Molecular cloning and expression analysis of interleukin (IL)-15 and IL-15 receptor alpha from rock bream, Oplegnathus fasciatus

Abstract

Mammalian interleukin (IL)-15 plays an important role in the activation of CD8(+) T cells and natural killer (NK) cells along with its receptor alpha (IL-15R alpha). To understand the potential roles of IL-15 and IL-15R alpha in fish, we identified IL-15 and IL-15R alpha cDNA from rock bream (Oplegnathus fasciatus) and investigated their gene expression profiles after bacterial and viral infection. Coding regions of rock bream (Rb) IL-15 and RbIL-15R alpha cDNAs were 534 and 402 bp encoding 177 and 133 amino acid residues, respectively. The sushi domain of IL-15R alpha was highly conserved between rock bream and other species. Unlike other IL-15R alpha s, RbIL-15R alpha does not have a transmembrane region. Gene expression of RbIL-15 and RbIL-15R alpha was widely expressed in different tissues of healthy fish, especially immune-related tissues. RbIL-15 and RbIL-15R alpha were highly induced in the kidney and spleen after infection with Edwardsiella tarda, Streptococcus iniae and red seabream iridovirus. Gene expression patterns of RbIL-15 and RbIL-15R alpha were similar in the kidney and spleen after pathogen infection. However, these genes were differentially induced in the liver after pathogen infection. These results suggest that the different responses of RbIL-15 and RbIL-15R alpha to pathogen infection may be induced by different tissues or cell types. (C) 2013 Published by Elsevier Ltd.