f455 Cor a 11

Summary

Cor a 11 is a 7S globulin vicilin-like seed storage protein from hazelnut (Corylus avellana). It is a cupin-superfamily protein (~48 kDa monomer, trimer ~150 kDa) localized in the nut cotyledon. Cor a 11 represents a major storage-protein allergen associated with severe, systemic hazelnut allergy, particularly in children and in individuals from birch-endemic regions with genuine nut sensitization. It belongs to the family of heat- and digestion-stable storage proteins together with Cor a 9 and Cor a 14.

Epidemiology

Hazelnut is among the most clinically relevant tree nuts in Europe, with geography- and age-dependent patterns of sensitization (Burney 2014). In birch-endemic northern Europe, mild oral-allergy syndrome predominates due to cross-reactivity with Bet v 1, whereas in southern Europe and among children, storage-protein sensitization (Cor a 9, Cor a 11, Cor a 14 and Cor a 16) is more common and linked to systemic reactions (Hansen 2009, Verweij 2012; Valbuena 2021, Elizur 2025). In a Belgian cohort, 36 % of preschoolers and 40 % of school-age children with systemic reactions had IgE to Cor a 11 (Verweij 2012). In a Spanish pediatric cohort, Cor a 11-specific IgE correlated strongly with severe reactions during oral food challenge (Valbuena 2021). 

Environmental Characteristics

Source and Tissue

The gene for Cor a 11 has been identified in the genomes of four Corylus species (Amoroso 2025). 

Cor a 11 is a 7S globulin (vicilin) expressed in the cotyledons of Corylus avellana kernels, forming part of the water-soluble globulin fraction together with Cor a 9 and Cor a 14.

Risk Factors

Primary ingestion-based sensitization occurs mainly in early childhood (Verweij 2012). Additional risk factors include an atopic background, and cross-reactivity with vicilins from walnut, peanut, or cashew (Barre 2008).

Clinical Relevance

Cor a 11 sensitization is a marker of systemic hazelnut allergy, independent of birch pollen sensitization. Hazelnut allergic children with IgE to Cor a 11 typically exhibit generalized or anaphylactic reactions, while adults with pollen-related oral allergy syndrome are rarely sensitized to Cor a 11 (Verweij 2012). In a Spanish pediatric study, Cor a 11 IgE predicted severe outcomes during food challenges (Valbuena 2021). This profile indicates persistent, high-risk hazelnut allergy with reactions even to small or processed quantities.

Diagnostic Relevance

Component-resolved diagnosis using recombinant Cor a 11 may improve discrimination between primary hazelnut allergy and birch-pollen cross-reactivity. IgE testing to Cor a 11 can predict true systemic allergy with high specificity, especially in combination with Cor a 9 and Cor a 14 component IgE testing (Valbuena 2021, Borres 2022).

Prevention and Therapy

There is currently no regulatory approved hazelnut component oral immunotherapy available. Management relies on avoidance, food labelling vigilance, and when indicated, adrenaline auto-injector prescription. A clinical study of hazelnut oral immunotherapy that included monitoring of immunological responses to storage proteins such as Cor a 11, Cor a 9, Cor a 14 and Cor a 16 has shown the treatment to be safe and effective (Elizur 2025).

Molecular Aspects

Cor a 11 is a cupin-fold 7S globulin (vicilin) with molecular weight ~48 kD forming trimeric assemblies (~150 kDa). It is glycosylated, heat- and digestion-stable, and retains conformational epitopes after roasting (Lauer 2004, Dubiela 2018, Borres 2022).  

Two Cor a 11 sequences of different length are listed in the WHO/IUIS Allergen Nomenclature Sub-Committee database, the full-length Cor a 11.0102 and Cor a 11.0101 which comprises amino acids 25-471 of the Cor a 11.0102 sequence.

Cross-reactivity

Cor a 11 shares 60–70 % amino-acid identity with vicilins from walnut (Jug r 2, Jug r 6), pecan (Car i 2), cashew (Ana o 1), and peanut (Ara h 1). Functional inhibition confirms overlapping IgE-binding epitopes which may contribute to clinical cross-reactivity among nuts (Barre 2008, Dubiela 2018).

Exposure

Cor a 11 has intermediate heat stability (Dubiela 2018) and may remain allergenic in processed foods such as chocolate or baked goods (Holzhauser 2000).

Explained Results

Allergen information

Cor a 11 is a 7S globulin (vicilin). It belongs to the group of heat- and digestion-stable seed storage proteins together with Cor a 9 and Cor a 14.

Clinical relevance

Cor a 11 sensitization is a marker of risk for systemic hazelnut allergy, independent of birch pollen sensitization.

Cross-reactivity

Cor a 11 shares 60–70 % amino-acid identity with vicilins from walnut (Jug r 2, Jug r 6), pecan (Car i 2), cashew (Ana o 1), and peanut (Ara h 1).

Compiled by Dr. Michael Spangfort 

Reviewed by Dr. Jonas Lidholm, November 2025