Association of HLA-class II alleles with risk of relapse in myeloperoxidase-antineutrophil cytoplasmic antibody positive vasculitis in the Japanese population.

Background. Disease relapse remains a major problem in the management of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). In European populations, HLA-DPB1^*04:01 is associated with both susceptibility and relapse risk in proteinase 3-ANCA positive AAV. In a Japanese population, we previously reported an association between HLA-DRB1^*09:01 and DQB1^*03:03 with susceptibility to, and DRB1^*13:02 with protection from, myeloperoxidase-ANCA positive AAV (MPO-AAV). Subsequently, the association of DQA1^*03:02, which is in strong linkage disequilibrium with HLA-DRB1^*09:01 and DQB1^*03:03, with MPO-AAV susceptibility was reported in a Chinese population. However, an association between these alleles and risk of relapse has not yet been reported. Here, we examined whether HLA-class II is associated with the risk of relapse in MPO-AAV. Methods. First, the association of HLA-DQA1^*03:02 with susceptibility to MPO-AAV and microscopic polyangiitis (MPA) and its relationship with previously reported DRB1^*09:01 and DQB1^*03:03 were examined in 440 Japanese patients and 779 healthy controls. Next, the association with risk of relapse was analyzed in 199 MPO-ANCA positive, PR3-ANCA negative patients enrolled in previously reported cohort studies on remission induction therapy. Uncorrected P values (P_uncorr) were corrected for multiple comparisons in each analysis using the false discovery rate method. Results. The association of DQA1^*(03:02 with susceptibility to MPO-AAV and MPA was confirmed in a Japanese population (MPO-AAV: P_uncorr=5.8x10^-7, odds ratio [OR] 1.74, 95% confidence interval [CI] 1.40-2.16, MPA: P_uncorr=1.1x10^-5, OR 1.71, 95%CI 1.34-2.17). DQA1^*03:02 was in strong linkage disequilibrium with DRB1^*09:01 and DQB1^*03:03 and the causal allele could not be determined using conditional logistic regression analysis. Relapse-free survival was shorter with nominal significance in carriers of DRB1^*09:01 (P_uncorr=0.049, Q=0.42, hazard ratio [HR]:1.87), DQA1^*03:02 (P_uncorr=0.020, Q=0.22, HR:2.11) and DQB1^*03:03 (Puncorr=0.043, Q=0.48, HR:1.91) than in non-carriers in the log-rank test. Conversely, serine carriers at position 13 of HLA-DRβ1 (HLA-DRβ1_13S), including DRB1^*13:02 carriers, showed longer relapse-free survival with nominal significance (P_uncorr=0.010, Q=0.42, HR:0.31). By combining DQA1^*03:02 and HLA-DRβ1_13S, a significant difference was detected between groups with the highest and lowest risk for relapse (P_uncorr=0.0055, Q=0.033, HR:4.02). Conclusion. HLA-class II is associated not only with susceptibility to MPO-AAV but also with risk of relapse in the Japanese population.