Characterization of three pro-inflammatory cytokines, TNFα1, TNFα2 and IL-1β, in cage-reared Atlantic bluefin tuna Thunnus thynnus

• We have fully sequenced Atlantic bluefin tuna BFT TNFα1, TNFα2 and IL-1β molecules.
• 3D models of three BFT cytokines are developed using homology modeling method.
• We analyzed in vivo tissue expression of BFT cytokines during farming process.
• The highest levels of TNFα1, TNFα2 and IL-1β were found in liver tissue.
• Expressions of three cytokines were significantly higher in damaged then wild tuna.

Atlantic bluefin tuna (BFT) (Thunnus thynnus) is of great economic significance for world aquaculture and therefore it is necessary to ensure optimal and sustainable conditions for the farming of this species. Intensive culture of fish may be limited by infectious diseases that can impact on growth performance and cause heavy losses. However, to date there are no reports of cloning and expression analysis of any major immune genes of Atlantic BFT although some immune genes are known in other BFT species. Therefore the aim of this study was to characterize the first cytokine molecules in Atlantic BFT, through: 1) Isolation of full-length cDNA and gene sequences of TNFα1, TNFα2 and IL-1β, 2) comparison of these molecules to known sequences in other vertebrates, especially teleost fish, by multiple sequence alignment, phylogenetic tree analysis and homology modeling; 3) Quantification of in vivo expression of these cytokines in selected tissues in reared BFT over the duration of the farming process. The results indicated that these three cytokines could have value for monitoring Atlantic BFT health status. Curiously, the liver seemed to be an important site of cytokine production during poor health conditions in this species, perhaps reflecting its role as an important organ involved in fish defenses.