An IL-1β homologue induced inflammation and antibacterial immune defense in Siberian sturgeon (Acipenser baeri)

Interleukin-1 beta is a key pro-inflammatory cytokine functioning in initiation of inflammatory responses against bacterial-and viral-infections. In the present study, a putative IL-1 beta counterpart was identified from Siberian sturgeon (Acipenser baeri) and designated as AbIL-1 beta. The Abil-1 beta cDNA sequence consists of 1130 bp with an open reading frame (ORF) of 585 bp, which encodes a 194 amino acid (aa) protein. Multiple amino acid sequence alignment revealed that a possible mature peptide could start at Leu(18), although no cut site for ICE (IL-1 beta converting enzyme) enzyme was present in Siberian sturgeon IL-1 beta. Even if AbIL-1 beta shares a relative low identity (33.6%) with another sturgeon type II IL-1 beta gene from Acipenser dabryanus, they still clustered together in phylogenetic tree. Endogenous Abil-1 beta was highly expressed in brain, blood, head kidney and spleen of healthy Siberian sturgeon, and remarkably up regulated in head kidney, spleen, and liver upon Aeromonas hydrophila (A. h) challenge. Consistently, in vitro stimulation test using heat-killed A.h and LPS significantly increased Abil-1 beta transcripts of primary spleen cells. To investigate the bactericidal capability of AbIL-1 beta, recombinant AbIL-1 beta (rAbIL-1 beta) was generated by prokaryotes. Pre-injection of rAbIL-1 beta reduced the bacterial load in sturgeon spleen after A.h infection. Further, rAbIL-1 beta was served as feed additive and demonstrated to enhance hybrid sturgeon's defense against A.h infection by increased expressional levels of immune-related genes (IL-1 beta, IL-6, IL-8, IgM and MHCII beta), elevated activities of serum lysosome, ACH50, and MPO, as well as higher percent survival. In summary, the current results suggested that AbIL-1 beta functions in immune regulation and could improve sturgeon's resistance to bacterial infection.

Automated summary

AbIL-1 beta was identified as a putative counterpart in Siberian sturgeon, showing significant enhanced expression in various tissues and up regulation upon bacterial challenge, indicating its role in immune regulation and improving resistance to bacterial infection.