Knowns and unknowns of TiLV-associated neuronal disease

Tilapia Lake Virus (TiLV) is associated with pathological changes in the brain of infected fish, but the mechanisms driving the virus's neuropathogenesis remain poorly characterized. TiLV establishes a persistent infection in the brain of infected fish even when the virus is no longer detectable in the peripheral organs, rendering therapeutic interventions and disease management challenging. Moreover, the persistence of the virus in the brain may pose a risk for viral reinfection and spread and contribute to ongoing tissue damage and neuroinflammatory processes. In this review, we explore TiLV-associated neurological disease. We discuss the possible mechanism(s) used by TiLV to enter the central nervous system (CNS) and examine TiLV-induced neuroinflammation and brain immune responses. Lastly, we discuss future research questions and knowledge gaps to be addressed to significantly advance this field.

Preparation and characterization of tilapia protein isolate - Hyaluronic acid complexes using a pH-driven method for improving the stability of tilapia protein isolate emulsion

This study aimed to investigate the non-covalent complexation between hyaluronic acid (HA) and tilapia protein isolate (TPI) on the stability of oil-in-water (O/W) TPI emulsion. The results showed that HA binds to TPI through electrostatic, hydrophobic, and hydrogen bonding interactions, forming homogeneous hydrophilic TPI-HA complexes. The binding of HA promoted the structural folding of TPI and altered its secondary structure during pH neutralization. The TPI-HA complexes presented significantly improved EAI and ESI (P < 0.05) when the HA concentration was 0.8 % (w/v). Emulsion characterization showed that HA promoted the transfer of TPI to the O/W interface, forming an emulsion with excellent stability, which, combined with the high surface charge and strong spatial site resistance effect of HA, improved TPI emulsion stability. Therefore, non-covalent complexation with HA is an effective strategy to improve the stability of TPI emulsion.

Interferon regulatory factors inhibit TiLV replication by activating interferon-a3 in tilapia (Oreochromis niloticus)

Tilapia lake virus (TiLV) is an emerging virus that seriously threatens the tilapia industries worldwide. Interferon regulatory factors (IRFs), which are the crucial mediators regulating the response of interferon (IFN) to combat invading viruses, have not yet been reported in tilapia during TiLV infection. Here, six IRF (IRF1, IRF2, IRF4, IRF7, IRF8, and IRF9) homologs from tilapia were characterized and analyzed. These IRFs typically shared the conserved domains and phylogenetic relationship with IRF homologs of other species. Tissue distribution analysis showed that all six IRF genes were expressed in various tissues, with the highest expression in immune-related tissues. Furthermore, overexpression of IRFs in tilapia brain (TiB) cells significantly inhibited TiLV propagation, as evidenced by decreased viral segment 8 gene transcripts and copy numbers of viral segment 1. More importantly, all six IRF genes significantly enhanced the promoter activity of type I interferon-a3 (IFNa3) in TiB cells, suggesting that tilapia IRF genes serve as positive regulators in activating IFNa3. Surprisingly, the promoter activity of IFNa3 mediated by IRF genes was markedly inhibited post-TiLV infection, indicating that TiLV antagonized IRF-mediated IFN immune response. Taken together, six IRF genes of tilapia are highly conserved transcription factors that inhibit TiLV infection by activating the promoter of IFNa3, which is in turn restrained by TiLV. These findings broaden our knowledge about the functionality of IRF-mediated antiviral immunity in tilapia against TiLV infection and host-TiLV interaction, which lays a foundation for developing antiviral strategies in tilapia cultural industries.

Formation and improvement mechanism of physical property and volatile flavor of fermented tilapia surimi by newly isolated lactic acid bacteria based on two dimensional correlation networks

Fermentation is an effective way to improve the gel properties of freshwater fish surimi. In this study, two newly isolated Lactiplantibacillus plantarum H30-2 and Pediococcus acidilactici H30-21 were used to improve the physical properties and volatile flavor of fermented tilapia surimi. L. plantarum H30-2 quickly improved the whiteness, gel strength, hardness, and chewiness within 18 h. Among 172 volatile compounds analyzed by HS-SPME-GC-MS, most pleasant core flavor compounds (OAV ≥ 1) were improved by L. plantarum H30-2. L. plantarum H30-2 could always adapt to the surimi environment while P. acidilactici H30-21 could not. Two dimensional correlation networks showed that Lactiplantibacillus and Lactococcus were responsible for the quality formation in surimi during natural fermentation or with starters, while the quality improvement after L. plantarum H30-2 addition mainly resulted from the increasing Lactiplantibacillus and its higher acetic acid production. L. plantarum H30-2 can be developed as a special starter using for tilapia surimi fermentation.

Chromosome level genome assembly and transcriptome analysis of E11 cells infected by tilapia lake virus

The E11 cell line, derived from striped snakehead fish (Channa striata), possesses a distinctive feature: it is persistently infected with a C-type retrovirus. Notably, it exhibits high permissiveness to piscine nodavirus and the emerging tilapia lake virus (TiLV). Despite its popularity in TiLV research, the absence of genome assembly for the E11 cell line and Channa striata has constrained research on host-virus interactions. This study aimed to fill this gap by sequencing, assembling, and annotating the E11 cell line genome. Our efforts yielded a 600.5 Mb genome including 24 chromosomes with a BUSCO score of 98.8%. In addition, the complete proviral DNA sequence of snakehead retrovirus (SnRV) was identified in the E11 cell genome. Comparative genomic analysis between the E11 cell line and another snakehead species Channa argus revealed the loss of many immune-related gene families in the E11 cell genome, indicating a compromised immune response. We also conducted transcriptome analysis of mock- and TiLV-infected E11 cells, unveiling new perspectives on virus-virus and host-virus interactions. The TiLV infection suppressed the high expression of SnRV in E11 cells, and activated some other endogenous retroviruses. The protein-coding gene comparison revealed a pronounced up-regulation of genes involved in immune response, alongside a down-regulation of genes associated with specific metabolic processes. In summary, the genome assembly and annotation of the E11 cell line provide valuable resources to understand the SnRV and facilitate further studies on nodavirus and TiLV. The RNA-seq profiles shed light on the cellular mechanisms employed by fish cells in response to viral challenges, potentially guiding the development of therapeutic strategies against TiLV in aquaculture. This study also provides the first insights into the viral transcriptome profiles of endogenous SnRV and evading TiLV, enhancing our understanding of host-virus interactions in fish.

Pathogenic bacteria prevalence in cultured Nile tilapia in Southwest Mexico: A real-time PCR analysis

The present study investigates molecular-based PCR techniques to estimate the prevalence of fish pathogens in southwest Mexico where recurrent mortality in the tilapia cultures has been observed. Sample of internal organs and lesions of Nile tilapia were taken and analysed in 2018, 2019, 2020 and 2022 to detect bacterial pathogens using PCR. No samples were taken in 2021 due to the COVID-19 pandemic. The real-time PCR conditions were optimized to allow a qualitative reliable detection of the bacteria from fixed fish tissue. A total of 599 pond- and cage-cultured tilapia from the southwestern Mexican Pacific (Guerrero, Oaxaca and Chiapas states) were analysed. In this tropical region, during 2018 and 2019 water temperatures of the tilapia cultures were generally with the optimal range to grow Nile tilapia, although extreme values were recorded on some farms. Most of the tilapia sampled were apparently healthy. No Francisella sp. was detected in any sample, and Staphylococcus sp. was the most prevalent (from 0% to 64%) bacteria from the three states over time. Low prevalence of Aeromonas sp. was found, from 0% to 4.3%, although the fish pathogen Aeromonas dhakensis was not detected. Sterptococcus iniae was only detected in Chiapas in 2019 at a low prevalence (1.4%), while the major tilapia pathogen S. agalactiae was detected at a high prevalence (from 0% to 59%) in the three Mexican states. This is the first detection of these pathogenic bacteria in rural farms using real-time PCR and constitutes a great risk for tilapia aquaculture in Mexico, as well as a potential dispersion of these pathogens to other aquaculture areas.

Inducible IL-2 production and IL-2+ cell expansion are landmark events for T-cell activation of teleost

As a multipotent cytokine, interleukin (IL)-2 plays important roles in activation, differentiation and survival of the lymphocytes. Although biological characteristics and function of IL-2 have been clarified in several teleost species, evidence regarding IL-2 production at the cellular and protein levels is still scarce in fish due to the lack of reliable antibody. In this study, we developed a mouse anti-Nile tilapia IL-2 monoclonal antibody (mAb), which could specifically recognize IL-2 protein and identify IL-2-producing lymphocytes of tilapia. Using this mAb, we found that CD3+ T cells, but not CD3- lymphocytes, are the main cellular source of IL-2 in tilapia. Under resting condition, both CD3+CD4-1+ T cells and CD3+CD4-1- T cells of tilapia produce IL-2. Moreover, the IL-2 protein level and the frequency of IL-2+ T cells significantly increased once T cells were activated by phytohemagglutinin (PHA) or CD3 plus CD28 mAbs in vitro. In addition, Edwardsiella piscicida infection also induces the IL-2 production and the expansion of IL-2+ T cells in the spleen lymphocytes. These findings demonstrate that IL-2 takes part in the T-cell activation and anti-bacterial adaptive immune response of tilapia, and can serve as an important marker for T-cell activation of teleost fish. Our study has enriched the knowledge regarding T-cell response in fish species, and also provide novel perspective for understanding the evolution of adaptive immune system.

