aquaculture, the utilization of probiotics has gained prominence, primarily due to their ability to enhance growth, boost immunity, and prevent diseases in aquatic species. This study primarily investigates the efficacy of Bacillus subtilis strains, both host-derived and from other sources, in influencing fish growth, immunity, lipid metabolism, and disease resistance. Employing a 42-day feeding trial, we divided hybrid grouper into four distinct groups: a control group on a basal diet and three experimental groups supplemented with 1 × 108 CFU/g of different Bacillus subtilis strains-BS, 6-3-1, and HAINUP40. Remarkably, the study demonstrated that the 6-3-1 and HAINUP40 groups exhibited significant enhancements across key growth parameters: final body weight (FBW), weight gain rate (WGR), feed intake (FI), feed efficiency ratio (FER), and feed conversion ratio (FCR). The investigation into lipid metabolism revealed that the 6-3-1 strain upregulated seven metabolism-related genes, HAINUP40 affected four metabolism-related genes, and the BS strain influenced two metabolism-related genes, indicating diverse metabolic impacts by different strains. Further, a notable reduction in liver enzymes AST and ALT was observed across all supplemented groups, implying improved liver health. Noteworthy was the BS strain's superior antioxidative capabilities, positively affecting all four measured parameters (CAT, GSH-Px, MDA). In the sphere of immune-related gene expression, the BS strain significantly decreased the expression of both inflammation and apoptosis-related genes, whereas the HAINUP40 strain demonstrated an upregulation in these genes. The challenge test results were particularly telling, showcasing improved survival rates against Vibrio harveyi infection in the BS and 6-3-1 groups, unlike the HAINUP40 group. These outcomes highlight the strain-specific nature of probiotics and their varying mechanisms of action within the host. In conclusion, this study reveals that probiotic strains, varying by source, demonstrate unique, strain-specific effects in promoting growth and modulating immunity in hybrid grouper. This research highlights the promise of tailored probiotic applications in improving aquaculture practices. Such advancements contribute to more sustainable and efficient fish farming methods.

Δfur mutant as a potential live attenuated vaccine (LAV) candidate protects American eels (Anguilla rostrata) from Vibrio harveyi infection

The eel farming industry is highly susceptible to Vibriosis. Although various types of vaccines against Vibriosis have been investigated, there is limited research on decreasing the virulence of Vibrions through gene knockout and utilizing it as live attenuated vaccines (LAV). In this study, we aim to develop a LAV candidate against Vibrio harveyi infection in American eels (Anguilla rostrata) using a ferric uptake regulator (fur) gene mutant strain of V. harveyi (Δfur mutant). After the eels were administrated with the Δfur mutant at the dose of 4 × 102 cfu/g body weight, the phagocytic activity of the leucocytes, plasma IgM antibody titers, activity of lysozyme and Superoxide Dismutase (SOD) enzyme, and gene expression levels of 18 immune related proteins were detected to evaluate the protection effect of the LAV. Preliminary findings suggest that the LAV achieved over 60% relative percent survival (RPS) after the American eels were challenged by a wild-type strain of V. harveyi infection on 28 and 42 days post the immunization (dpi). The protection was mainly attributed to increased plasma IgM antibody titers, higher levels of lysozyme, enhanced activity of SOD and some regulated genes encoded immune related proteins. Together, the Δfur mutant strain of V. harveyi, as a novel LAV vaccine, demonstrates promising protective effects against V. harveyi infection in American eels, thus presenting a potential candidate vaccine for fish farming.

FIRST REPORT OF RAPHIDASCARIS LOPHII INFECTION IN BLUEFIN SEAROBIN (CHELIDONICHTHYS SPINOSUS)

This study reports on diseased Chelidonichthys spinosus fish that were originally obtained from the Taiwan Strait for exhibition in an aquarium. These fish showed abnormal swimming behavior, eye damage and skin lesions. Gross examination and histopathology revealed that the C. spinosus was suffering from severe nematode infections in the pyloric caeca, liver and mesentery. Marine nematodes from internal organs were verified by partially sequencing the internal transcribed spacer (ITS) gene. Sequencing results revealed that the nematodes shared 99.75% sequence identity with Raphidascaris lophii (GenBank accession No. MW132926). Additionally, secondary Vibrio harveyi infections were also detected in some C. spinosus. This is the first report of R. lophii infection in C. spinosus.

