Effect of vitamin D on the immunomodulation of head kidney after Edwardsiella ictaluri challenge in yellow catfish (Pelteobagrus fulvidraco).

Edwardsiella ictaluri (E. ictaluri) causes severe infections in yellow catfish (Pelteobagrus fulvidraco), which leads to a massive loss in the aquaculture industry especially in catfish commercial production. Previous studies have confirmed that vitamin D is essential in immune regulation in mammals. Based on next-generation sequencing, this study explored the immunomodulatory effects of dietary vitamin D on the head kidney of yellow catfish after E. ictaluri challenge. Current results showed that increasing the content of dietary vitamin D within the experimental concentration range (1120IU/kg-16600IU/kg) could reduce the mortality of the yellow catfish after E. ictaluri challenge. Results of the next-generation sequencing showed that dietary vitamin D regulates the immune mechanism of the head kidney mainly through three pathways i.e. negative regulation of interferon-β production, negative regulation of interleukin-6 production and neutrophil chemotaxis. Proteins HSPA8, MAP4K4 and MRC1 may be involved in vitamin D-mediated immunoregulation in the head kidney. qPCR results showed that increasing the content of dietary vitamin D can improve the immune function of the yellow catfish by down-regulating ifn-β and pro-inflammatory factors tnf-α, il1-β, il-6, il-8 and up-regulating the anti-inflammatory factor il-10. The above results indicated that dietary addition of vitamin D regulated the immune response in head kidney of yellow catfish and helped the fish to resist the negative effects of infection by E. ictaluri in a dose-dependent manner.