Ole e 3, a Candidate for in vivo Diagnosis of Polcalcin Sensitization

Abstract

<b><i>Introduction:</i></b> Polcalcins belong to the family of calcium-binding proteins. They are ubiquitous in the plant kingdom and highly conserved, which leads to these panallergens showing a high degree of inter-cross-reactivity. They are responsible for allergic polysensitization, and therefore, their diagnosis is necessary for correct selection of immunotherapy. The objectives were to develop a method to purify native polcalcin with intact allergenic properties and to validate its use for diagnosis of polcalcin sensitization. <b><i>Methods:</i></b> Ole e 3 was purified by immunoaffinity chromatography using anti-rChe a 3 polyclonal antibodies and identified by mass spectrometry. Calcium-binding assays were performed in immunoblot and ELISA assays. Diagnostic capacity of Ole e 3 was analyzed by ELISA and compared to ImmunoCAP with sera from a pollen-sensitized population. Cross-reactivity with other polcalcins was investigated by ImmunoCAP inhibition. <b><i>Results:</i></b> Immunogenicity of purified Ole e 3 was not affected by the addition of calcium. However, the presence of a calcium chelator agent completely inhibited IgG binding by immunoblot and produced a 32.3% reduction in IgE binding by ELISA. Ole e 3 enabled diagnosis of polcalcin-sensitized patients, and a good correlation was revealed with ImmunoCAP. A 50% inhibition in IgE binding was obtained with 2.8 ng of Ole e 3 for rBet v 4 and 3.9 ng for rPhl p 7. <b><i>Discussion/Conclusion:</i></b> Native Ole e 3 was purified by maintaining its allergenic properties. This innovative method enables obtaining this active native allergen to be used for in vivo diagnosis of polcalcin sensitization.