Wangorsch A Jamin A Lidholm J Gräni N Lang C Ballmer-Weber B Vieths S Scheurer S 2017 SCOPE English walnut (Juglans regia) belongs to the most important allergenic tree nuts. Co-sensitization with birch (Betula verrucosa) pollen has been reported. We aimed to identify a walnut allergen homologous to the major birch pollen allergen Bet v 1. METHODS AND RESULTS A cDNA encoding a Bet v 1-homologous allergen (Jug r 5) in walnut kernels was cloned by RT-PCR. Jug r 5 was expressed in Escherichia coli, purified by column chromatography and characterized by circular dichroism spectroscopy. Specific IgE levels to walnut, Bet v 1, and Jug r 5 in birch pollen allergics (n = 16) with concomitant walnut allergy were measured by ImmunoCAP: 44% of the patients were tested positive to walnut while 94% were reactive to Jug r 5, and 100% to Bet v 1. Jug r 5 and Bet v 1 allergens showed bidirectional IgE cross-reactivity by competitive ELISA and were capable of inducing histamine release from effector cells. Immunoblot competition experiments demonstrated the presence of IgE-reactive Jug r 5 in walnut extract, but at low levels. CONCLUSION A Bet v 1-like allergen was identified in walnut. Diagnostic use of Jug r 5 will compensate for the low sensitivity of walnut extract for patients with birch pollen associated walnut allergy. https://sonar.ch/global/documents/22999 eng info:eu-repo/semantics/altIdentifier/doi/10.1002/mnfr.201600902 info:eu-repo/semantics/altIdentifier/pmid/28070926 Molecular nutrition & food research. - 2017 Bet v 1 like Juglans regia Jug r 5 PR-10 Walnut allergy Allergens Amino Acid Sequence Antigens, Plant Betula Cross Reactions Female Histamine Release Humans Hypersensitivity Immunoblotting Immunoglobulin E Juglans Nuts Plant Proteins Pollen Identification and implication of an allergenic PR-10 protein from walnut in birch pollen associated walnut allergy. http://purl.org/coar/resource_type/c_6501