Peanut cross‐reacting allergens in seeds and sprouts of a range of legumes

Abstract

Recently, peanut-allergic patients have reported symptoms upon ingestion of bean sprouts produced from various legumes. This study was designed to identify immunoreactivity to seeds and sprouts of legumes other than peanut in sera from peanut-allergic patients. Crude protein extracts of seeds and sprouts (comprising cotelydons and hypocotyls/epicotyls) of peanut, soybean, green pea, blue lupine, mung bean, alfalfa, broad bean, and azuki bean were prepared. The reactivity of sera from 10 peanut-allergic patients to these extracts was analysed by indirect histamine release (HR), enzyme-allergosorbent test (EAST), EAST inhibition, and Western blots. Skin prick tests (SPTs) were performed on the patients with fresh legume seeds as well as four commercial legume sprouts, and food challenges with soybean, pea, and lupine were performed on a subgroup of the patients. All legume seeds and commercial sprouts induced positive SPTs in some of the patients. Indirect HR experiments indicated an extensive co-reactivity between peanut and the legumes, and cross-reactivity was observed for soybean, pea, and lupine seeds as well as lupine hypocotyls in EAST inhibition experiments. Of the 16 protein extracts, soybean, pea, and lupine seed extracts produced visible bands in Western blots. The symptoms reported by peanut-allergic patients after legume sprout intake might be caused by cross-reactivity of peanut-specific antibodies. The intake of raw legume sprouts might cause symptoms in peanut-allergic patients.