IDENTIFICATION OF COMMON ALLERGENIC STRUCTURES IN MUGWORT AND RAGWEEDPOLLEN

Background: Despite the rare occurrence of ragweed in Middle Europe, a surprisingly high number of patients allergic to mugwort, a frequentl y encountered weed, display IgE reactivity against ragweed pollen alle rgens. Objective: The aim of this study was to investigate whether the high prevalence of IgE reactivity against ragweed in patients allergi c to mugwort is caused by the presence of common allergenic determinan ts. We also sought to characterize any cross-reactive allergens. Metho ds: Common allergenic structures in mugwort and ragweed pollen were ch aracterized by qualitative IgE immunoblot inhibition experiments perfo rmed with natural allergen extracts and recombinant allergens. The deg ree of cross-reactivity was estimated by quantitative CAP-FEIA competi tions. The clinical significance of cross-reactive IgE antibodies was studied with histamine release experiments and nasal provocation tests . Results: Mugwort and ragweed RAST values were significantly correlat ed in a population of 82 Austrian patients allergic to mugwort. IgE an tibodies cross-reacted with allergens of comparable molecular weight t hat were present in both extracts: By using recombinant birch profilin and specific antisera for IgE inhibition experiments, profilin was id entified as one of the cross-reactive components in mugwort and ragwee d pollen. Preincubation of sera from patients allergic to mugwort with mugwort extract inhibited IgE binding to ragweed pollen extract great er than 80%. Mugwort and ragweed pollen extract induced comparable his tamine release and reduction of nasal air how in a patient with IgE re activity against the major mugwort allergen Art v 1. Conclusion: In ad dition to profilin, mugwort and ragweed pollen contain a number of cro ss-reactive allergens, among them the major mugwort allergen Art v 1. Cross-reactive IgE antibodies can lead to clinically significant aller gic reactions.