Identification and florfenicol-treatment of pseudomonas putida infection in gilthead seabream (Sparus aurata) fed on tilapia-trash-feed

The present study aimed to determine the major cause of the high mortality affecting farmed gilthead seabream (Sparus aurata) and controlling this disease condition. Fifteen diseased S. aurata were sampled from a private fish farm located at Eldeba Triangle, Damietta, fish showed external skin hemorrhages, and ulceration. Bacterial isolates retrieved from the diseased fish were identified biochemically as Pseudomonas putida and then confirmed by phylogenetic analysis of the 16 S rRNA gene sequence. P. putida was also isolated from three batches of tilapia-trash feed given to S. aurata. Biofilm and hemolytic assay indicated that all P. putida isolates produced biofilm, but 61.11% can haemolyse red blood cells. Based on the antibiotic susceptibility test results, P. putida was sensitive to florfenicol with minimum inhibitory concentrations ranging between 0.25 and 1.0 µg mL- 1, but all isolates were resistant to ampicillin and sulfamethoxazole-trimethoprim. Pathogenicity test revealed that P. putida isolate (recovered from the tilapia-trash feed) was virulent for S. aurata with LD50 equal to 4.67 × 107 colony forming unit (CFU) fish- 1. After intraperitoneal (IP) challenge, fish treated with 10 mg kg- 1 of florfenicol showed 16.7% mortality, while no mortality was recorded for the fish group that received 20 mg kg- 1. The non-treated fish group showed 46.7% mortality after bacterial challenge. HPLC analysis of serum florfenicol levels reached 1.07 and 2.52 µg mL- 1 at the 5th -day post-drug administration in the fish groups received 10 and 20 mg kg- 1, respectively. In conclusion, P. putida was responsible for the high mortality affecting cultured S. aurata, in-feed administration of florfenicol (20 mg kg- 1) effectively protected the challenged fish.

Changes in volatile compounds and lipid oxidation in various tissues of Nile tilapia (Oreochromis niloticus) during ice storage

Changes in the lipid oxidation and volatile compounds of a variety of tilapia tissues (Oreochromis niloticus) including the muscle, gills, and skin during ice storage were investigated by evaluating peroxide values (PVs), lipoxygenase (LOX) activity, fatty acid (FA) composition, and volatile substances. LOX activity and PV were determined in the gills, skin, and muscles throughout 9 days of storage in ascending order to the extended storage time. The highest level of LOX activity was found in the gills, whereas the highest PV was determined in the skin. FA content of all tissues decreased during the storage period. Oleic acid was the predominant monounsaturated fatty acid, whereas linoleic acid and docosahexaenoic acid were the main polyunsaturated fatty acids and omega-3 in all tissues. The fish gills were shown to have the highest level of volatile compounds followed by the skin and muscle, based on headspace solid-phase microextraction coupled with gas chromatography and mass spectrometry. Principal component analysis indicated gradual changes in the volatile compound composition with increasing storage time. 2-Butanone and nonanal in the muscle, 6-methyl-2-heptanone and 2-nonenal in the gills, and 1-heptanol, and 1-nonanol in the skin were found to be the potential freshness indicators. In addition, hexanal could be a general potential marker for measuring the degree of lipid oxidation in all tissues. PRACTICAL APPLICATION: Understanding the volatile compound formation related to lipid oxidation within storage time at various tissues of tilapia could be critical to the side-stream processing to yield the desired quality.

Assessing the effect of β-glucan diets on innate immune response of tilapia macrophages against trichlorfon exposure: an in vitro study

The widespread use of pesticides in some areas where fish species such as tilapia are farmed may cause damage to the environment and affect commercial fish and therefore, human health. Water leaching with the pesticide trichlorfon, during the fumigation season in the field, can affect water quality in fish farms and consequently affect fish health. At the same time, the use of immunomodulatory compounds such as β-glucan supplied in the diet has become widespread in fish farms as it has been shown that improves the overall immune response. The present research examines the immunomodulatory impacts observed in macrophages of Nile tilapia (Oreochromis niloticus) after being fed a diet supplemented with β-glucan for 15 days, followed by their in vitro exposure to trichlorfon, an organophosphate pesticide, at concentrations of 100 and 500 µg mL-1 for 24 h. The results showed that β-glucan diet improved the viability of cells exposed to trichlorfon and their antioxidant capacity. However, β-glucan did not counteract the effects of the pesticide as for the ability to protect against bacterial infection. From the present results, it can be concluded that β-glucan feeding exerted a protective role against oxidative damage in cells, but it was not enough to reduce the deleterious effects of trichlorfon on the microbicidal capacity of macrophages exposed to this pesticide.

Innate immunity response of zafirlukast treated-tilapia during foreign body inflammation

There is limited knowledge regarding the blockade of cysteinyl leukotriene receptors (CysLTRs) and their effects in teleost fish. The present study investigated the effects of Zafirlukast, antagonist of CysLTR1 receptor, on the foreign body inflammatory reaction in Nile tilapia (Oreochromis niloticus). Zafirlukast-treated tilapia demonstrated a decrease in the formation of multinucleated foreign body giant cells and Langhans cells on the round glass coverslips implanted in the subcutaneous tissue, along with a significant reduction in white blood cell counts and decreased production of reactive oxygen species. There was an increase in serum levels of α2-macroglobulins, as well as a decrease in ceruloplasmin and haptoglobin. Zafirlukast treatment led to a significant decrease in the area of splenic melanomacrophage centers and a reduction in the presence of lipofuscin. These findings highlight the potential anti-inflammatory effects of zafirlukast treatment in tilapia and indicate its action on CysLTR1 receptor, modulating the innate immune response of tilapia during the foreign body reaction. The comprehension of chronic inflammation mechanisms in fish has become increasingly relevant, especially concerning the utilization of biomaterials for vaccine and drug delivery.

A sustainable strategy for generating highly stable human skin equivalents based on fish collagen

Tissue engineered skin equivalents are increasingly recognized as potential alternatives to traditional skin models such as human ex vivo skin or animal skin models. However, most of the currently investigated human skin equivalents (HSEs) are constructed using mammalian collagen which can be expensive and difficult to extract. Fish skin is a waste product produced by fish processing industries and identified as a cost-efficient and sustainable source of type I collagen. In this work, we describe a method for generating highly stable HSEs based on fibrin fortified tilapia fish collagen. The fortified fish collagen (FFC) formulation is optimized to enable reproducible fabrication of full-thickness HSEs that undergo limited contraction, facilitating the incorporation of human donor-derived skin cells and formation of biomimetic dermal and epidermal layers. The morphology and barrier function of the FFC HSEs are compared with a commercial skin model and validated with immunohistochemical staining and transepithelial electrical resistance testing. Finally, the potential of a high throughput screening platform with FFC HSE is explored by scaling down its fabrication to 96-well format.

The opioid peptide leucine enkephalin modulates hypothalamic-hypophysial axis in the cichlid fish Oreochromis mossambicus

In vertebrates, opioid peptides are thought to be involved in the regulation of reproduction; however, the significance of enkephalins in testicular function remains unclear. We examined the influence of δ-opioid receptor agonist leucine enkephalin (L-ENK) on the hypophysial-testicular axis of the cichlid fish Oreochromis mossambicus. Treatment with a low dose of L-ENK (60 µg) caused a significant increase in the numbers of primary and secondary spermatocytes and early and late spermatids, concomitant with intense immunolabelling of testicular androgen receptors, but did not significantly alter serum luteinizing hormone (LH) and 11-ketotestosterone (11-KT) levels compared to those of controls. Nevertheless, treatment with a high dose of L-ENK (200 µg) caused a significant reduction in the numbers of secondary spermatocytes as well as late spermatids associated with marginal immunolabelling of androgen receptors and significantly lower concentrations of serum 11-KT and LH compared to controls. In addition, the serum cortisol level was not affected in low-dose L-ENK-treated fish, but its level was significantly increased in the high-dose L-ENK-treated group. Together, these findings indicate that a low dose of L-ENK stimulates the germ cells at the meiosis stage and promotes further stages of spermatogenesis, whereas a high concentration of L-ENK inhibits spermatogenesis at the advanced stages. This effect appears to be mediated through the suppression of testicular steroidogenesis and the reduction of LH release in the pituitary gland of tilapia. The findings also suggest that elevated L-ENK levels in teleosts may exert their inhibitory influence on the hypophysial-testicular axis via glucocorticoids.

Non-destructive prediction of TVB-N using color-texture features of UV-induced fluorescence image for freeze-thaw treated frozen-whole-round tilapia

BACKGROUND

The investigation of UV-induced fluorescence imaging coupled with machine learning was conducted to non-destructively detect the total volatile basic nitrogen (TVB-N) of frozen-whole-round tilapia (FWRT) during freezing and thawing. The UV-induced fluorescence images of FWRT at the wavelength of 365 nm were acquired by self-developed fluorescence image acquisition system. In total, 169 color and texture features based on RGB, hue-saturation-intensity and L*a*b* color spaces and gray level co-occurrence matrix were extracted, respectively. Successive projections algorithm (SPA) was employed to select the optimal 16 features to achieve feature dimension reduction modeling. With full and extracted features as input, the models of partial least squares regression (PLSR), least-squares support vector machine (LSSVM) and convolutional neural network (CNN) were established for TVB-N prediction.

