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Abstract: TH-PO602

Characterization of the Immune-Dominant Region on the CysR Domain of Phospholipase A2 Receptor 1 (PLA2R1) Targeted by Autoreactive Memory B Cells

Session Information

Category: Glomerular Diseases

  • 1402 Glomerular Diseases: Clinical, Outcomes, and Therapeutics

Authors

  • Reinhard, Linda, III. Department of Medicine, University Medical Center Hamburg Eppendorf, Hamburg, Germany
  • Montagner, Sara, Novartis AG, Basel, Basel-Stadt, Switzerland
  • Marchant, Martine, Novartis AG, Basel, Basel-Stadt, Switzerland
  • Zhou, Zheng, Novartis AG, Basel, Basel-Stadt, Switzerland
  • Catalano, Marco, 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, Germany
Background

Membranous nephropathy (MN) is caused by PLA2R1-ab in 70-80% of patients. The mechanisms how this highly specific and persistent autoreactive memory response is generated in these patients, remain unclear and all current treatment options for MN are unspecific.

Methods

Using ELISA and Western Blot, the isotypes, affinity and amount of PLA2R1-ab in patients with MN were studied. Circulating memory PLA2R1-specific B cells were isolated from patients with PLA2R1-induced MN and after cloning of the B cell receptors, monoclonal human PLA2R1-ab (PLA2R1-mAb) were produced and used to dissect the epitope binding site. Using inhibition assays, we studied the relevance of this epitope for ab binding and complement activation.

Results

In a cohort of 105 patients with PLA2R1-induced MN, we detected a high affinity IgG4-dominated immune response with expansion of IgG4 memory B cells and plasma blasts. In ca. 1/3 of patients, the PLA2R1 immune response was IgG1-dominant. Four of the five produced human PLA2R1-mAb recognized an overlapping epitope patch on the CysR domain, while the last mAb bound to the CTLD1 domain. PLA2R1-mAb show high affinity (0.2 pM), used different heavy- and light-chain variable region genes and carried high levels of somatic mutations in complementary-determining regions, consistent with antigenic selection. PLA2R1-mAb showed a strong inhibition of serum PLA2R1-ab binding from patients with PLA2R1-induced MN both in vitro and in vivo in a transgenic PLA2R1-specific rat model. In patients with circulating CTLD1-ab, the combination of CysR- and CTLD1-mAb showed an additive inhibitory effect of 85% in vitro and 75% in vivo. PLA2R1-ab positive sera from patients with PLA2R1-induced MN showed strong complement activation in an in vitro complement activity assay. In a competition assay, the PLA2R1-mAb led to abrogation of complement activation by the patients’ sera, pointing toward a key functional role for the identified PLA2R1 epitopes in patients with MN.

Conclusion

The detailed characterization of the immune dominant epitope patch on the CysR domain of PLA2R1 targeted by PLA2R1 autoreactive memory B cells will facilitate the development of treatment strategies aimed at depletion of PLA2R1 specific memory B cells and plasma blasts.

Funding

  • Clinical Revenue Support