Watermelon Profilin: Characterization of a Major Allergen as a Model for Plant-Derived Food Profilins

Background: Plant profilins have been reported as minor allergens. They are a well-known pan-allergen family responsible for cross-reactivity between plant-derived foods and pollens. Watermelon profilin has been reported to be a major allergen in watermelon (Citrullus lanatus).The aim of this study was to characterize recombinant watermelon profilin, confirming its reactivity for diagnostic purposes and the development of immunotherapy. Methods: Native profilin was purified from watermelon extract by affinity chromatography using poly-L-proline. Recombinant His-tagged profilin was produced in Pichia pastoris yeast using pPICZαA vector and purified by metal chelate affinity chromatography. ELISA and immunoblot were carried out with sera from 17 watermelon-allergic patients. Biological activity was tested by the basophil activation test. Results: Native profilin and recombinant profilin were purified and identified by mass spectrometry. Both show similar IgE reactivity in vitro and are biologically active. Conclusions: Similarities were found in the IgE-binding patterns and biological activity of recombinant profilin and native profilin. Recombinant profilin may be a powerful tool for specific diagnosis.