IgE cross-reactivity between the major peanut allergen Ara h 2 and the nonhomologous allergens Ara h 1 and Ara h 3 (1)
Ara h 2 was described as pre-eminent in importance because it was identified as a predictor of clinical reactivity to peanut and more potent in degranulating basophils than Ara h 1 and Ara h 3. Monosensitization to a single peanut allergen is relatively rare, and patients with monosensitization to Ara h 2 had a significantly lower symptoms severity score than polysensitized subjects and a lower level of allergen-specific IgE against peanut extract and Ara h 2. Cosensitization to Ara h 2 and Ara h 1, Ara h 3, or both appeared to be predictive of more severe reactions.
Generally, high IgE cross-reactivity was observed among the investigated molecules confirmed by inhibition studies.
A comparison of these sequences with Ara h 2.0201 yielded 4 regions on the Ara h 2 sequence, which matched similar peptides on Ara h 1, Ara h 3, or both. A comparison of Ara h 6 with Ara h 1 and Ara h 3 yielded 4 matching regions, 2 with similarities to Ara h 1 and 2 matching Ara h 3. The loop region was covered by 3 overlapping peptides centered on the 3 occurrences of the repetitive sequence DPYSPS.
Nine of 10 sera recognized peptide-AH2-3a, and 7 sera each recognized peptides AH2-1 and AH2-3c.
Preincubation of the sera with 1 nmol/L of Ara h 1 to Ara h 3 completely abolished IgE binding to all tested peptides. For all peptides, the highest inhibiting capacity was observed for Ara h 2.
A mixture of the 3 IgE-binding Ara h 2 peptides inhibited IgE binding to Ara h 1, Ara h 2, and Ara h 3 in a dose-dependent manner.
Ara h 2 and Ara h 6 are major elicitors of anaphylaxis in mice and are sufficient for effective desensitization of mice with peanut allergy.
