Preferential HLA-DRB1*11–dependent presentation of CUB2-derived peptides by ADAMTS13-pulsed dendritic cells

Abstract

Key Points• ADAMTS13 derived peptides presented on HLA-DR; implications for acquired TTP.• CUB2 domain peptide binds to risk-allele HLA-DRB1*11.Autoantibodies directed against ADAMTS13 prohibit the processing of von Willebrand factor multimers, initiating a rare and life-threatening disorder called acquired thrombotic thrombocytopenic purpura (TTP). Recently, HLA-DRB1*11 has been identified as a risk factor for the development of acquired TTP. Here, we identified ADAMTS13-derived peptides presented on MHC class II alleles from 17 healthy donors. Dendritic cells from a panel of both HLA-DRB1*11-positive and -negative donors were pulsed with ADAMTS13, and the HLA-DR-presented peptide repertoire was analyzed by mass spectrometry. Interestingly, at low antigen concentrations, HLA-DRB1*11-or DRB1*03-positive donors presented a limited number of CUB2-derived peptides. Pulsing of dendritic cells using higher concentrations of ADAMTS13 resulted in the presentation of larger numbers of ADAMTS13-derived peptides by both HLA-DRB1*11-positive and -negative donors. Although the presented peptides were derived from several ADAMTS13 domains, inspection of the peptide profiles revealed that CUB2 domainderived peptides were presented with a higher efficiency when compared with other peptides. Remarkably, dendritic cells from DRB1*11 donors pulsed with higher concentrations of ADAMTS13-present derivatives of a single CUB2-derived peptide. We hypothesize that functional presentation of CUB2-derived peptides on HLA-DRB1*11 contributes to the onset of acquired TTP by stimulating low-affinity, self-reactive CD41 T cells. (Blood. 2013;121(17):3502-3510) Introduction Acquired thrombotic thrombocytopenic purpura (TTP) is a rare and life-threatening disorder characterized by the production of autoantibodies directed toward ADAMTS13, a plasma metalloprotease responsible for the cleavage of ultra-large von Willebrand factor (UL-VWF) multimers.1-3 Deficiency of ADAMTS13 causes the accumulation of UL-VWF strings on the surface of endothelial cells of the vessel wall and in the circulation. 4 Prolonged exposure of UL-VWF strings on the surface of endothelial cells promotes platelet adhesion, leading to low platelet counts and microvascular thrombosis. 5,6 The majority of the inhibitory anti-ADAMTS13 antibodies that develop in patients affected by acquired TTP targets a single epitope composed of Arg568, Phe592, Arg660, Tyr661, and Tyr665 on the outer surface of the spacer domain. This exposed region is crucial for binding of ADAMTS13 to unfolded VWF A2 domain.7-9 Antibodies targeting the CUB 1-2 and TSP2-8 regions of ADAMTS13 have also been detected in the plasma of several patients with acquired TTP. 10,11 The pathogenic role of anti-TSP2-8 and anti-CUB1-2 is still unclear. The carboxy-terminal ADAMTS13 TSP2-8 and CUB 1-2 regions not only modulate processing of VWF under flow 12-14 but are also necessary for the binding of ADAMTS13 to endothelial cells. 15A number of studies have shown that anti-ADAMTS13 antibodies detected in the plasma ...

The class I scavenger receptor CD163 promotes internalization of ADAMTS13 by macrophages

“…17 These findings reveal a critical role for DCs in the initiation of CD4 1 T-cell responses to ADAMTS13 in patients with acquired TTP.…”

Identification of N‐linked glycosylation and putative O‐fucosylation, C‐mannosylation sites in plasma derived ADAMTS13

“…Several studies have shown that protein glycans may be crucial also for T-cell recognition of autoantigens in autoimmune disorders [10]. Previously we have shown that antigen presenting cells derived from HLA-DRB1*11-positive individuals present a CUB2 domain derived peptide FINVAPHARIA (residues 1327-1338) [27]. Since HLA-DRB1*11 is considered to be a risk factor for the development of acquired TTP [28][29][30] functional presentation of this CUB2 domain-derived peptide might contribute to the onset of acquired TTP [27].…”

“…Previously we have shown that antigen presenting cells derived from HLA-DRB1*11-positive individuals present a CUB2 domain derived peptide FINVAPHARIA (residues 1327-1338) [27]. Since HLA-DRB1*11 is considered to be a risk factor for the development of acquired TTP [28][29][30] functional presentation of this CUB2 domain-derived peptide might contribute to the onset of acquired TTP [27]. Presentation of the FINVAPHARIA peptide (residues 1327-1338) may potentially be affected by the presence of an N-linked glycan at N1354.…”

“…Presentation of the FINVAPHARIA peptide (residues 1327-1338) may potentially be affected by the presence of an N-linked glycan at N1354. Moreover, non-DRB1*11 donors present a second CUB domain peptide ASYILIRDTHSLRTTA (residues 1355-1370) which is right adjacent to N1354 [27]. This raises the possibility that differential glycosylation at N1354 might contribute to the onset of acquired TTP in patients capable of presenting such peptides.…”

CD4+ T cells from patients with acquired thrombotic thrombocytopenic purpura recognize CUB2 domain-derived peptides

“…[9][10][11] We have explored the repertoire of ADAMTS13 peptides presented on major histocompatibility complex class II (MHC-II). 12 Pulsing of dendritic cells from healthy donors showed preferential presentation of the CUB2 domain-derived peptide FINVAPHAR on HLA-DRB1*11. 12 In addition, we observed presentation of a CUB2 domain peptide with the core sequence ASYILIRD on antigen-presenting cells derived from HLA-DRB1*03-positive individuals.…”