beta(1,2)-xylose and alpha(1,3)-fucose residues have a strong contributionin IgE binding to plant glycoallergens

Primary structures of the N-glycans of two major pollen allergens (Lol p 11 and Ole e 1) and a major peanut allergen (Ara h 1) were determined. Ole e 1 and Ara h 1 carried high mannose and complex N-glycans, whereas Lol p 11 carried only the complex. The complex structures all had a beta(1,2)-xylose linked to the core mannose, Substitution of the proximal N-acetylglucosami ne with an alpha(1,3)-fucose was observed on Lol p 11 and a minor fraction of Ole e 1 but not on Ara h 1, To elucidate the structural basis for IgE re cognition of plant N-glycans, radioallergosorbent test analysis with protea se digests of the three allergens and a panel of glycoproteins with known N -glycan structures was performed. It was demonstrated that both alpha(1,3)- fucose and beta(1,2)-xylose are involved in IgE binding. Surprisingly, xylo se-specific IgE antibodies that bound to Lol p 11 and bromelain did not rec ognize closely related xylose-containing structures on horseradish peroxida se, phytohemeagglutinin, Ole e 1, and Ara h 1, On Lol p 11 and bromelain, t he core beta-mannose is substituted with just an alpha(1,6)-mannose. On the other xylose-containing N-glycans, an additional alpha(1,3)-mannose is pre sent. These observations indicate that IgE binding to xylose is sterically hampered by the presence of an alpha(1,3)-antenna.