Vig r 6, the cytokinin‐specific binding protein from mung bean (Vigna radiata) sprouts, cross‐reacts with Bet v 1‐related allergens and binds IgE from birch pollen allergic patients’ sera

Abstract

Scope Birch pollen associated allergy to mung bean sprouts is caused by cross‐reactivity between the birch pollen allergen Bet v 1 and the mung bean allergen Vig r 1. We aimed to determine the allergenicity of the cytokinin‐specific binding protein from mung bean (Vig r 6), another allergen related to Bet v 1 with only 31% sequence identity. Methods and results Bet v 1, Gly m 4, Vig r 1, and Vig r 6 were produced in Escherichia coli. In an ELISA, 73 and 32% of Bet v 1‐sensitized birch‐allergic patients’ sera (n = 60) showed IgE binding to Vig r 1 and Vig r 6, respectively. Of 19 patients who reported allergic reactions or had positive prick‐to‐prick tests to mung bean sprouts, 79% showed IgE binding to Vig r 1 and 63% showed IgE binding to Vig r 6. Bet v 1 completely inhibited IgE binding to both mung bean allergens. Vig r 6 showed partial cross‐reactivity with Vig r 1 and activated basophils sensitized with mung bean allergic patients’ sera. Conclusion We demonstrated IgE cross‐reactivity despite low sequence identity between Vig r 6 and other Bet v 1‐related allergens. Thus, IgE binding to Vig r 6 may contribute to birch pollinosis‐associated mung bean sprout allergy.