Scientific Study

Allergy to peanut and tree nuts is characterised by a high frequency of life-threatening anaphylactic reactions and typically lifelong persistence. Although peanut is the most common cause of nut allergy; peanut allergic patients are frequently also sensitive to tree nuts. It is not known if this is due to cross-reactivity between peanut and tree nut allergens. In this study; the major peanut allergen Ara h 2 was cloned from peanut cDNA; expressed in E. coli cells as a His-tag fusion protein and purified using a Ni-NTA column. Immunoblotting; ELISA and basophil activation indicated by CD63 expression all confirmed the IgE reactivity and biological activity of rAra h 2. To determine whether or not this allergen plays a role in IgE cross-reactivity between peanut and tree nuts; inhibition ELISA was performed. Pre-incubation of serum from peanut allergic patients with increasing concentrations of almond or Brazil nut extract inhibited IgE binding to rAra h 2. Purified rAra h 2-specific serum IgE antibodies also bound to proteins present in almond and Brazil nut extracts by immunoblotting. This indicates that the major peanut allergen; Ara h 2; shares common IgE-binding epitopes with almond and Brazil nut allergens; which may contribute to the high incidence of tree nut sensitisation in peanut allergic individuals.