Jun o 1, a Cross-reactive Juniperus oxycedrus Allergen With Unique Structural and Immunogenic Properties

BACKGROUND AND OBJECTIVE: Juniperus oxycedrus, from the Cupressaceae family, is widespread in the Mediterranean. However, the allergenic relevance of its pollen remains underexplored. Objective: This study aimed to characterize Jun o 1, an allergen of J oxycedrus that is homologous to major allergens in related species. METHODS: Native Jun o 1, its nonglycosylated Escherichia coli-expressed form (rJun o 1), and Cup a 1 were purified by affinity chromatography. Jun o 1 was characterized by SDS-PAGE, 2D-electrophoresis, Western blot (WB), and mass spectrometry and compared with the homologous cypress allergen, Cup a 1. Enzymatically and chemically deglycosylated Jun o 1 was also analyzed. Specific IgE binding and cross-reactivity were evaluated using ELISA, WB, and mast cell activation assays with sera from 57 Spanish cypress-allergic patients. IgG binding was tested using sera from rJun o 1-immunized mice. RESULTS: Jun o 1 exists as multiple isoforms and assembles into oligomers, whereas Cup a 1 comprises multiple isoforms without oligomerization. IgE binding to Jun o 1, including mast cell activation, is critically influenced by the combined presence of protein and carbohydrate determinants. Compared to Cup a 1, Jun o 1 exhibited greater IgE-binding inhibition for J oxycedrus extract in sera from Cupressaceae-sensitized allergic patients from this tree's autochthonous regions. The highest rate of monosensitization in this group was to J oxycedrus. CONCLUSION: Jun o 1 is a relevant and potential major allergen in cypress allergy. Structural and immunogenic similarities with Cup a 1 lead to cross-reactivity, although it also exhibits unique properties, resulting from combined IgE-reactive protein and glycan determinants.