Recombinant lipid transfer protein Cor a 8 from hazelnut: a new tool for in vitro diagnosis of potentially severe hazelnut allergy

BACKGROUND: Cor a 1.04 has been identified as the major hazelnut allergen in 65 European patients with positive double-blind, placebo-controlled food challenge results to hazelnut. Recently, the 11S globulin Cor a 9 was shown to be a pollen-independent hazelnut allergen in the United States, whereas preliminary data suggest the lipid transfer protein (LTP) as an important birch pollen-unrelated hazelnut allergen in Europe. OBJECTIVE: We sought to recruit a group of European patients allergic to hazelnut without birch pollen allergy and to identify and clone the major food allergen(s) in this study population. METHODS: We recruited 26 such Spanish patients, including 10 patients with anaphylaxis. IgE immunoblotting was performed with hazelnut extract. Hazelnut LTP Cor a 8 was cloned by using a PCR strategy, purified, and subjected to IgE immunoblotting. Recombinant Cor a 8, rCor a 1.0401, and rCor a 2 (profilin) were further investigated by means of enzyme allergosorbent test. Immunoblot inhibition experiments were used to compare the immunologic properties of natural and recombinant LTP. RESULTS: A 9-kd major allergen was identified in hazelnut extract. Cloning, sequencing, heterologous expression, and inhibition experiments identified it as an LTP. The prevalence of specific IgE antibody reactivity to LTP was 62% in hazelnut extract and 77% when recombinant LTP was tested by means of immunoblotting. IgE immunoblot inhibition with hazelnut extract showed that natural Cor a 8 and rCor a 8 shared identical epitopes. Only one patient had positive reactivity to Cor a 1.04, and no patients had positive reactivity to Cor a 2. Two sera bound to high-molecular-weight allergens. The LTP was denominated as Cor a 8 and submitted to the allergen database of the World Health Organization/International Union of Immunological Societies Allergen Nomenclature Subcommittee. CONCLUSIONS: Cor a 8 is a relevant allergen for a majority of Spanish patients with hazelnut allergy that can cause severe allergic reactions.