Detection of potentially allergenic material in 12 hydrolyzed milk formulas

Hypoallergenic milk formulas are used as an alternative diet for infants wh o have allergies to cow's milk when breast-feeding is not possible. These p roducts are based on proteins, which have been heat-treated and hydrolyzed to a different degree in order to cleave antibody-binding structures. Even extensively hydrolyzed products have occasionally been observed to elicit a llergic reactions in sensitized infants, however. Therefore, the parameters of relevance to allergenic potential require more investigation. The objec tive of the present study was to investigate 12 different hydrolyzed milk f ormulas for their contents of potentially allergenic protein material, i.e. material that may induce allergenicity or elicit allergic responses in alr eady sensitized individuals. Analytical methods applied were gel filtration , sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), nat ive PAGE, immunoblotting, dot-immunobinding, and ELISA. Care was taken to a ssure that all protein fractions were investigated, including supernatants and precipitates following centrifugation of the milk formulas. By gel filt ration, protein material with apparent molecular masses of 7 to >30 kDa was detected. Analysis by SDS-PAGE of formula precipitates showed that protein s with a molecular mass above 20 kDa were present even in some of the exten sively hydrolyzed formulas. Residual antigenic P-lactoglobulin was found by ELISA in all products. By immunoblotting and dot-immunobinding with antibo dies against total whey, caseins, or Kunitz soybean trypsin inhibitor, we o bserved antigenic material mainly in partially hydrolyzed products. We conc luded that SDS-PAGE of formula supernatants and precipitates gave the most differentiated profile of hydrolyzed formulas and that this method is well suited for screening potential allergenicity.