Pathogenicity of Human Anti-PLA2R1 Antibodies in Minipigs: A Pilot Study

Abstract

Significance Statement Membranous nephropathy (MN) is an autoimmune kidney disease characterized by immune deposits in the glomerular basement membrane. Circulating anti-phospholipase A2 receptor 1 (PLA2R1) antibodies are detectable in 70%–80% of patients with MN, but experimental evidence of pathogenicity has been lacking. This study demonstrates the pathogenicity of human anti-PLA2R1 antibodies in minipigs, a model for MN that intrinsically expresses PLA2R1 on podocytes. After passive transfer of human anti-PLA2R1 antibody-containing plasma from patients with PLA2R1-associated MN to minipigs, antibodies were detected in the minipig glomeruli, but not in response to plasma from healthy controls. The minipigs developed histomorphological characteristics of MN, local complement activation in the glomeruli, and low-level proteinuria within 7 days, showing that human anti-PLA2R1 antibodies are pathogenic. Background Primary membranous nephropathy (MN) is an autoimmune kidney disease in which immune complexes are deposited beneath the epithelium in the glomeruli. The condition introduces a high risk for end-stage kidney disease. Seventy percent to 80% of patients with MN have circulating antibodies against phospholipase A2 receptor 1 (PLA2R1), and levels correlate with treatment response and prognosis. However, experimental evidence that human anti-PLA2R1 antibodies induce MN has been elusive. Methods In passive transfer experiments, minipigs received plasma or purified IgG from patients with PLA2R1-associated MN or from healthy controls. Anti-PLA2R1 antibodies and proteinuria were monitored using Western blot, ELISA, and Coomassie staining. Kidney tissues were analyzed using immunohistochemistry, immunofluorescence, electron microscopy, and proteomic analyses. Results Minipigs, like humans, express PLA2R1 on podocytes. Human anti-PLA2R1 antibodies bound to minipig PLA2R1 in vitro and in vivo. Passive transfer of human anti-PLA2R1 antibodies from patients with PLA2R1-associated MN to minipigs led to histological characteristics of human early-stage MN, activation of components of the complement cascade, and low levels of proteinuria. We observed development of an autologous, later phase of disease. Conclusions A translational approach from humans to minipigs showed that human anti-PLA2R1 antibodies are pathogenic in MN, although in the heterologous phase of disease only low-level proteinuria developed.