Molecular Regulation of the Immune Function in the Gills of Gilthead sea bream (Sparus aurata) fed with immunostimulant diets

Abstract

Over the past 10 years, different immunostimulants have been tested 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 β-glucans. The majority of the studies reported are based upon cellular response assays such as phagocyte activity and ROS and simple blood measurements such as total serum IgM content. 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 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. Gills samples were taken at 2, 7, 14 and 28 days post diet. All samples were divided for microarray analysis (specific Sparus aurata 44K microarray, Agilent custom design) and in situ hybridization (ISH) analysis. 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 immunological processes such as inflammation, T and B cell response amongst others but 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.

Date of Award	6 Nov 2015
Original language	English
Supervisor	Lluis Tort Bardolet (Tutor) & Simon Anthony Mackenzie (Director)