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

Oral tolerance against food proteins has been achieved in different animal models with use of native or moderately hydrolyzed proteins as inducers. However, native proteins remain highly allergenic, although it has been demonstrated that protein hydrolyzates and resulting peptides can lose their allergenicity.

This study was designed to evaluate the ability of beta-lactoglobulin hydrolyzate and peptides to induce oral tolerance to native beta-lactoglobulin and to identify tolerogenic beta-lactoglobulin peptides with low allergenicity.

beta-Lactoglobulin was hydrolyzed by trypsin and fractionated by ion 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 specific IgE in sera and intestinal samples. Specific T-cell responses were analyzed by splenocyte proliferation. Antigenicity of hydrolyzate and fractions was evaluated by specific ELISA inhibition.

Mice fed either beta-lactoglobulin hydrolyzate or 2 fractions of the hydrolyzate were tolerized against beta-lactoglobulin. Specific serum and intestinal IgE were suppressed. Delayed-type hypersensitivity and proliferative responses were inhibited. One tolerogenic fraction was found to be 50 times less antigenic than the total beta-lactoglobulin hydrolyzate was.

These findings support the strategy of inducing oral tolerance in "at-risk" patients by means of tolerogenic cow's milk peptides or hydrolyzate.