Background: Peach is a common elicitor of food allergic reactions. Peach-induced immediate reactions may occur as benign pollen-food syndromes, usually due to birch pollen-related PR-10 cross-reactivity in temperate climates, and as potentially severe primary food allergies, predominantly related to nsLTP Pru p 3 in Mediterranean regions. The newly described peach allergen Pru p 7 has gained recent attention as a potential peach allergy severity marker. Sensitization to Pru p 7 and its allergenic homologues of the gibberellin-regulated protein family occurs in areas with high Cupressaceae tree pollen exposure. Objective:We sought to investigate the distribution, clinical characteristics and molecular associations of Pru p 7 sensitization among subjects with suspected peach allergy in different regions of France. Methods: Subjects with suspected peach allergy (n = 316) were included. Diagnostic work-up was performed according to current guidelines, including open food challenge when required. IgE antibody measurements and competition experiments were performed using the ImmunoCAP assay platform. Results: Sensitization to Pru p 7 was present in 171 (54%) of all subjects in the study and in 123 of 198 (62%) diagnosed as peach allergic, more than half of whom were sensitized to no other peach allergen. Frequency and magnitude of Pru p 7 sensitization were associated with the presence of peach allergy, the clinical severity of peach-induced allergic reactions and the level of cypress pollen exposure. Cypress pollen extract completely outcompeted IgE binding to Pru p 7. Pru p 7 was extremely potent in basophil activation tests. Conclusion and Clinical Relevance: A subtype of Cupressaceae pollinosis, characterized by Pru p 7 sensitization, can be an underlying cause of severe peach allergy. K E Y W O R D S allergens and epitopes, anaphylaxis, basophil, cypress pollinosis, food allergy, IgE, immunological tests, peamaclein, Pru p 7

To the Editor, The basophil activation test (BAT) has been reported to increase the accuracy of diagnosing peanut allergy and decrease the need for oral food challenges. [1][2][3] However, BAT has been largely restricted to research settings because basophils are unstable ex vivo and the activation assay is ideally done within 3-4 hours of sample acquisition. 4 If activation could be performed easily in the clinical setting and sent to a processing facility for cytometry, BAT could become more broadly accessible. In this pilot study, we evaluated a novel peanut-BAT (P-BAT) method that preserves basophil activation to determine its feasibility as a diagnostic method of peanut allergy.The main objective was to determine whether basophils from peanut allergic patients, stimulated with P-BAT reagents, maintain consistent activation read-outs measured up to 5 days after initial activation. Basophils in whole blood were stimulated with six peanut concentrations (0.0001-10 mg/ml) on day 0 via a novel method developed by Beckman-Coulter and activation was measured by CD63 + CD203c + expression via flow cytometry on days 0, 1, 3, and F I G U R E 1 Basophil activation is preserved with P-BAT. A. Basophil activation dose-response curve for each patient on day 0, 1, 3, and 5 after collection, summarized by area under the curve and CD-max at day 0. B. Marginal means of the AUC for responders show no difference between days 0,1and 3 (p > 0.05). C. ICC demonstrates high consistency of measured activation between days. D. FPC clusters demonstrate samples from the same patient assigned to the same cluster (each cluster within colored circles represents a drug-response pattern) are reliable BAT Day D0 D1 D3 D5

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