The nanocomposite of chitosan-vitamin C modulates the expression of immune and antioxidant-related genes in Nile tilapia stressed with lead (Pb)

Abstract Fish cultivated in a polluted environment usually face complicated disease cases. Pollution is an evitable event in aquaculture that weakens surface immunity, delaying and lowering the immune responses of aquatic animals. In an indoor experiment, Nile tilapia were reared in water polluted with lead (Pb) at a concentration of 51 µg/l for 8 weeks. A trial was conducted to mitigate the immunosuppression using pre-acclimatized Nile tilapia that were subdivided into six groups in which the exposed fish treated with nanocomposite (chitosan-vitamin C-protected nanoparticles (CVC-NPs)) consisted of 1 g of chitosan nanoparticles containing 400 mg vitamin C/kg fish and 200 mg vitamin C/kg fish feed for 1 week. Fish exposed to Pb pollution were immunocompromised as gene expression of immune-related cytokine and antioxidant enzymes significantly declined. Innate immunity was drastically impacted as OBA, phagocytosis and serum antibacterial activity (SAA) showed low values compared to the control fish; meanwhile, exposed fish was challenged against Streptococcus agalactiae and showed a high mortality rate (MR%). Dietary nanocomposite could restore normal immune status, and supplemented fish achieved low MR% with significantly high gene expression of proinflammatory cytokines. It was concluded that adding 200 mg of CVC-NPs/kg fish feed for 1 week could effectively protect Nile tilapia from S. agalactiae , having superiority over the high dose of 400 mg of CVC-NPs.