The maize major allergen, which is responsible for food-induced allergic reactions, is a lipid transfer protein

Background: Cereals are the most important nutritional component in the hum an diet. Food-induced allergic reactions to these substances therefore have serious implications, and exhaustive diagnosis Is required. Such diagnosis is still difficult because of the incomplete knowledge about major cereal allergens. In particular, few food-induced allergic reactions to maize have been reported, and no information on the allergenic proteins is available. Objective: Having observed several anaphylactic reactions to maize, we plan ned a study to identify maize major allergens and cross-reactivity with oth er cereals, as well as to peach because the majority of patients also react ed to Prunoideae fruits. Methods: Twenty-two patients with systemic symptoms after maize ingestion a nd positive skin prick test responses and serum-specific IgE antibodies to maize were selected. The IgE-reactivity pattern was identified by SDS-PACE and immunoblotting. The major allergen identified was then purified by HPLC and characterized by mass spectrometry, determination of the isoelectric p oint value, and N-terminal amino acid sequencing. Results: Sera from 19 (86%) of the 22 patients recognized a 9-kd protein, t hus confirming this as the maize major allergen. This protein had an isoele ctric point of greater than 9, a molecular mass of 9047.0 d, and no glycosy lation. Determination of its N-terminal sequence showed that it was a lipid transfer protein (LTP). By using immunoblotting-inhibition experiments, we demonstrated that the LTP cross-reacts completely with rice and peach LTPs but not with wheat or barley LTPs. N-terminal sequence of the 16-kd allerg en (recognized by 36% of patients) showed it to be the maize inhibitor of t rypsin, This protein cross-reacts completely with grass, wheat, barley, and rice trypsin inhibitors. Conclusion: The major allergen of maize is an LTP with a molecular weight o f 9 kd that is highly homologous with the peach LTP, the major allergen of the Prunoideae subfamily.