Mechanisms of allergy and clinical immunologyHLA-DRA variants predict penicillin allergy in genome-wide fine-mapping genotyping

BackgroundImmediate reactions to β-lactams are the most common causes of anaphylactic reactions and can be life-threatening. The few known genetic factors influencing these reactions suggest a link with atopy and inflammation.ObjectiveWe performed a fine-mapping genome-wide association study of the genetic predictors of β-lactam allergy to better understand the underlying mechanisms.MethodsWe studied 387 patients with immediate allergic reactions to β-lactams and 1124 paired control subjects from Spain. We replicated the results in 299 patients and 362 paired control subjects from Italy.ResultsWe found significant associations with the single nucleotide polymorphisms rs4958427 of ZNF300 (c.64-471G>A, P = 9.9 × 10−9), rs17612 of C5 (c.4311A>C [p.Glu1437Asp], P = 7.5 × 10−7), rs7754768 and rs9268832 of the HLA-DRA | HLA-DRB5 interregion (P = 1.6 × 10−6 and 4.9 × 10−6), and rs7192 of HLA-DRA (c.724T>G [p.Leu242Val], P = 7.4 × 10−6) in an allelic model, with similar results in an additive model. Single nucleotide polymorphisms of HLA-DRA and ZNF300 predicted skin test positivity to amoxicillin and other penicillins but not to cephalosporins. A haplotype block in HLA-DRA and the HLA-DRA | HLA-DRB5 interregion encompassed a motif involved in balanced expression of the α- and β-chains of MHC class II, whereas rs7192 was predicted to influence α-chain conformation. HLA-DRA rs7192 and rs8084 were significantly associated with allergy to penicillins and amoxicillin (P = 6.0 × 10−4 and P = 4.0 × 10−4, respectively) but not to cephalosporins in the replication study.ConclusionsGene variants of HLA-DRA and the HLA-DRA | HLA-DRB5 interregion were significant predictors of allergy to penicillins but not to cephalosporins. These data suggest complex gene-environment interactions in which genetic susceptibility of HLA type 2 antigen presentation plays a central role.