IgE-binding to vicilin-like antimicrobial peptides is associated with systemic reactions to macadamia nut
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LETTER TO THE EDITOR
Clinical and Translational Allergy Open Access
IgE‑binding to vicilin‑like antimicrobial peptides is associated with systemic reactions to macadamia nut Anna M. Ehlers1,2* , Stefanie Rohwer3, Henny G. Otten1, Bettina Brix3, Thuy‑My Le1,2, Waltraud Suer3 and André C. Knulst1,2
Abstract Background: Macadamia nut can induce fatal allergic reactions and changes in dietary habits will raise their con‑ sumption in industrialised countries. Until now diagnosis of macadamia nut allergy by sIgE solely relies on the maca‑ damia nut extract, but single components are lacking. Methods: Macadamia nut proteins recognised by IgE from 2 macadamia nut extract positive sera were identified by mass spectrometry (vicilin-like antimicrobial peptides: VLAP). Sensitisation to macadamia nut extract and heterolo‑ gously expressed isoform VLAP-2–3 was evaluated in 82 nut allergic (NA) and 27 tolerant (NT) patients (no tree nut allergy reported) comprehending 10 macadamia nut allergic (MA) and 18 explicitly reported macadamia nut toler‑ ant patients (MT), using line blots. Co-sensitisation to additional VLAP isoforms and other vicilins was evaluated in 8 MA, 12 MT and 14 NA patients sensitised to VLAP-2–3. Functional properties were determined by indirect basophil activation. Results: Even though proteins recognised by IgE were identified as VLAP-2–1, 2–2 and 2–3, only peptides specifically belonging to VLAP-2–3 were detected by mass spectrometry. The macadamia nut extract was recognised by 33% of NA patients (27/82) including 3 MA patients and 26% of NT patients (7/27, 3 MT). Similarly, 29% of NA (24/82) patients showed partly strong sIgE-binding to VLAP-2–3 including 3 MA patients with systemic reactions to macadamia nut. Contrary, VLAP-2–3 was recognised by only 2 NT (1 MT) patients (7%) with very low sIgE titres. Simultaneous recogni‑ tion of the isoforms VLAP-2–1 and 2–2 was observed in all patients positive for VLAP-2–3 with partly reduced sIgE titres in 59% of these patients. Additionally, all three VLAP isoforms were able to repeatedly induce BAT reactivity upon sensitisation with a MA serum. Conclusion: VLAP proteins are the first described macadamia nut components with serological and functional aller‑ genic properties and they are associated with systemic reactions to macadamia nut. Keywords: 7S globulin, Vicilin, Food allergy, IgE-binding, Macadamia nut
*Correspondence: [email protected] 1 Center for Translational Immunology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands Full list of author information is available at the end of the article
To the editor: Macadamia nut belongs to the group of tree nuts being able to induce even fatal allergic reactions [1, 2]. Even though macadamia nut is currently responsible for a small number of tree nut allergic reactions [3], it is hypothesized that the number will raise due to changes in dietary habits and increasing use in pastry and confectionery [4]. So far, specific IgE (sIgE) diagnostics of
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