RESULTS

Results indicated that the full features-based CNN performed better than SPA based prediction models (SPA-PLSR and SPA-LSSVM). The CNN model was determined to be the optimal with an RP2 value of 0.9779, RMSEP value of 1.1502 × 10-2  g N kg-1 and RPD value of 6.721 for TVB-N content predictiin.

CONCLUSION

The CNN method based on UV fluorescence imaging technology has potential for quality and safety detection of FWRT. © 2023 Society of Chemical Industry.

Analysis of changes in volatile compounds and evolution in free fatty acids, free amino acids, nucleotides, and microbial diversity in tilapia (Oreochromis mossambicus) fillets during cold storage

BACKGROUND

Aquatic products are rich in nutrients and unique in flavor, and are popular among the public. However, aquatic products are extremely susceptible to quality degradation during storage, of which odor deterioration is the most obvious and influential aspect. Odor deterioration in aquatic products is widespread and severely affects overall flavor and quality. In this study, odor deterioration and flavor-related quality degradation of tilapia during cold storage are discussed, focusing on the changes in volatile compounds and the evolution of free fatty acids (FFAs), free amino acids (FAAs), nucleotides, and microbial diversity.

RESULTS

A total of 63 volatile compounds were detected by gas chromatography-mass spectrometry, including 11 hydrocarbons, 10 alcohols, 6 aldehydes, 8 ketones, 6 esters, 9 aromatics, 3 phenols, and 10 other compounds. Microbial diversity analysis revealed that Acinetobacter, Psychrobacter, Vagococcus, and Myroides were the main dominant species of tilapia at the end of cold storage and predicted that microorganisms could influence the flavor of tilapia by participating in important metabolic pathways. Meanwhile, the evolution of FFAs, FAAs, and nucleotides also had a significant impact on odor deterioration, as evidenced by the contribution of unsaturated fatty acids (such as oleic acid and linoleic acid), Lys, and off-flavor nucleotides (HxR and Hx) to the undesirable flavor. Oxidation of oleic acid and linoleic acid resulted in changes in aldehydes, with Lys, HxR, and Hx being key flavor precursors and off-flavor contributors.

CONCLUSION

This study contributes to a comprehensive overview of odor deterioration and the evolution of flavor-related quality in tilapia during cold storage, providing new insights into the regulation of overall flavor and quality. © 2023 Society of Chemical Industry.

Differentiation of protein types extracted from tilapia byproducts by FTIR spectroscopy combined with chemometric analysis and their antioxidant protein hydrolysates

This research aimed to characterize protein types including sarcoplasmic protein (SP), myofibrillar protein (MP), and alkali-aided protein extract (AP) prepared from tilapia byproducts using water, 0.6 M NaCl, and alkaline solution (pH 11), respectively compared to freeze-dried minced tilapia muscle (CONTROL). Principal component analysis was performed from second derivative FTIR spectra to differentiate protein type. The AP mostly contained β-sheet structure and had low total sulfhydryl content and surface hydrophobicity. SP can be distinguished from MP by the loading plots of the FTIR bands representing the α-helical structure. While the bands for lipids and β-sheet of protein were noted for differentiating AP from CONTROL. After being hydrolyzed by Protease G6, the AP hydrolysate disclosed the highest ABTS radical scavenging activity, while the SP hydrolysate revealed the strongest metal chelating ability. Thus, an understanding of how fish processing waste can be utilized in the production of antioxidant protein hydrolysates has been achieved.

Phenotypic, molecular detection, and Antibiotic Resistance Profile (MDR and XDR) of Aeromonas hydrophila isolated from Farmed Tilapia zillii and Mugil cephalus

In the present study, Aeromonas hydrophila was isolated from Tilapia zillii and Mugil cephalus samples collected during different seasons from various Suez Canal areas in Egypt. The prevalence of A. hydrophila, virulence genes, and antibiotic resistance profile of the isolates to the commonly used antibiotics in aquaculture were investigated to identify multiple drug resistance (MDR) and extensive drug-resistant (XDR) strains. In addition, a pathogenicity test was conducted using A. hydrophila, which was isolated and selected based on the prevalence of virulence and resistance genes, and morbidity of natural infected fish. The results revealed that A. hydrophila was isolated from 38 of the 120 collected fish samples (31.6%) and confirmed phenotypically and biochemically. Several virulence genes were detected in retrieved A. hydrophila isolates, including aerolysin aerA (57.9%), ser (28.9%), alt (26.3%), ast (13.1%), act (7.9%), hlyA (7.9%), and nuc (18.4%). Detection of antibiotic-resistant genes revealed that all isolates were positive for blapse1 (100%), blaSHV (42.1%), tetA (60.5%), and sul1 (42.1%). 63.1% of recovered isolates were considered MDR, while 28.9% of recovered isolates were considered XDR. Some isolates harbor both virulence and MDR genes; the highest percentage carried 11, followed by isolates harboring 9 virulence and resistance genes. It could be concluded that the high prevalence of A. hydrophila in aquaculture species and their diverse antibiotic resistance and virulence genes suggest the high risk of Aeromonas infection and could have important implications for aquaculture and public health.

Microplastics and nanoplastics induced differential respiratory damages in tilapia fish Oreochromis niloticus

With the increasing micro(nano)plastics (MNPs) pollution in aquatic environments, fish respiration is encountering a huge threat. Herein, polystyrene (PS) MNPs with three sizes (80 nm, 2 µm, and 20 µm) were exposed to tilapia Oreochromis niloticus at an environmentally relevant concentration of 100 μg/L for 28 days and their impacts on respiratory function were investigated. Based on the results of oxygen consumption and histological analysis, all the three treatments could induce respiratory damages and such impacts were more severe for the 2 µm and 20 µm treatments than for the 80 nm treatment. These results were explained by the more significant upregulation of egln3 and nadk, and the downregulation of isocitrate. Transcriptomics and metabolomics further revealed that TCA cycle played a key role in respiratory dysfunction induced by micro-sized PS particles, and cytokine and chemokine related functions were simultaneously enriched. Although nano-sized PS particles had the potential to penetrate the respiratory epithelium and reached the internal structure of the O. niloticus gills, they were easily expelled through the blood circulation. Our results highlighted the serious threat of MNPs to fish respiration and provided insights into the differential toxicological mechanisms between micro-sized and nano-sized particles, thus assisting in ecological risk assessments.

Systemic and mucosal immune responses in red tilapia (Oreochromis sp.) following immersion vaccination with a chitosan polymer-based nanovaccine against Aeromonas veronii

A mucoadhesive chitosan polymer-based nanoplatform has been increasingly recognized as an effective mucosal vaccine delivery system for fish. The present study aimed to investigate the effectiveness of immersion vaccination with a chitosan polymer-based nanovaccine to elicit an immune response in serum and mucus of red tilapia and evaluate its protective efficacy after immersion challenge with a heterogenous strain of Aeromonas veronii UDRT09. Six hundred red tilapia (22 ± 1.8 g) were randomly allocated into four experimental groups: control, empty-polymeric nanoparticle (PC), formalin-killed vaccine (FKV), and chitosan polymer-based nanovaccine (CS-NV) in triplicate. The specific IgM antibody levels and their bactericidal activity were assessed in serum and mucus for 28 days after immersion vaccination and followed by immersion challenge with A. veronii. The immersion vaccine was found to be safe for red tilapia, with no mortalities occurring during the vaccination procedure. The specific IgM antibody levels and bactericidal activity against A. veronii in both serum and mucus were significantly higher in red tilapia vaccinated with CS-NV compared to the FKV and control groups at all time points. Furthermore, the serum lysozyme activity, ACH50, and total Ig levels demonstrated a significant elevation in the groups vaccinated with CS-NV compared to the FKV and control groups. Importantly, the Relative Percentage Survival (RPS) value of the CS-NV group (71 %) was significantly higher than that of the FKV (15.12 %) and PC (2.33 %) groups, respectively. This indicates that the chitosan polymer-based nanovaccine platform is an effective delivery system for the immersion vaccination of tilapia.

A cell line derived from heart of rainbow trout is refractory to Tilapia lake virus

Cell lines are important in vitro models to answer biological mechanisms with less genetic variations. The present study was attempted to develop a cell line from rainbow trout, where we obtained a cell line from the heart, named "RBT-H." The cell line was authenticated using karyotyping and cytochrome c oxidase subunit I (COI) gene sequencing. The karyotype demonstrated diploid chromosome number (2n) as 62 and the sequence of partial COI gene was 99.84% similar to rainbow trout COI data set, both suggesting the origin of RBT-H from the rainbow trout. The heart cell line was mycoplasma-free and found to be refractory to infection with the Tilapia lake virus. The RBT-H cell line is deposited in the National Repository of Fish Cell Line (NRFC) at ICAR-NBFGR, Lucknow, India, with Accession no. NRFC0075 for maintenance and distribution to researchers on request for R&D.

