Evaluation of the antigenicity of hydrolyzed cow’s milk protein formulas using the mouse basophil activation test

Abstract Hypoallergenic infant formulasare widely used for infants with cow’s milk allergy. The aim of this study was to assess the utility of the mouse basophil activationtest (BAT) in the evaluation of residual antigenicity in these formulas. Whole blood samples derived from β- lactoglobulin- or casein-immunized mice were incubated with one of the following formulas: conventional, partially hydrolyzed, or extensively hydrolyzed. Basophilic activationwas analyzed by flow cytometry using an IgE-dependent activation marker CD200R1 and an IgG-dependent activation marker CD200R3. Systemic anaphylaxiswas induced by i.v. injection of milk formulaand results were compared. Conventional formula induced pronounced changes in CD200R1 and CD200R3 expression on basophils, whereas extensively hydrolyzed formulas did not elicit any changes in these markers. Similarly, challenge with conventional formula induced anaphylaxis, whereas extensively hydrolyzed formulas did not induce anaphylaxis. Although the partially hydrolyzed formula also induced basophilic activationand systemic anaphylaxis, the magnitude of these effects was smaller than that observed with the conventional formula. Compared to CD200R1, the observed trend in CD200R3 expression resembled the results obtained from systemic anaphylaxistest more closely. These findings show that mouse BAT, in particular using CD200R3, is highly useful for the evaluation of antigenicity of milk formulas.