Oral bovine serum albumin immune-stimulating complexes improve the immune responses and resistance of large yellow croaker (Pseudosciaena crocea, Richardson, 1846) against Vibrio alginolyticus

This study aimed to investigate effects of bovine serum albumin immune-stimulating complexes (BSA ISCOMs) on immune-related genes expression, serum nonspecific immunity and disease resistance of large yellow croaker (Pseudosciaena crocea). Fish were fed diets containing 3.5 ml of BSA ISCOMs per kg feed (experimental group) or 3.5 ml of phosphate-buffered saline per kg feed (control group) for 1 week. The liver, spleen, head-kidney tissues were sampled for determining gene expression of myxovirus-resistant protein (Mx), major histocompatibility complex class II alpha chain (MHC II alpha), tumour necrosis factor-alpha (TNF-alpha) and interleukin-10 (IL-10) 30 and 90 days after feeding. Also, blood samples were collected for determining activities of serum superoxide dismutase (SOD), interferon alpha (IFN-alpha), TNF-alpha and alkaline phosphatase (ALP). TNF-alpha and MHCII alpha gene expression in the liver, spleen, head-kidney, as well as IFN-alpha, TNF-alpha and ALP activities in the serum, of experimental fish were significantly higher 30 days after feeding; while only TNF-alpha and MHC II gene expression in the head-kidney remained upregulated 90 days after feeding. The cumulative mortality of the experimental fish was significantly lower than control. This study indicated that BSA ISCOMs improved the immune response and induced protective immunity in large yellow croaker.