FCER2: A pharmacogenetic basis for severe exacerbations in children with asthma

Background

Although inhaled corticosteroids (ICSs) generally protect against severe exacerbations in asthma, they may result in elevated IgE levels, which are associated with exacerbations.

Objective

To determine whether variation in the low-affinity IgE receptor gene, FCER2, is associated with severe exacerbations defined as emergency department visits and/or hospitalizations in patients with asthma on ICSs.

Methods

We resequenced, then genotyped 10 FCER2 single nucleotide polymorphisms (SNPs) in 311 children randomized to inhaled budesonide as part of the Childhood Asthma Management Program. We evaluated the association of FCER2 variants with IgE levels and presence or absence of severe exacerbations over the 4-year clinical trial. We also evaluated differences in cellular expression of the novel FCER2 SNP, T2206C.

Results

In white subjects, 3 FCER2 SNPs were significantly associated (P < .05) with elevated 4-year IgE level; each was also associated with increased severe exacerbations. Final multivariable models demonstrated associations between T2206C and severe exacerbations in both white and African American children (hazard ratio, 3.95; 95% CI, 1.64-9.51; and hazard ratio, 3.08; 95% CI, 1.00-9.47), despite ICS use. Interaction models supported a true gene-environment effect in white subjects (interaction P = .004). T2206C was also associated with decreased FCER2 expression (P = .02).

Conclusion

FCER2 predicts the likelihood of treatment protocol success in asthma. The associations of T2206C with IgE level, severe exacerbations, and FCER2 expression may provide a mechanistic basis for the observed findings.

Clinical implications

Genetic variation in FCER2 may help form a prognostic model for ICS response in asthma.

Key words: Asthma, CD23, FCER2, exacerbation, corticosteroid, pharmacogenetic, hospitalization

Abbreviations used: CAMP, Childhood Asthma Management Program, FCER2, Fc fragment of IgE, low-affinity II receptor gene (the gene encoding for CD23), ICS, Inhaled corticosteroid, OR, Odds ratio, SNP, Single nucleotide polymorphism