Chicken egg lysozyme enhanced the growth performance, feed utilization, upregulated immune-related genes, and mitigated the impacts of Aeromonas hydrophila infection in Nile tilapia (Oreochromisniloticus)

Functional supplements, including lysozyme, are highly approved as immunostimulant and antibacterial agents with a high potential for use in aquaculture. In this regard, Nile tilapia was treated with lysozyme at 0, 0.5, 1, 1.5, and 3 g/kg for 60 days, then challenged with Aeromonas hydrophila. Fish were stocked in 15 glass aquaria (70 L each) with an equal initial weight of 10.72 ± 0.71 g per fish and 15 fish per aquarium. The regression analysis revealed that dietary lysozyme supplementation at 1.83-2 g/kg enhanced the growth performance, protein efficiency ratio, and protein productive value while reducing the feed conversion ratio of tilapia. Markedly, tilapia treated with lysozyme had a low mortality rate (30-50 %) compared to the control, which recorded a 70 % mortality rate after 15 days of challenge with A. hydrophila. The regression analysis also revealed that the highest lysozyme activity of tilapia-fed lysozyme for 60 days is achieved by 2.05 g/kg lysozyme. The expression of Nf-κb, IL-1β, and IL-8 genes is upregulated in tilapia-fed lysozyme at 0.5, 1, 1.5, and 3 g/kg for 60 days before and after A. hydrophila infection. The expression of GPX and CAT genes was higher in tilapia-fed lysozyme at 0.5, 1, 1.5, and 3 g/kg for 60 days before and after A. hydrophila infection. Before infection, the relative transcription of the lysozyme and C3 was upregulated in tilapia-fed lysozyme at 0.5, 1, 1.5, and 3 g/kg. However, lysozyme gene expression in tilapia treated with 0.5 g/kg lysozyme had no significant differences from those fed 0 g/kg lysozyme. After infection, the relative transcription of the lysozyme gene was upregulated in tilapia fed 1 and 1.5 g/kg, while tilapia fed 1 g/kg lysozyme had the highest C3 gene transcription. After infection, the hepatocytes in the livers of fish fed 0 g/kg lysozyme exhibited a noticeable fatty alteration, along with congestion, a light infiltration of inflammatory cells, and the start of necrosed cell regeneration. However, the livers of fish that received lysozyme were normal except for infiltrations of perivascular and interstitial mononuclear cells, depending on the supplementation dose. In conclusion, dietary lysozyme is recommended at 1.83-2.05 g/kg to gain high growth performance, immune response, and high resistance to A. hydrophila in Nile tilapia.

Flavor formation of tilapia byproduct hydrolysates in Maillard reaction

The Maillard reaction (MR) of tilapia byproduct protein hydrolysates was investigated for the use of byproduct protein as a food ingredient and to mask its fishy odor and bitter flavor. The flavor differences in tilapia byproduct hydrolysates before and after the MR were analyzed to explore the key flavor precursor peptides and amino acids involved in MR. The results suggested that eight key volatile substances, including 2,5-dimethylpyrazine, 2-pentylfuran, hexanal, octanal, nonanal, (E)-2-decenal, decanal, and 1-octen-3-ol contributed most to the MR products group (ROAV > 1). Ten volatile compounds, including 1-octen-3-ol, hexanal, 2-pentylfuran, 2,5-dimethylpyrazine, methyl decanoate, and 2-octylfuran, were the flavor markers that distinguished the different samples (VIP > 1). The four most consumed peptides were VAPEEHPTL, GPIGPRGPAG, KSADDIKKAF, and VWEGQNIVK. Umami peptides and bitter free amino acids (FAAs) were the key flavor precursor peptide and FAAs, respectively. Overall, the hydrolysates of tilapia byproducts with flavor improved by MR are a promising strategy for the production of flavorings.

A comparative study on inhibition of lung cancer cells by nanoemulsion, nanoliposome, nanogold and their folic acid conjugates prepared with collagen peptides from Taiwan tilapia skin

Valorization of fish processing waste to obtain value-added products such as collagen and bioactive peptides is a vital strategy to increase the economic value, reduce disposal problems, and prevent harmful impacts on both environment and health. This study aims to isolate two collagen peptides from Taiwan Tilapia skin and prepare 12 nanopeptides including nanoemulsion (NE), nanoliposome (NL), and nanogold (NG) without and with folic acid/chitosan (FA/CH) or FA ligand conjugation for comparison of their inhibition efficiency towards lung cancer cells A549 and normal lung cells MRC5. Acid-soluble collagen (yield, 21.58 %) was extracted using 0.5 M acetic acid and hydrolyzed to obtain two tilapia skin collagen peptides TSCP1 (482 Da) and TSCP2 (172 Da) respectively using 2.5 % and 12.5 % alcalase, with sample-to-water ratio at 1:30 (w/v), pH 8, temperature 50 °C, and hydrolysis time 6 h. Characterization of collagen peptides revealed the presence of type 1 collagen with a high amount of amino acids including glycine (32.6-33.1 %), alanine (13.6-14.0 %), proline (10.0-10.5 %), and hydroxyproline (7.3-7.6 %). TSCP1, TSCP2, and 12 nanopeptides showed a higher cytotoxicity towards A549 cells than MRC5 cells, with TSCP2 and its 6 nanopeptides exhibiting a lower IC50 compared to TSCP1 and its 6 nanopeptides. The mean particle size was 15.7, 33.6, and 16.0 nm respectively for TSCP2-NE, TSCP2-NL, and TSCP2-NG, but changed to 14.4, 36.3, and 17.9 nm following ligand conjugation with a shift in zeta potential from negative to positive for TSCP2-NE-FA/CH and TSCP2-NL-FA/CH. All nanopeptides were more effective than peptides in inhibiting the growth of A549 cells, with the lowest IC50 value being shown for TSCP2-NL-FA/CH (5.32 μg/mL), followed by TSCP2-NE-FA/CH (8.3 μg/mL), TSCP2-NE (22.4 μg/mL), TSCP2-NL (82.7 μg/mL), TSCP2-NG-FA (159.8 μg/mL), TSCP2-NG (234.0 μg/mL) and TSCP2 (359.7 μg/mL). Cell proportions of sub-G1, S, and G2/M phases increased dose-dependently, with a possible cell cycle arrest at G2/M phase. The proportion of necrotic cells was the highest for TSCP2, TSCP2-NE, TSCP2-NE-FA/CH, and TSCP2-NL, while that of late apoptotic cells dominated for TSCP2-NL-FA/CH, TSCP2-NG, and TSCP2-NG-FA. Similarly, TSCP2 and its 6 nanopeptides showed a dose-dependent rise in caspase-3, caspase-8, and caspase-9 activities for execution of apoptosis, with the ligand-conjugated nanopeptides being the most efficient, followed by nanopeptides and peptides. The outcome of this study demonstrated an effective strategy for valorization of Taiwan tilapia skin to obtain collagen peptides and their nanopeptides possessing anticancer activity and form a basis for in vivo study in the future.

Microalgae as fishmeal alternatives in aquaculture: current status, existing problems, and possible solutions

Fishmeal is an indispensable ingredient for most aquatic animals. However, the finite supply and escalating price of fishmeal seriously limit its use in aquaculture. Thus the development of new, sustainable protein ingredients has been a research focus. Microalgae are potential fishmeal alternatives owing to their high protein content and balanced amino acid profile. Studies suggest that suitable replacement of fishmeal with microalgae is beneficial for fish growth performance, but excessive replacement would induce poor growth and feed utilization. Therefore, this paper aims to review research on the maximum substitutional level of fishmeal by microalgae and propose the main issues and possible solutions for fishmeal replacement by microalgae. The maximum replacement level is affected by microalgal species, fish feeding habits, quality of fishmeal and microalgal meals, and supplemental levels of fishmeal in the control group. Microalgae could generally replace 100%, 95%, 95%, 64.1%, 25.6%, and 18.6% fishmeal protein in diets of carp, shrimp, catfish, tilapia, marine fish, and salmon and trout, respectively. The main issues with fishmeal replacement using microalgae include low production and high production cost, poor digestibility, and anti-nutritional factors. Possible solutions to these problems are recommended in this paper. Overall, microalgae are promising fishmeal alternatives in aquaculture.

Evaluating the persistence of malachite green residues in tilapia and pacu fish

Although banned in food-producing animals, residues of malachite green (MG) and its primary metabolite, leucomalachite green (LMG), have been found in fish due to illegal use in aquaculture and the release of industrial wastewater, which represent a serious risk to food and environmental securities. This study aimed to investigate the residue depletion profile of MG and LMG in edible tissues of Nile tilapia (Oreochromis niloticus) and pacu (Piaractus mesopotamicus) cultured simultaneously under the same environmental conditions to support control measures in case of abuse. An analytical method involving QuEChERS sample preparation and liquid chromatography coupled to tandem mass spectrometry was developed, validated, and applied to quantify MG and LMG residues in fish fillets from two depletion experiments after treatment by immersion bath (MG at 0.10 mg L-1 for 60 min). During the experiment, the average water temperature was 30 ºC, while the pH was 6.9. The method is selective, precise (CV = 0.4 - 22%) and accurate (recovery 92 - 114%). The limits of detection and quantification are 0.15 and 0.5 ng g-1, respectively. In both species, the sum of MG and LMG residues were quantified up to the 32nd day post-exposure, and the concentrations were significantly higher in the pacu fillets (up to 3284 ng g-1) than in Nile tilapia (up to 432 ng g-1). The sums of MG and LMG residues were below 2 ng g-1 at 44 days and 342 days for Nile tilapia and pacu, respectively - the Minimum Required Performance Limit (MRPL) for analytical methods intended to monitor forbidden substances in food according to old European Commission guidelines. The persistence of MG residues in pacu may be attributed to its higher lipid content, which favors the accumulation of the non-polar metabolite LMG. These results provide insights into the concern about human, animal, and environmental health risks resulting from unauthorized use or aquatic contamination by industrial wastewater containing MG residues.

infection in tilapia

Nocardiosis has caused high mortalities among fish cultures; however, the effects of Nocardia infections in the fish gastrointestinal microbiota are unknown. In this research, tilapia was infected with Nocardia sp., to analyze the effect of infection on the gastrointestinal microbiota. Tilapia infected with Nocardia sp. reported a 46 % survival (100 % in non-infected). Moreover, the infection caused severe damage to the stomach microbiota, with a loss of diversity and a significant increase of Proteobacteria (94.8 %), resulting in a negative correlation network between Proteobacteria and other important phyla. Nocardia sp. is an emerging pathogen capable of inducing dysbiosis and causing significant mortalities.

