Stimulation of non-specific immunity, gene expression, and disease resistance in Nile Tilapia, Oreochromis niloticus (Linnaeus, 1758), by the methanolic extract of the marine macroalga, Caulerpa scalpelliformis

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.

Evaluation of immunostimulatory attributes of Asparagus racemosus and Withania somnifera supplemented diets in fish, Channa punctatus (Bloch, 1793)

With the progression of aquaculture industry, there has been a spurt in dietary supplementation with economically viable medicinal herbs having enough immunostimulatory potential. This also aids in avoidance of environmentally undesirable therapeutics that are almost inevitable to safeguard fish against an array of diseases in aquaculture practices. The study aims to determine the optimal dose of herbs that can stimulate substantial immune response in fish for reclamation of aquaculture. Immunostimulatory potential of the two medicinal herbs- Asparagus racemosus (Shatavari), Withania somnifera (Ashwagandha), individually, and in combination, with a basal diet was screened up to 60 days in Channa punctatus. 300 laboratory acclimatized healthy fish (14 ± 1 g; 11 ± 1 cm) were divided into ten groups- C, S1, S2, S3, A1, A2, A3, AS1, AS2, and AS3, based on the composition of dietary supplementation, in triplicates, with 10 specimens per group. The hematological index, total protein and lysozyme enzyme activity were performed after 30 and 60 days, while qRT-PCR analysis of lysozyme expression was done after 60 days of the feeding trial. The significant (P < 0.05) increments in hematological indices- (TEC, TLC, DLC, Hb, Hct, MCV, MCH and MCHC), total protein content and serum lysozyme activity, after 30 and 60 days; whereas upregulation of lysozyme transcript levels, both in liver and muscle tissues after 60 days of the feeding trial were recorded in groups- AS1, AS2, and AS3. The maximal increment in lysozyme expression was recorded in AS3, both in liver and muscle tissues, with 3.75 ± 0.13 and 3.21 ± 0.18-folds, respectively. However, increments were non-significant (P > 0.05) for MCV in AS2 and AS3 after 30 days; and for MCHC in AS1 for both the durations; whereas in AS2 and AS3, after 60 days of the feeding trial. A positive correlation (P < 0.05) among lysozyme expression, MCH, lymphocytes, neutrophils, total protein content, and serum lysozyme activity in AS3, after 60 days, conclusively, evinces that a 3% dietary supplementation with both A. racemosus and W. somnifera enhances immunity and health profile of the fish, C. punctatus. The study, thus finds ample scope in augmentation of aquaculture production and also paves the way for more researches for biological screenings of potential immunostimulatory medicinal herbs that can be appropriately incorporated in the fish diet.

Effects of low-light stress on aquacultural water quality and disease resistance in Nile tilapia

Light intensity has an important environmental influence on the quality and yield of aquatic products. It is essential to understand the effects of light intensity on water quality and fish metabolism before large-scale aquaculture is implemented. In this study, two low-intensity light levels, 0 lx and 100 lx, were used to stress Nile tilapia (Oreochromis niloticus), with a natural light level (500 lx) used as control. The pH, dissolved oxygen and ammonia contents were significantly lower in the water used in the 0 lx and 100 lx groups than in controls, while the levels of nitrite and total phosphorus were apparently higher. Moreover, the numbers of heterotrophic bacteria, Vibrio and total coliforms in aquaculture water were 157.1%, 314.2% and 502.4% higher, respectively, after 0 lx light stress for 15 days. The survival rate of Nile tilapia decreased significantly to 90.6% under 0 lx light on the 15th day. Of the immune-related genes, the expressions of IFN-γ, IL-12 and IL-4 were 390.3%, 757.8% and 387.5% higher under 0 lx light and 303.3%, 471.2% and 289.7% higher under 100 lx light, respectively. These results indicate that low-intensity light changes the physicochemical parameters of aquaculture water and increases the number of bacteria it hosts while decreasing the survival rate and increasing the disease resistance of Nile tilapia.

Growth hormone secretagogue peptide-6 enhances oreochromicins transcription and antimicrobial activity in tilapia (Oreochromis sp.)

Growth Hormone-Releasing Peptide 6 (GHRP-6) (His-(D-Trp)-Ala-Trp-(D-Phe)-Lys-NH2) is an agonist of the growth hormone secretagogue receptor. GHRP-6 mimics the effect of ghrelin. The present study focuses on the immunomodulatory effects of GHRP-6 in tilapia with and without the presence of Pseudomonas aeruginosa infection. GHRP-6 up-regulated the transcription levels of three piscidin-like antimicrobial peptides (Oreochromicins I, II, and III) and granzyme in a tissue-dependent manner. Antimicrobial activity stimulation in serum (lysozyme and anti-protease activity) was also confirmed. Besides, GHRP-6 enhanced the in vitro antimicrobial activity against P. aeruginosa in tilapia gills mucus and serum samples and decreased the bacterial load in vivo after infection with this Gram-negative bacterium. Our results evidenced, for the first time, a direct link between a growth hormone secretagogue ghrelin mimetic in fish and the enhancement of antimicrobial peptides transcription, which suggests that this secretagogue is capable to lead the activation of microbicidal activity in tilapia. Thus, these results open new possibilities for GHRP-6 application in aquaculture to stimulate the teleost immune system as an alternative treatment against opportunistic bacteria.

