New developments in the diagnosis and treatment of hymenoptera venom allergy

According to most textbooks, diagnostic tests with Hymenoptera venoms are reliable, and immunotherapy with these venoms in Hymenoptera-venom-allergic patients leads in near to 100% to full protection. Careful analysis of the literature shows however that the specificity of diagnostic tests is far from perfect and that both efficacy and tolerance, especially in patients receiving honeybee venom immunotherapy, are still suboptimal. The major allergens of honeybee and vespid venoms are now available in recombinant form. Preliminary trials analyzing diagnostic tests with recombinant allergens in honeybee venom allergy are promising: the specificity is clearly increased in both skin testing and in determining venom-specific IgE antibodies when compared to natural venom allergens. An important recent finding is the frequent association of severe Hymenoptera venom allergy and elevated basal serum levels of the mast-cell-specific enzyme tryptase. Elevated levels are found in up to 30% of the patients with a history of severe shock reactions following Hymenoptera stings. The current findings indicate that basal tryptase levels indicating an increased mast cell load are much more frequent than previously thought and are a risk factor for severe or even fatal sting reactions. Premedication with antihistamines in the initial phase of venom immunotherapy reduced both local and systemic allergic side effects in several controlled studies. In a retrospective analysis of one of these trials it was found that reexposure during immunotherapy resulted in significantly more systemic allergic reactions in patients on placebo than on antihistamine premedication, suggesting that initial antihistamine premedication might increase the efficacy of venom immunotherapy. Different ways of allergen modification for venom immunotherapy have been proposed. While the results with chemical modifications were not convincing, recent studies with T-cell epitope peptides from the major bee venom allergen phospholipase A(2) look promising. Patient-tailored cocktails of recombinant venom allergens or isoforms thereof may be another possibility in the future. A number of prospective studies analyzing the duration of venom immunotherapy required for long-term protection have been published in the last decade. While most patients are still fully protected 1 year after discontinuation of therapy, relapses may occur in up to 20% of patients reexposed many years after treatment. Various risk factors for such relapses have been identified.