Comparative transcriptome analysis reveals potential regulatory mechanisms of genes and immune pathways following Vibrio harveyi infection in red drum (Sciaenops ocellatus)

Red drum (Sciaenops ocellatus), as an important economical marine fish, has been affected by various bacterial diseases in recent years. Vibrio harveyi cause fatal vibriosis in S. ocellatus, leading to massive mortality and causing significant setbacks in aquaculture. However, the regulatory mechanisms of S. ocellatus response to V. harveyi infection are poorly understood. In this regard, we performed transcriptomic analysis with head kidney tissues of S. ocellatus after V. harveyi infection from 12 h to 48 h to reveal genes, gene expression profiles, and pathways involved in immune and inflammation responses. Specifically, a total of 9,599, 5,728, and 7144 differentially expressed genes (DEGs) were identified after V. harveyi infection at 12 h, 24 h, and 48 h, respectively, and 1,848 shared DEGs have been identified from the above three comparison groups. Subsequent pathway analysis revealed that the shared DEGs following V. harveyi were involved in complement and coagulation cascades (C1R, C1QC, C3, C4, C5, C7, C8A, C8B, C8G, C9, CFB, CFH, and CFI), MAPK signaling pathway, chemokine signaling pathway (CCL19, CXCL8, CXCL12, CXCL14, CCR4, CCR7, and CXCR2), PPAR signaling pathway (PPAR-α, PPAR-γ and PPAR-β), and TNF signaling pathway. Finally, the expression patterns of DEGs in head kidney tissues and S. ocellatus macrophages were validated by qRT-PCR, suggesting the reliability of RNA sequencing for gene expression analysis. This dynamic transcriptome analyses provided insights into gene expression regulation and immune related pathways involved in S. ocellatus after V. harveyi infection, and provides useful information for further study on the immune defense mechanisms in S. ocellatus as well as other teleost species.

MicroRNA transcriptome analysis reveals the immune regulatory mechanism of Crassostrea hongkongesis against Vibrio harveyi infection

MicroRNAs (miRNAs) are small non-coding RNA molecules that modulate target-genes expression and play crucial roles in post-transcriptional regulation and immune system regulation. The Hong Kong oyster (Crassostrea hongkongesis), as the main marine aquaculture shellfish in the South China Sea, not only has high economic and ecological value, but also is an ideal model for conducting research on pathogen host interaction. Vibrio harveyi, a Gram negative luminescent marine bacterium, is widely distributed in coastal water environments and can cause large-scale death of C. hongkongesis. However, little in formation is available on the immune regulatory mechanisms of C. hongkongesis infected with V. harveyi. Therefore, we performed microRNA transcriptome analysis for elucidating the immunoregulation mechanism of C. hongkongesis infected with V. harveyi. The results show that a total of 308468208 clean reads and 288371159 clean tags were obtained. 222 differentially expressed miRNAs were identified. A total of 388 target genes that were differentially expressed and negatively correlated with miRNA expression were predicted by 222 DEmiRs. GO enrichment analysis of 388 DETGs showed that they were mainly enriched in the immune-related term of membrane-bounded vesicle, endocytic vesicle lumen, antigen processing and presentation of exogenous peptide antigen via MHC class I, antigen processing and presentation of peptide antigen via MHC class I, and other immune-related term. KEGG enrichment analysis showed that DETGs were mainly enriched in the Complement and coagulation cascades, Herpes simplex virus 1 infection, Bacterial invasion of epithelial cells, Antigen processing and presentation and NOD-like receptor signaling pathway. The 16 key DEmiRs and their target genes form a regulatory network for seven immune-related pathways. These results suggest that V. harveyi infection induces a complex miRNA response with wide-ranging effects on immune gene expression in the C. hongkongesis. This study explored the immune response of C. hongkongesis to V. harveyi infection at the level of miRNAs, which provides new ideas for the healthy culture and selective breeding of C. hongkongesis.

The dynamic immune response of the liver and spleen in leopard coral grouper (Plectropomus leopardus) to Vibrio harveyi infection based on transcriptome analysis.

