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.