Evaluation of IgE Antibodies to Recombinant Peanut Allergens in Patients with Reported Reactions to Peanut

Abstract

Background: Peanut may cause severe reactions in allergic individuals. The objective was to evaluate IgE antibodies to various recombinant (r) peanut and birch pollen allergens in relation to IgE levels to whole peanut extract and severe allergic reactions to peanut. Methods: Seventy-four Swedish peanut-allergic patients (age: 14–61 years) reported previous peanut exposure and associated symptoms using a questionnaire. Their IgE reactivity to peanut, birch pollen and individual allergen components was analyzed using ImmunoCAP®. Results: Of the 48 subjects sensitized to Ara h 1, 2 or 3, 60% had peanut-specific IgE levels >15 kU_A/l, while 100% of the subjects without detectable IgE to these allergens had low peanut-specific IgE levels (<10 kU_A/l). The levels of IgE to rAra h 8, rBet v 1 and birch pollen were highly correlated (r_S = 0.94, p < 0.0001). Fifty-eight patients reported adverse reactions after accidental or deliberate peanut exposure (oral, inhalation or skin) of whom 41 had IgE to rAra h 1, 2 or 3. Symptoms of respiratory distress were associated with sensitization to Ara h 1, 2 or 3 (56 vs. 18%, p < 0.01). Two cases of anaphylaxis were reported among the individuals sensitized to Ara h 1–3. IgE to rAra h 8, rAra h 9, profilin or cross-reactive carbohydrate determinants were not associated with severe symptoms. Conclusions: The results indicate that IgE reactivity to Ara h 1, 2 and 3 is associated with severe reactions after exposure to peanut in Swedish patients.

Component-Resolved IgE Profiles in Austrian Patients with a Convincing History of Peanut Allergy

“…All but 1 of the patients who were sensitized to Ara h 2 and Ara h 6 showed concomitant sensitization to Ara h 1 and/or Ara h 3. Our findings are in line with others showing that Ara h 2 is the most important peanut allergen [1,2,3,4,5,6,11,21,22]. Data about the prevalence and diagnostic value of Ara h 6 are rare, but in accordance with our results two studies showed that both peanut 2S albumins are recognized by IgE from the same patients in almost all cases and that the diagnostic accuracy of IgE specific to Ara h 6 in adults is as good as for Ara h 2 [1,7].…”

“…Interestingly, we found significantly higher levels of Ara h 6-specific IgE compared with IgE levels specific for Ara h 2, possibly due to the higher IgE affinity and IgE epitope availability of the purified natural Ara h 6 compared with recombinant Ara h 2 presented on the ImmunoCAP ISAC 112. In contrast to earlier studies, recent studies have increasingly suggested a positive correlation between the severity of symptoms and the level of specific IgE, especially to Ara h 2, but also to Ara h 1 and Ara h 3 [3,6,9,23]. We showed that patients experiencing anaphylaxis after exposure to peanut had significantly higher levels of sIgE against Ara h 1, Ara h 2, Ara h 3 and Ara h 6 as compared to patients suffering from milder symptoms such as OAS, although not all patients with severe reactions had high IgE levels to Ara h 2.…”

“…It emerged that patterns of IgE binding to peanut proteins may vary according to geographical location [1,2,3,4,5,6,11,21,24]. Sensitization to Ara h 8 is more prominent in peanut-allergic patients exposed to pollen from Fagales trees, such as birch or alder, and, according to recent studies from Sweden, isolated Ara h 8 sensitization is a marker of a mild reaction if any [11,14].…”

“…The peanut seed storage proteins Ara h 1, Ara h 2, Ara h 3 and Ara h 6 are largely recognized as the major allergens in patients who are primarily sensitized to peanut. Among them, Ara h 2 has been described as the most important peanut allergen, with a sensitization rate of 42-100% depending on the study population, whereas the sensitization rate to Ara h 1 and Ara h 3 is lower, in the range of 30-80 and 16-61%, respectively [1,2,3,4,5,6]. The diagnostic value of Ara h 6, which has only recently become available on ImmunoCAP ISAC, has been shown to be equivalent to Ara h 2 with a positive predictive value of 95% [7].…”

“…Consequently, high sensitization rates to Ara h 8 were primarily found in patients allergic to Fagales tree pollen such as birch in Central and Northern Europe (65-70%) [2,3,5] or alder in Japan (42%) [6]. Ara h 8 sensitization usually indicates tolerance to peanuts or occasionally only causes mild oral symptoms [14].…”