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Allergenic and antigenic activity of peptide fragments in a whey hydrolysate formula
E M Van Hoeyveld1, M Escalona-Monge, L F de Swert
1Department of Internal Medicine, University Hospital Gasthuisberg, Leuven, Belgium.
Background:
Milk hydrolysates, although frequently used as substitutes in cases of cow's milk allergy, show a reduced but never a complete abolishment of antigenicity and allergenicity.
Objective:
Our purpose was to determine the lower molecular weight limit of peptides to elicit skin reactions and to bind IgE antibodies in vitro.
Methods:
Using FPLC, an ultrafiltrated whey hydrolysate, was fractionated in different molecular weight fractions. Skin-prick tests were performed with the hydrolysate and its fractions in five cow's milk allergic children, and RAST inhibition tests were done using the serum of these children.
Results:
On the basis of the lowest extinction values between two peaks of the chromatogram, seven fractions with molecular weights between 15000 and 125 Da were obtained. Peptides of > 2600 Da elicited a clearly positive skin reaction and inhibited IgE-binding, while peptides of < 1400 Da did not give any positive skin reaction but were still able to inhibit to a small extent IgE-binding to the hydrolysate.
Conclusion:
Our findings suggest that for skin reactivity peptides of > 1400 Da are needed. The minimal molecular mass for IgE binding in vitro appears to be situated between 1400 and 970 Da. Such peptides might be used to develop a safe formula for patients reacting to milk hydrolysates or even for tolerance induction.