Antimicrobials from Seaweeds for Food Applications

The exponential growth of emerging multidrug-resistant microorganisms, including foodborne pathogens affecting the shelf-life and quality of foods, has recently increased the needs of the food industry to search for novel, natural and eco-friendly antimicrobial agents. Macroalgae are a bio-diverse group distributed worldwide, known to produce multiple compounds of diverse chemical nature, different to those produced by terrestrial plants. These novel compounds have shown promising health benefits when incorporated into foods, including antimicrobial properties. This review aims to provide an overview of the general methods and novel compounds with antimicrobial properties recently isolated and characterized from macroalgae, emphasizing the molecular pathways of their antimicrobial mechanisms of action. The current scientific evidence on the use of macroalgae or macroalgal extracts to increase the shelf-life of foods and prevent the development of foodborne pathogens in real food products and their influence on the sensory attributes of multiple foods (i.e., meat, dairy, beverages, fish and bakery products) will also be discussed, together with the main challenges and future trends of the use of marine natural products as antimicrobials.

Bioinformatic Characterization of Sulfotransferase Provides New Insights for the Exploitation of Sulfated Polysaccharides in Caulerpa

Caulerpa is an unusual algal genus from Caulerpaceae (Chlorophyta, Bryopsidales). Species from this family produce a wide range of metabolites suitable for biotechnology applications. Among these, sulfated polysaccharides (SPs) are often highly desirable for pharmaceutical and nutraceutical applications. Here, we provide a classification of sulfotransferases from Caulerpa; these important enzymes catalyze the nodal step for the biosynthesis of SPs. For this, we performed phylogenetic, genomic, expression analyses and prediction of the protein structure on sulfotransferases from Caulerpa. Sequences, domains and structures of sulfotransferases generally shared common characteristics with other plants and algae. However, we found an extensive duplication of sulfotransferase gene family, which is unique among the green algae. Expression analysis revealed specific transcript abundance in the pinnae and rachis of the alga. The unique genomic features could be utilized for the production of complex SPs, which require multiple and specific sulfation reactions. The expansion of this gene family in Caulerpaceae would have resulted in a number of proteins characterizing the unique SPs found in these algae. We provide a putative biosynthetic pathway of SPs, indicating the unique characteristics of this pathway in Caulerpa species. These data may help in the future selection of Caulerpa species for both commercial applications and genetic studies to improve the synthesis of valuable products from Caulerpa.

Ziziphus mauritiana supplementation of Nile tilapia (Oreochromis niloticus) diet for improvement of immune response to Aeromonas hydrophila infection

This study evaluated the effectiveness of dietary Ziziphus mauritiana leaf powder (ZLP) to control Aeromonas hydrophila infection in Nile tilapia and reduce damage to vital immune organs. Four experimental groups were fed a diet supplemented with ZLP at concentrations of 0, 5, 10, and 20 g/kg (w/w) for 6 weeks. At the end of the feeding trial, all groups were intraperitoneally injected with pathogenic A. hydrophila. It was found that Z. mauritiana significantly (P < 0.05) upregulated (lysozyme, interleukin 1 beta) and superoxide dismutase gene expressions as well as improved the activity of serum lysozyme and liver antioxidant enzymes. The fish that were fed a ZLP-supplemented diet also exhibited significantly higher survival rates after A. hydrophila challenge than those that were fed a ZLP-free diet (P < 0.05). Supplementation of 10 g/kg ZLP most effectively reduced the histopathological alterations caused by A. hydrophila challenge in the liver, spleen, kidney, and muscle of the fish. In conclusion, ZLP can be effective in controlling A. hydrophila infection in Nile tilapia (particularly at a concentration of 10 g/kg) through enhancement of its immune and antioxidant status.

Effect of Chlorella vulgaris enriched diet on growth performance, hemato-immunological responses, antioxidant and transcriptomics profile disorders caused by deltamethrin toxicity in Nile tilapia (Oreochromis niloticus)