Tilapia-Derived Granular Hydrogel as a 3D Scaffold Promoting Rapid Wound Healing

The skin, a crucial organ that protects the body, is vulnerable to external damage. Traditional tissue regeneration methods, including bulk hydrogels, aim to facilitate wound healing by interacting with host cells and providing a conducive environment. However, the nanoscale porosity of conventional hydrogels limits cell penetration and tissue regeneration. To overcome this, hydrogels composed of microgels have emerged as promising alternatives. In this study, we propose a granular hydrogel using decellularized tilapia skin. The tilapia skin-based microgels are cost-effective, immune-friendly, and have a high collagen content. Microgels based on the decellularized extracellular matrix of tilapia were successfully fabricated by using microfluidics. Through the assembly of these microgels using adhesive hyaluronic acid-catechol, the resulting 3D granular hydrogel scaffold facilitated enhanced cell growth, accelerated cell differentiation, and successful healing of full-thickness wounds in a mouse model. This study reveals the potential of tilapia skin-based granular hydrogel assembly in wound healing, overcoming conventional hydrogel limits.

Optimization of sequence and chiral content enhances therapeutic potential of tilapia piscidin peptides

Because antimicrobial peptides (AMPs) often exhibit broad-spectrum bactericidal potency, we sought to develop peptide-based antimicrobials for potential clinical use against drug-resistant pathogens. To accomplish this goal, we first optimized the amino acid sequence of a broad-spectrum AMP known as Tilapia Piscidin 4 (TP4). Then, we used the optimized sequence to create a pair of heterochiral variants (TP4-α and TP4-β) with different percentages of D-enantiomers, as poly-L peptides often exhibit poor pharmacokinetic profiles. The conformations of the peptide pair exhibited inverted chirality according to CD and NMR spectroscopic analyses. Both heterochiral peptides displayed enhanced stability and low hemolysis activities. Irrespective of their different d-enantiomer contents, both heterochiral peptides exhibited bactericidal activities in the presence of human serum or physiological enzymes. However, the peptide with higher d-amino acid content (TP4-β) caused better bacterial clearance when tested in mice infected with NDM-1 K. pneumoniae. In addition, we observed a relatively higher hydrogen bonding affinity in a simulation of the interaction between TP4-β and a model bacterial membrane. In sum, our results demonstrate that the current design strategy may be applicable for development of new molecules with enhanced stability and in vivo antimicrobial activity.

Dietary citric acid decreased the theront number of Cryptocaryon irritans (Ciliata) in seawater-adapted tilapia (Oreochromis niloticus)

Cryptocaryoniasis remains a major parasitic disease and economic challenge for marine aquaculture. Cryptocaryoniasis in marine fish is caused by Cryptocaryon irritans (Ciliata). A theront is a motile, free-swimming stage in the life cycle of C. irritans, which is typically the infective stage that actively seeks out a host to initiate infection. Population density and growth rate of theronts were investigated in Nile tilapia, Oreochromis niloticus fed with citric acid-supplemented feed. The experiment involved feeding three diets with graded levels of citric acid (0, control diet, 0.5, 1 and 1.5 g kg-1 diet), to seawater-adapted Nile tilapia (O. niloticus) juveniles for 21 days. The results showed that citric acid in the fish feed had an impact on the theront number of C. irritans in a manner of dose-dependent. In the experimental cohort administered a diet supplemented with 1.5 g kg-1 citric acid, the population density of theronts was observed to be significantly reduced, measured at 29 ± 3.34, as opposed to 473.34 ± 16.48 in the control group at the culmination of the experiment. The observed population growth rate of theronts was significantly higher in the control group than in the group administered the citric acid feed (p < .005). The growth rate (r d-1 ) was 0.12 in control, 0.05 in 0.5 g kg-1 , 0.031 in 1 g kg-1 , and - 0.031 in 1.5 g kg-1 citric acid-supplemented groups. Fish growth and feed conversion ratio were not affected by the citric acid in the feed. In conclusion, the findings of this investigation provide a valuable addition to our understanding of the potential protective effects of citric acid supplementation for fish against the C. irritans parasite. This is evidenced by the observed reduction in theronts present in the water.

Application of films developed with tilapia gelatin (Oreochromis niloticus), added with pitomba plant extract (Talisia esculenta) in Hawaii papaya

In the present study, a film based on the gelatin skin of tilapia (Oreochromis niloticus) was developed, using surfactants and adding plant extract of pitomba seed (Talisia esculenta). The aim was to investigate the mechanical and barrier properties of the cover, as well as its effectiveness in conserving papayas against diseases caused by fungi. The film presented tensile strength of 38.78 MPa, elongation of 120.49%, and water vapor permeability of 5.90 g.mm.h-1.m2.kPa-1 when equally composed of SDS and Tween 80, in a percentage of 40% in relation to the total mass of the film. The films lasted 12 d in an environment with a relative humidity of 75% (25 ºC), longer than the shelf life of papaya (limited to 8 d). With applying the film with the extract, the incidence of diseases such as anthracnose, fusariosis, and stem rot caused by these microorganisms in papaya was reduced.

Immune response and protective efficacy of Streptococcus agalactiae vaccine coated with chitosan oligosaccharide for different immunization strategy in nile tilapia (Oreochromis niloticus)

In the past decade, the outbreak of Streptococcus agalactiae has caused significant economic losses in tilapia farming. Vaccine immunization methods and strategies have gradually evolved from single-mode to multi-mode overall prevention and control strategies. In this study, an inactivated vaccine of S. agalactiae with a chitosan oligosaccharide (COS) adjuvant was constructed using different administration methods: intraperitoneal injection (Ip), immersion combined with intraperitoneal injection (Im + Ip), immersion combined with oral administration (Im + Or), and oral administration (Or). Safety analysis revealed no adverse effects on tilapia, and the vaccine significantly promoted fish growth and development when administered through Im + Or or Or immunization. Following vaccination, innate immunity parameters including SOD, ACP and CAT activities were all significantly enhanced. Additionally, specific serum IgM antibodies reached their highest level at the 6th week post vaccination. Skin and intestinal mucus IgT antibodies reached peaked at the 6th and 7th week post vaccination, respectively. The relative peak expression values for IL-8, IL-12, MHC-I, MHC-II, IgM, IgT, CD4, CD8, TNFα, IFNγ from Im + Ip group were significantly higher than those in Ip group, Im + Or group and Or group in most cases (p < 0.05). Importantly, the relative protection survival of Im + Ip group was the highest (78.6%), followed by the Ip group (71.4%), the Or group (64.3%) and the Im + Or group (57.1%). In summary, this study encourages further research on multi-channel immunization strategies of other kinds of vaccines in other aquatic economic animals to improve their disease resistance.

Assessment of Tilapia Skin Collagen for Biomedical Research Applications in Comparison with Mammalian Collagen

Collagen is an important material for biomedical research, but using mammalian tissue-derived collagen carries the risk of zoonotic disease transmission. Marine organisms, such as farmed tilapia, have emerged as a safe alternative source of collagen for biomedical research. However, the tilapia collagen products for biomedical research are rare, and their biological functions remain largely unexamined. In this study, we characterized a commercial tilapia skin collagen using SDS-PAGE and fibril formation assays and evaluated its effects on skin fibroblast adhesion, proliferation, and migration, comparing it with commercial collagen from rat tails, porcine skin, and bovine skin. The results showed that tilapia skin collagen is a type I collagen, similar to rat tail collagen, and has a faster fibril formation rate and better-promoting effects on cell migration than porcine and bovine skin collagen. We also confirmed its application in a 3D culture for kidney cells' spherical cyst formation, fibroblast-induced gel contraction, and tumor spheroid interfacial invasion. Furthermore, we demonstrated that the freeze-dried tilapia skin collagen scaffold improved wound closure in a mouse excisional wound model, similar to commercial porcine or bovine collagen wound dressings. In conclusion, tilapia skin collagen is an ideal biomaterial for biomedical research.

