Depleting autoreactive B-cells using targeted photodynamic therapy

In many autoimmune pathologies, including Rheumatoid Arthritis (RA), only a small percentage of the total B cell population is autoreactive and sustain disease. Yet, current immunotherapy treatments often eliminate the entire B-cell population, leading to immune deficiency. We developed an approach to selectively eliminate autoreactive B cells with targeted photodynamic therapy (tPDT). We designed a construct containing a peptidic antigen (diCCP4) that selectively binds the autoreactive B cell receptor (BCR) and additionally included the photosensitizer IRDye700DX. We tested the construct on a modified Ramos B-cell line (Ramos 3F3), expressing this specific autoreactive BCR. After brief exposure to 689 nm light, the photosensitizer selectively eliminates the modified Ramos cells, whilst the construct is not cytotoxic to cells lacking the autoreactive BCR. In a 3D coculture of the Ramos autoreactive B cell line with peripheral blood mononuclear cells (PBMCs) we observed only a minimal response of the untargeted cells. These results highlight the potential of tPDT against autoreactive B cells in autoimmune disease.