Background
Peanut oral immunotherapy (PNOIT) induces persistent tolerance to peanut in a subset of patients and induces specific antibodies which may play a role in clinical protection. The contribution of induced antibody clones to clinical tolerance in PNOIT is unknown, however.
Objective
We hypothesized that PNOIT induces a clonal, allergen-specific B cell response, which could serve as a surrogate for clinical outcomes.
Methods
We used a fluorescent Ara h 2 multimer for affinity-selection of Ara h 2-specific B cells, and subsequent single cell immunoglobulin amplification. Diversity of related clones was evaluated by next-generation sequencing (NGS) of immunoglobulin heavy chains from circulating memory B cells using 2×250 paired-end sequencing on the Illumina MiSeq platform.
Results
Expression of class-switched antibodies from Ara h 2 positive cells confirms enrichment for Ara h 2 specificity. PNOIT induces an early and transient expansion of circulating Ara h 2 specific memory B cells that peaks at week 7. Ara h 2-specific sequences from memory cells have rates of non-silent mutations consistent with affinity maturation. The repertoire of Ara h 2-specific antibodies is oligoclonal. NGS-based repertoire analysis of circulating memory B cells, reveals evidence for convergent selection of related sequences in 3 unrelated subjects, suggesting the presence of similar Ara h 2-specific B cell clones.
Conclusions
Using a novel affinity selection approach to identify antigen-specific B cells, we demonstrate that the early PNOIT induced Ara h 2-specific BCR repertoire is oligoclonal, somatically hypermutated and shares similar clonal groups among unrelated individuals consistent with convergent selection.