Carbohydrate epitopes as a cause of cross-reactivity in patients allergic to Hymenoptera venom

BACKGROUND: Among patients with allergy to insect stings, double positivity in tests for IgE antibodies specific to honey bee and wasp venoms is a frequent diagnostic problem. True double sensitization and possible cross-reactivity of venom hyaluronidases and with carbohydrate determinants must be considered in such patients. We studied the frequency of sensitization to carbohydrate determinants and the role of these in double positivity in tests for specific IgE antibodies. MATERIALS AND METHODS: A group of 66 patients (41 men, 25 women; 16–66 years) with double positivity for wasp and bee venoms were tested in the FEIA inhibition test in order to distinguish true double sensitization from cross-reactivity. Patients were tested for the presence of IgE antibodies specific to oilseed rape (OSR) pollen and MUXF3 allergens, both of which are rich in cross-reacting carbohydrate epitopes. RESULTS: Inhibition tests revealed true double sensitization in 37 patients (56.1%) and cross-reactivity in 29. Among those showing cross-reactivity, five were sensitized to honey bee venom and 24 to wasp venom. The median value of IgE specific for OSR pollen in patients sensitized to honey bee venom was 4.350 IU/ml, in patients sensitized to wasp venom 0.61 IU/ml, and in patients with double sensitization 0.25 IU/ml (P = 0.028, Kruskal–Wallis test). Findings for IgE specific for MUXF3 were similar. Discordance between OSR pollen positivity and MUXF3 positivity was found in 11.1% of the patients. CONCLUSION: The values of IgE specific for OSR pollen and MUXF3 in patients with primary sensitization to either honey bee venom or wasp venom were significantly higher than in patients with double sensitization. These results confirm that IgE antibodies against carbohydrates epitopes are a frequent cause of double positivity in tests for anti-venom IgE antibodies.