Utility of epitope-specific IgE, IgG4, and IgG1 antibodies for the diagnosis of wheat allergy.

BACKGROUND: The bead-based epitope assay (BBEA) has been used to identify epitope-specific (es) antibodies and successfully utilized to diagnose clinical allergy to milk, egg and peanut. OBJECTIVE: This study aimed to identify es-IgE, es-IgG4 and es-IgG1 of wheat proteins and determine the optimal peptides to differentiate wheat-allergic from wheat-tolerant using the BBEA. METHODS: Children and adolescents who underwent an oral food challenge to confirm their wheat allergy status were enrolled. Seventy-nine peptides from alpha/beta-gliadin, gamma-gliadin (γ-gliadin), omega-5-gliadin (ω-5-gliadin), high and low molecular weight glutenin were commercially synthesized and coupled to LumAvidin beads. Machine learning (ML) methods were used to identify diagnostic epitopes and performance was evaluated using DeLong's test. RESULTS: The analysis includes 122 children (83 wheat-allergic and 39 wheat-tolerant, 57.4% male). ML coupled with simulations identified wheat es-IgE, but not es-IgG4 or es-IgG1 to be most informative for diagnosing wheat allergy. Higher es-IgE binding intensity correlated with the severity of allergy phenotypes, with wheat anaphylaxis exhibiting the highest es-IgE binding intensity. In contrast, wheat-dependent exercise-induced anaphylaxis (WDEIA) showed lower es-IgG1 binding than all other groups. A set of 4 informative epitopes from ω-5-gliadin, and γ-gliadin were the best predictors of wheat allergy with an AUC of 0.908 (sensitivity=83.4%, specificity=88.4%), higher than the performance exhibited by wheat-specific IgE (AUC=0.646, p < 0.001). The predictive ability of our model was confirmed in an external cohort of 71 patients (29 allergic, 42 non-allergic), with an AUC of 0.908 (sensitivity=75.9%, specificity=90.5%). CONCLUSION: The wheat BBEA demonstrated greater diagnostic accuracy compared to existing specific IgE tests for wheat allergy.

Epitope-Specific IgE at 1 Year of Age Can Predict Peanut Allergy Status at 5 Years.

BACKGROUND: Currently, there is no laboratory test that can accurately identify children at risk of developing peanut allergy. Utilizing a subset of children randomized to the peanut avoidance arm of the LEAP trial, we monitored the development of epitope-specific (ses-)IgE and ses-IgG4 from 4-11 months to 5 years of age. OBJECTIVE: The aim of the study was to evaluate the prognostic ability of epitope-specific antibodies to predict the result of an oral food challenge (OFC) at 5 years. METHODS: A Bead-Based Epitope Assay was used to quantitate IgE and IgG4 to 64 sequential (linear) epitopes from Ara h 1-3 proteins at 4-11 months, 1 and 2.5 years of age in 74 subjects (38 of them with a positive OFC at 5 years). Specific IgE (sIgE) to peanut and component proteins was measured using ImmunoCAP. Machine learning methods were used to identify the earliest time point to predict 5-year outcome, developing prognostic algorithms based only on 4-11 month samples, 1-year or 2.5-year, and a combination of them. Data from 74 children were iteratively split 3:1 into training and validation sets, and machine learning models were developed to predict the 5-year outcome. A test set (n = 90) from an independent cohort was used for final evaluation. RESULTS: Elastic-Net algorithm combining ses-IgE and IgE to Ara h 1, 2, 3, and 9 proteins could predict the 5-year peanut allergy status of LEAP participants with an average validation accuracy of 64% at baseline. Samples taken at 1 year accurately predicted a 5-year OFC outcome with 83% accuracy. This performance remained consistent when evaluated on an independent CoFAR2 cohort with an accuracy of 78% for the 1-year model. CONCLUSION: IgE antibody profiles at 1 year of age are predictive of peanut OFC at 5 years in children avoiding peanuts. If further confirmed, this model may enable early identification of infants who may benefit from early immunotherapeutic interventions.

Evolution of epitope-specific IgE and IgG4 antibodies in children enrolled in the LEAP trial.

