Immunomodulation by dietary vitamin C in healthy and aflatoxin B 1-induced immunocompromised rohu ( Labeo rohita)

Abstract

The aim of this study was to examine the immunomodulatory effect of high levels of dietary vitamin C in healthy and immunocompromised rohu ( Labeo rohita) treated with aflatoxin B 1 (AFB 1). Four groups of rohu were fed experimental diets containing either no vitamin C or supplemented with vitamin C at 500 ppm for 60 days. On the first day of feeding, one group fed the high vitamin C diet and one fed the vitamin C deficient diet, were injected intraperitoneally with a single doses of AFB 1 at 1.25 mg kg −1 body weight. The effect of AFB 1 and high dietary vitamin C on specific and non-specific immunity, and disease resistance against Aeromonas hydrophila were examined in the rohu. The ability of vitamin C to counteract immunosuppression induced by AFB 1 was also examined. Specific immunity indicated by haemagglutination and haemolysin titres against sheep red blood cells (SRBC), and bacterial agglutination appeared to be unaffected by either the AFB 1 treatment or the vitamin C enriched diet. A significant reduction was observed in the non-specific immunity of AFB 1-treated fish, however, indicated by lowered bactericidal and lysozyme activities. High dietary vitamin C, on the other hand, enhanced the non-specific immunity of fish, including an enhanced phagocytic ratio and increased serum lysozyme activity. Feeding a high level of dietary vitamin C to AFB 1-treated fish increased these parameters to levels similar to those found in control fish. High dietary vitamin C significantly ( p<0.05) enhanced protection against Aeromonas hydrophila infection in both healthy and immunocompromised fish. Results from this study help to establish the beneficial effect of dietary vitamin C on AFB 1-induced immunosuppression, as well as confirming the immunostimulatory effect of vitamin C in rohu.