Involvement of carbohydrate on phospholipase A sub(2), a beevenom allergen, in in vivo antigen-specific IgE synthesis in mice

Carbohydrates on allergens are known to be important for allergenicity. However, most findings have been made with epitope analysis. In this study, we investigated the involvement of N-glycan on phospholipase A sub(2) (PLA2), the major allergen of honeybee venom, in in vivo synthesis of specific IgE in mice. CBA/J and C57BL/6 mice were sensitized intranasally with either native or deglycosylated PLA2 in the absence of adjuvant. After repeated sensitization, serum Ab titers against PLA2 were determined. PLA2 was deglycosylated chemically with anhydrous trifluoromethanesulfonic acid (TFMS). CBA/J mice showed PLA2-specific IgE production after repeated sensitization with native PLA2. They also produced PLA2-specific IgG1 predominantly, suggesting that Th2-type Ab production was induced. When we used deglycosylated PLA2 as a competitor in ELISA for detecting PLA2-specific IgE, deglycosylated PLA2 completely inhibited the binding between native PLA2 and IgE. Deglycosylated PLA2 had the same potential for inducing specific IgE synthesis as native PLA2, since sensitization with deglycosylated PLA2 also elicited IgE production in CBA/J mice. These results suggest that carbohydrate on PLA2 is less important than previously thought not only as a dominant IgE epitope but also in synthesis of PLA2-specific IgE in vivo.