Proteomic approach to investigate allergens involved in severe walnut allergy

Background: Despite the increasing prevalence of walnut allergy (WA), no allergen components have been established as markers of disease severity. This study aimed to identify proteins specifically associated with severe WA in children. Methods: We analyzed 48 children aged 3.4–16 years who underwent an oral food challenge to walnut between February 2019 and March 2022. Children with positive and negative reactions were categorized into a WA group and walnut sensitization (WS) group, respectively. The dose-adjusted reaction severity of WA patients was quantified using the Anaphylaxis Scoring Aichi's total score divided by the cumulative protein dose that induced symptoms (TS/Pro). Using the median TS/Pro value in all cases of the WA group as a cut-off, 11 of 21 WA patients with stored sera were classified as high TS/Pro (TS/Pro ≥154.1); the remaining 10 patients were classified as low TS/Pro. Immunoblotting, mass spectrometry, and enzyme-linked immunosorbent assay (ELISA) were used to identify candidate markers of WA severity. Results: Jug r 1-specific IgE (sIgE) levels were higher in the WA group, but were not significantly associated with TS/Pro. Immunoblotting and mass spectrometry detected phospholipase D alpha 1 (PLDa1) in 5/11 (45.5%) high TS/Pro patients and 1/10 (10%) low TS/Pro patients (p =.149). ELISA with recombinant PLDa1 confirmed similar results. Moreover, the absorbance of recombinant PLDa1-sIgE was significantly correlated with TS/Pro (ρ = 0.47, p =.032). Conclusions: PLDa1 (Jug r 9) is a candidate marker of WA severity. The early identification of children at risk of severe WA may aid clinicians in optimizing their management strategies.