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Kidney Week

Abstract: SA-PO835

Identification of Anti-Peroxidasin Antibodies in Human and Experimental Glomerulonephritis

Session Information

Category: Glomerular Diseases

  • 1401 Glomerular Diseases: From Inflammation to Fibrosis

Authors

  • Costa, Lyndon H., Imperial College London, London, London, United Kingdom
  • Dhutia, Amrita, Imperial College London, London, London, United Kingdom
  • Pusey, Charles D., Imperial College London, London, London, United Kingdom
  • McAdoo, Stephen Paul, Imperial College London, London, London, United Kingdom
  • Prendecki, Maria, Imperial College London, London, London, United Kingdom
Background

Peroxidasin (Pxdn) is an extracellular matrix (ECM) haem peroxidase critical for forming sulfilimine bonds which crosslink type 4 collagen. Sulfilimine bonds contribute to structural integrity and stability of the ECM and act to sequester the Goodpasture antigen giving it immune privilege. Autoantibodies to peroxidasin have previously been identified in patients with anti-glomerular basement (GBM) disease and MPO-ANCA associated vasculitis (MPO-AAV).

Methods

Circulating anti-Pxdn IgG was measured by ELISA in serum from patients (anti-GBM disease, AAV, and healthy volunteers) and rats with experimental autoimmune glomerulonephritis (EAG), an autoimmune model of anti-GBM disease. For coating, recombinant rat peroxidasin was expressed in HEK293 cells and purified; human peroxidasin was from a commercial source (Origene). Antibody specificity was confirmed using immunoblotting. Expression of Pxdn, deposited IgG, and smooth muscle actin (SMA) in kidney tissue was assessed by indirect immunofluorescence (IF).

Results

Circulating anti-Pxdn IgG antibodies were detected in 29.4% of (15/51) patients with anti-GBM disease, 14.2% (2/14) of patients with active MPO-AAV, and 0% (0/6) patients with active PR3-AAV (Fig 1A). Circulating anti-Pxdn IgG antibodies were detectable at day 28 after induction of EAG (peak glomerular injury) in 86.7% (13/15) of rats (Fig 1B). Anti-PXDN antibodies were detectable at low titre from day 18 suggesting they may arise later than anti-α3(IV)NC1 antibodies which are detected from day 7. IF staining of kidney tissue in EAG identified Pxdn at areas of glomerular injury and crescent formation. Pxdn co-localised with SMA but not with deposited rat IgG (Fig 1C).

Conclusion

We confirm the presence of anti-Pxdn antibodies in patients with glomerular disease. In EAG, anti-Pxdn antibodies were evident after the development of antibodies against α3(IV)NC1 and glomerular Pxdn expression was only detected after disease onset: thus we suggest anti-Pxdn antibodies may arise by a process of inter-molecular epitope spreading in the diseased glomerulus.