Real time quantification of the immune gene expression inrainbow trout fed different forms of probiotic bacteria Lactobacillius rhamnosus

Abstract

Whether it is better to use viable or non-viable pro bionts in aquaculture is still a matter of debate. In this study, the molecular immunomodulation in rainbow trout Oncorhynchus mykissinduced by viable or killed forms of the probiont Lactobacillus rhamnosus JCM 1136 was investigated. Three forms of this probiont: (1) heat-killed (HK), (2) live spray (LI) and (3) freeze dried (FD) were incorporated into a basal (control) diet for rainbow trout O. mykiss. The LI and FD diets are referred to as viable diets. A rearing trial, in tripli cate, was conducted for 30 days, with the control and probiotic diets as treatments. The cytokine genes such as the tumour necrosis factor (TNF), transform ing growth factor (TGF-b), interferon (IFN) and immune gene Immunoglobulin (Ig) found in tissues from the kidney and spleen were assessed for their expression pattern by real-time polymerase chain re action. The tested immune genes were up-regulated in the treatment groups, sometimes even in many folds like in the case of the Ig gene. The TNF gene was found to be highly (Po0.05) up-regulated (5000-fold) in groups fed both viable forms (LI, FD). With regard to the TGF-b gene, the spleen of the HK and FD groups showed signi¢cant up-regulation of 20- and 30-folds respectively. The IFN gene was up regulated (Po0.05) in all treatments, but more in the viable diet treatments. Kidney and spleen tissues showed similar expression patterns, i.e. all of these genes were up-regulated more with the viable diets that with the control, and in most cases, the viable diets induced a higher expression of the immune genes than the HK diet.