Decrease in antigenic and allergenic potentials of ovomucoid by heating in the presence of wheat flour: dependence on wheat variety and intermolecular disulfide bridges.

The antigenic and allergenic activities of ovomucoid (OM) remaining in soluble fractions of pasta-like model samples of wheat flour mixed with egg white were investigated by ELISA competitive inhibition and immunoblotting analyses using a rabbit anti-OM IgG and the serum IgE specific for OM in patients allergic to egg white. The mixture of egg white and wheat flour of soft, hard, and durum varieties was kneaded for 10-50 min and benched for 1 h at RT, and then small pieces of the dough were heated in boiling 1% NaCl solution for 15 min. Even before heating, only after the kneading for 30 min or more, but not after kneading for only 20 min, followed by the benching, the antigenic activity of OM which remained in the phosphate-buffered saline extract from the dough markedly decreased. Almost no antigenic activity of OM was detected in the extracts of heated samples. Furthermore, in the extracts of heated durum samples, only a trace of or almost no IgE-reactive OM was detected against the five patients' sera. These reductive effects of wheat on the OM antigenicity and allergenicity were more remarkable in the durum variety than in the others. No detectable proteins were extracted with 1% SDS from the heated samples, whereas OM was extracted with 1% SDS containing 10% 2-mercaptoethanol, suggesting heat-induced polymerization through intermolecular disulfide bonds among OM and wheat.