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

ABSTRACT: 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 laboratory 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 clustered, regularly interspaced, short palindromic repeats (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 NOD/SCID/IL2rγnull (NSG) mice receiving MIR155HGΔexon3 human T cells provide protection from lethal acute GVHD compared with mice that received human T cells with intact miR-155. MIR155HGΔexon3 human T cells persist in the recipients displaying decreased proliferation potential, reduced pathogenic T helper-1 cell 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 antileukemic response.

Mechanisms of tertiary lymphoid structure formation: cooperation between inflammation and antigenicity.

To mount an effective anti-tumor immune response capable of controlling or eliminating disease, sufficient numbers of lymphocytes must be recruited to malignant tissue and allowed to sustain their effector functions. Indeed, higher infiltration of T and B cells in tumor tissue, often referred to as "hot tumors", is prognostic for patient survival and predictive of response to immunotherapy in almost all cancer types. The organization of tertiary lymphoid structures (TLS) in solid tumors is a unique example of a hot tumor whereby T and B lymphocytes aggregate with antigen presenting cells and high endothelial venules reflecting the cellular organization observed in lymphoid tissue. Many groups have reported that the presence of preexisting TLS in tumors is associated with a superior adaptive immune response, response to immunotherapy, and improved survivorship over those without TLS. Accordingly, there is significant interest into understanding the mechanisms of how and why TLS organize so that they can be elicited therapeutically in patients with few or no TLS. Unfortunately, the most commonly used mouse models of cancer do not spontaneously form TLS, thus significantly restricting our understanding of TLS biology. This brief review will summarize our current state of knowledge of TLS neogenesis and address the current gaps in the field.