First report on chemometric modeling of tilapia fish aquatic toxicity to organic chemicals: Toxicity data gap filling

The Toxic Substances Control Act (TSCA) mandates the Environmental Protection Agency (EPA) to document chemicals entering the US. Due to the vast range of toxicity endpoints, experimental toxicological study for all chemicals is impossible to conduct. To address this, in silico methods like QSAR and read-across are strategically used to prioritize testing for chemicals lacking ecotoxicity data. Aquatic toxicity is one of the most critical endpoints directly related to aquatic species, mainly fish, followed by direct to indirect effects on humans through drinking water and fish as food, respectively. Therefore, we have employed the ToxValDB database to curate acute LC50 toxicity data for three Tilapia species covering two different genera, an ideal species for aquatic toxicity testing. Employing the curated dataset, we have developed multiple robust and predictive QSAR and quantitative read-across structure-activity relationship (q-RASAR) models for Tilapia zillii, Oreochromis niloticus, and Oreochromis mossambicus which helped to understand the toxicological mode of action (MoA) of the modeled chemicals and predict the aquatic toxicity of new untested chemicals followed by toxicity data gap filling. The best three QSAR models showed encouraging statistical quality in terms of determination coefficient R2 (0.94, 0.74, and 0.77), cross-validated leave-one-out Q2 (0.90, 0.67 and 0.70), and predictive capability in terms of R2pred (0.95, 0.77, and 0.74) for T. zillii, O. niloticus, and O. mossambicus datasets, respectively. The developed best mathematical models were used for the prediction of aquatic toxicity in terms of pLC50 for 297 untested organic chemicals across three major Tilapia species ranging from 1.841 to 8.561 M in terms of environmental risk assessment.

Ecotoxicity of commonly used oilfield-based emulsifiers on Guinean Tilapia (Tilapia guineensis) using histopathology and behavioral alterations as protocol

This study examined the histological aberrations in the gill and liver tissues and behavioural changes of Tilapia guineensis fingerlings exposed to lethal concentrations of used Oilfield-based emulsifiers for 96 h. Various concentrations of the surfactants were tested, ranging from 0.0 to 15.0 ml/L. The behaviour of the fish was observed throughout the experiment, and the results showed that increasing concentrations of the surfactants led to progressively abnormal behaviour, including hyperventilation and altered opercular beat frequency. These behavioural changes indicated respiratory distress and neurotoxic effects. Histological analysis revealed structural aberrations in the gill and liver tissues, with higher concentrations causing more severe damage, such as lesions, necrosis, inflammation, and cellular degeneration. This implies that surfactants released even at low concentrations are capable of inducing changes in the tissues of aquatic organisms. These findings highlight the toxic effects of the surfactants on fish health and provide biomarkers of toxicity. Future research should focus on understanding the specific mechanisms and long-term consequences of surfactant toxicity on fish genetic composition, populations, and ecosystems to implement effective conservation measures.

Isolation, in vitro, and in vivo pathogenicity test of Tilapia lake virus (TiLV) and development of a prognostic semi-quantitative lesion scoring system for differentiating clinical/subclinical infection in farmed tilapia (Oreochromis niloticus L.)

Tilapia lake virus ('TiLV-MH-2022') was recently recovered from the naturally infected farmed tilapia. Reverse transcription-polymerase chain reaction (RT-PCR) using segment 1 specific primers, followed by Sanger sequencing, confirmed the infection. The pairwise sequence homology of segment 1 showed its close relationship with the previous isolates. The virus was successfully detected from the mucus, which emphasised the possibility of non-invasive screening of tilapia on a large scale. The virus inoculum prepared from the infected tissues was tested for in vivo and in vitro pathogenicity. Around 100-140 nm-sized electron-dense virus particles were observed in the infected OnlL cells. Based on the onset of symptoms and lesions, all RT-PCR-positive fish were categorised into two groups, 'clinical' and 'subclinical'. A lesion-scoring technique was developed for assessing the pathogenicity of the virus isolate. The external and internal gross lesions and histopathological alterations in the critical organs of the fish, such as the brain, kidney, gills, and liver, were assessed on a scale of 0 (no gross lesion) to 5 (most severe lesions). Overall lesion score was significantly high in the clinical and subclinical groups for gross and histopathology, respectively. This study is the first such attempt to standardise a semi-quantitative lesion scoring technique for TiLV infection, which establishes a clinical relevance and prognostic ability to distinguish between the apparent and inapparent infection.

A nanocarrier immersion vaccine encoding surface immunogenic protein confers cross-immunoprotection against Streptococcus agalactiae and Streptococcus iniae infection in tilapia

Streptococcosis is a highly contagious aquatic bacterial disease that poses a significant threat to tilapia. Vaccination is a well-known effective measure to prevent and control fish bacterial diseases. Among the various immunization methods, immersion vaccination is simple and can be widely used in aquaculture. Besides, nanocarrier delivery technology has been reported as an effective solution to improve the immune effect of immersion vaccine. In this study, the surface immunogenic protein (Sip) was proved to be conserved and potential to provide cross-immunoprotection for both Streptococcus agalactiae (S. agalactiae) and Streptococcus iniae (S. iniae) by multiple sequences alignment and Western blotting analysis. On this basis, we expressed and obtained the recombinant protein rSip and connected it with functionalized carbon nanotubes (CNT) to construct the nanocarrier vaccine system CNT-rSip. After immersion immunization, the immune effect of CNT-rSip against above two streptococcus infections was evaluated in tilapia based on some aspects including the serum specific antibody level, non-specific enzyme activities, immune-related genes expression and relative percent survival (RPS) after bacteria challenge. The results showed that compared with control group, CNT-rSip significantly (P < 0.05) increased the serum antibody levels, related enzyme activities including acid phosphatase, alkaline phosphatase, lysozyme and total antioxidant capacity activities, as well as the expression levels of immune-related genes from 2 to 4 weeks post immunization (wpi), and all these indexes peaked at 3 wpi. Besides, the above indexes of CNT-rSip were higher than those of rSip group with different extend during the experiment. Furthermore, the challenge test indicated that CNT-rSip provided cross-immunoprotection against S. agalactiae and S. iniae infection with RPS of 75 % and 72.41 %, respectively, which were much higher than those of other groups. Our study indicated that the nanocarrier immersion vaccine CNT-rSip could significantly improve the antibody titer and confer cross-immuneprotection against S. agalactiae and S. iniae infection in tilapia.

Pathology caused by introduced Neoergasilus japonicus (Copepoda: Ergasilidae) to the skin of indigenous Tilapia sparrmanii in South Africa and scanning electron microscopy study of wound-inflicting structures

Neoergasilus japonicus, a fish ectoparasite indigenous to eastern and southern Asia, has been introduced to various regions, including Europe and North and South America, where it spreads at an alarming rate. The parasite is not host-specific. It was also collected from the Vaal-Orange and Limpopo river systems in South Africa. This report describes the morphology of the wound-inflecting structures in N. japonicus and relates their morphology to the pathological effect on Tilapia sparrmanii. Host tissue with parasites attached was imbedded in resin for histological sectioning and stained with haematoxylin and eosin. Additional specimens were prepared for scanning electron microscopy. Adult female parasites attach by inserting the hooked tips of the antennae into the epidermis. The maxillulae are minute but have sharp tips. The maxillae have sharp tips on the endopod and brush-like setae on the exopod. The mandibles are armed with sharp tips. These structures are used to remove the epidermis of the host and brush it into the buccal cavity. Host tissue in the intestine confirms that adult females consume host tissue leaving the dermis exposed to opportunistic diseases. The microscopic size of the parasite prevents casual observation, and its occurrence in Africa is, therefore, probably underreported.

Sequential rearrangement and stereochemical reorganization to design an antimicrobial peptide with enhanced stability

Antimicrobial peptides (AMPs) are natural molecules that function within the innate immune system to counteract pathogenic invasion and minimize the detrimental consequences of infection. However, utilizing these molecules for medical applications has been challenging. In this study, we selected a model AMP with poor stability, Tilapia Piscidin 4 (TP4), and modified its sequence and chirality (TP4-γ) to improve its potential for clinical application. The strategy of chirality inversion was inspired by the cereulide peptide, which has a DDLL enantiomer pattern and exhibits exceptional stability. Sequential substitution of key residues and selective chirality inversion yielded a less toxic peptide with enhanced stability and notable antimicrobial activity. In addition to its superior stability profile and antimicrobial activity, TP4-γ treatment reduced the level of LPS-induced nitric oxide (NO) release in a macrophage cell line. This reduction in NO release may reflect anti-inflammatory properties, as NO is widely known to promote inflammatory processes. Hence, our heterochiral peptide construct shows a more suitable pharmacokinetic profile than its parental compound, and further studies are warranted to develop the molecule for potential clinical application.

Interaction between liposome and myofibrillar protein in surimi: Effect on gel structure and digestive characteristics

This study investigated the effects of the interaction between liposomes and myofibrillar protein (MP) on tilapia surimi. The strong interaction between liposomes and MP was primarily mediated through hydrogen bonding and hydrophobic interaction. Liposomes caused the unfolding of MP structure, resulting in the decrease of α-helix content and transformation of spatial structure. Notably, the appropriate ratio of liposomes improved the gel properties of tilapia surimi. The water distribution, microstructure, and texture characteristics further confirmed that liposomes strengthened the structure of surimi gel through non-covalent bonds. However, excessive liposomes (1.0 %) weakened gel characteristics and texture. Moreover, the proper ratio of liposomes enhanced the stability of surimi gels during digestion, reducing protein digestibility from 66.0 % to 54.8 %. Curcumin-loaded liposomes in gel matrix notably delayed digestion and improved bioavailability. This delay in digestion was attributed to the ability of liposomes to decrease the interaction between MP and digestive enzymes. This study provides new insight into the application of liposomes in protein-rich food matrixes.

