Immunological Interaction of HLA-DPB1 and Proteinase 3 in ANCA Vasculitis is Associated with Clinical Disease Activity

Dhruti P. Chen; Elizabeth A. McInnis; Eveline Y. Wu; Katherine G. Stember; Susan L. Hogan; Yichun Hu; Candace D. Henderson; Lauren N. Blazek; Simon Mallal; Edita Karosiene; Bjoern Peters; John Sidney; Eddie A. James; William W. Kwok; J. Charles Jennette; Dominic J. Ciavatta; Ronald J. Falk; Meghan E. Free

doi:10.1681/ASN.2021081142

Visual Abstract

Significance Statement

In a longitudinal, prospective cohort study, we observed that patients with PR3-ANCA vasculitis and HLA-DPB1*04:01 are more likely to experience disease flares, which informed our hypothesis that HLA has an immunopathogenic role. We found that an epitope of PR3 (PR3_225-239) has high affinity for HLA-DPB1*04:01. By examining patient peripheral blood mononuclear cells, we demonstrated that PR3_225-239 presentation by HLA-DPB1*04:01 stimulates PR3_225-239–specific autoreactive T cells. This may explain the associated increased relapse risk. However, in patients who are in long-term remission off therapy, HLA-DPB1⁺ cells bind PR3_225-239 at levels seen in healthy controls. The diminished interaction between HLA-DPB1 and autoantigen in long-term remission signals immunological nonresponsiveness, creating a foundation to define immunological remission.

Abstract

Background PR3-ANCA vasculitis has a genetic association with HLA-DPB1. We explored immunologic and clinical features related to the interaction of HLA-DPB1*04:01 with a strongly binding PR3 peptide epitope (PR3_225–239).

Methods Patients with ANCA vasculitis with active disease and disease in remission were followed longitudinally. Peripheral blood mononuclear cells from patients and healthy controls with HLA-DPB1*04:01 were tested for HLA-DPB1*04:01 expression and interaction with a PR3 peptide identified via in silico and in vitro assays. Tetramers (HLA/peptide multimers) identified autoreactive T cells in vitro.

Results The HLA-DPB1*04:01 genotype was associated with risk of relapse in PR3-ANCA (HR for relapse 2.06; 95% CI, 1.01 to 4.20) but not in myeloperoxidase (MPO)-ANCA or the combined cohort. In silico predictions of HLA and PR3 peptide interactions demonstrated strong affinity between ATRLFPDFFTRVALY (PR3_225–239) and HLA-DPB1*04:01 that was confirmed by in vitro competitive binding studies. The interaction was tested in ex vivo flow cytometry studies of labeled peptide and HLA-DPB1*04:01-expressing cells. We demonstrated PR3_225–239 specific autoreactive T cells using synthetic HLA multimers (tetramers). Patients in long-term remission off therapy had autoantigenic peptide and HLA interaction comparable to that of healthy volunteers.

Conclusions The risk allele HLA-DPB1*04:01 has been associated with PR3-ANCA, but its immunopathologic role was unclear. These studies demonstrate that HLA-DPB1*04:01 and PR3_225–239 initiate an immune response. Autoreactive T cells specifically recognized PR3_225–239 presented by HLA-DPB1*04:01. Although larger studies should validate these findings, the pathobiology may explain the observed increased risk of relapse in our cohort. Moreover, lack of HLA and autoantigen interaction observed during long-term remission signals immunologic nonresponsiveness.