Evaluation of the IgE cross-reactions among vespid venoms. A possible approach for the choice of immunotherapy.

Background: Hymenoptera venom allergy can be effectively cured with specific immunotherapy, thus the correct identification of the allergen is essential. In the case of multiple skin and serum positivities it is important to know if a cross-reaction among venoms is present. We studied by CAP-inhibition assays the degree of cross-reactivity between Vespula vulgaris and Polistes dominulus.

Methods: Serum samples were obtained from consecutive patients with a clinical history of grade III-IV reactions to hymenoptera sting and with nondiscriminative skin/CAP positivity to both Vespula and Polistes. Inhibition assays were carried out with a CAP method, incubating the sera separately with both venoms and subsequently measuring the specific immunoglobulin E (IgE) to venoms themselves.

Results: Forty-five patients (33 male, mean age 40 years, age range 12-74, total serum IgE 242 +/- 168 kU/l) were included. Their specific IgE to Vespula and Polistes were 12.03 +/- 5.70 kU/l and 10.7 +/- 2.0 kU/l (P = NS), respectively. At the CAP-inhibition assays, in 25 patients a >75% heterologous inhibition by P. dominulus venom against V. vulgaris-specific IgE was found. In six subjects V. vulgaris venom effectively inhibited the P. dominulus-specific IgE. In the remaining 14 cases the CAP-inhibition test provided intermediate and not discriminative results.

Conclusion: In 31/45 patients, the double sensitizations to venoms were probably the result of cross-reactions and the CAP-inhibition allowed identifying the true double sensitizations. This approach may be helpful for the correct prescription of immunotherapy in the case of V. vulgaris and P. dominulus double positivity.