Amino acid variants in the HLA-DQA1 and HLA-DQB1 molecules explain the major association of variants with relapse status in pediatric patients with steroid-sensitive nephrotic syndrome.

BACKGROUND

Management of patients with steroid-sensitive nephrotic syndrome (SSNS) is challenging because of frequent relapses. Causal variants in the human leukocyte antigen (HLA) class II region that are associated with relapse remain undetermined.

METHODS

We collected a cohort of East Asian individuals comprising 206 pediatric patients with SSNS and 435 healthy controls from Southwest China. Ninety children with steroid-sensitive nephrotic syndrome without relapse (SSNSWR) and 116 children with steroid-dependent and/or frequent relapse nephrotic syndrome (SDNS/FRNS) were genotyped using Sanger sequencing. We then measured the transcriptional level, allele expression imbalance (AEI) and functional proteins of HLA-DQA1 and HLA-DQB1 in different stages of SDNS/FRNS.

RESULTS

rs1464545187 in ANKRD36 was associated with an approximately 1.69-fold greater risk for SSNSWR (P = 0.04; 95% confidence interval [CI], 1.05-2.72). Clustered risk variants in HLA-DQA1 and HLA-DQB1 were significantly associated with SDNS/FRNS (rs1047989: P = 2.26E-07, odds ratio [OR] = 2.25, 1.65-3.05; rs9273471: P = 5.45E-05, OR = 1.84, 1.37-2.46; HLA-DQB106:02: P = 0.017, OR = 0.19, 0.04-0.77). The genotype distributions of rs1047989, 2:171713702, rs1049123, rs9273471, and HLA-DQB106:02 in patients with SSNS were significantly different from those in healthy controls. rs1047989 (HLA-DQA1) was significantly associated with a greater number of infections at relapse in SDNS/FRNS patients (P = 0.045, OR = 6.79, 95% CI: 1.29-168.52). Flow cytometry showed that the proportion of cells expressing HLA-DQA1/DQB1 (HLA-DQA1, P = 0.0046; HLA-DQB1, P = 0.0045) was lowest in the relapse stage. In addition, the mRNA levels of HLA-DQA1 and HLA-DQB1 were significantly greater in the relapse group than in the remission group (HLA-DQA1, P = 0.03; HLA-DQB1, P = 0.002). No significant AEIs were detected in the different stages of SDNS/FRNS. The rs1047989 variant is likely to affect the structure and stability of HLA-DQA1.

CONCLUSION

rs1464545187 is a risk locus for SSNSWR but not SDNS/FRNS in Chinese children. Functional variations in HLA-DQA1 and HLA-DQB1 are implicated in regulating the immune response of SSNS patients, which may explain the typical triggering of SDNS/FRNS onset by infections.