The natural profilin from Russian thistle (Salsola kali) contains a low IgE-binding ability isoform--molecular and immunological characterization

Abstract

Chenopodiaceae pollens such as those from Salsola kali and Chenopodium album are important causes of allergy in Mediterranean areas because of the progress of desertification in European countries. Among the various allergenic protein families, profilins constitute a group of pan-allergens that are involved in polysensitization and pollen-food allergy syndrome. Two-dimensional electrophoresis analysis of S. kali profilin highlighted a polymorphic pattern, with several isoforms that have different molecular features (isoelectric point and molecular mass) and immunological features. Two isoforms have been cloned and sequenced. Sal k 4.02 and Sal k 4.03 displayed non-conservative amino acid changes in critical positions of the IgE epitopes. Both isoforms were produced in Escherichia coli and structurally and spectroscopically characterized. Changes in the electrophoretic mobility and in their IgG and IgE immunological behavior were observed in comparison with Che a 2, their counterpart from C. album. The IgE-binding ability of Sal k 4.03 is similar to that of Che a 2, whereas Sal k 4.02 showed a 35% reduction in IgE binding in 86% of patients, suggesting a hypoallergenic character. Three-dimensional modeling allowed us to propose which amino acid residues are involved in those immunological changes based on epitope mapping studies previously performed in other profilins. These profilin isoforms constitute suitable candidates for specific immunotherapy with recombinant allergens.