DISCUSSION
We sequenced the HLA region of 24 patients with delayed and 20 with immediate hypersensitivity to penicillins in order to analyze the risk association for all high-resolution alleles with delayed hypersensitivity. We observed a strong association ofDRB3*02:02:01:02 and DRB3*02:02:01:01 alleles with the risk of penicillin delayed hypersensitivity in the 24 Italian patients. It is noteworthy that as many as 83% of the cases carried a DRB3*02:02 allele. The frequency of homozygous cases for the variants of the HLA-DRB3locus was higher in group A (with selective hypersensitivity to ampicillin and amoxicillin) than in the less selective groups B and C, suggesting that the association reflects the specificity of hapten recognition. The association of the HLA-DRB3 locus with an increased risk of penicillin delayed hypersensitivity was confirmed by the in silico study of genetic variants of the HLA-DRB3genomic region in Spanish patients. The protein encoded by theHLA-DRB3 gene belongs to the HLA class II beta chain paralogs, including DRB1, DRB4, and DRB5. It is part of a heterodimer consisting of an alpha chain (DRA) and a beta one (DRB) and is involved in the antigen presentation of peptides derived from extracellular proteins. The association of HLA-DRB3*02:02 with the risk of penicillin delayed hypersensitivity has never been reported for any other drug category so far. The HLA-DRB3*02:02 allele is independently and strongly associated with an increased risk of PLA2R -related idiopathic membranous nephropathy in a Chinese population.23 Therefore, our results suggest investigating the increased risk of delayed reactions to penicillins in this disease.
Only one study had previously evaluated the genetic determinants that contribute to the risk of delayed hypersensitivity to penicillins. This Italian case-control study assessed HLA-A2 and HLA-DRw52alleles in 24 patients with MPE caused by delayed hypersensitivity to aminopenicillins and 522 subjects from the general population.15 The HLA-A2 and HLA-DRw52alleles were significantly more prevalent among cases. However, we did not replicate this result in the NGS of the MHC region in our study. A French study assessed nine variants on genes controlling cytokine production (i.e., IL1 , IL1B , IL1RN , IL2 ,IL4 , IL5 , IL10 , IL16 , and TNF ) in 118 patients with well-defined cutaneous adverse drug reactions and 236 controls.27 Several responsible drugs were considered in the study, including beta-lactams. The haplotype combining IL1RN A2 and IL1B 511Calleles was associated with an increased risk of DRESS (OR = 3.22; 95% CI: 1.23-8.41).27 However, the number of cases was too limited to evaluate the specific risk of reactions to penicillins.
We compared our data with pharmacogenetic research on immediate penicillin allergy. Most studies have evaluated genetic determinants of immediate reactions to beta-lactams utilizing a candidate-gene approach. They found an association with genes involved in IgE production, atopy, and inflammation, including 3 genes validated by replications:ILR4 , NOD2 , and LGALS3 .13,28-30It is noteworthy that no association with HLA-DRB1*10:01 ,ILR4 , NOD2 , or LGALS3 was identified by GWAS in our patients with delayed hypersensitivity reactions to penicillins. Despite the vicinity of the HLA-DRB1 /3 /4 /5 loci in chromosome 6, it is noteworthy that we did not find any association between the risk of delayed reactions to penicillins and the rs7754768 and rs9268832 of the HLA-DRA |HLA-DRB5inter-region in a GWAS performed in Italian and Spanish populations.11 Similarly, we found no risk association of delayed reactions with the rs71542416 within the Class II HLA region, which is associated with the risk of immediate beta-lactam allergy in GWAS performed in Italian and Spanish populations.12
In conclusion, we showed that the HLA-DRB3*02:02 alleles are strongly associated with an increased risk of delayed hypersensitivity to penicillins, at least in Southwestern Europe. In regard to the severity of some of the reactions, the interest for using the determination of HLA-DRB3*02:02 alleles in the risk management of delayed hypersensitivity to penicillins should be evaluated in further studies of larger populations of different origin.