Novel ELISA for thrombospondin type 1 domain-containing 7A autoantibodies in membranous nephropathy

Kidney Int. 2019 Mar;95(3):666-679. doi: 10.1016/j.kint.2018.10.024.

Abstract

Autoantibodies against phospholipase A2 receptor 1 (PLA2R1) and thrombospondin type 1 domain-containing 7A (THSD7A) are emerging as biomarkers to classify membranous nephropathy (MN) and to predict outcome or response to treatment. Anti-THSD7A autoantibodies are detected by Western blot and indirect immunofluorescence test (IIFT). Here, we developed a sensitive enzyme-linked immunosorbent assay (ELISA) optimized for quantitative detection of anti-THSD7A autoantibodies. Among 1012 biopsy-proven MN patients from 6 cohorts, 28 THSD7A-positive patients were identified by ELISA, indicating a prevalence of 2.8%. By screening additional patients, mostly referred because of PLA2R1-unrelated MN, we identified 21 more cases, establishing a cohort of 49 THSD7A-positive patients. Twenty-eight patients (57%) were male, and male patients were older than female patients (67 versus 49 years). Eight patients had a history of malignancy, but only 3 were diagnosed with malignancy within 2 years of MN diagnosis. We compared the results of ELISA, IIFT, Western blot, and biopsy staining, and found a significant correlation between ELISA and IIFT titers. Anti-THSD7A autoantibodies were predominantly IgG4 in all patients. Eight patients were double positive for THSD7A and PLA2R1. Levels of anti-THSD7A autoantibodies correlated with disease activity and with response to treatment. Patients with high titer at baseline had poor clinical outcome. In a subgroup of patients with serial titers, persistently elevated anti-THSD7A autoantibodies were observed in patients who did not respond to treatment or did not achieve remission. We conclude that the novel anti-THSD7A ELISA can be used to identify patients with THSD7A-associated MN and to monitor autoantibody titers during treatment.

Keywords: ELISA; THSD7A; clinical outcome; malignancy; membranous nephropathy; sex.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Autoantibodies / analysis*
  • Autoantibodies / immunology
  • Biomarkers / analysis
  • Biopsy
  • Drug Monitoring / methods
  • Enzyme-Linked Immunosorbent Assay / methods
  • Feasibility Studies
  • Female
  • Glomerulonephritis, Membranous / diagnosis*
  • Glomerulonephritis, Membranous / drug therapy
  • Glomerulonephritis, Membranous / immunology
  • HEK293 Cells
  • Humans
  • Immunosuppressive Agents / therapeutic use*
  • Male
  • Middle Aged
  • Receptors, Phospholipase A2 / immunology
  • Retrospective Studies
  • Sensitivity and Specificity
  • Thrombospondins / immunology*
  • Time Factors
  • Treatment Outcome

Substances

  • Autoantibodies
  • Biomarkers
  • Immunosuppressive Agents
  • PLA2R1 protein, human
  • Receptors, Phospholipase A2
  • Thrombospondins
  • thrombospondin type I domain containing 7A protein, human