HLA-A*02:01-directed chimeric antigen receptor/forkhead box P3-engineered CD4+ T cells adopt a regulatory phenotype and suppress established graft-versus-host disease

Abstract Background aims To investigate the feasibility of using CD4 + T cells genetically modified to express an allo-HLA directed CAR and FOXP3 to suppress T cell proliferation and cytokine secretion in GvHD. Methods: Human CD4+ T cells from A*02:01 negative donors were transduced to express A*02 CAR and FOXP3 and co-cultured in mixed lymphocyte reaction assays to demonstrate T cell suppression. A*02- CAR/FOXP CD4+ T cells were then injected into mice engrafted with allogeneic T cells in a GvHD mouse model. Results CD4+ T cells genetically modified to express allo-HLA-directed CAR and FOXP3 proliferate rapidly, downregulate CD127 and interferon-γ, express high CD25 and Helios and convert to a stable antigen-dependent suppressive phenotype. In mixed lymphocyte reaction assays, these cells potently suppressed T-cell proliferation and secreted IL-10. In a graft-versus-host disease model, A*02-CAR/FOXP3 CD4+ T cells outperformed polyclonal Tregs by reducing liver and lung inflammation, inhibiting pro-inflammatory cytokine production and limiting grafted CD3+ T-cell expansion. Conclusions CD4 + T cells expressing allo-antigen directed HLA-specific CAR and FOXP3 act as potent, specific and stable suppressors of inflammation that out-perform their Treg counterparts both in vitro and in vivo.