Reduction of Allergenicity of Milk Protein by Conjugation with Acidic Oligosaccharides

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Bovine β-lactoglobulin-alginic acid oligosaccharide (β-LG-ALGO) conjugate was prepared by the Maillard reaction to reduce the allergenicity and improve the functional properties of β-LG. The molar ratio of β-LG to ALGO in the conjugates was 1 : 6. The isoelectric point of the conjugate was <4.6, which is lower than that of β-LG. Carbohydrate binding sites in β-LG were identified to be 60Lys, 77Lys, lOOLys, 138Lys and141Lys. CD spectra indicated that secondary structure of β-LG was almost maintained after conjugation with ALGO. Fluorescence studies suggested that the conformation around Trp had not changed in the conjugate and that the surface of the conjugate was covered with saccharide chain. Structural analyzes with monoclonal antibodies indicated that the conformation around 15Val29Ile and 8Lys-19-Trp in the conjugate had changed, while native structure was maintained around 125Thr-135Lys. By conjugation with ALGO, β-LG was endowed with high heat stability and improved emulsifying ability. The antiβ-LG antibody response was markedly reduced after immunization with the β-LG- ALGO conjugates in BALB/c, C57BL/6 and C3H/He mice. We determined the B and T cell epitopes of β-LG and the conjugate recognized in these mice and found that the linear epitope profiles of the β-LG- ALGO conjugate were similar to those of β-LG, while the immune response for each epitope was dramatically reduced. Masking of epitopes by ALGO was considered to be responsible for the decreased immunogenicity of the β-LG in the conjugate.