Saccharomyces cerevisiae Supplementation Enhances Growth and Immune Response in Nile Tilapia During Winter Stress

Effects of starvation and subsequent re-feeding on intestinal microbiota, and metabolic responses in Nile tilapia, Oreochromis niloticus

Streptococcosis caused by Streptococcus agalactiae (S. agalactiae) is a major bacterial disease affecting the production of Nile tilapia (Oreochromis niloticus L.), causing significant economic losses due to mortality in the growing phase. Vaccination is the most effective method for preventing streptococcosis on Nile tilapia farms. In Brazil, the major tilapia-producing regions have long production cycles (6-10 months) and harvest tilapias weighing over 900 g for fillet production. Thus, data on the duration of the humoral immune response and protection in farmed tilapia have not been reported or are poorly described. Furthermore, the efficiency of serological testing for the long-term monitoring of immune responses induced by vaccination against S. agalactiae has never been addressed. This study evaluated the duration of protection and humoral immune response induced in Nile tilapia vaccinated against S. agalactiae until 300 days post-vaccination (dpv). The immunization trial was composed of two groups: vaccinated (Vac), vaccinated intraperitoneally with a commercial vaccine, and unvaccinated (NonVac) group, injected fish with sterile saline solution. At 15, 30, 150, 180, 210, and 300 dpv, blood sampling was conducted to detect anti-S. agalactiae IgM antibodies using indirect Enzyme-Linked Immunosorbent Assay (ELISA), and the fish were challenged with pathogenic S. agalactiae to determine the duration of vaccine protection through relative percentage survival (RPS). Spearman's rank correlation was performed between the ELISA optical density (OD) of vaccinated tilapia and the duration of vaccine protection (RPS). The mean cumulative mortality in NonVac and Vac groups ranged from 65 to 90% and less than 35%, respectively. The average RPS was 71, 93, 94, 70, 86, and 67% at 15, 30, 150, 180, 210, and 300 dpv, respectively. RPS revealed that the vaccine provided protection from 15 to 300 dpv. The specific anti-S. agalactiae IgM antibody levels were significantly higher in the Vac group than that non-Vac group up to 180 dpv. The vaccinated fish exhibited significant protection for up to 10 months after vaccination. There was a positive correlation between the antibody response and RPS. This study revealed that a single dose of commercial vaccine administered to Nile tilapia can confer long-term protection against S. agalactiae and that indirect ELISA can monitor the duration of the humoral immune response for up to six months following vaccination. Finally, vaccine protection over six months can be associated with other components of the fish immune system beyond the humoral immune response by IgM antibodies.

Effects of chronic alkalinity stress on immune response in Nile tilapia (Oreochromis niloticus) infected with Aeromonas hydrophila

The effects of Thai ginseng, Boesenbergia rotunda powder on mucosal and serum immunity, disease resistance, and growth performance of Nile tilapia (Oreochromis niloticus) fingerlings

Streptococcosis caused by Streptococcus agalactiae is a major economic problem for Nile tilapia Oreochromis niloticus production worldwide. Inactivated vaccines are considered an efficient method for controlling streptococcosis. However, during the vaccination process, stress during fish handling could affect the immune response. Immunomodulators, such as thymomodulin, act on the immune system and can improve vaccination responses. Thus, the aim of this study was to assess the immunomodulatory effect of thymomodulin in O. niloticus vaccinated against S. agalactiae. For this, fish were distributed in a factorial design (2x2x6), corresponding to two levels of thymomodulin supplementation (0.0 and 0.3%), two treatments (sterile phosphate buffered saline and inactivated S. agalactiae vaccine). Initially, fish received thymomodulin supplementation for 30 days. Next, fish were vaccinated by injection intraperitoneal (i.p.) of heat inactivated S. agalactiae vaccine. 15 days after vaccination, all fish were challenged i.p. with S. agalactiae and blood samples were collected at 7, 14, 21 days post infection (DPI). Results revealed that fish supplemented with thymomodulin vaccinated or not developed better protection against S. agalactiae than vaccinated fish without thymomodulin. Furthermore, fish vaccinated and supplemented with thymomodulin presented high levels of antibodies after 14 and 21 DPI, suggesting that thymomodulin can promote the immune response in Nile tilapia.

pik3r3b, a novel immune-related gene in Nile tilapia (Oreochromis niloticus): Identification, expression and analysis of antibacterial activity

