Alteration On The Expression Of Sweetfish Interleukin-12B Gene Upon Listonella Anguillarum Infection

Interleukin-12B (IL-12B), a subunit of IL-12, plays an important role in the inflammatoryresponse in mammals against intracellular pathogenic bacteria. In the study, the cDNA sequenceencoding IL-12B gene of sweetfish,1152bp in length excluding3’-poly A tail, was obtained fromde-novo transcriptome sequencing of sweetfish macrophages. The sequence contained a completeopen reading frame (ORF), which encoded a propeptide of303amino acids (aa). A22-aa signalpeptide was predicted to be existed at its N-terminus. Sequence analysis showed that sweetfish IL-12B shared the highest homology with that of Atlantic salmon (50%protein sequence identity)50%amino acid sequence identity with that of Atlantic salmon. IL-12B mRNA was mainlyexpressed in the head kidney, weakly expressed in the spleen, gills and intestine of healthysweetfish. Upon Listonella anguillarum infection, IL-12B mRNA expression dramaticallyincreased in the head kidney and PBL, and reached peak value at12hpi. Western blot analysisindicated that serum IL-12B significantly increased in sweetfish infected by L. anguillarum. Inconclusion, IL-12B may be involved in the progress of immune response in sweetfish againstmicrobial infections.