The following is a summary of “IgE cross-inhibition between Ara h 1 and Ara h 2 is explained by complex formation of both major peanut allergens,” published in the AUGUST 2023 issue of Allergy & Immunology by Warmenhoven, et al.
Surprisingly, IgE cross-reactivity has been reported between the major peanut allergens Ara h 1, 2, and 3, despite their very low sequence identities. For a study, researchers sought to investigate the unexpected cross-reactivity observed between major peanut allergens.
Using a variety of methods, including sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), the Western blot test, liquid chromatography-tandem mass spectrometry (LC-MS/MS), and sandwich enzyme-linked immunosorbent assay (ELISA), the study evaluated the cross-contamination of purified natural Ara h 1, 2, 3, and 6. Serum from 43 patients with peanut allergies was used to study IgE cross-reactivity using ELISA and ImmunoCAP inhibition. Both intact natural and recombinant allergens, as well as synthetic peptides representing postulated Ara h 1 and Ara h 2 cross-reactive epitopes, were used in the experiments.
The findings revealed that purified nAra h 1 and nAra h 3 contained small but significant amounts of Ara h 2 and Ara h 6 (<1%), as confirmed by various techniques, including sandwich ELISA, SDS-PAGE/Western blot analysis, and LC-MS/MS. IgE cross-inhibition between the 2S albumins and Ara h 1 and Ara h 3 was only observed with naturally purified allergens, not recombinant or synthetic peptides. The apparent cross-reactivity disappeared when purified nAra h 1 was treated under reducing conditions, suggesting that Ara h 2 and Ara h 6 contaminations might be covalently bound to Ara h 1 via disulfide interactions.
The study concluded that true cross-reactivity between peanut 2S albumins and Ara h 1 and Ara h 3 could not be confirmed. Instead, it was shown that cross-contamination with small quantities of these allergens led to significant cross-inhibition, which could be misinterpreted as molecular cross-reactivity. The presence of contaminating 2S albumins in purified nAra h 1 and nAra h 3 can overestimate their importance as major allergens in diagnostic tests. Therefore, recombinant Ara h 1 and Ara h 3 were suggested as a preferred alternative.