BACKGROUND: In the LEAP (Learning Early About Peanut Allergy) trial, early consumption of peanut in high-risk infants was found to decrease the rate of peanut allergy at 5 years of age. Sequential epitope-specific (ses-)IgE is a promising biomarker of clinical peanut reactivity. OBJECTIVE: We sought to compare the evolution of ses-IgE and ses-IgG4 in children who developed (or not) peanut allergy and to evaluate the immunomodulatory effects of early peanut consumption on these antibodies. METHODS: Sera from 341 children (LEAP cohort) were assayed at baseline, 1, 2.5, and 5 years of age, with allergy status determined by oral food challenge at 5 years. A bead-based epitope assay was used to quantitate ses-IgE and ses-IgG4 to 64 sequential epitopes from Ara h 1 to Ara h 3 and was analyzed using linear mixed-effect models. RESULTS: In children avoiding peanut who became peanut allergic, the bulk of peanut ses-IgE did not develop until after 2.5 years. Minimal increases of ses-IgE occurred after 1 year in consumers, but not to the same epitopes as those in children developing peanut allergy. No major changes in ses-IgE were seen in nonallergic or sensitized children. IgE in sensitized consumers was detected against peanut proteins. ses-IgG4 increased over time in most children regardless of consumption or allergy status. CONCLUSIONS: Early peanut consumption in infants at high risk of developing peanut allergy appears to divert the immunologic response to a presumably "protective" effect. In general, consumers tend to generate ses-IgG4 earlier and in greater quantities than nonconsumers do, whereas only avoiders tend to generate significant quantities of ses-IgE.

Early epitope-specific IgE antibodies are predictive of childhood peanut allergy.

BACKGROUND: Peanut allergy is characterized by the development of IgE against peanut antigen. OBJECTIVE: We sought to evaluate the evolution of epitope-specific (es)IgE and esIgG4 in a prospective cohort of high-risk infants to determine whether antibody profiles can predict peanut allergy after age 4 years. METHODS: The end point was allergy status at age 4+ years; samples from 293 children were collected at age 3 to 15 months and 2 to 3 and 4+ years. Levels of specific (s)IgE and sIgG4 to peanut and component proteins, and 50 esIgE and esIgG4 were quantified. Changes were analyzed with mixed-effects models. Machine learning algorithms were developed to identify a combination of antigen- and epitope-specific antibodies that using 3- to 15-month or 2- to 3-year samples can predict allergy status at age 4+ years. RESULTS: At age 4+ years, 38% of children were Tolerant or 14% had Possible, 8% Convincing, 24% Serologic, and 16% Confirmed allergy. At age 3 to 15 months, esIgE profiles were similar among groups, whereas marked increases were evident at age 2 and 4+ years only in Confirmed and Serologic groups. In contrast, peanut sIgE level was significantly lower in the Tolerant group at age 3 to 15 months, increased in Confirmed and Serologic groups but decreased in Convincing and Possibly Allergic groups over time. An algorithm combining esIgEs with peanut sIgE outperformed different clinically relevant IgE cutoffs, predicting allergy status on an "unseen" set of patients with area under the curves of 0.84 at age 3 to 15 months and 0.87 at age 2 to 3 years. CONCLUSIONS: Early epitope-specific plus peanut-specific IgE is predictive of allergy status at age 4+ years.

Epitope-Based IgE Assays and Their Role in Providing Diagnosis and Prognosis of Food Allergy.

With advances in molecular and computational science, epitope-specific IgE antibody profiling has been developed and recently brought into clinical practice. Epitope-based testing detects IgE antibodies that directly bind to antigenic sites of an allergen, providing increased resolution specificity and fewer false-positive results for diagnosing food allergy. Epitope-binding profiles may also serve as prognostic markers of food allergy and help predict quantities of allergen that would provoke a reaction (ie, eliciting dose, possible severity of a reaction after allergen ingestion, and outcomes of treatment options such as oral immunotherapy [OIT]). Future studies are under way to discover additional applications of epitope-specific antibodies for multiple food allergens.