Kidney Week

Abstract: PO1468

Netrin G1 Is a Novel Target Antigen in Membranous Nephropathy

Session Information

• Glomerular Diseases: Immunology and Inflammation in IgANP, C3GP, TMA, and Nephrotic Diseases
  November 04, 2021 | Location: On-Demand, Virtual Only
  Abstract Time: 10:00 AM - 12:00 PM

Category: Glomerular Diseases

• 1202 Glomerular Diseases: Immunology and Inflammation

Authors

• Reinhard, Linda, Universitatsklinikum Hamburg-Eppendorf, Hamburg, Hamburg, Germany

Linda Reinhard, PhD

• Machalitza, Maya, Universitatsklinikum Hamburg-Eppendorf, Hamburg, Hamburg, Germany

Maya Machalitza,

• Wiech, Thorsten, Universitatsklinikum Hamburg-Eppendorf, Hamburg, Hamburg, Germany

Thorsten Wiech,

• Ferru, Nicoletta, Universitatsklinikum Hamburg-Eppendorf, Hamburg, Hamburg, Germany

Nicoletta Ferru,

• Hoxha, Elion, Universitatsklinikum Hamburg-Eppendorf, Hamburg, Hamburg, Germany

Elion Hoxha,

• Stahl, Rolf A., Universitatsklinikum Hamburg-Eppendorf, Hamburg, Hamburg, Germany

Rolf A. Stahl,

Background

PLA₂R is the main target antigen in membranous nephropathy (MN), representing 70-80% of cases. In the past years a number of confirmed, or potential target antigens, such as THSD7A, NELL1, HTRA1, Sema3B and PCDH7 have been reported, showing that the pathophysiology of PLA₂R-antibody (ab) negative MN represents a diverse repertoire of antigens with low frequency.

Methods

Western blot (WB) analysis was used to identify sera of MN patients with IgG4 specific signals binding to antigens in the membrane fraction of human glomerular extracts (HGE). Only sera which were negative for PLA₂R- and THSD7A-ab were used. IgG4-ab from the serum of an index patient was purified and used to immunoprecipitate the corresponding target antigen from the membrane fraction of HGE. The purified antigen in the eluate was identified by mass spectrometry. Recombinant protein was used to confirm the reactivity of patient sera by WB and identify other patients in a large cohort of MN patients. The deposition of the target antigen in the glomerular immune deposits was confirmed by immunohistochemistry (IHC).

Results

Using this approach, we identified Netrin G1 (NTNG1) as a novel target antigen in MN. NTNG1 is a 50 kDa secreted glycoprotein, which is attached to the cell surface by a GPI anchor (Fig. A, B). We identified NTNG1-ab in two out of 110 PLA₂R- and THSD7A-ab negative MN patients. A follow-up of 5 years was available for the index patient. During this time, both proteinuria and NTNG1-ab persisted while renal function was stable. Further, a granular positivity for NTNG1 along the glomerular capillary wall was confirmed in the kidney biopsy by IHC (Fig. C), but was undetectable in the negative control (PLA₂R-ab positive MN).

Conclusion

We report NTNG1 as a novel target antigen in MN, occurring with low frequency and expanding the repertoire of antigens in patients with MN. Its prevalence, pathogenetic and clinical roles remain to be defined.

Funding

• Government Support – Non-U.S.