Circulating Ara h 6 as a marker of peanut protein absorption in tolerant and allergic humans following ingestion of peanut‐containing foods

Abstract

Background Bioaccessibility of food allergens may be a key determinant of allergic reactions. Objective To develop a protocol allowing the detection of the major peanut allergen, Ara h 6, in the bloodstream following ingestion of low amounts of peanut and to compare Ara h 6 bioaccessibility by food matrix. We further assessed for differences in absorption in healthy versus peanut‐allergic volunteers. Methods A blood pretreatment combining acidic shock and thermal treatment was developed. This protocol was then applied to blood samples collected from human volunteers (n = 6, healthy controls; n = 14, peanut‐allergic patients) at various time‐points following ingestion of increasing levels of peanut incurred in different food matrices (cookies, peanut butter and chocolate dessert). Immunodetection was performed using an in‐house immunoassay. Results An original pretreatment protocol was optimized, resulting in irreversible dissociation of human antibodies‐Ara h 6 immune complex, thus rendering Ara h 6 accessible for its immunodetection. Ara h 6 was detected in samples from all volunteers following ingestion of 300‐1000 mg peanut protein, although variations in the kinetics of passage were observed between individuals and matrices. Interestingly, in peanut‐allergic subjects, Ara h 6 could be detected following ingestion of lower doses and at higher concentrations than in non‐allergic volunteers. Conclusions and Clinical Relevance The kinetics and intensity of Ara h 6 passage in bloodstream depend on both individual and food matrix. Peanut‐allergic patients appear to demonstrate higher absorption rate, the clinical significance of which warrants further evaluation.

Is allergen absorption a key determinant of severity in food-induced reactions?

“…4 The detection of food proteins in serum following consumption is challenging. 5 Nonetheless, we have previously reported that absorption kinetics for peanut are significantly different in peanut-allergic volunteers compared with nonallergic controls (Fig 1). For any given dose of peanut ingestion, there is higher Ara h 6 detection in serum samples from peanut-allergic individuals compared with controls, and peanut can be detected in the blood after much lower levels of ingestion, compared with controls.…”

Developments in the field of allergy in 2020 through the eyes of Clinical and Experimental Allergy

“…This coincided with a number of studies evaluating the burden of peanut allergy and calling for improved protection for people with food allergy 69‐71 . Investigation of component IgE as a marker for ingestion, an immunological target and a discriminator with added diagnostic value also continues to be a busy area of science 72‐79 . Characteristics of infant food anaphylaxis were defined in one of the most extensive published series—hives, hypotonia and hypotension were common features in a French series with 61 infant cases, compared with 386 cases in preschool children 80 .…”

The Effector Function of Allergens

“…Furthermore, digestion products of peanut 2S albumins yield a large and a small subunit (5 and 9 kDa) that remain associated by disulfide bridges so that the resulting heterodimer is as immunoreactive as the intact protein. Hence, immunoreactive Ara h 2 and Ara h 6 can be still detected and quantified in the bloodstream and in breast milk of non-peanut allergic human volunteers after peanut consumption or in the blood of peanut allergic patients after oral food challenge (61). These proteins have been shown to bind IgE and to be active in functional assays with RBL SX-38 cells (60,(62)(63)(64)(65)(66).…”