Correlation of IgE/IgG4 milk epitopes and affinity of milk-specific IgE antibodies with different phenotypes of clinical milk allergy.

BACKGROUND: Results from large-scale epitope mapping with a peptide microarray have been shown to correlate with clinical features of milk allergy.
OBJECTIVES: We sought to assess IgE and IgG4 epitope diversity and IgE affinity in different clinical phenotypes of milk allergy and identify informative epitopes that might be predictive of clinical outcomes of milk allergy.
METHODS: Forty-one subjects were recruited from a larger study on the effects of ingesting heat-denatured milk proteins in subjects with milk allergy. Using food challenges, subjects were characterized as being clinically reactive to all forms of milk (n = 17), being tolerant to heated milk (HM) products (n = 16), or having outgrown their milk allergy (n = 8). Eleven healthy volunteers without milk allergy served as control subjects. A peptide microarray was performed by using the previously published protocol.
RESULTS: Subjects with milk allergy had increased epitope diversity compared with those who outgrew their allergy. HM-tolerant subjects had IgE-binding patterns similar to those who had outgrown their allergy, but IgG4-binding patterns that were more similar to those of the allergic group. Binding to higher numbers of IgE peptides was associated with more severe allergic reactions during challenge. There was no association between IgG4 peptides and clinical features of milk allergy. Using a competitive peptide microarray assay, allergic patients demonstrated a combination of high- and low-affinity IgE binding, whereas HM-tolerant subjects and those who had outgrown their milk allergy had primarily low-affinity binding.
CONCLUSIONS: Greater IgE epitope diversity and higher affinity, as determined by using the peptide microarray, were associated with clinical phenotypes and severity of milk allergy.