CRD testing showed that the IgE response to a particular peanut protein, called Ara H2
, may prove useful in separating children with true allergies from those with a peanut sensitivity.
After intraperitoneal sensitization, the IgG2a antibodies were directed mainly toward Ara h2
and, to a lesser extent, to Ara h1; after oral sensitization, they were directed against all three major peanut allergens.
The Ara h2 peanut allergen is recognized by serum IgE from > 90% of patients with peanut allergy, thus establishing the importance of this protein in the etiology of the disease (Burks et al.
The Ara h2 protein was exposed to proteases encountered in the GI tract to determine whether the native protein structure, as mediated by disulfide bonds, played any role in protecting it from degradation.
Several methods have been used to gain a better understanding of the structural properties of Ara h2 that may contribute to its stability and allergenicity.
To determine if the most protease-resistant Ara h2 fragments contained IgE-binding epitopes, the protein was exposed to chymotrypsin, and the reactions were electrophoresed on SDS-PAGE gels, blotted to nitrocellulose, and probed with serum IgE from a pool of peanut-sensitive patients.
The study demonstrated "Ousing specific IgE response to Ara h2
may be a useful tool in predicting clinical peanut reactivity in sensitized individuals.
Positive controls should be antigens positive in humans, such as peanut Ara h2 and peanut lectin, brazil nut 2S-albumin, ovomucoid, ovalbumin, and [beta]-lactoglobulin.
2001) both reported a threshold of 100 [micro]g total peanut protein or 6 [micro]g of the peanut allergen Ara h2, and a no-observable effect level (NOEL) of between 30 and 50 [micro]g peanut protein or 2-3 [micro]g of Ara h2 in patients with peanut allergy, using DBPCFCs.
Food Allergen Allergen serving Threshold ([micro]g) Peanut Ara h2 6% of total 100 peanut protein protein (a) or 6 Ara h2 (Wensing et al.