Anaphylaxis to Peanut in a Patient Predominantly Sensitized to Ara h 6

Abstract

Diagnosis of peanut allergy has improved thanks to component-resolved diagnostics. Peanut allergen component Ara h 2 is considered to indicate true peanut allergy. The component Ara h 6 is structurally similar to Ara h 2, but the diagnostic value of analyzing IgE antibodies to Ara h 6 is unclear. A boy sensitized (≥0.35 kU_A/l) to Ara h 8 but not to Ara h 1, Ara h 2 and Ara h 3 was challenged with peanut and developed grade II anaphylaxis. In serum collected at the time of challenge a doubling of IgE to the peanut allergen extract was observed compared to allergy testing 9 months earlier. In contrast, IgE levels to Ara h 1, Ara h 2, Ara h 3 and to Ara h 8 were rather unchanged. After another 2 months, Ara h 6 was analyzed and revealed a level of 24 kU_A/l whilst Ara h 2 was 0.12 kU_A/l. We suggest that IgE sensitization to Ara h 6 caused the reaction and conclude that analyses of IgE levels to peanut and peanut components should be performed in connection with a challenge. Furthermore, levels to Ara h 2 below 0.35 kU_A/l may still indicate a risk of severe reaction at the time of challenge since in rare cases, Ara h 6 IgE antibodies may be present without occurrence of IgE antibodies to Ara h 2.

Component-Resolved Diagnosis of Peanut Allergy and Its Possible Origins of Sensitization in China

“…Some other clinically relevant peanut allergen component, such as Ara h 6, may exist in our population. Asarnoj et al [25] had reported a case of anaphylaxis to peanuts in a patient with a high level of anti-Ara h 6 IgE but a low level of anti- Ara h 2 IgE. Further studies should take this allergen into consideration.…”

Peanut component Ara h 8 sensitization and tolerance to peanut

“…30 He did not follow the study protocol because he was participating in a pilot investigation for this study. After the final dose of 10 g of peanut at challenge, he experienced grade II anaphylaxis.…”

Ara h 1 and Ara h 6 Sensitization Causes Clinical Peanut Allergy in Ara h 2-Negative Individuals

“…All of these sensitizations have been shown to cause allergic reactions [32, 43, 45]. Ara h 6 monosensitization has been found on rare occasions in other studies, but in our study 2 individuals out of 6 peanut allergic and Ara h 2-negative individuals were monosensitized to Ara h 6, which could indicate that Ara h 6 monosensitization is common in the Icelandic peanut allergic population [30]. In contrast to what has been shown in Spain, sensitization to Ara h 9 was not shown to be clinically important in Iceland, although the cases may be too few to generalize [46].…”

“…Ara h 2 and Ara h 6 are both 2S albumins and have 59% amino acid homology, which causes Ara h 6 to cross-react extensively with Ara h 2 [29]. In rare cases, individuals can be sensitized to Ara h 6 without being sensitized to Ara h 2 [30, 31]. Ara h 8 is a homologue of the major birch pollen allergen Bet v 1 and it is rarely associated with severe allergic reactions.…”