GAS1: A New β-Glucan Immunostimulant Candidate to Increase Rainbow Trout (Oncorhynchus mykiss) Resistance to Bacterial Infections With Aeromonas salmonicida achromogenes

Abstract

β-glucans are prebiotic and/or food additives used by the aquaculture industry to enhance the immune response of fish. Their efficiency may vary according to their origin and structure. In this study, the immunostimulant effects of two β-glucan types extracted from wild-type baker’s yeast (Saccharomyces cerevisiae) and its null-mutant Gas1 were investigated. Gas1 has a beta-1,3-glucanosyltransferase activity necessary for cell wall assembly. Using a positive (commercial product MacroGard®) and a negative control (a diet without glucans), we evaluated the immune responses and disease resistance of rainbow trout juveniles (mean weight, ~44 g) fed control, low (0.2%) and high (0.5%) doses of Macrogard®, Gas1, and Wild type-β-glucan after a short-term (15 days, D15) or mid-term (36 days, D36) feeding periods. We found that β-glucan supplemented diets did not affect growth performance, mortality, splenic index, or leukocyte respiratory burst activity on D15 nor D36. However, each β-glucan triggered different immune effectors, depending of the doses or length of exposure compared to others and/or the negative control. Indeed, high dose of MacroGard® significantly increased lysozyme activities at D15 compared with the control and other diets (p<0.05). At D36, MacroGard β-glucan enhanced the production of lymphocytes in comparison with the control diet (p<0.05). Regarding WT β-glucan, at D36, WT-β-glucan, especially the high dose, provided the highest enzymatic activities (lysozyme and ACH50) and Ig level (p<0.01). Furthermore, on D36, Gas1 also increased lysozyme activity, Ig proportion, and some immune genes (mcsfra, hepcidin) compared with MacroGard® (p<0.05). Besides, both doses of Gas1-β-glucans increased the resistance of juveniles to bacterial infection highlighted by a higher survival rate at 14 days post-challenge compared with the control and other types and doses of β-glucans (p<0.05). In conclusion, our results suggest that Gas1-β-glucan could represent a promising immunostimulant that would help to prevent diseases in aquaculture even more efficiently than other β-glucans already in use. Mode of action and particular efficiency of this new Gas1 mutant are debated.

The Pathogen Aeromonas salmonicida achromogenes Induces Fast Immune and Microbiota Modifications in Rainbow Trout

“…The strain was identified as a A. salmonicida achromogenes using biolog system and was deposited in the BCCM collection (Belgian coordinated collection of microorganisms) with code LMG p-31558. The virulence and LD50 was assessed during a preliminary test infection, and various bacterial doses were performed to determine the LD50 CFU of the targeted rainbow trout population (LD50 = 3.1 × 107 CFU/100 g fish body weight) [ 25 ]. Bacteria were isolated from a unique colony in sterile brain heart infusion (BHI) solid medium (Sigma Aldrich, Saint-Louis, MO, USA) and then incubated at 22 °C for 18 h. Bacteria were cultured until reaching 3.1 × 10 9 CFU/mL just before the start of the experiment.…”

GAS1RR, an immune-related enhancer RNA, is related to biochemical recurrence-free survival in prostate cancer

“…GAS1 (Growth Arrest-Specific Protein 1) is a tumor suppressor validated in a large number of published papers, it appears that the GAS1 protein is an integral plasma membrane protein, and its expression is linked to growth cessation. When GAS1 is overexpressed from a constitutive promoter in quiescent cells, the serum-induced cell cycle transition from the G0 to the S phase of the cell cycle is inhibited without affecting the normal early serum res ponse, [11][12][13][14][15][16][17] and we discovered the eRNA GAS1RR (GAS1 Adjacent Regulatory RNA), located nearby its putative target GAS1, was observably interrelated with beneficial clinical and pathological features and longer time to BCR in PCa patients. In addition, by analyzing the data from Tumor Immune Estimation Resource (TIMER) database, we found GAS1RR may influence the proportion of immune cells.…”

Effects of diets containing β‐glucan on survival, growth performance, haematological, immunity and biochemical parameters of rainbow trout ( Oncorhynchus mykiss ) fingerlings

“…The effect of β-glucan on the fish immune system depends on the type of fish species, the structure of the β-glucan, the dose and the duration used (Cornet et al, 2021). β-glucans are unique among immune stimulants because of their ability to improve immunity without over-activating them (Rodrigues et al, 2020).…”