Reduced Immunogenicity Of Bovine Milk Protein By Conjugation With Oligosaccharides

Conjugation with saccharides is one of the effective ways to reduce the immunogeniciity of allergic protein in food. It can reduce the immunogeniciity of allergic protein through shielding the epitope of allergic protein by conjugating with saccharides. In the present reaserch, the two more important allergic bovine milk protein, P-lactoglobulin andαs1-casein were conjugated with galactooligosaccharide and chitooligosaccharide respectively, antigenicity and immunogenicity of these conjugates were investigated by animal experiments and ELISA assay. The present study indicated that,1)β-lactoglobulin was conjugated with galactooligosaccharide and chitooligosaccharide by Mailand Reaction, and their antigenicity was investigated by competitive ELISA. The results indicated the antigenicity of the both milk protein conjugated with oligosaccharide were reduced effectively. Kd (the dissociation constant of antigen and antibody) of conjugates with galactooligosaccharide was rised 5.8 times compared toβ-lactoglobulin, while Kd of conjugates with chitooligosaccharide was rised 2.7 times. Conjugation with galactooligosaccharide was more effective method to reduce antigenicity of P-lactoglobulin.2) The results of animal experiments and ELISA assay indicated that the immunogeniciity of P-lactoglobulin was reduced for 18%and 15%respectively, after being combined with galactooligosaccharide and chitooligosaccharide respectively. Conjugation with galactooligosaccharide was more effective method to reduce immunogeniciity ofβ-lactoglobulin. At the same time, IgE production induced by conjugates with galactooligosaccharide of P-lactoglobulin was reduced for 15%, compared toβ-lactoglobulin.3) Casein was extracted from bovine milk by the method of isoelectric precipitation,αs-casein was separated from casein according the characters of it (1,αs-casein is soluble in higher concentration urea, and not in lower concentration urea.2,αs-casein is a Ca2+ sensitive protein),αs1-casein was isolated fromαs-casein by anion-exchange chromatography. The results of anion-exchange chromatography showed thatαs1-casein was eluted out, when the eluent volume fraction of B% was to be 55%(1 mol/L NaCl as gradient elution). Anion exchange chromatography and SDS-PAGE assay showeddαs1-casein components was separated well.4) The results of animal experiments and ELISA assay indicated that the antigenicity and immunogeniciity ofαs1-casein were reduced, after being combined with galactooligosaccharide and chitooligosaccharide respectively. Kd of conjugates with galactooligosaccharide was rised 3.7 times, while Kd of conjugates with chitooligosaccharide was rised 2.5 times. Conjugation with galactooligosaccharide was more effective method to reduce antigenicity and immunogeniciity ofαs1-casein. In conclusion, conjugation with galactooligosaccharide was a more effective method to reduce antigenicity and immunogeniciity ofβ-lactoglobulin andαs1-casein.