Molecular characterization of an IL-1β gene from the large yellow croaker (Larimichthys crocea) and its effect on fish defense against Vibrio alginolyticus infection

Interleukin 1β (IL-1β), the first interleukin to be characterized, plays a key role in regulating the immune response. In this study, we determined the cDNA and genomic DNA sequences of the IL-1β gene from the large yellow croaker, Larimichthys crocea. Phylogenetic analysis indicated that the IL-1β (LcIL-1β) gene was most closely related to that of European seabass (Dicentrarchus labrax), sharing 67.8% amino acid identity. In healthy large yellow croaker, LcIL-1β transcription was detected in all tested tissues, with the highest level found in the head kidney. Upon Vibrio alginolyticus infection, LcIL-1β transcription in all tested tissues was significantly upregulated. Intraperitoneal injection of recombinant LcIL-1β (rLcIL-1β) improved the survival rate and reduced the tissue bacterial load after V. alginolyticus infection. In addition, rLcIL-1β induced monocytes/macrophages (MO/MΦ) chemotaxis and increased phagocytosis and bactericidal activity in vitro. These results suggest that LcIL-1β plays an important role in the large yellow croaker immune response against V. alginolyticus.