The use of carbohydrates as an immunomodulator in carp (Cyprinus carpio)

Fish diseases are the most important challenge that is facing the development of the aquaculture industry. Recently, there has been substantial interest to control fish diseases through the use of immunomodulators, such as β-glucans that activate a range of immune parameters. These carbohydrates are extracted from different sources and thus vary in their effectiveness. To develop a new biomaterial, with improved therapeutic and biological activities, β-glucans were modified by sulphation, which is a final chemical modification process to obtain derivatives of sulphated polysaccharide. In vitro experiments were used to establish the effect of different glucans and modified carbohydrates from animal and plant sources on the cytotoxicity and respiratory burst activity of carp pronephric cells and carp leukocytes cell lines (CLC). Dose response and administration time of glucans were examined using nitroblue tetrazolium (NBT) and MTT tetrazolium assays in CLCs. After screening 75 modified carbohydrates; only 9 were selected for their positive dose responses. The cellulose drive carbohydrate, sulphated tylose (CHO 1), induced greater respiratory burst activity in both cell types. The reproducibility of the sulphation process was established using a range of biological parameters, and analysing CHO 1 structure using FTIR and NMR analysis. Carp immune responses were determined after injection with CHO 1 alone or as an adjuvant in vaccines against Aeromonas hydrophila. The CHO1 proved to be an effective immune adjuvant in fish, enhancing and modulating a range of innate and adaptive immune response including: serum lysozyme and complement activity, leukocytes numbers and the expression of immune-related genes in carp organs e.g. cytokines (IL1β, IFNγ), complement component3 and lysozyme, as well the antibody titre against Aeromonas hydrophila was significantly improved. The potential of using CHO 1 and producing synthetic carbohydrates with identified structures maximise their role as adjuvants for vaccine or immunostimulant in anti-infective therapies has been established