title: Deglycosylation of myeloperoxidase uncovers its novel antigenicity.
abstract: Myeloperoxidase (MPO) is a common target antigen of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis and is recognized in one-third of patients with anti-glomerular basement membrane (GBM) disease. Our previous study identified over 60% of patients with anti-GBM disease recognizing linear peptides of MPO heavy chain. Here we tested whether aberrant glycosylation alters MPO antigenicity through exposure of neo-epitopes on MPO molecules. Atypical glycosylated MPO molecules, including all possible glycosylation types, were prepared by exoglycosidase and endoglycosidase treatments. Antibodies were detected from the sera of 40 patients with anti-GBM disease without the coexistence of MPO-ANCA. Circulating antibodies against aberrant glycosylated MPO existed in 21 of these patients. Non-glycan MPO and MPO with only N-acetylglucosamine had high frequencies of recognition (16 and 15 patients, respectively). Antibodies binding to aberrant glycosylated MPO could not be inhibited by intact MPO or GBM antigen. When applied to ethanol-fixed neutrophils from normal individuals, these antibodies yielded a typical cytoplasmic staining pattern (c-ANCA). Antigen specificity was detected in 90% of the antibodies using five peptides containing one of the five N-glycosylation sites each, mostly on N323, N355, and N391. The antibodies were restricted to IgG1 subclass, could activate complement, and induce neutrophil degranulation in vitro. Thus, aberrant glycosylated MPO exposed neo-epitopes and was recognized by half of the patients with anti-GBM disease. Their antibodies possessed pathogenic characteristics and may be associated with kidney injury.
authors.affiliation: Renal Division, Peking University First Hospital, Institute of Nephrology, Peking University, Beijing, China; Key Laboratory of Renal Disease, Ministry of Health of China, Beijing, China; Key Laboratory of Chronic Kidney Disease Prevention and Treatment, Ministry of Education of China, Beijing, China; Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China; Peking-Tsinghua Center for Life Sciences, Beijing, China.
authors.forename: Jun-Tao
authors.initials: JT
authors.lastname: Yu
authors.affiliation: Renal Division, Peking University First Hospital, Institute of Nephrology, Peking University, Beijing, China; Key Laboratory of Renal Disease, Ministry of Health of China, Beijing, China; Key Laboratory of Chronic Kidney Disease Prevention and Treatment, Ministry of Education of China, Beijing, China.
authors.forename: Jian-Nan
authors.initials: JN
authors.lastname: Li
authors.affiliation: Renal Division, Peking University First Hospital, Institute of Nephrology, Peking University, Beijing, China; Key Laboratory of Renal Disease, Ministry of Health of China, Beijing, China; Key Laboratory of Chronic Kidney Disease Prevention and Treatment, Ministry of Education of China, Beijing, China.
authors.forename: Jia
authors.initials: J
authors.lastname: Wang
authors.affiliation: Renal Division, Peking University First Hospital, Institute of Nephrology, Peking University, Beijing, China; Key Laboratory of Renal Disease, Ministry of Health of China, Beijing, China; Key Laboratory of Chronic Kidney Disease Prevention and Treatment, Ministry of Education of China, Beijing, China.
authors.forename: Xiao-Yu
authors.initials: XY
authors.lastname: Jia
authors.affiliation: Renal Division, Peking University First Hospital, Institute of Nephrology, Peking University, Beijing, China; Key Laboratory of Renal Disease, Ministry of Health of China, Beijing, China; Key Laboratory of Chronic Kidney Disease Prevention and Treatment, Ministry of Education of China, Beijing, China. Electronic address: cuizhao@bjmu.edu.cn.
authors.forename: Zhao
authors.initials: Z
authors.lastname: Cui
authors.affiliation: Renal Division, Peking University First Hospital, Institute of Nephrology, Peking University, Beijing, China; Key Laboratory of Renal Disease, Ministry of Health of China, Beijing, China; Key Laboratory of Chronic Kidney Disease Prevention and Treatment, Ministry of Education of China, Beijing, China; Peking-Tsinghua Center for Life Sciences, Beijing, China.
authors.forename: Ming-Hui
authors.initials: MH
authors.lastname: Zhao
mesh_terms: D000918:Antibody Specificity; D001323:Autoantibodies / Q000097:blood*; D001666:Binding Sites, Antibody; D016022:Case-Control Studies; D015550:Cell Degranulation; D003167:Complement Activation; D000939:Epitopes; D005921:Glomerulonephritis / Q000097:blood / Q000175:diagnosis / Q000201:enzymology / Q000276:immunology*; D006031:Glycosylation; D006470:Hemorrhage / Q000097:blood / Q000175:diagnosis / Q000201:enzymology / Q000276:immunology*; D006801:Humans; D008171:Lung Diseases / Q000097:blood / Q000175:diagnosis / Q000201:enzymology / Q000276:immunology*; D009504:Neutrophils / Q000201:enzymology / Q000276:immunology; D009195:Peroxidase / Q000276:immunology* / Q000378:metabolism*; D011485:Protein Binding; D011499:Protein Processing, Post-Translational
chemical_list: D001323:Autoantibodies; D000939:Epitopes; D009195:Peroxidase
keywords: ANCA; anti-GBM disease; antigenicity; glycosylation; myeloperoxidase