2S protein Ara h 7.0201 has unique epitopes compared to other Ara h 7 isoforms and is comparable to 2S proteins Ara h 2 and 6 in basophil degranulation capacity. Issue 7 (11th April 2018)

• Record Type: Journal Article
• Authors: Hayen, S. M.; Ehlers, A. M.; den Hartog Jager, C. F.; Garssen, J.; Knol, E. F.; Knulst, A. C.; Suer, W.; Willemsen, L. E. M.; Otten, H. G.
• Is Part Of: Clinical & experimental allergy. Volume 48:Issue 7(2018)
• Page Start: 890
• Page End: 897
• Publication Date: 2018-04-11
• Subjects: allergens and epitopes -- basophil -- food allergy -- IgE; Allergy -- Periodicals; Immunology -- Periodicals; 616.97
• DOI: 10.1111/cea.13134
• Languages: English
• ISSNs: 0954-7894

Abstract

Summary: Background: Screening for specific IgE against 2S albumin proteins Ara h 2 and 6 has good positive predictive value in diagnosing peanut allergy. From the third 2S member Ara h 7, 3 isoforms have been identified. Their allergenicity has not been elucidated. Objective: This study investigated the allergenicity of Ara h 7 isoforms compared to Ara h 2 and 6. Methods: Sensitization of 15 DBPCFC‐confirmed peanut‐allergic patients to recombinant Ara h 2.0201, Ara h 6.01 and isoforms of recombinant Ara h 7 was determined by IgE immunoblotting strips. A basophil activation test (BAT) was performed in 9 patients to determine IgE‐cross‐linking capacities of the allergens. Sensitivity to the allergens was tested in 5 patients who were sensitized to at least 1 Ara h 7 isoform, by a concentration range in the BAT. 3D prediction models and sequence alignments were used to visualize differences between isoforms and to predict allergenic epitope regions. Results: Sensitization to Ara h 7.0201 was most frequent (80%) and showed to be equally potent as Ara h 2.0201 and 6.01 in inducing basophil degranulation. Sensitization to Ara h 7.0201 together with Ara h 2.0201 and/or 6.01 was observed, indicating the presence of unique epitopes compared to the other 2 isoforms. Differences between the 3 Ara h 7 isoforms were observed in C‐terminal cysteine residues, pepsin and trypsin cleavage sites and 3 single amino acid substitutions. Conclusion & clinical relevance: The majority of peanut‐allergic patients are sensitized to isoform Ara h 7.0201, which is functionally as active as Ara h 2.0201 and 6.01. Unique epitopes are most likely located in the C‐terminus or an allergenic loop region which is a known allergenic epitope region for Ara h 2.0201 and 6.01. Due to its unique epitopes and allergenicity, it is an interesting candidate to improve the diagnostic accuracy for peanut allergy.