Effect of chemical modification of κ-carrageenan on its inhibitory effect against heterocyclic amine (HAs) formation in roasted tilapia fish patties

Sulfated κ-carrageenan (S-KC), carboxymethylated κ-carrageenan (C-KC), acetylated κ-carrageenan (A-KC) and phosphorylated κ-carrageenan (P-KC) were synthesized and tested for their inhibitory effect on heterocyclic amine (HAs) formation in roasted tilapia fish patties. Fish patties with 1 % of each hydrocolloid prepared by 90 % of fish and 10 % of an aqueous hydrocolloid dispersion were determined for HAs-levels after roasting. P-KC showed the strongest inhibitory effect against total HAs formation (20.95 %). Moreover, P-KC increased the content of creatinine and glucose but decreased the content of free amino acids in fish patties, indicating that P-KC may compete with creatinine and glucose to react with amino acids to suppress HAs generation. In addition, P-KC plus naringenin had a stronger inhibitory effect against HAs formation than P-KC or naringenin alone. P-KC at 1 % (w/w) and P-KC (0.5 %, w/w) plus naringenin (0.5 %, w/w) showed no significant effects on the color and textural properties compared to the control group (100 % fish), and had less impact on food quality than 1 % (w/w) KC. Therefore, our results suggest that chemical modification could enhance the inhibitory effect of some hydrocolloids on HAs formation, and an appropriate combination of hydrocolloids and flavonoids contributes to the attenuation of dietary exposure to genotoxic HAs.

BNC-rSS, a bivalent subunit nanovaccine affords the cross-protection against Streptococcus agalactiae and Streptococcus iniae infection in tilapia

Streptococcal disease has severely restricted the development of global tilapia industry, which is mainly caused by Streptococcus agalactiae (S. agalactiae) and Streptococcus iniae (S. iniae). Vaccination has been proved to be a potential strategy to control it. In this study, a multi-epitope subunit vaccine Sip-Srr (SS) was prepared based on the B-cell antigenic epitopes prediction and multiple sequence alignment analysis of Sip and Srr sequences. Furthermore, the BNC-rSS nanocarrier vaccine system was constructed by connecting the rSS protein with modified bacterial nanocellulose (BNCs) and characterized by Fourier Transform Infrared Spectroscopy and Scanning Electron Microscope, the immersion immune effect against S. agalactiae and S. iniae infection was evaluated. The results showed that compared with the control group, BNC-rSS significantly enhanced serum antibody production, related enzyme activities and immune-related genes expression. It was noteworthy that BNC-rSS vaccine improved immune protection of tilapia, with survival rates of 66.67 % (S. agalactiae) and 60.00 % (S. iniae), respectively, compared with those of rSS vaccine (30 % and 33.33 %, respectively). Our study indicated that the BNC-rSS nanovaccine could elicit robust immune responses in tilapia by immersion immunization, and had the potential to offer cross-protection against S. agalactiae and S. iniae infection in tilapia.

Optimizing rice-fish co-culture: Investigating the impact of rice spacing density on biochemical profiles and production of genetically modified tilapia (Oreochromis spp.) and Cyprinus carpio

Rice fish co-culture synergistically boosts food production, resulting in numerous advantages across the environmental, social, and financial domains. A study was conducted to investigate the effects of three different rice spacing densities, rice high density (RHD) 9inch×12inch, rice medium density (RMD) 12inch × 12inch, rice low density (RLD) 15inch×12inchon both rice and fish. Various parameters were assessed to evaluate the performance of the co-culture system, including water quality, growth parameters, muscle quality, soil characteristics, rice stem characteristics, and rice yield parameters. When comparing the species, it was observed that GMT (Genetically Male Tilapia) demonstrated superior weight gain (303.13g vs 296.41g) and specific growth rate (1.16 vs 1.15). Regarding the proximate composition, results showed that RMD had the highest crude protein and fat content compared to RLD and RHD. GMT also exhibited greater crude protein and fat content than Cyprinus carpio, with RMD showing the highest values. Treatment groups significantly influenced the amino acid profile of experimental species, with RMD exhibiting the highest values. GMT showed significantly higher levels of essential, non-essential, half-essential, and umami amino acids compared to Cyprinus carpio. The interaction between RMD and GMT further demonstrated significant differences in various amino acid categories with RMD. A non-significant difference was observed among the treatments regarding soil biochemical characteristics. Regarding the rice stem characters, the height of the plant, panicle length, and stem length of rice were found to be comparable in the RMD and RLD groups however, significantly higher in RHD. Regarding rice yield parameters, no significant differences were observed among the other treatment groups, except for yield per hectare (yield/ha), which was significantly higher in the RHD group compared to RMD and RLD. Additionally, 1000-grain weight and panicle number (ears per hill) were significantly higher in the RLD treatment than in the other treatments. In conclusion, our findings indicate that the RMD treatment consistently yielded superior results compared to RLD and RHD. Furthermore, within the rice-fish co-culture system, GMT proved to be a more competent species compared to Cyprinus carpio. The study provides data to understand the interactions between rice spacing density, fish growth and overall productivity can guide the development of sustainable and profitable rice-fish co-culture systems.

Impacts of tilapia aquaculture on native fish diversity at an ecologically important reservoir

Background

The Temengor Reservoir is the second largest reservoir in Peninsular Malaysia. Located in the northwestern state of Perak, it was selected to develop a large-scale tilapia (Oreochromis niloticus) aquaculture facility within the Aquaculture Industrial Zone (AIZ) in 2008 due to its favourable environmental conditions. No record of tilapia has ever been reported in the natural waters prior to this. However, a post-establishment study recorded tilapia sightings in the natural waters of this lake. The cultured tilapia was easily recognizable with the elongated mouth and body, and long caudal fin. It is postulated that these were escapees from the floating cages that had invaded the natural waters and would negatively impact the native fish species. To test our hypothesis, we investigated the impact of the aquaculture facility on native fish diversity through a spatial design.

Methods

The study was focused on assessing the impact of tilapia culture at sites nearer to the AIZ vs more distant sites, the former with a greater likelihood of receiving escapees. Two major sites were chosen; within 5 km (near-cage) and within 5-15 km (far-cage) radii from the AIZ. Fish sampling was conducted using multiple mesh sizes of gill nets (3.7, 5.1, 6.5, 7.6, and 10.2 cm) deployed at the littoral zone of the sampling points. Species diversity, abundance, dietary habits, and habitat preference were investigated.

Results

The CPUE (individual/hour) of native fish species at the far-cage site of the AIZ Reservoir was found to be significantly higher (p < 0.05) than that at the near-cage site. Principal component analysis (PCA) based on diet and habitat preferences showed that the tilapia, O. niloticus had almost overlapping diet resources and habitat with native fish species.

Conclusion

We conclude that there is a correlation between the reduced catches of native species (based on CPUE) and the high presence of tilapia. Thus, appropriate actions must be implemented for strategic and effective planning in terms of native fish conservation.

Effects of Sous-Vide on Quality, Structure and Flavor Characteristics of Tilapia Fillets

To investigate the effects of traditional high-temperature cooking and sous-vide cooking on the quality of tilapia fillets, muscle microstructure, texture, lipid oxidation, protein structure, and volatile compounds were analyzed. In comparison with samples subjected to traditional high-temperature cooking, sous-vide-treated samples exhibited less protein denaturation, a secondary structure dominated by α-helices, a stable and compact structure, a significantly higher moisture content, and fewer gaps in muscle fibers. The hardness of the sous-vide-treated samples was higher than that of control samples, and the extent of lipid oxidation was significantly reduced. The sous-vide cooking technique resulted in notable changes in the composition and relative content of volatile compounds, notably leading to an increase in the presence of 1-octen-3-ol, α-pinene, and dimethyl sulfide, and a decrease in the levels of hexanal, D-limonene, and methanethiol. Sous-vide treatment significantly enhanced the structural stability, hardness, and springiness of muscle fibers in tilapia fillets and reduced nutrient loss, enriched flavor, and mitigated effects on taste and fishy odor.

Correlation of Streptococcus agalactiae concentration on immune system and effective dose of inactivated vaccine for Chitralada 3 strain Nile tilapia (Oreochromis niloticus) in Thailand

The main pathogen in the Nile tilapia (Oreochromis niloticus) culture, Streptococcus agalactiae, causes economic harm. Infected fish's immune systems worked to eliminate of the infection. This study demonstrated the effect of different bacterial concentrations on tilapia immunity and optimal vaccine concentration to induce immunity in Nile tilapia. The experiment was performed at 102, 104, 106, 108, and 1010 CFU/fish of S. agalactiae compared with the control (PBS) through intraperitoneal injection for 72 h. Fish that survived employed to gather blood, and immune responses were assessed through measures of the survival rate include blood smears, antibody titers, and immunoglobulin gene expression. The vaccine experiment investigated formalin-inactivated S. agalactiae vaccination and administered S. agalactiae injections for 14 days. The statistic revealed a significant difference (p < 0.05) in the 108 and 1010 CFU/fish injections with high survival rates (62.22% and 53.33%, respectively). Immunoglobulin gene expression was highly represented in the 1010 CFU/fish injection; antibody titers were significantly improved from the control group, and antibody levels were high in the 1010 CFU/fish injection. The analysis of blood cell types using the blood smear method revealed a progressive increase in leucocytes, particularly lymphocytes, neutrophils, and monocytes, in the treatment group compared to the control group. Moreover, the erythrocyte/leucocyte ratio decreased significantly in response to the high bacterial injection, indicating an increase in leucocytes. Conversely, the erythrocyte level stayed ed within at the 7.03-9.70 × 102 cell/ml and shown no significant difference (p > 0.05). The lymphocytes were almost two-fold in 1010 CFU/fish compared to 108 CFU/fish. As depicted in the lowest concentration of 106 CFU/fish, the vaccine performance had a high relative percent survival (RPS) at 86.67%. This research suggested that the tilapia infected with high S. agalactiae concentrations did not affect the mortality of the tilapia, and vaccine concentration was effective in 106 CFU/fish.

