Identification and immunologic characterization of an allergen, alliin lyase, from garlic (Allium sativum).

Background: Garlic (Allium sativum) is one of the most common relishes used in cooking worldwide. Very few garlic allergens have been reported, and garlic allergy has been rarely studied.

Objective: The aim of the study was to identify allergenic proteins in garlic and to investigate their importance in allergies to other Allium species (leek, shallot, and onion).

Methods: A crude extract of garlic proteins was separated by SDS-PAGE and 2-dimensional electrophoresis; immunoblotting was then performed with the use of individual and pooled sera from patients with garlic allergy, and the major IgE-binding proteins were analyzed by amino acid sequencing and mass spectrometry. The putative allergens were further purified by chromatography; the antigenicity, allergenicity, and IgE-binding cross-reactivity of the purified protein were then studied by immunoblotting, periodate oxidation, skin tests, and IgE-binding inhibition assays.

Results: A major allergen, alliin lyase, was identified by mass spectrometry and Edman sequencing and purified to homogeneity through the use of a simple 2-step chromatographic method. Skin tests showed that the purified protein elicited IgE-mediated hypersensitive responses in patients with garlic allergy. Periodate oxidation showed that carbohydrate groups were involved in the antigenicity, allergenicity, and cross-reactivity. Garlic alliin lyase showed strong cross-reactivity with alliin lyases from other Allium species, namely leek, shallot, and onion.

Conclusions: Alliin lyase was found to be a major garlic allergen in a garlic-allergic group of patients in Taiwan. The wide distribution of alliin lyase in Allium suggests it may be a new cross-reactive allergen.