Leopard coral grouper (Plectropomus leopardus) is one of the most important cultured fish in the Pacific and Indian oceans. Vibrio harveyi is a serious pathogen causing serious skin ulceration and high mortality in P. leopardus. To gain more insight into the tissue-specific and dynamic immune regulation process of P. leopardus in response to V. harveyi infection, RNA sequencing (RNA-seq) was used to examine the transcriptome profiles in the spleen and liver at 0, 6, 12, 24, 48, and 72h post-infection. The upregulated differentially expressed genes (DEGs) were predominantly involved in the immune response in the spleen and liver at the early infection stage (6-12 h), and downregulated DEGs were mainly involved in metabolic processes in the liver at the early and middle infection stage (6-48 h). Moreover, an overview of the immune response of P. leopardus against V. harveyi was exhibited including innate and adaptive immune-related pathways. Afterwards, the results of WGCNA analysis in the spleen indicated that TAP2, IRF1, SOCS1, and CFLAR were the hub genes closely involved in immune regulation in the gene co-expression network. This study provides a global picture of V. harveyi-induced gene expression profiles of P. leopardus at the transcriptome level and uncovers a set of key immune pathways and genes closely linked to V. harveyi infection, which will lay a foundation for further study the immune regulation of bacterial diseases in P. leopardus.

Application of Fragmented Extracellular Self-DNA (esDNA) Concept as an Alternative Prophylactic Approach against Vibrio parahaemolyticus and Vibrio harveyi Infection in Brine Shrimp Artemia

The purpose of this study was to investigate species specific inhibitory effects of esDNA isolated from two conspecific organisms: Vibrio parahaemolyticus (VP) and Vibrio harveyi (VH), and to assess the functional role of esDNA to enhance the survival rate of Artemia sp. In an in vitro study, nine doses of Extracellular self-DNA of Vibrio parahaemolyticus (esDNAVP) and Vibrio harveyi (esDNAVH) were used as the target for the challenge test with the conspecific bacteria. In an in vivo study, the protective effect of esDNA was then tested in nauplii of the brine shrimp Artemia at various priming times and concentrations of esDNA under gnotobiotic conditions prior to challenge with VP and VH at the concentration of 5 × 105 CFU mL-1. The results from in vitro study showed that the use of esDNAVP at levels of 24.02 and 48.05 ng µl-1 and esDNAVH at concentrations of 13.33 and 26.67 ng µl-1 were able to inhibit the growth of the conspecific species when added to the culture medium at the concentration level of 5 × 105 CFU mL-1. The results from in vivo study showed that the use of 24.02; 48.05 and 72.07 ng µl-1 of esDNAVP as well as the use of 13.33; 26.67 and 40.00 ng µl-1 of esDNAVH inhibited the growth of VP and VH and enhanced the survival rate of Artemia sp compared to the control treatment (P&lt;0.05). Taken together, we confirmed that esDNA obtained from the extraction and random fragmentation from esDNAVP and esDNAVH, produces a species-specific inhibitory effect on the same species and can serve as a potential alternative strategy for disease control to deliver the functionality of esDNA to the fish and shrimp.

Dietary supplementation of Polygonum chinense improves the immunity of Asian seabass, Lates calcarifer (Bloch, 1790) against Vibrio harveyi infection

Aquaculture plays a significant role in the overall fish production in Malaysia, contributing a substantial quantity of food-fish amounting to roughly 573,683 tonnes with an estimated economic value of US$860 million in 2022. However, diseases have become a significant limitation for aquaculture production. Therefore, herbal immunostimulant has been considered a natural and practical approach of preventing disease infection in fish. The ability of Polygonum chinense extract (PCE) on haemato-biochemistry parameters, immunomodulatory properties, and disease resistance of Lates calcarifer (Asian seabass) under Vibrio harveyi challenge was evaluated in this study, with a focus on dose-response associations and variability over various exposure durations (0-, 7- and 14-day post-infection). A total of 480 Asian seabass (9.5 ± 0.2 g) were distributed in 12 aquaria and fed four diets supplemented with 0 (control), 2, 5 and 10 g/kg diet for 60 days before being challenged with V. harveyi. Dietary PCE significantly improved (P < 0.05) survival, with the dose of 10 g/kg showing the highest survival rate (90 %) when compared to the control (60 %). Additionally, hematological (red and white blood cell counts, hemoglobulin, packed cell volume, and mean corpuscular volume) and immunological (activities of lysozyme, phagocytic activity and respiratory burst, and serum total immunoglobulin) properties were significantly increased (P < 0.05) in comparison to the control group. In contrast, serum aspartate aminotransferase and alanine aminotransferase levels, as well as glucose level were significantly reduced (P < 0.05) in PCE-fed fish compared to the control group. Conclusively, the current study discovered that supplementing fish feed with P. chinense extract improves fish haemato-biochemical profile, immunocompetence and disease resistance to V. harveyi infection.