The toxic effect of deltamethrin (DM) was documented in aquaculture. There is no obtainable data on the effect of Chlorella vulgaris against DM toxicity. The current study focused on the effect of dietary supplementation with C. vulgaris (CV) on growth performance, innate immune response, antioxidant activities, and transcriptomics disorders induced by sub-lethal dose of DM in Oreochromis niloticus. A total number of 216 O. niloticus divided into four groups with tri-replicates. The 1^st control group (CT) fed a basal diet, the second group fed diet enriched with 5% CV. The third group was exposed to DM (15 μg/L), where the last group fed CV and simultaneously exposed to DM as previous-mentioned. The procedure of CV feeding and DM exposure were continued for two months. Exposures to DM revealed in stunting of the growth parameters and lessening of survival ratio of tilapias with a significant decline of the erythrogram (macrocytic hypochromic anemic picture), and leucocytes immune cells and related parameters (immunoglobulin M, lysozyme) and sever shifting in the antioxidant indicators. Sever raise was monitored in hepatic and kidney markers. Also, genes expression related to immune and antioxidant parameters were severely impacted. Where tilapias received CV showed a significant increase in the growth and immune parameters besides to an improvement of hematological, antioxidant values and their related genes expressions. The fourth group that received CV simultaneous with DM exposure showed a soothing of the previous indicators and markers toward the values of tilapias fed on basal diet (CT). In turn, CV supplementation may be presented a protective effect alongside DM toxicity in O. niloticus appeared through soothing of the immune, antioxidant and related genes expressions in addition to its hepato-renal protective effects. Therefore, the current study recommended that an incorporating of 5% CV for tilapias diet could improve their growth performance, immunity, antioxidant and transcriptomics disorders induced by deltamethrin.

Efficacy of dietary Nano-selenium on growth, immune response, antioxidant, transcriptomic profile and resistance of Nile tilapia, Oreochromis niloticus against Streptococcus iniae infection

As recently applicable, there are few studies on the impact of using nano-selenium (nano-Se) on varied fish species. Where nothing reachable focused on its impact on tilapias so, the present analysis evaluated the efficacy of using nano-Se in tilapias on immune response, antioxidant defense compared by conventional Se form. 480 O. niloticus fingerlings were haphazardly grouped firstly into three groups with four replicates of each. The control one (CT) was fed on a basal diet. The second and third one supplemented with 0.7 mg/kg^-1 Se and nano-Se respectively for ten weeks. At the start day of the ninth week, two replicates from each group were injected by Streptococcus iniae where, the remaining replicates stand without challenge. Enhancement of growth performance measurements were noted in nano-Se compared to Se or CT groups. Existed anemia in S. iniae tilapias became alleviated by using nano-Se that also, improves the alteration of leucogram induced by challenge. Elevation of aminotransferases, alkaline phosphatase, lactate dehydrogenase (ALT, AST, ALP and LDH) and creatinine in Se and CT challenged replicates that seemed nearly normal by using nano-Se. Usage of nano-Se showed more powerful antioxidant activities than Se. There were an expansion of immunoglobulin M, lysozymes, glutathione peroxidase, nitric oxide, superoxide dismutase and catalase (IgM, LYZ, GPx, NO, SOD, CAT) and their related gene expression in nano-Se with contrast in Se or CT challenged groups. Nile tilapias challenged by S. iniae disclosed substantial expansion in the percentage of mortality in CT challenged fish (93.33%), followed by the group supplemented with Se (73.33%), whereas the lowermost one at fish supplemented by nano-Se (26.66%). The mortalities have been stopped from the 5^th, 12^th and 14^th days in, nano-Se, Se and CT respectively. It can be concluded that using of Se 0.7 mg/kg^-1induce immunosuppressive, antioxidant, liver and kidneys negative impact on tilapias where the same dose from nano-Se was more potent immunomodulating and antioxidant. Also it is attend in counteracting the serious impact induced by S. iniae challenge.

Immune response evaluation in Balb/c mice after crude extract of Anisakis typica sensitization

BACKGROUND AND AIM

Anisakis is a global challenge for a fish product which may lead to a decrease in economic value and consumers' preference. Skipjack (Katsuwonus pelamis) in Kupang, Nusa Tenggara Timur, Indonesia, have important economic value for local fisheries. Anisakis typica is one of the Anisakis species which potent to induce an allergic reaction. However, the study about A. typica involved in the dendritic cells (DCs), T helper 1 (Th1), T helper 2 (Th2), and regulatory T cells (Tregs) is still limited. This study aimed to analyze the dynamic changed of the immune system including DCs, CD4+ T cells, and Tregs after 1 week of A. typica sensitization.

MATERIALS AND METHODS

Twenty-four male Balb/C mice were randomly divided into four groups (n=6), mice treated with crude A. typica extract (CAE) 50, 75, and 100 mg/kg BW, respectively. CAE was given orally per day for a week. At the end of the experiment, the animals were sacrificed and the spleen was collected. DCs were labeled as CD11c+ interleukin-6+ (IL-6+); CD4+ T cells were distinguished as Th1 (CD4+ interferon-γ+ [IFN-γ+]) and Th2 (CD4+ IL-4+ and CD4+ IL-5+); Tregs were labeled as CD4+CD25+CD62L+. The expression of each cell was determined by flow cytometry.

RESULTS

Our result described that CAE elicits CD11c+ IL-6+, CD4+ IFN-γ+, CD4+ IL-4+, and CD4+ IL-5+ and reduces CD4+CD25+CD62L+ significantly (p<0.05) in dose-dependent manner in mice after A. typica infection.

CONCLUSION

The Th1/Th2 ratio after A. typica crude extract treatment exhibits a mixed pattern rather than the classical model allergy to food antigens. Our study is expected as a basic understanding of the changes in immune response after A. typic a infection.