Microplastics Contamination in the Edible Fish Mozambique Tilapia (Oreochromis mossambicus) from the Selvampathy Wetland of Coimbatore, Tamil Nadu, India

The present study investigated the microplastics (MPs) contamination in the gastrointestinal (GI) tract, gills and muscle of the Mozambique tilapia, Oreochromis mossambicus sampled from the Selvampathy Lake of Coimbatore, Tamil Nadu. MPs abundance was found in 10 to 28, 8 to 27, and 4 to 12 particles and their size ranged between 4.4 and 210, 4.6 to 180, and 4.5 to 194 μm in the GI tract, gills and muscle, respectively. MPs were dominantly shaped as fibres (95%) and fragments (5%) with the following colour pattern of blue > black > pink > transparent > and others. Extracted MPs polymer nature were polyethylene (54%), polyamide (38%) and polypropylene (8%). The present study reveals that the edible fish O. mossambicus had MPs that can be transferred to consumers. Moreover, urban discharges, including domestic wastes, agricultural and rainwater runoff, might be possible MPs sources to the studied wetland.

Quantitative benefit and risk assessment of arsenic and nutrient levels in tilapia products sold on Chinese e-commerce platforms

E-commerce platforms have become a significant sales channel for processed tilapia products such as frozen tilapia fillets, pickled tilapia, and canned tilapia in China. As food safety issues are worldwide concerned, the imbalance between the nutritional benefits of fish and the risk of contamination has become a major constraint on fish consumption. Therefore, it is necessary to assess the safety of tilapia products sold on e-commerce platforms. We conducted a quantitative benefit-risk assessment of arsenic and nutrient levels for tilapia products sold on Chinese e-commerce platforms using the hazard quotient (HQ). A total of 147 tilapia products were collected from the central Chinese e-commerce platforms Tmall, Taobao, and Jingdong for arsenic determination. Arsenic concentrations in tilapia products ranged from 0.004 to 0.820 mg·kg-1. The inorganic arsenic content of tilapia products was lower than the national limit (0.1 mg·kg-1). One-way analysis of variance revealed that there was no significant difference in arsenic levels in tilapia products among different regions (p > 0.05), while there was a significant difference in product form, with canned tilapia containing significantly higher arsenic levels than frozen tilapia fillets and pickled tilapia fillets (p < 0.05). We conducted an aquaculture experiment to analyze the nutrient levels of tilapia. The mean value of EPA + DHA content of tilapia was 20.634 mg·100 g-1. The HQ values of tilapia products ranged from 0.004 to 0.736. In a word, the nutritional benefits of consuming tilapia products exceed the risk of arsenic exposure. These data can help demonstrate that tilapia products are low-risk, high-yield nutritious food and provide relevant safety recommendations for consumers purchasing processed tilapia products online.

Combined effects of water salinity and ammonia exposure on the antioxidative status, serum biochemistry, and immunity of Nile tilapia (Oreochromis niloticus)

Growing Nile tilapia in brackish water showed promising results, but the possibility of ammonia exposure can interrupt health status and productivity. Herein, the study tested the combined effects of water salinity and ammonia exposure on the antioxidative status, serum biochemistry, and immunity of Nile tilapia. Fish were assigned to eight groups where fish were reared in saline water (5, 10, and 15 ppt) with continuous or intermittent (every 3 days) total ammonia (TAN) exposure (5 mg TAN/L) (2 × 4 factorial design). After 30 days, the water salinity, TAN, and their interaction were markedly (P < 0.05), affecting the growth performance (final weight, weight gain, and specific growth rate) and survival rate of Nile tilapia. The growth performance and survival rate were markedly lower in tilapia grown in 15 ppt with continuous TAN exposure than in the remaining groups. The results showed that fish exposed to higher salinity levels (10 and 15 ppt) and continuous TAN exposure had a more robust antioxidative response, as evidenced by higher superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) activities and lower malondialdehyde (MDA) levels in the homogenates of the gills, intestines, and livers. The gills were notably affected, with congestion of primary filaments blood vessels and degeneration or shedding of secondary filaments epithelium, especially at salinity levels of 10 and 15 ppt. Additionally, the intestines displayed hyperplasia and inflammatory cell infiltration of intestinal mucosa at 5-10 ppt salinity, degeneration and sloughing of the intestinal epithelium at 15 ppt saline water, and increased goblet cell number at salinity of 10 ppt. The study found that continuous TAN exposure had a more significant impact on the fish, especially at higher salinity levels. Water salinity, TAN, and their interaction significantly affected all measured blood bio-indicators (total, albumin, globulin, ALT, AST, creatinine, urea, glucose, and cortisol levels). The phagocytic activity and index were markedly lowered in fish reared in 15 ppt with continuous TAN exposure, while the lysozyme activity was decreased in fish grown in 5, 10, and 15 ppt with continuous TAN exposure. In conclusion, Nile tilapia showed the possibility of growth with normal health status in brackish water (5-10 ppt); however, continuous TAN exposure can impair the productivity of tilapia, especially with high salinity (15 ppt).

A study on the delayed effect of tilapia skin collagen on skin aging for mice and its possible mechanism

OBJECTIVE

Study the possible mechanism and delayed effect of tilapia skin collagen on skin aging for mice.

MATERIALS AND METHODS

Kunming (KM) mice were randomly divided into the aging model group, the normal group, the positive control group (vitamin E) and the low, medium, high dose tilapia skin collagen groups (2.0, 4.0, 8.0 mg/g). The normal group was only injected with saline at the back and the neck. The other groups were injected subcutaneously with 5% D-galactose and ultraviolet light jointly to establish the aging model. After modeling, the positive control group was treated with a dose of 10% vitamin E once a day, and the low, medium, high dose tilapia skin collagen group was separately applied 2.0, 4.0, 8.0 mg/g of tilapia skin collagen for 40 days. The changes of skin tissue morphology, water content, hydroxyproline (Hyp) content, and superoxide dismutase (SOD) activity in mice were studied at the day 10, 20, 30, 40, 50.

RESULTS

Compared with the normal group, the skin of mice in the aging model group was thinner, looser, and the skin moisture content, Hyp content, SOD activity were all decreased. For mice of the low, medium, high dose tilapia skin collagen group, the thickness of dermis increased, possessing close arrangement, and the moisture content, Hyp content, SOD activity were up-regulated significantly, which effectively alleviated the aging process of skin. The dose of tilapia skin collagen was directly proportional to the anti-aging effect.

CONCLUSIONS

Tilapia skin collagen has an obvious effect on improving skin aging.

In vitro determination of probiotic efficacy of Bacillus subtilis TLDK301120C24 isolated from tilapia against warm water fish pathogens and in vivo validation using gnotobiotic zebrafish model

Eco-friendly alternatives such as probiotics are needed to prevent economically relevant infectious diseases for a successful disease-free harvest in aquaculture. The use of antibiotics has been the favored practice, but its empirical and indiscriminate use has led to antibiotic resistance in the aquatic environment and residues in the food fish. With this rationale, a probiotic was isolated from tilapia, a commercially important cultured fish worldwide. The characteristics of the probiotic were checked against common bacterial pathogens affecting aquaculture. In vitro tests demonstrated the inhibitory effects of the isolated probiotic on the growth of Aeromonas hydrophila, Edwardsiella tarda, Vibrio anguillarum, and V. alginolyticus. The candidate probiotic, referred to as TLDK301120C24, was identified as Bacillus subtilis by a battery of biochemical tests and genotypic confirmation by 16S rDNA sequencing. The in vitro results revealed the ability of the probiotic to withstand the gut conditions that included pH range of 3-9, salt concentration of 0.5-6%, and bile salt concentration of up to 6%. The isolate could hydrolyze starch (12-14 mm clearance zone), protein (20-22 mm clearance zone), and cellulose (22-24 mm clearance zone). Further, the inhibitory ability of the probiotic against aquatic pathogens was determined in vivo using gnotobiotic zebrafish by employing a novel approach that involved tagging the probiotic with a red fluorescent protein and the pathogens with a green fluorescent protein, respectively. The colonizing ability of probiotics and its inhibitory effects against the pathogens were evaluated by fluorescence microscopy, PCR, and estimation of viable counts in LBA + Amp plates. Finally, the competitive inhibition and exclusion of fish pathogens A. hydrophila and E. tarda by B. subtilis was confirmed semi-quantitatively, through challenge experiments. This study shows the potential of B. subtilis as a probiotic and its excellent ability to inhibit major fish pathogens in vivo and in vitro. It also shows promise as a potent substitute for antibiotics.