Proteomic profiling of Juniperus oxycedrus and Cupressus arizonica pollen reveals quantitative interspecies differences in the IgE-binding protein repertoire associated with Mediterranean Cupressaceae allergy.

BACKGROUND: Diagnosis and allergen-specific immunotherapy for Mediterranean allergy rely on extracts standardized to group-1 allergens, such as Cup a 1 from Cupressus arizonica, potentially overlooking interspecies variability. The native species Juniperus oxycedrus, widespread in Spain, may contribute to sensitization, but its clinical relevance and allergen repertoire remain poorly characterized. OBJECTIVE: To characterize and compare the allergen and IgE-binding protein composition of J. oxycedrus and C. arizonica pollen extracts and assess their sensitizing relevance in Spain. METHODS: Pollen extracts were analyzed using SDS-PAGE, two-dimensional electrophoresis (2-DE), Western blotting (WB), and mass spectrometry (MS). 241 patients with allergic rhinitis and/or conjunctivitis from seven Spanish regions underwent skin prick testing and specific IgE for extracts and Jun o 1/Cup a 1, by ELISA. Cross-reactivity was assessed by competitive ELISA and WB inhibition. RESULTS: Proteomics and 2-DE showed a more complex protein profile in J. oxycedrus than in C. arizonica pollen extract (423 vs. 251 proteins, 146 shared). Among patients, 35% were sensitized to Cupressaceae, with more frequent monosensitization to J. oxycedrus. 2-DE/WB showed ≥60 IgE-binding spots in J. oxycedrus vs. 5 in C. arizonica, including group-1 allergen isoforms and IgE-reactive components (calreticulin, superoxide dismutase, aconitate hydratase, aldose 1-epimerase, and enolase) with lower abundance in C. arizonica. Inhibition assays indicated high but asymmetric cross-reactivity, consistent with the differences in IgE-binding protein abundance. CONCLUSION: J. oxycedrus and C. arizonica pollen extracts display broadly similar IgE-reactive repertoires but differ in the relative abundance. Such differences may affect regional sensitization and limit the effectiveness of group 1-based diagnosis and therapy.