Vitamin Dprotects turbot (Scophthalmus maximus L.) from bacterial infection.

Abstract

Accumulating evidence supports that vitamin D(VD) possesses immunomodulatory properties besides its classical actions in calcium and bone homeostasis. In this study, juvenile turbots were fed with the diets containing 0 IU/kg VDor the optimum dose of 400 IU/kg VDfor 8 weeks. To investigate the effects of VDon anti-infectious immunity in fish, 10 CFU Edwardsiella tarda was injected intraperitoneally to each juvenile turbot after the feeding trial. Our results showed that the mortality of infected turbots with dietary VDwas much lower than that in VDdeficient group, and the supplementation of dietary VDsignificantly reduced the bacterial load in the spleen of infected turbots. Further analysis demonstrated that the production of reactive oxygen species (ROS) in haemocytes and lysozyme activity in serum was elevated, and the responses of T cells and B cells were modulated in VD-supplemented turbots. Moreover, the inflammation was significantly exacerbated in the infected turbots fed with 0 IU/kg VDcompared to the fish fed with 400 IU/kg VD. In addition, the head kidney macrophages (HKMs) in turbots were isolated and incubated with VDin vitro, the results showed that VDsignificantly promoted the bactericidal activity in HKMs. In conclusion, our study has shown clear evidence that VDpositively regulates the innate and adaptive immunity in fish, which is beneficial to the defense in fish against pathogen infection.