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Abstract: SA-PO956

Monoclonal Characterization of Autoreactive PLA2R1 Antibody Responses in Membranous Nephropathy (MN)

Session Information

Category: Glomerular Diseases

  • 1402 Glomerular Diseases: Clinical, Outcomes, and Trials

Authors

  • Reinhard, Linda, III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Hamburg, Germany
  • Montagner, Sara, Novartis AG, Basel, Basel-Stadt, Switzerland
  • Marchant, Martine, Novartis AG, Basel, Basel-Stadt, Switzerland
  • Iazeolla, Mariavittoria, Novartis AG, Basel, Basel-Stadt, Switzerland
  • Lavoisier, Alexandra, Novartis AG, Basel, Basel-Stadt, Switzerland
  • Traggiai, Elisabetta, Novartis AG, Basel, Basel-Stadt, Switzerland
  • Hoxha, Elion, III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Hamburg, Germany
Background

Membranous nephropathy (MN) is caused by circulating antibodies, which in 70-80% of cases are directed against PLA2R1. The CysR domain of the PLA2R1 is the immune dominant domain and all patients with PLA2R1-induced MN exhibit antibodies against this domain of the protein. Today, all treatment options for MN are unspecific concerning the molecular disease pathogenesis.

Methods

We isolated PBMCs from patients with PLA2R1-induced MN. Using tagged PLA2R1, PLA2R1-specific B cells were isolated and the corresponding B cell receptors were cloned, in order to produce monoclonal human PLA2R1-antibodies (PLA2R1-mAb) corresponding to autoantibodies from patients with MN. The inhibitory potential of these PLA2R1-mAb for human PLA2R1-antibody binding to PLA2R1 was tested in vitro by competition ELISA using 60 sera from patients with PLA2R1-induced MN and in vivo in a rat model, which expresses the human PLA2R1 (hPLA2R1) specifically on podocytes.

Results

In total, four PLA2R1-mAb were cloned from PLA2R1-specific B cells from patients with MN and bound epitopes on the CysR domain. Every PLA2R1-mAb was tested for its inhibitory capability using 60 PLA2R1-antibody positive sera from patients with PLA2R1-induced MN. The PLA2R1-mAb inhibited the PLA2R1-antibody binding capacity of the patient sera by 45% - 96%. The inhibitory effect of each PLA2R1-mAb was independent of the PLA2R1-antibody level of the sera; i.e. the PLA2R1-mAb with the highest inhibition of 96% exhibited a PLA2R1-antibody inhibition of 95%, 96% and 96%, when sera with PLA2R1-anitbody level of 40-79 U/ml, 80-250 U/ml and > 250 U/ml were used, respectively. PLA2R1-mAb were injected into a rat with podocyte-specific hPLA2R1-expression prior to passive transfer of human PLA2R1-antibodies from patients with MN. This PLA2R1-mAb led to an inhibition of PLA2R1-antibody binding by 80% in vivo.

Conclusion

We report for the first time the characterization of human monoclonal antibodies specific for PLA2R1 derived from memory B cells of MN patients. Cloned autoantibodies showed strong inhibition of PLA2R1 autoantibody binding both in vitro and in vivo, opening the possibility of a potential PLA2R1 epitope specific treatment.

Funding

  • Commercial Support – Novartis, Basel, Switzerland