Pseudomonas aeruginosa is known to be multidrug-resistant organisms so its infection is challenging. This study aimed to use the sponge-like reduced protocol in preparation of P. aeruginosa ghosts (PAGs) as a vaccine alternative and evaluate its competency in stimulating the immune response in Nile tilapia. Characterization of PAGs was done using the light, fluorescent and transmission electron microscope. 240 fish have been divided into four groups (60 fish each; three groups were injected with a high, medium, or low dose of PAGs, and a control group. Total and differential leukocyte count, phagocytic activity, lysozyme activity, and gene expression of some immune-related genes were done after the first and booster ghost dose injection. All fish groups were challenged intraperitoneally with P. aeruginosa (1 × 107 CFU ml−1); the mean percent mortality was calculated. Significant immunization potency of the large dose of PAGs was prominent. It is associated with a significant increased number of WBCs, heterophile, lymphocytes, and monocytes. Also the phagocytic activity and indexes were significantly increased by the high and moderate dose of PAGs. Additionally, significant upregulation of immune-related gene (MHC-II) and inflammatory-related gene (IL8) and maintained expression level of TLR7 were recorded. We conclude that chemically prepared P. aeruginosa ghosts maintained both the 3D structure and surface molecules of live bacteria and also are capable of inducing specific immune responses in Nile Tilapia, and reduced mortalities in challenged fish. Our results indicate the advantage of this procedure for production of bacterial ghost, which can be used in wide a range of hosts.

IκBα phosphorylation and associated NF-κB activation are essential events in lymphocyte activation, proliferation, and anti-bacterial adaptive immune response of Nile tilapia

Objective This study aimed to assess the effects of a potential probiotic feed mixture containing Pseudomonas putida, in comparison to a yeast product (Saccharomyces cerevisiae), on the growth, immune response, and protection against Aeromonas hydrophila infection in Nile Tilapia Oreochromis niloticus. Methods Nile Tilapia were divided into three groups and subjected to a 60-day feeding regimen: the first group served as a control, receiving a commercial diet; the second group received a basal diet mixed with 1 × 107 CFU/g diet of P. putida; and the third group was fed a basal diet mixed with 1 g/kg diet of dried S. cerevisiae, resulting in a final concentration of 107 CFU/g of feeds. After 2 months of supplementation, various parameters including survival rate, body weight gain, feed conversion rate, specific growth rate, serum lysozyme activity, phagocytic activity, nitroblue tetrazolium activity, and disease resistance against A. hydrophila were evaluated. Result Both probiotic-treated groups exhibited significant improvements compared to the control group. Specifically, enhanced survival rates, body weight gains, feed conversion rates, and specific growth rates were observed in the probiotic-treated groups. Moreover, these groups demonstrated increased serum lysozyme, phagocytic, and nitroblue tetrazolium activities, indicative of an improved immune response. Notably, the probiotic-treated groups displayed enhanced resistance against A. hydrophila infection. Histopathological examination revealed that P. putida significantly augmented the nonspecific immune response in Nile Tilapia. Conclusion This preliminary study underscores the potential benefits of P. putida supplementation in Nile Tilapia diets. The inclusion of P. putida resulted in enhanced growth performance, improved immune status, and effective control of A. hydrophila infection. These findings suggest that P. putida holds promise as a valuable component in feed mixtures for promoting the growth and health of Nile Tilapia.

The role of HMGB2 in the immune response of Nile tilapia (Oreochromis niloticus) to streptococcal infection

Herbal supplements are suitable for improving fish health and combating diseases in fish culture. However, the mechanism of action of many herbal mixtures remains unclear. This study was conducted to evaluate the effects of traditional Chinese medicine (TCM; a mix of Astragalus membranaceus, Angelica sinensis, and Crataegus hupehensis at a ratio of 1:1:1 on a weight basis) on growth, immune response, and disease resistance in Nile tilapia Oreochromis niloticus. Experimental fish (mean±SE weight=57±1g) were divided into two groups: a control group and a TCM (10g/kg) group. After 4weeks of the experimental trial, a significant increase in weight gain and specific growth rate and a lower feed conversion ratio were observed in fish fed a TCM-supplemented diet compared with control fish. Similarly, the immune response of Nile Tilapia in the TCM group showed enhanced lysozyme, superoxide dismutase, catalase, and immunoglobulin levels compared with the control fish. In comparison with the control, fish fed TCM showed significant up-regulation of β-defensin, lysozyme, heat shock protein 70, superoxide dismutase, and catalase genes in the intestine and head-kidney tissues. After a Streptococcus agalactiae challenge, survival of Nile Tilapia in the TCM group was 70% compared with 35% in the control. These results indicate that the TCM mixture in this study can elevate the immune response and disease resistance of Nile Tilapia.

