Resumen de Molecular regulation of the immune function in the gills of gilthead sea bream (sparus aurata) fed with immunostimulant diets
Over the past 15 years, in order to maintain fish health and to improve fish performance, the aquaculture has used immunostimulants as dietary additives in fish farms to improve weight gain, feed efficiency, and/or disease resistance in more than 18 fish species including: Carp, Yellow croaker, Turbot, Atlantic salmon and seabream, amongst others. The compounds tested are varied including bacterial components, polysaccharides, animal, plant and algae extract, nutritional factors, and even hormones and cytokines and some synthetics such as Levamisole. However, even although a lot of interest and studies have been carried out, commercially available immunostimulant diets mainly contain -glucans. The majority of the studies reported are based upon hemato-immune and non-specific immune measurements. All studies have shown positive results, but little is known about the underlying molecular response to dietary administration of immunostimulants. In order to evaluate the β-glucan transcriptomic response in gills we analyzed and evaluated gene expression profiles associated with exposure to immunostimulant diets over time, using both a molecular and cellular approach.
Experimentally, 360 healthy Gilthead seabream (Sparus aurata) of average body weight of 38±7.3 g were separated in 27 tanks and fed with two Skretting immunostimulant diets (diet A and diet B) and a control diet (diet C). Each diet were fed at a feeding rate of 3% of body weight twice daily for 28 days with a period of 14 days of pre-acclimation. Samples were taken at 2, 7, 14 and 28 days post diet. The serum parameters showed an increase in lysozyme, glucose and PGE2, while a decrease was observed in cortisol and lactate at 7 and 14 days of feeding (dof) in diet B and only at 14 dof in diet A. No differences in mortality rate were observed. Gills were analyzed using an specific Sparus aurata 44K oligonucleotide-microarray and in situ hybridization (ISH). A diet dependent and a loop analysis were carried out, with control diet as a reference point. Microarray results shown a differential expression of genes associated to inflammatory (TNFRSF1A, C/EBPB, CLEC4E, CMA-1, Caspase 1, Transcription factor PU.1, SOCS1, CD18, CSF3R and Hepcidin), T cell-mediated immune response (CD209, MHC IIα, TCRβ, TCRγ, CD8α, CD3ζ, CD40 and CD82), and apoptosis (Perforin 1, BCAP31, and IFI35). However, the intensity and magnitude of the modulation of these responses was not high. ISH analysis showed localization of immunological transcripts in a specific cellular type in the primary lamellae of gilthead seabream gills. The results indicate that β-glucan administered in diet produces an immunostimulant effect in gills of seabream.
