Pathogenic IgE-recognising epitopes and tolerance-related IgG4 epitopes in patients with and without cow’s milk allergy

Introduction

An enzyme-linked immunosorbent assay (ELISA) system capable of profiling IgE-recognising epitopes in patients with cow’s milk allergy (CMA) was established previously. This assay can reveal qualitative differences and imbalances between IgE- and IgG4-recognising epitopes as well as quantify IgE specific to the mixture of 14 epitopes (14 epitopes-ALL) that correlate with the value obtained using the ImmunoCAP sIgE(milk) test. To apply this system clinically, we determined the cutoff range of IgE contents detected by the 14 epitopes-ALL, and identified pathogenic IgE-epitopes and tolerance-related IgG4-epitopes by comparing the profiles of both IgE and IgG4.

Methods

Serum samples from 38 patients with CMA and 34 non-CMA volunteers were assessed to determine their IgE levels towards 14 epitopes using our ELISA system. Epitope profiles of the samples were analysed individually. Using clinical data on oral immunotherapy status and allowed milk intake assessed by the oral food challenge test, the IgE and IgG4 profiles were compared to extract pathogenic, non-pathogenic, and tolerance-related epitope candidates.

Results

The cutoff range of IgE was 1.5–4.5 ng/mL with an area under the curve of 89% in receiver operating characteristic analysis. Serum samples of ImmunoCAP class 3 and lower classes were divided into upper and lower proportions by this cutoff range, which can be useful for predicting risk of eliciting symptoms by allergenic food exposure. Extraction of candidate pathogenic and non-pathogenic epitopes showed that pathogenic epitopes formed a cluster in hydrophobic regions of caseins and appeared to be near each other on the molten globule of micelles.

Conclusions

The 14 epitopes of cow’s milk allergens are useful for determining the allergen-specific IgE concentration in patients with CMA. The IgE vs. IgG4 profile identified pathogenic, non-pathogenic, and tolerance-related epitopes. This profiling analysis may explain why oral immunotherapy is effective in some individuals but not others.

Key Messages

• IgE antibodies recognising 14 cow’s milk allergen epitopes correlate with IgE values detected using ImmunoCAP.

• This test can accurately assess risk of symptoms in patients with class 3 ImmunoCAP sIgE.

• Epitope-based quantitative/qualitative analyses of antibodies are reliable for assessing allergic symptoms and oral immunotherapy effects.