Characteristics of allergenic potential of clinically significant class PR-10 strawberry allergen

Despite its economic importance and health benefits, strawberries ( Fragaria × ananassa ) may cause IgE-mediated allergic reactions, primarily manifesting as oral allergy syndrome. The primary sensitizing factor is the Fra a 1allergen. This protein is a member of the PR-10 (pathogenesis-related proteins) family, being a structural homologue of the major birch pollen allergen Bet v 1. This study assessed the allergenic potential of the Fra a 1 strawberry allergen and analyzed the effect of heat treatment on its structural and functional properties. We have obtained a recombinant Fra a 1 allergen. Fluorescence spectroscopy has demonstrated the ability of this protein to bind a wide range of fatty acids, thus confirming functional activity of the recombinant analogue. Circular dichroism demonstrated that heating to 98 °C caused irreversible changes in the protein's secondary structure. ELISA testing demonstrated that pre-boiling (99 °C, 15 minutes) leads to a significant partial reduction (up to 30%) of the Fra a 1 ability to bind cross-reactive polyclonal anti-Bet v 1 IgG, whereas binding to specific IgE from sera of patients with pollen and food allergy was decreased in only half the cases. A study of proteolysis kinetics revealed rapid in vitro degradation of the allergen by pepsin, which was not accelerated by its preheating. Furthermore, Fra a 1 exhibited relative resistance to in vitro digestion by lysosomal enzymes of human macrophages compared to birch Bet v 1 and soybean Gly m 4. These data indicate partial thermal stability of the Fra a 1 allergen, its ability to retain IgE-binding activity in some sensitized individuals, and its susceptibility to proteolytic degradation that may modulate its immunogenicity. The results of our study are important for assessing the risks associated with consumption of heat-treated strawberries and developing strategies to reduce allergenicity.