P3: Isolation and characterisation of human GPCR autoantibodies

• Applicants: Privatdozentin Dr. Anke Fähnrich; Professor Dr. Thomas Krey; Privatdozentin Dr.-Ing. Antje Müller
• Subject Area: Rheumatology ; Immunology ; Clinical Immunology and Allergology
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 552470287

Autoantibodies targeting G protein-coupled receptors (GPCR) can serve as valuable biomarkers of cardiovascular diseases and act as allosteric modulators of their respective receptors. These autoantibodies are thought to play a significant role in the pathophysiology of vascular diseases like systemic sclerosis or atherosclerosis. However, detecting, identifying and characterizing these effector autoantibodies remain a challenge. To discern receptor-specific from -unspecific effects, monoclonal antibodies against GPCR represent an invaluable tool. Recent advancements in single-cell sequencing and B cell isolation techniques have enabled the isolation of antigen-specific B cells, and recombinant production of the corresponding immunoglobulins, for example as IgG. These steps represent an elegant state-of-the-art approach to isolate and characterize monoclonal antigen-specific antibodies and will thus be utilized in this project. Our proposal aims to i) identify and ii) characterize monoclonal autoantibodies targeting CXCR4 as well as angiotensin II type 1 receptor (AT1R) from peripheral blood and/or tissue of patients with pulmonary arterial hypertension and atherosclerosis related to systemic sclerosis. We will implement two complementary strategies for isolating and characterizing human monoclonal GPCR autoantibodies. We will isolate CXCR4-specific antibody sequences from patient and healthy donor peripheral blood mononuclear cells by multi-colour flow cytometry using fluorophore-labelled CXCR4 peptidiscs followed by single B cell sequencing. In parallel, we will isolate antibody sequences of AT1R-specific B cells from tissue-near and tissue samples of systemic sclerosis and atherosclerosis patients by single-cell sequencing and spatial transcriptomics, followed by bioinformatic similarity analysis with known AT1R antibody sequences. Antibody candidates will be recombinantly produced as intact IgG or as Fab / single chain variable fragments and tested for binding of their respective antigen. Promising autoantibodies recognizing CXCR4 or AT1R will be further functionally and biochemically characterized. To characterize the corresponding B cells producing these autoantibodies, single cell transcriptomic data will be mapped to reference B cell data sets. We envision our project to isolate interesting monoclonal autoantibodies targeting the two GPCR and to provide detailed insights into interactions of these monoclonal autoantibodies and their cognate receptors, thereby modulating its functions in a (patho-)physiological manner.

• DFG Programme: Research Units
• Subproject of: FOR 5930: Autoantibodies against G protein-coupled receptors as drivers of vasculopathies (AbsInVasc)
• International Connection: United Kingdom
• Cooperation Partner: Professor Dmitry Veprintsev