Rock bream (Oplegnathus fasciatus) IL-12p40: Identification, expression, and effect on bacterial infection

• An IL-12p40 homologue, OfIL-12p40, was identified in rock bream.
• OfIL-12p40 possesses a conserved IL-12p40 domain and a WSxWS signature motif.
• Bacterial infection enhanced OfIL-12p40 expression in kidney and spleen.
• rOfIL-12p40 stimulated the respiratory burst activity of peripheral blood leukocytes.
• rOfIL-12p40 enhanced the resistance of rock bream against bacterial infection.

IL-12p40, also called IL-12β, is a subunit of the proinflammatory cytokines interleukin (IL)-12 and IL-23. In teleost, IL-12p40 homologues have been identified in several species, however, the biological function of fish IL-12p40 is essentially unknown. In this work, we reported the identification and analysis of an IL-12p40, OfIL-12p40, from rock bream (Oplegnathus fasciatus). OfIL-12p40 is composed of 361 amino acids and possesses a conserved IL-12p40 domain and a WSxWS signature motif characteristic of known IL-12p40. Constitutive expression of OfIL-12p40 occurred in multiple tissues and was highest in kidney. Experimental infection with bacterial pathogen upregulated the expression of OfIL-12p40 in kidney and spleen in a time-dependent manner. Purified recombinant OfIL-12p40 (rOfIL-12p40) stimulated the respiratory burst activity of peripheral blood leukocytes in a dose-dependent manner. rOfIL-12p40 also enhanced the resistance of rock bream against bacterial infection and upregulated the expression of innate immune genes in kidney. Taken together, these results indicate that OfIL-12p40 possesses cytokine-like property and plays a role in immune defense against bacterial infection.