IgE binding to linear epitopes of Ara h 2 in peanut allergic preschool children undergoing oral Immunotherapy

Abstract

Background: For patients with peanut allergy, there are currently no methods to predict who will develop sustained unresponsiveness (SU) after oral immunotherapy (OIT).

Objective: Assess IgE binding to peanut (PN), Ara h 2, and specific linear epitopes of Ara h 2 as predictors of the important clinical parameters: eliciting dose threshold and attainment of SU following OIT.

Methods: Samples and clinical data were collected from children undergoing OIT. PN- and Ara h 2-sIgE were quantified by ImmunoCAP® . IgE binding to linear peptides of Ara h 2 and Ara h 6 was measured with peptide microarrays.

Results: Values of PN-sIgE correlated with eliciting dose (P = .001) and with a higher likelihood of achieving SU (P < .0001), but these relationships were lost at higher values for PN-sIgE (≥14 kIU for eliciting dose and ≥35 kIU/L for SU). In subjects with PN-sIgE ≥ 14 kIU/L, binding of IgE to epitopes 5 and 6 of Ara h 2 was associated with a lower eliciting dose at baseline challenge (P < .001; Pc < .02). In subjects with PN-sIgE ≥ 35 kIU/L, a combined model of IgE binding to epitopes 1, 5 and 6 with PN-sIgE was highly predictive of attainment of SU (AUC of 0.86; P = .0067).

Conclusion: In young patients with peanut allergy, measurement of PN-sIgE and IgE binding to specific linear epitopes of Ara h 2 in baseline samples may allow stratification of patients regarding sensitivity to challenge and outcome of OIT.

Keywords: IgE; allergens; food allergy; immunotherapy; oral immunotherapy; peanut allergy; tolerance induction.

Conflict of interest statement

Conflict of Interest Statement: DR, SSN, JC, SE and CMGM have no relevant conflicts of interest.

© 2019 EAACI and John Wiley and Sons A/S. Published by John Wiley and Sons Ltd.

Figures

FIGURE 1.

Increased levels of PN-sIgE are associated with lower eliciting dose upon oral challenge (A-C). This is true for the entire cohort (A) and for those with PN-sIgE

FIGURE 2.. IgE binding to epitopes 5 and 6 is associated with lower eliciting dose upon oral challenge.

A) Subjects (n = 23; all with PN-sIgE of ≥ 14 kIU/L) were separated into those that did not have strong evidence of binding to either epitope 5 or epitope 6 (z < 3; open triangles) and those that had strong evidence of binding (z ≥ 3; closed triangles) (see Table E2). B) The raw data (signal from epitope 5 plus the signal from epitope 6) are plotted against the eliciting dose.

FIGURE 2.. IgE binding to epitopes 5 and 6 is associated with lower eliciting dose upon oral challenge.

A) Subjects (n = 23; all with PN-sIgE of ≥ 14 kIU/L) were separated into those that did not have strong evidence of binding to either epitope 5 or epitope 6 (z < 3; open triangles) and those that had strong evidence of binding (z ≥ 3; closed triangles) (see Table E2). B) The raw data (signal from epitope 5 plus the signal from epitope 6) are plotted against the eliciting dose.

FIGURE 3.. For all subjects, levels of PN-sIgE and Ara h 2-sIgE are inversely associated with attainment of sustained unresponsiveness.

Data shown are for all who were dosed in the DEVIL study (n = 46) (A, B) (Table 1E). Data from subjects who did not achieve SU due to withdrawals are shown as filled squares and those who completed OIT and did not achieve SU are shown in open squares. Cut-offs of PN-sIgE of ≥ 35 kIU/L (dashed line in A) and ≥ 24 kIU/L (dashed line in B) are shown.

FIGURE 3.. For all subjects, levels of PN-sIgE and Ara h 2-sIgE are inversely associated with attainment of sustained unresponsiveness.

Data shown are for all who were dosed in the DEVIL study (n = 46) (A, B) (Table 1E). Data from subjects who did not achieve SU due to withdrawals are shown as filled squares and those who completed OIT and did not achieve SU are shown in open squares. Cut-offs of PN-sIgE of ≥ 35 kIU/L (dashed line in A) and ≥ 24 kIU/L (dashed line in B) are shown.

FIGURE 4.. Among subjects with PN-sIgE of ≥ 35 kIU/L, IgE binding to epitope 1 of Ara h 2 is inversely associated with attainment of sustained unresponsiveness.

These are the samples with PN-sIgE of ≥ 35 kIU/L. A) PN-sIgE, B) Ara h 2-sIgE and C) binding of IgE to eitope 1 of Aa h 2. Data from subjects who did not achieve SU due to withdrawals are shown as filled squares and those who completed OIT and did not achieve SU are shown in open squares.

FIGURE 5.. Receiving operator curve.

Data are shown for subjects with PN-sIgE of ≥35 kIU/L. An ROC curve for PN-sIgE (green dashed line), cumulative IgE binding to epitopes 1, 5 and 6 of Ara h 2 (orange solid line) and a composite analysis using PN-sIgE and cumulative IgE binding to epitopes 1, 5 and 6 of Ara h 2 (blue dashed line).

FIGURE 6.. Localization of epitopes 1, 5 and 6 on the reported structure of Ara h 2.

This is the X-ray crystal structure of Ara h 2 (PDB entry 3OB4) where the missing flexible loop regions were generated by modeling as described in. A) ribbon structure and B) surface analysis. Epitopes are color coded: 1, orange, 5, yellow and 6, pink.