Fra a 1.02 Is the Most Potent Isoform of the Bet v 1-like Allergen in Strawberry Fruit

Abstract

The strawberry fruit proteins Fra a 1.01E-1.08 are homologues of the major birch pollen allergen Bet v 1. Three of the proteins are known to have essential biological functions in pigment formation during fruit ripening and seem to be responsible for allergic reactions to strawberry fruit. We evaluated the cross-reactive allergenic potential of these putative strawberry allergens in patients allergic to birch pollen. Activation of basophils of eight atopic patients was studied using different concentrations of Fra a 1 isoforms. Bet v 1a was used as control and as atopic patient selection criterion. Although Fra a 1.01E-1.08 have amino acid sequence identities of 74.5-97.5% with Fra a 1.02, the basophil activation mediated by the eight Fra a 1 proteins differed substantially. Fra a 1.03 and Fra a 1.02 showed the highest activation of basophils, 73 and 66% of total basophils, respectively. On the basis of the high relative expression of the gene Fra a 1.02 in ripe strawberry fruits of allergenic varieties, Fra a 1.02 was identified as the main strawberry allergen of the Bet v 1 superfamily. Knowledge of the allergenic potential of Fra a 1.02/1.03 will help to improve food safety and can serve as a valuable marker for the development of red-fruited hypoallergenic strawberry cultivars.

Physical interaction between the strawberry allergen Fra a 1 and an associated partner FaAP: Interaction of Fra a 1 proteins and FaAP

“…But at a higher oligomerization status, for example, dimers, the allergenic potential increases and they can be identified as hyperallergenic proteins . Lately, Fra a 1.01E was identified as a hypoallergenic strawberry allergen in a basophil activation test as low concentrations (0.5, 5, and 50 ng) were applied in the test . In addition, further BAT analyses were performed with a higher concentration of 500 ng recombinant Fra a 1 proteins.…”

“…Although Fra a 1.01E has been proposed as the major strawberry allergen, 13,14 gene expression analysis and basophil activation tests revealed Fra a 1.02 as the main strawberry allergen of the Bet v 1 superfamily. 17 The recently elucidated solution structure of Fra a 1.01E exhibits a high similarity to the crystal structure of the major cherry allergen Pru av 1 and the major birch pollen allergen Bet v 1 (sequence identity of 79.4% and 53.8%, respectively) and a glycine-rich loop motif (residues [46][47][48][49][50][51] was verified as a highly conserved feature throughout the Bet v 1 superfamily. 18 Fra a 1.01E/1.02/1.03 proteins have a high sequence similarity.…”

“…However, the recent identification of novel Fra a 1 genes and the complete genome sequence of the related species F. vesca show that the genus Fragaria contains a family of 13–21 Fra a 1 homologous genes, depending of the selection criterion, and Fra a 1A–1E are probably allelic forms of Fra a 1.01 . Although Fra a 1.01E has been proposed as the major strawberry allergen, gene expression analysis and basophil activation tests revealed Fra a 1.02 as the main strawberry allergen of the Bet v 1 superfamily …”

“…The pairwise identity of the amino acid sequence of Fra a 1.01E and Fra a 1.03 with Fra a 1.02 is 78.9% and 80.1%, respectively. The sequence identity of the 3 isoforms relating to Bet v 1 accounts for 54%, 58.4%, and 59%, respectively …”

Expression Profiling of Strawberry Allergen Fra a during Fruit Ripening Controlled by Exogenous Auxin

“…The Fra a proteins are a major allergen group identified in strawberry [2]. The Fra a proteins consist of several isoforms encoded by many Fra a genes [3,4,5]. Sixteen sequences corresponding to Fra a genes have been identified in diploid strawberry Fragaria vesca based on genomic sequence information [6,7].…”