CRISPR/Cas9 deletion of MIR155HG in human T cells reduces incidence and severity of acute GVHD in a xenogeneic model.

Acute graft-versus host disease (GVHD) is a major complication of allogeneic hematopoietic cell transplantation (allo-HCT). Using preclinical mouse models of disease, previous work in our lab has linked microRNA-155 (miR-155) to the development of acute GVHD. Transplantation of donor T cells from miR-155 host gene (MIR155HG) knockout mice prevented acute GVHD in multiple murine models of disease while maintaining critical graft-versus-leukemia (GVL) response, necessary for relapse prevention. In this study, we used CRISPR/Cas9 genome editing to delete miR-155 in primary T cells (MIR155HGΔexon3) from human donors, resulting in stable and sustained reduction in expression of miR-155. Using the xenogeneic model of acute GVHD, we show that NSG mice receiving MIR155HGΔexon3 human T cells provide protection from lethal acute GVHD compared to mice that received human T cells with intact miR-155. MIR155HGΔexon3 human T cells persist in the recipients displaying decreased proliferation potential, reduced pathogenic Th1 population and infiltration into GVHD target organs such as the liver and skin. Importantly, MIR155HGΔexon3 human T cells retain GVL response significantly improving survival in an in vivo model of xeno-GVL. Altogether, we show that CRISPR/Cas9 mediated deletion of MIR155HG in primary human donor T cells is an innovative approach to generate allogeneic donor T cells that provide protection from lethal GVHD while maintaining robust anti-leukemic response.