Recent Insights into Plant Allergens and the Development of Neoglycopolymers for Anti-allergic Drug Design

Plant allergens that cause pollinosis and food allergies are often N-glycosylated. Plant antigenic N-glycans contain antigenic β1,2-xylosyl and/or α1,3-fucosyl residues in the tri-mannosyl core structure, and some structures have N-acetylglucosamine or Le^a epitope at their non-reducing terminal. Recently, it has been shown that plant antigenic N-glycans of pollens and plant food allergens are cross-reactive but are minor epitopes of serum immunoglobulin E (IgE) of allergic patients and are not involved in induction of allergic symptoms. On the other hand, the core structure of the plant antigenic N-glycan, free Man₃Xyl₁Fuc₁GlcNAc₂ (M3FX), has been found to suppress cedar pollen allergen Cry j 1-specific Th2 immune responses (cell proliferation and IL-4 production), suggesting that M3FX may be a lead compound for drugs against pollen allergies. In order to elucidate the suppressive mechanism of Th2 immune response, it will be necessary to synthesize neoglycopolymers carrying multivalent M3FX to enhance the immunomodulatory activity of M3FX. In this review, we describe the structural features of plant antigenic N-glycans found in pollen and plant food allergens and the role of serum IgE in cedar pollinosis and peanut allergy to plant antigenic N-glycans as well. Subsequently, we introduce methods for preparing glycopeptides containing plant antigenic N-glycans and neoglycopolymers synthesis.