Peptides obtained by tryptic hydrolysis of bovine beta-lactoglobulin induce specific oral tolerance in mice

Background: Oral tolerance against food proteins has been achieved in diffe rent animal models with use of native or moderately hydrolyzed proteins as inducers. However, native proteins remain highly allergenic, although it ha s been demonstrated that protein hydrolyzates and resulting peptides can lo se their allergenicity. Objective: This study was designed to evaluate the ability of beta-lactoglo bulin hydrolyzate and peptides to induce oral tolerance to native beta-lact oglobulin and to identify tolerogenic beta-lactoglobulin peptides with low allergenicity. Methods: beta-Lactoglobulin was hydrolyzed by trypsin and fractionated by i on exchange chromatography. Peptide enrichment of fractions was evaluated. Balb/c mice were fed beta-lactoglobulin hydrolyzate or fractions by single gavage at day 1. Five days later animals were challenged intraperitoneally with native beta-lactoglobulin. At day 27 delayed-type hypersensitivity was performed. Twenty-four hours later mice were bled, and intestinal contents and spleens were collected. Oral tolerance was measured by titrating speci fic IgE in sera and intestinal samples. Specific T-cell responses were anal yzed by splenocyte proliferation. Antigenicity of hydrolyzate and fractions was evaluated by specific ELISA inhibition, Results: Mice fed either beta-lactoglobulin hydrolyzate or 2 fractions of t he hydrolyzate were tolerized against beta-lactoglobulin. Specific serum an d intestinal IgE were suppressed. Delayed-type hypersensitivity and prolife rative responses were inhibited. One tolerogenic fraction was found to be 5 0 times less antigenic than the total beta-lactoglobulin hydrolyzate was. Conclusion: These findings support the strategy of inducing oral tolerance in "at-risk" patients by means of tolerogenic cow's milli, peptides or hydr olyzate.