Abstract: TH-OR029

Ubiquitin Carboxyl-Terminal Hydrolase L1 Is a Podocyte Target of IgG Antibodies in Idiopathic Nephrotic Syndrome (INS)

Session Information

Category: Glomerular

  • 1001 Glomerular: Basic/Experimental Immunology and Inflammation

Authors

  • Deschênes, Georges, Hospital Robert Debre, Paris, France
  • Jamin, Agnes, INSERM U1149 & ELR8252 CNRS, 75018 Paris, France
  • Berthelot, Laureline, INSERM U699, Paris, France
  • Monteiro, Renato C., Bichat Medical School, Paris, France
Background

The efficiency of B cell-depleting treatments highlights the involvement of B cells in INS. This study searched for identifying antibodies (Abs) directed against podocytes in patients with INS.

Methods

The study was performed using a biobank including 86 patients sampled at various stages of INS and 76 controls. Fractions of plasma obtained by size exclusion chromatography and tested on cultured podocyte adhesion; specificities of IgG Abs contained in the plasma fraction of interest were studied through immunoprecipitation of a podocyte lysate then identification of cognate antigens by liquid chromatography-mass spectrometry.

Results

Cultured podocyte detachment was observed with one specific plasma fraction in 16/34 INS relapsing patients, 1/11 INS patients in remission and 0/25 controls. IgG were isolated from this specific plasma fraction in 3 INS relapsing patients (all detaching cultured podocytes), 3 from the same INS patients in remission (all not detaching cultured podocytes) and in 3 controls, then used to immunoprecipitate a podocyte lysate. Comparative proteomic analysis allowed selecting 5 proteins according to statistical and biological criteria. Specific Abs were tested and only anti-Ubiquitin Carboxyl-Terminal Hydrolase L1 (UCHL1) IgG led to podocyte detachment. Pre-incubation of either anti-UCHL1 IgG Abs or plasma fractions with recombinant UCHL1 prevented podocyte detachment. Plasma levels of anti-UCHL1 IgG Abs were increased in 18/42 relapsing INS patients over the highest level of 38 controls (median=0.20 AU/*g of total IgG;IQ0.15-0.29;range0.07-0.85). For those 18 patients, the level of anti-UCHL1 IgG Abs in 43 samples available at various stage of INS was confirmed to be significantly higher in relapse (n=23;median=1.22AU/µg of total IgG; IQ 0.92-1.90) compared to remission (n=20;median=0.51;IQ 0.33-0.77;p<0.001). In those 18 INS patients, proteinuria correlated with anti-UCHL1 IgG Abs level (n=43,r=0.57,p<0.001).

Conclusion

UCHL1 is involved in the adhesion of cultured podocytes. UCHL1 is a target of circulating IgG Abs in a subset of relapsing INS patients.

Funding

  • Private Foundation Support