Effect of β-1, 3 glucan binding protein based zinc oxide nanoparticles supplemented diet on immune response and disease resistance in Oreochromis mossambicus against Aeromonas hydrophila

Recently, several immunostimulants such as beta-glucan, microbial and plant products have been used as dietary supplements to combat disease outbreaks in aquaculture. The present study investigates the potential of Portunus pelagicus beta-1, 3 glucan binding protein based zinc oxide nanoparticles (Pp beta-GBP-ZnO NPs) supplemented diet on growth, immune response and disease resistance in Mozambique tilapia, Oreochromis mossambicus. The immune related protein beta-GBP was purified from the haemolymph of P. pelagicus using Sephadex G-100 affinity column chromatography. Pp beta-GBP-ZnO NPs was physico-chemically characterized and experimental feed was formulated. Fish were separately fed with commercial diet (control-group I) and Pp beta-GBP (group II, III, IV), Pp beta-GBP-ZnO NPs (group V, VI, VII), chem-ZnO NPs (VIII, IX, X) mixed diet at the concentration of 0.001%, 0.002% and 0.004% respectively. Triplicate groups of O. mossambicus were fed with experimental diets twice a day for 30 days. Fish receiving Pp beta-GBP-ZnO NPs supplemented diet showed a significant increase (P < 0.05) in growth performance. Cellular immune responses (myeloperoxidase activity, lysozyme activity and reactive oxygen species activity) and humoral immune responses (complement activity, antiprotease activity and alkaline phosphatase activity) were evaluated at an interval of 15 days during the feeding trial. Results demonstrate that both cellular and humoral immune responses were substantially increased (P < 0.05) in fish fed with 0.004% of Pp beta-GBP-ZnO NPs supplemented diet than others. Antibiofilm potential of Pp beta-GBP-ZnO NPs against Aeromonas hydrophila was visualized through confocal laser scanning microscopy (CLSM), which reveals reduction in the preformed biofilm thickness to 10 mu m at the concentration of 50 mu g/ml. Furthermore, after 30 days of feeding trial, fish were challenged with aquatic fish pathogen A. hydrophila (1 x 10(7) cells ml(-1)) through intraperitoneal injection. Challenge study displayed a reduced mortality rate in fish fed with diet containing Pp beta-GBP-ZnO NPs. Thus our study suggests that dietary supplementation of Pp beta-GBP-ZnO NPs at 0.004% may have a potential effect to enhance the immune system and survival of O. mossambicus.