Correction of T-Cell Repertoire and Autoimmune Diabetes in NOD Mice by Non-myeloablative T-Cell Depleted Allogeneic HSCT

Anti-viral CD8 central memory veto cells as a new platform for CAR T cell therapy

Central memory CD8 T cells exhibit marked veto activity enhancing engraftment in several mouse models of T cell-depleted bone marrow (TDBM) allografting. Graft-versus-host disease (GVHD) can be prevented by stimulation of mouse or human memory CD8 T cells against their cognate antigens under cytokine deprivation, in the early phase of culture followed by further expansion with IL21, IL15, and IL7. Thus, human anti-viral CD8 central memory veto T cells generated from CMV and EBV-positive donors are currently evaluated in a clinical trial at MD Anderson Cancer Centre (MDACC). Results in 15 patients indicate a low risk of GVHD. Considering that these cells could offer an attractive platform for CAR cell therapy, we evaluated methodologies for their effective transduction with 2 retroviral vectors. Initially, a vector directed against Her2 was tested and optimal transduction was attained at day 5 of culture. The transduced cells were expanded for an additional 7 days and exhibited marked anti-tumor reactivity ex-vivo while retaining their veto activity. Transduction with a vector directed at CD19 was effectively attained at days 4-5 allowing for substantial harvest of transduced cells at day 12 of culture. These Veto-CD19CAR central memory CD8 T cells exhibited marked anti-tumor reactivity in-vitro and in-vivo without GVHD, measured following transplantation into immune-deficient mice. These results strongly suggest that Veto-CAR T cells offer an attractive platform for CAR T cell therapy without gene editing for addressing the risk of GVHD or graft rejection.

Overcoming NK-mediated rejection by anti-3rd-party central memory veto CD8 T cells through downregulation of DNAM-1 on alloreactive NK cells

Anti-3rd-party central memory veto CD8 T (veto Tcm) cells can overcome T cell-mediated graft rejection under mild conditioning without causing significant graft versus host disease (GVHD). We previously demonstrated that these veto Tcm cells can effectively delete anti-donor T cell clones through a Fas-FasL mechanism, whereas their ability to neutralize alloreactive natural killer (NK) cells and the mechanism of such potential activity remained unknown. Using "nude" mice as recipients of allogeneic T cell-depleted hematopoietic stem cell transplantation (HSCT), we demonstrate effective inhibition of NK-mediated rejection by Tcm cells. Ex vivo studies revealed that Tcm cells express high levels of CD155, the ligand of the activating receptor DNAX accessory molecule-1 (DNAM-1). Conjugate formation between alloreactive NK cells and the veto cells induces NK anergy through a unique mechanism mediated by DNAM-1 internalization and degradation. These insights on veto Tcm cells and their impact on alloreactive NK cells offer potential translational approaches for haploidentical bone marrow transplantation and off-the-shelf chimeric antigen receptor (CAR) cell therapies.