Résumé
The CureRA project consists in developing a new generation of immunotherapy for Rheumatoid arthritis (RA) by targeting precisely a rare ACPA+ B cell population, associated with disease severity.Our work aimed first at designing and establishing human B cell lines engineered with constructs enabling expression of membrane-bound or secreted recombinant ACPA similar to the ACPA+ B cells found in RA. Using plasmids encoding various human monoclonal ACPAs we transduced lymphoblastic (LB) and plasmablastic (PB) cell lines and managed to establish different cell lines with various levels of expression and/or secretion of ACPAs, mimicking the clonal heterogeneity observed in RA patients.Then, using the tools generated, we established the proof of concept of an innovative immunotherapy targeting specifically ACPA+ B cells. This strategy relies on a new class of biotherapeutic molecules carrying citrullinated peptide with the ACPA immunodominant epitope of the human fibrin, coupled with a human Fc fragment to interact with immune cells and use their effector functions to eradicate the ACPA+ B.In a first series of experiments, the therapeutic molecule was used in vitro, in antibody-dependent cell-mediated cytotoxicity (ADCC) experiments using expanded human NK cells as effector cells. Based on encouraging results, we carried up complementary in vivo experiments using an immunocompromised mice model allowing the injection of the human target cells developed previously and effector cells. The specific targeting of ACPA+ transduced human B cells was evaluated using co-injection of non-transduced B cells as negative control.Results showed a highly specific recognition of targeted ACPA+ B cells, sparing the ACPA negative B cells.In conclusion, the establishment of human B cell lines with phenotypes and properties similar to those of ACPA+ B cells found in RA patients constitute a crucial tool for the development of new targeted therapies, unravelling the strong therapeutic potential of this innovative immunotherapy.