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- Materials and methods
The American Polistes species venom mixture – that of P. annularis, P. fuscatus, P. metricus and P. exclamans– was the only commercially available mixture for diagnosis and therapy until 1996. However, these species of Polistes are not present in Europe, where P. dominulus and P. gallicus and to a lesser extent P. nimphus are widespread. The aim of this study was to assess the allergenic differences among the commercial American mix, P. dominulus and P. gallicus venom in European patients and therefore to verify if this mixture is suitable for diagnosis in these patients. We carried out skin tests, radioallergosorbent tests (RAST) and RAST inhibition in Italian patients with adverse reactions to Polistes stings. RAST inhibition results demonstrated that cross-reactivity between the American and European species is only partial and that P. dominulus and P. gallicus venoms have exclusive allergens. Skin tests and direct RAST confirmed these results and also showed that European Polistes venom is more suitable than the American mix in Italian patients. Moreover, we found a high rate of cross-reactivity between P. dominulus and P. gallicus. To conclude, P. dominulus and/or P. gallicus venoms are necessary for diagnosis and therefore in the therapy of European patients.
Polistes is the most common genus among social waSPS. Polistes dominulus (Pd), Polistes gallicus (Pg) and, to a lesser extent Polistes ninphus, are the most widely spread in Europe (1). Only a mixture of the American Polistes species (A Pm) –P. annularis, P. fuscatus, P. metricus and P. exclamans– was commercially available until 1996, when Anallergo (Florence, Italy) started the production of Pd venom. The American species are not present in Europe.
The aim of this study was to assess the allergenic differences among the A Pm, Pd and Pg venoms in European patients. We carried out skin tests, radioallergosorbent test (RAST) and RAST inhibition in Italian patients with adverse reactions to Polistes stings.
- Top of page
- Materials and methods
Among the genus Polistes, P. dominulus, P. gallicus and, to a lesser extent, P. nimphus are the most widely spread in Europe, while P. annularis, P. fuscatus, P. metricus and P. exclamans are present in the USA (1). The latter are not present in Europe.
Recent systematic studies (8, 9) have confirmed that North American and European species of Polistes belong to different subgenera and are phylogenetically distant. The most common European species –P. dominulus, P. gallicus, P. nimphus and P. biglumis– belong to the subgenus Polistes sensu stricto while the most common North American native species –P. exclamans, P. annularis and P. metricus and P. fuscatus– are included in the subgenera Aphanilopterus and Fuscopolistes (g). We already know that cross-reactivity among European species of Polistes is very strong whereas that between European and American species is weaker (4). Our RAST inhibition studies demonstrate that adsorption with the A Pm only slightly inhibits IgE binding to the European venoms. This, therefore, suggests the presence of exclusive allergens in the latter.
No in vivo studies in European patients have been carried out to compare the venoms from the American and European Polistes. RAST inhibition studies, carried out in only four patients, compared Pd with single American species but not with the commercial A Pm (10). Our study is the first to describe in vivo tests with Pd and Pg venom, carried out in European patients.
Our in vivo results confirm the data previously obtained in vitro on the allergenic differences between American and European Polistes (10–13). It is particularly important to note that our four patients, whose skin tests were negative to the A Pm, showed positive skin tests to European Polistes venoms; two of them had severe reactions – grade IV of Mueller classification – and skin tests positive to 1 μg/ml. This further stresses that there is no correlation between skin test reactivity and severity of the reaction and also the need for performing skin tests up to this concentration (4).
The man suffering from urticaria pigmentosa, with a history of a very severe anaphylactic shock after a Polistes sting (positively identified by the patient) is an emblematic case. It clearly demonstrates that omitting to perform skin tests for Pd venom would have repeated the wrong diagnosis of non IgE-mediated anaphylaxis and deprived the patient of life-saving immunotherapy (14).
So far we have treated 130 patients with the same Pd venom used for in vivo and in vitro tests (Anallergo). As regards safety, we have never observed systemic reactions or other side effects (15). Our data also demonstrate an excellent degree of protection from field stings, numbering 59 of 60 field stings without adverse reactions in 26 patients (M. G. Severino, pers. obs.).
In conclusion, our data raise the problem of the need to introduce the now commercially available European Pd venom extract into clinical practice.