Is aboriginal food less allergenic? Comparing IgE-reactivity of eggs from modern and ancient chicken breeds in a cohort of allergic children

Abstract

Background: Hen's egg allergy ranks among the most frequent primary food allergies in children. We aimed to investigate sensitization profiles of egg allergic patients and compare in vitro IgE reactivities of eggs from ancient chicken breeds (Araucana and Maran) with those from conventional laying hen hybrids.

Methodology: Egg allergic children (n = 25) were subjected to skin prick test, double blind placebo controlled food challenge, and sensitization profiles to Gal d 1-5 were determined by allergen microarray. IgE binding and biological activity of eggs from different chicken breeds were investigated by immunoblot, ELISA, and mediator release assays.

Principal findings: We found that Gal d 1 and Gal d 2 are generally major egg allergens, whereas Gal d 3-5 displayed high sensitization prevalence only in patients reacting to both, egg white and yolk. It seems that the onset of egg allergy is mediated by egg white allergens expanding to yolk sensitization in later stages of disease. Of note, egg white/yolk weight ratios were reduced in eggs from Auraucana and Maran chicken. As determined in IgE immunoblots and mass analysis, eggs from ancient chicken breeds did not differ in their protein composition. Similar IgE-binding was observed for all egg white preparations, while an elevated allergenicity was detected in egg yolk from Araucana chicken.

Conclusion/significance: Our results on allergenicity and biological activity do not confirm the common assumption that aboriginal food might be less allergenic. Comprehensive diagnosis of egg allergy should distinguish between reactivity to hen's egg white and yolk fractions to avoid unnecessary dietary restrictions to improve life quality of the allergic child and its family.

Figure 1. Age distribution and sensitization profile to hen's egg allergens.

(A) Egg sensitized subjects (n = 474) were clustered according to age (1–15 years) and gender. (B) Sensitization prevalence to Gal d 1–5 of allergic patients reactive to egg white and yolk (P1–12) and those sensitized to egg white only (P13–25) are presented in grey (yolk positive) and white bars (yolk negative), respectively.

Figure 2. Identification of allergenic egg components.

IgE-reactive egg white (A) and yolk (B) extract components from Araucana (A), Maran (M), and conventional laying hen hybrid (H) breeds were detected by IgE immunoblotting (left charts). IgE-reactive bands (A1–5 and Y1–5) were excised from polyacrylamide gels (right charts), and subjected to mass spectrometry analysis. Corresponding proteins, their molecular weights (MW), and SwissProt/TrEMBL accession numbers are given in the tables.

Figure 3. Allergenicity of egg white and yolk from different chicken breeds.

Specific IgE levels to native and heat-treated egg white (A and B) and yolk (C and D) from Araucana (black circles), Maran (white circles), and conventional laying hen hybrid breeds (grey circles) were determined by ELISA. Circles represent values obtained from individual patients' sensitized to egg white (n = 25) and yolk (n = 12). Mean values are shown as solid line and whiskers indicate the standard error of the mean. Statistical analysis was performed using the Wilcoxon signed rank test. **<0.01; *<0.02.

Figure 4. Biological activities of egg white and yolk from different chicken breeds.

Transfected RBL-2H3 cells were passively sensitized with a serum pool of 8 patients. Mediator release was triggered with increasing concentrations of egg white (A) and yolk (B) extract.