Autoantibodies against Linear Epitopes of Myeloperoxidase in Anti–Glomerular Basement Membrane Disease

Abstract

Background and objectives Approximately 20%-30% of patients with anti-glomerular basement membrane disease present coexisting anti-myeloperoxidase (MPO) autoantibodies. We previously showed the recognition of a linear fragment of the MPO heavy chain N-terminus ( 1 H, MPO 279-409 ) in plasma from most double-positive patients. Herein, we investigated the frequency of autoantibodies against overlapping 1 H-derived linear peptides in plasma from patients with anti-glomerular basement membrane disease.Design, setting, participants, & measurements We synthesized 13 overlapping linear peptides ( 1 H-1 to 1 H-13) covering MPO . We retrospectively collected plasma samples from 67 patients with anti-glomerular basement membrane disease from 1996 to 2012, and we screened them for IgG autoantibodies by ELISA using intact human MPO and the overlapping peptides as antigens, and we further investigated the clinical significance. Autoantibody binding to the linear MPO structure was confirmed by Western blotting.Results We followed up the 67 patients until 2015, with a median follow-up time of 10.0 (2.3-36.0) months, and 56 ESRD events occurred among the 67 patients with follow-up data. Plasma from 23.9% (16) of the patients recognized intact human MPO, whereas 62.7% (42) plasma samples recognized MPO 279-409 linear peptides. Of the 13 linear peptides, 1 H-4 (44.8%, 30 patients) and 1 H-12 (40.3%, 27 patients) exhibited the highest recognition frequencies. Patients with autoantibodies against 1 H-11 or 1 H-12 (MPO 371-400 ) were older (46.1618.8 versus 34.1616.6 years; P,0.01), had higher serum creatinine upon diagnosis (median 7.8 mg/dl, interquartile range 4.9-12.6 mg/dl versus median 5.4 mg/dl, interquartile range 2.4-7.3 mg/dl; P=0.02), and had a higher probability of progressing to ESRD; however, multivariate Cox regression analysis showed that 1 H-11 or 12 reaction was not an independent risk factor for renal failure (hazard ratio, 1.2; 95% confidence interval, 0.8 to 2.8; P=0.19).Conclusions Autoantibodies against linear peptides of MPO can be detected in the majority of patients with antiglomerular basement membrane disease, and several are associated with disease severity. The potential common pathogenic mechanism between anti-glomerular basement membrane antibodies and anti-MPO autoantibodies in anti-glomerular basement membrane disease requires further investigation.

Patients double-seropositive for ANCA and anti-GBM antibodies have varied renal survival, frequency of relapse, and outcomes compared to single-seropositive patients

“…The recent observation that a high proportion of patients with anti-GBM disease have autoantibodies reactive to linear epitopes of MPO might support this hypothesis, as it suggests reactivity to conformational epitopes might arise as a consequence of inter- and intramolecular epitope spreading initiated by anti-GBM disease. 33 Whether additional environmental or genetic factors predispose to forming both antibodies is unclear. The genetic associations of both anti-GBM disease and AAV are increasingly well-described, 34 , 35 and both conditions have strong associations with certain HLA genes.…”

Anti-Glomerular Basement Membrane Disease

“…Conversely, a recent study found that up to 60% of anti-GBM cases also had antibodies directed against linear epitopes of MPO, versus 24% recognizing intact MPO. The authors hypothesize that MPO-ANCA recognizing linear and conformational epitopes may arise sequentially, via a process of inter-and intramolecular epitope spreading (87). We recently analyzed the outcomes of a large cohort of these "doublepositive" patients from four centers in Europe, and found that they experience the early morbidity and mortality of anti-GBM disease, with severe kidney and lung disease at presentation, requiring aggressive immunosuppressive therapy and plasma exchange (88).…”

Successful treatment of steroid-refractory double-positive ANCA and anti-GBM disease with a combination of plasma exchange and immunosuppression: A case report and literature review

“…Prior cases of double-positive disease have demonstrated that double-positive patients with MPO-ANCA positivity have worse prognosis than double-positive patients with PR3-ANCA positivity: the mortality of double-positive patients with MPO-ANCA and PR3-ANCA are 33% (18 of 55) and 22% (4 of 18), respectively. Of note, a recent study showed that the majority (63%, 42 of 67) of patients with anti-GBM disease are positive for autoantibodies against the linear fragment of the MPO heavy chain N-terminus, whereas only 24% (16 of 67) of them were positive for intact MPO [ 17 ]. Furthermore, several autoantibodies against the MPO linear fragment are associated with disease severity, including high serum creatinine levels and high probability of progression to end-stage renal disease.…”