Molecular Mechanisms of Membranous Nephropathy – New Avenues Towards an Individualized Therapy

• Applicant: Dr. Nicola Tomas
• Subject Area: Nephrology
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 405934253

Membranous nephropathy (MN) is an autoimmune renal disease with autoantibodies against proteins expressed on glomerular podocytes such as PLA2R1 and THSD7A. However, the molecular mechanisms that lead to glomerular damage in MN are largely unknown and the mainstay of treatment relies on systemic immunosuppressive therapies. In previous work, we have developed a mouse model of THSD7A-associated MN that allows further investigation of pathogenic events induced by autoantibody binding. In an unbiased approach to decipher pathways of glomerular damage, we will use mass spectrometry to analyze expression profiles of cytoskeletal, focal adhesion, and slit diaphragm as well as podocyte signaling proteins. Specific targets will then be further investigated using immunoblotting and confocal microscopy. Moreover, a major goal of the proposed project is the establishment of an autoimmune model of MN. To this end, mice will be immunized with the THSD7A antigen and evaluated for autoantibody generation and disease development. In case that self-tolerance is not overcome using this approach, several strategies will be applied. An exemplary promising approach to induce autoantibody generation in mice is the adoptive transfer of splenocytes from immunized Thsd7a-/- knockout mice to immunodeficient Rag2-/- knockout mice. Based on the gained pathomechanistic insights and the established new models, we will evaluate innovative, mechanism-directed therapies in preclinical trials. The first strategy here is autoantibody-depletion by means of reengineered therapeutic antibodies. In these therapeutic antibodies, the variable region is replaced by an autoantibody-binding domain and the antibody heavy chain carries mutations that enhance endosomal degradation of the antibody-autoantibody immune complex. Second, we will evaluate efficacy of B cell and plasma cell depletion by interfering with the proteasomal system. Third, we will generate chimeric autoantigen receptor (CAAR) expressing T or NK cells and evaluate whether these cells are capable of killing antigen-specific B cells through the specificity of the B cell receptor. Another important part of the proposed project is the translation of the preclinical findings. We will validate potential new biomarkers for their relevance in human MN using a translational platform and correlate these markers with clinical characteristics and individual disease outcome in our patients. In summary, the proposed project aims to unravel mechanisms of glomerular injury signaling and to develop novel, pathogenesis-based, individualized therapies.

• DFG Programme: Independent Junior Research Groups