This study investigated the effects of a combination of Leucas aspera, Oxy-cyclodextrin and sodium bentonite (LOB) on growth, digestive enzyme activity, innate immune response, haematology, and expression of immune-related genes in Nile tilapia. A total of 240 juvenile fish (20.15±0.05g) were randomly distributed into four dietary groups in triplicate and fed respective diets containing a graded level of LOB at 0 g kg-1 (Control), 0.3 g kg-1 (T1), 0.6 g kg-1 (T2) and 0.9 g kg-1 diet (T3) for 60 days. After 60 days, higher growth was observed in fish fed T2 diet (P < 0.05). Digestive enzyme activities and innate immune parameters were significantly higher in T3 group. Some of the haematological parameters reported statistically higher counts in T2 group (P<0.05), whereas erythrocyte indices and WBC counts were significantly higher in T3 group. Liver- kidney activities were recorded low in T3 group. Urea and creatinine were higher in control group, whereas T2 group recorded the least value. The highest relative expression of IL-1β, IgM-heavy chain, TGF-β and IFN-γ were recorded in T2 group, but TNF-α was upregulated in T3 group. The results showed that 0.6 - 0.9 g kg1 of LOB is recommended for inclusion in diet.

Response of chemokine receptors CXCR2 and integrin β2 after Streptococcus agalactiae and Aeromonas hydrophila challenge in GIFT strain of Nile tilapia Oreochromis niloticus

Zn is one of the essential elements to maintain normal fish metabolic process (including growth, development and reproduction), which have different chemical status in nature including inorganic, organic and nano-sized. In this work, the efficacy of gluconic acid zinc (Glu-Zn), nano zinc oxide (Nano ZnO), zinc sulphate (ZnSO4) on the growth performance, tissue mineral elements deposition, antioxidant activity and immune response of the tilapia fish Nile tilapia (Oreochromis niloticus) was evaluated. Three experimental diets were prepared by adding different forms of Zn sources (ZnSO4 as a control group) with same Zn concentration (40 mg/kg) and used to feed fish for 60 days. The biological trial results displayed that the growth performance of Nile tilapia has not obviously affected by different Zn form source supplement. However, Glu-Zn and Nano ZnO supplements have significantly stimulated the Zn and Cu absorption deposition efficiency in the fish tissues as compared to ZnSO4 group. Besides, there was a significant increase in Cu-Zn superoxide dismutase (35.03 U/mgprot), alkaline phosphatase (79.34 U/mgprot), aspartate aminotransferase (23.42 U/L), alanine aminotransferase (18.45 U/L), glutathione peroxidase (171.24 U/mgprot) and fatty acid synthase (11.55 ng/mL) content in Glu-Zn treatment. Additionally, Glu-Zn supply significantly increased serum lysozyme (9.91 U/mL), immunoglobulin M (0.48 g/L), complement 3 (0.74 g/L) and complement 4 (0.95 g/L) activity of Nile tilapia. Also, compared to ZnSO4 diet, lysozyme (11.44 U/mL) and complement 4 (0.63 g/L) content were obviously higher in fish fed Nano Zn diet. These findings revealed that supplementation with Glu-Zn as a Zn source in feed is better than ZnSO4 for improving tissue mineralization, antioxidant stress, alleviate lipid peroxidation and immunity response of Nile tilapia. Meantime, Nano ZnO also played a positive role in the tissue mineralization and immunity response of Nile tilapia.

The purpose of this study was to evaluate the effects of red yeast (Sporidiobolus pararoseus) produced from crude glycerol, as a by-product of the biodiesel production process, on the growth, innate immunity, expression of immune-related gene, and resistance of Nile tilapia against challenge with Streptococcus agalactiae. Fish were fed diets supplied with different concentrations of S. pararoseus dried cells at 0.0 (control; T1), 5.0 (T2), 10.0 (T3), and 20.0 (T4) g kg-1 diets for 90days. The results showed that final body weight, weight gain, and average daily gain were significantly higher in fish fed T3 and T4 compared to the control group (p < 0.05). Likewise, significant (p < 0.05) increases in total carotenoid content, liver superoxide dismutase activity (SOD), and serum lysozyme and albumin were observed in Nile tilapia fed S. pararoseus, with the highest (p < 0.05) values displayed in fish fed the T4 diet. Moreover, up-regulation of IL-1β transcription in Nile tilapia spleen and liver was observed in fish feeding group T4. In a challenge test against S. agalactiae, the fish survival rate was significantly higher in fish fed red yeast compared to the control group (p < 0.05). The highest bactericidal activity found in the T4 group (p < 0.05). However, no significant differences were found in hematology, blood chemical, malondialdehyde (MDA), body chemical composition, organosomatic indices, and myeloperoxidase (p > 0.05) in all treatments. The present results suggested that red yeast S. pararoseus (20.0gkg-1) can be used as a potential supplementation on growth, immune response, and disease resistance of Nile tilapia.