CE17 - Recherche translationnelle en santé

PLA2R negative membranous nephropathies: antigens, models and patients – SeroNegMN

Submission summary

Although membranous nephropathy (MN) is a rare auto-immune disease (incidence, 1/100 000), it is the commonest cause of nephrotic syndrome in adults. Since 2009, the identification of the podocyte antigen M-type phospholipase A2 receptor 1 (PLA2R), has induced major changes in the standard of care thanks to antibody measurement. However in about 20 % of patients, the nature of the antigen remained elusive. In 2019, we identified exostosin-1/exostosin-2 (EXT1/2) and neural EGF-like-1 (NELL-1) proteins, and in 2020, Semaphorin 3B (Sema3B) mostly in children. Our main objectives are: 1) to unravel the mechanism of EXT1/2-, NELL-1 and Sema3B-associated MN, 2) to identify the remaining antigens in PLA2R-negative MN during adulthood and childhood, 3) to set up specific assays for circulating antibodies to improve diagnosis, monitoring and patient care.
The project will be conducted by 2 Partners. Partner 1 (Pierre Ronco) has described the first MN antigen (neutral endopeptidase) and 4 additional antigens and translated their findings to the bedside. Partner 2 (Emmanuelle Plaisier) has considerable expertise in the care of patients with rare forms of nephrotic syndrome, including MN. The partners in Europe and at Mayo Clinic (Sanjeev Sethi) will ensure a large recruitment of patients including 2270 with primary MN (700 PLA2R-negative), 530 with lupus class- V, and 105 children.
The project will be organized in 4 workpackages to which both Partners will contribute experimentally (P1) and clinically (P2) and use cutting-edge technology such as mass spectrometry on tissue and imaging mass cytometry (IMC).
WP1: Further characterization of EXT1/2-associated MN and pathophysiological mechanisms
These studies will determine whether EXT1/2 is an antigen or a biomarker and the exact prevalence of EXT1/2 among class V membranous lupus nephritis. They will include:
• Fine mapping of EXT1/EXT2 in podocytes and immune deposits using high-resolution confocal microscopy and IMC;
• Characterization of reactivity of IgG eluted from laser microdissected glomeruli and of deposited EXT1/EXT2 by gel analysis and MS searching for a neo-epitope;
• In vitro studies of urinary podocytes isolated from patients;
• Development of an experimental model in rodent;
• Immunohistochemistry studies of lupus nephropathies and clinical correlations.
WP2: Further characterization of NELL-1 associated MN and pathophysiological mechanisms
These studies will give insight into the pathogenesis and determine the prevalence of cancer. They will include:

• Fine mapping of NELL-1 in podocytes by confocal microscopy and IMC;
• Sequencing NELL-1 gene in tumoral tissue in cancer-associated MN, searching for mutations altering antigenicity;
• Development of an experimental model of cancer-related MN;
• Prevalence studies of cancer in NELL-1 associated MN. .

WP3: Identification of novel antigens
These studies will further investigate the role of Sema3B and chase the antigens responsible for the remaining cases of MN.
• The following steps will be followed: fine mapping of Sema3B in podocytes, in vitro studies, epidemiology of Sema3B associated MN;
• New antigens in "primary" MN and membranous lupus nephritis will be identified by laser microdissection of glomeruli followed by MS (collaboration with S. Sethi), imaging and immunopathological studies.

WP4: Development of assays for circulating antibodies

• We will develop sensitive and quantitative methods including dot blots and ELISA.
• These assays will be scaled up by the EUROIMMUN company.

The scientific, medical, societal and economic impacts of this project are quite substantial in term of i) new approaches for the investigation of organ-specific auto-immune disease, ii) improved diagnosis and monitoring, including in children, iii) interactions with the general public and Patients' associations, and iv) valorization.

Project coordination

Pierre RONCO (Maladies Rénales Fréquentes et Rares : des Mécanismes Moléculaires à la Médecine Personnalisée)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

UMR_S1155 Maladies Rénales Fréquentes et Rares : des Mécanismes Moléculaires à la Médecine Personnalisée
AP-HP Assistance Publique-Höpitaux de Paris, Day hospital/CRMR, Tenon hospital
Charles University, Department of Nephrology, Prague,
Medical University Vienna, Department of Medicine III, Division of Nephrology and Dialysis
Mayo Clinic / Department of Laboratory Medicine and Pathology
Medical University Vienna, University Department of Paediatrics and Adolescent Medicine, Division of Paediatric Nephrology and Gastroenterology
Ospedale Pediatrico Bambino Gesù, IRCCS / Renal Diseases Research Unit, Genetics and Rare Diseases Research Division
Cliniques universitaires Saint-Luc / Département de Néphrologie
Radboud Institute for Health Sciences, Department of Nephrology, Radboud

Help of the ANR 439,995 euros
Beginning and duration of the scientific project: December 2020 - 36 Months

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