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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

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

S M Hayen, A M Ehlers, C F den Hartog Jager, J Garssen, E F Knol, A C Knulst, W Suer, L E M Willemsen, H G Otten

Clin Exp Allergy. 2018 Jul;48(7):890-897.

PMID: 29542223

Abstract:

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.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP84477872	H-7		84477-87-2	Price

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