Assessment of lupin allergenicity in the cholera toxin model: induction of IgE response depends on the intrinsic properties of the conglutins and matrix effects.

BACKGROUND

The well-established murine model of IgE-mediated food allergy, based on oral administration of antigen and cholera toxin (CT), has within the previous years been used to evaluate various food proteins. Nonetheless, little knowledge on the factors that determine the allergenicity of food proteins is available so far. The use of proteins from the legume seed Lupinus albus as food ingredients calls for an evaluation of their allergenic potential, and therefore, we applied the cited model to investigate the putative allergenicity of three lupin protein preparations representing different matrices in which the four types of conglutins are present in varying concentrations.

METHODS

Weekly, BALB/c A mice were orally immunized with the three lupin protein products together with CT. Total specific antibodies and IgE were determined by ELISA and Western blotting.

RESULTS

A dose-dependent Ig response against the analyzed proteins was observed for all three lupin products, while IgE responses against conglutins beta, gamma and delta, but not against conglutin alpha, were primarily detected after oral administration of lupin flakes. Whereas no differences among the samples for total specific Ig responses were seen, orally administered lupin flake extracts were much more efficient in inducing a conglutin-specific IgE response compared with fractionated lupin protein products.

CONCLUSIONS

Although the lupin-specific Ig response induced by coadministration of CT and lupin proteins appears to be dose dependent, the IgE response appears to depend merely on some intrinsic properties of the proteins as well as some factors of the protein matrix.