Short communication Evaluation of the IgE cross-reactions among vespid venoms. A possible approach for the choice of immunotherapy Hymenoptera venom hypersensitivity is sustained by a virtually ÔpureÕ Immunoglobulin E (IgE)-mediated reac- tion, where the inflammatory process is absent or negligible. In this situation, specific immunotherapy (SIT) is highly effective, and the allergen-specificity of the vaccine plays a crucial role. In clinical practice, the identification of the causal venom for prescribing SIT is essentially based on the clinical history, the identification of the stinging insect, the skin prick (and intradermal) test and the venom-specific IgE measurement (1, 2). As a matter of fact, some patients display multiple skin and/or serum positivities, so that multiple extracts for immuno- therapy are usually prescribed and administered. Obvi- ously, this may result in increased costs, increased risks of adverse events and, possibly, in sensitization to new allergens. On the other hand, the multiple positivities may be due, at least in some cases, to cross-reactions among components of venoms that belong to different hymen- optera species (3, 4), so that vaccination with one single venom could suffice. Cross-reactions may, in fact, occur among Vespidae, (e.g. Polistes and Vespula)(5), but they have also been described between bees and Vespidae (6). The cross-reactivity between the venoms of Vespula vulgaris and Polistes dominulus (European paper wasp) has not been investigated yet. Thus, we attempted to identify and to quantify such cross-reactivity by means of CAP-inhibition assays in patients with multiple sensiti- zations to those hymenoptera. Material and methods Consecutive adult patients, referred to our service (between June 2004 and September 2006) for hymenop- tera venom allergy, and with skin/serum positivity to both Vespula and Polistes were studied. The clinical aspects and severity of reactions to stings were graded according to Mueller (7). The routine diagnosis involved skin tests and CAP- assay. Prick tests were performed with standardized extracts at increasing concentrations from 0.01 to 100 lg/ml, whereas intradermal tests involved the injec- tion of 0.02 ml extract at 0.001 to 1 lg/ml concentrations. The tests were carried out with extracts of Apis mellifera, 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 nondiscrimi- native 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 ¼ 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. B. Caruso 1 , P. Bonadonna 2 , M. G. Severino 3 , M. Manfredi 3 , A. Dama 2 , M. Schiappoli 2 , P. Rizzotti 1 , G. Senna 2 , G. Passalacqua 4 1 Laboratory of Clinical Chemistry and Haematology, Verona General Hospital, Verona; 2 Allergy Service, Verona General Hospital, Verona; 3 Laboratory and Clinical Allergy Services S. Giovanni di Dio Hospital Firenze, Firenze; 4 Allergy and Respiratory Diseases, DIMI, University of Genoa, Genoa, Italy Key words: CAP-inhibition; cross-reactivity; Immuno- globulin E; Polistes dominulus; Vespula vulgaris. Giovanni Passalacqua MD Allergy and Respiratory Diseases Department of Internal Medicine Padiglione Maragliano L.go R. Benzi 10 16132 Genoa Italy Accepted for publication 30 January 2007 Allergy 2007: 62: 561–564 Ó 2007 The Authors Journal compilation Ó 2007 Blackwell Munksgaard DOI: 10.1111/j.1398-9995.2007.01353.x 561