Chimeric HLA Antibody Receptor (CHAR) T Cells to Specifically Eliminate HLA-DQ-Specific B Cells

CAR T cell therapy has revolutionized the treatment of hematological malignancies by effectively eliminating tumor cells. In the field of kidney transplantation, comparable cellular therapies are being explored to facilitate transplantation and prevent graft rejection. Chimeric HLA antibody receptor (CHAR) T cells are a promising therapy for eliminating HLA-specific B cells in sensitized patients and potentially ameliorating antibody-mediated rejection. We previously demonstrated that HLA class I CHAR T cells selectively eliminated HLA class I-specific B cells with high specificity. Since HLA sensitization is most often directed against HLA-DQ of the allograft, we developed HLA-DQ2 and HLA-DQ7 CHAR T cells to target B cells with corresponding HLA specificity.

We designed viral vectors encoding HLA-DQ CHARs composed of HLA-DQA1*05:01 alpha chain with either HLA-DQB1*02:01 (HLA-DQ2) or HLA-DQB1*03:01 (HLA-DQ7) beta chains, CLIP peptide, and intracellular 4-1BB costimulatory and CD3ζ signaling domains. Upon production of HLA-DQ CHAR T cells, we evaluated CHAR expression, cytotoxic activity, production of cytokines and cytotoxic mediators, and sensitivity to immunosuppressive drugs in in vitro models. We further assessed the cytotoxic activity of HLA-DQ CHAR T cells in an immunodeficient mouse model and in primary material from sensitized individuals.

CHAR-transduced Jurkat Triple Parameter Reporter (JurkatTPR) cells expressing reporter constructs for T cell activation markers showed robust activation upon specific stimulation. Primary CD8+ T cells expressing HLA-DQ2 and HLA-DQ7 CHAR molecules specifically eliminated HLA-DQ2- or HLA-DQ7-specific B cells, respectively, and produced interferon gamma, soluble Fas ligand, perforin, and granzyme B. Maintenance immunosuppressive drug regimens initiated at the time of co-incubation with target cells had limited effects on CHAR T-cell functionality. Finally, HLA-DQ CHAR T cells effectively eliminated HLA-DQ-specific B cells in an in vivo mouse model, as well as in primary material from sensitized individuals.

HLA-DQ2 and HLA-DQ7 CHAR T cells, the first HLA class II CHAR T cells, selectively and effectively eliminated corresponding HLA-DQ-specific B cells in vitro, in vivo, and in primary material from sensitized individuals.