Allogeneic stem cell transplantation (ASCT) is a curative therapy for hematologic malignancies but hampered by graft-versus-host disease (GVHD) due to dysregulated donor T cells and disease relapse from insufficient graft versus tumor (GVT) effects of donor T cells. Therefore, an innovative strategy to optimize the immune regulation after ASCT is urgently needed to improve the transplant outcome.
CD1d-restricted invariant Natural Killer (iNK) T cells can influence adaptive immunity toward tumor surveillance or immune-suppression via production of Th1 or Th2-type cytokines and exert anti-tumor effects via direct tumor cytolysis or facilitating the cross-priming of antigen specific T cells. Thus, iNK T cells can play as a master-regulator to prevent GVHD and promote GVT effects in ASCT. Here, we explored the therapeutic utility of ex vivo expanded human iNKT cells in ASCT.
First, a single antigenic stimulation preferentially expanded human iNK T cells from adult donor (AD) and cord blood (CB) to a clinically meaningful number in extremely high purity. CB-derived iNK T cells were highly enriched with IL-10 producing NRP1+Th2+CD4+ iNK T cells (NKT10) and displayed superior in vitro and in vivo anti-GVH effects compared with AD-iNK T cells. Despite superb regulatory properties, CB-iNK T cells exerted direct anti-tumor activity against CD1dhigh B lymphoblastic cells when pulsed with agonist glycolipid antigen and HLA-A2+ myeloid leukemia cells when engineered to express 8F4CAR, chimeric antigen receptor targeting PR1/HLA-A2 myeloid antigen. Moreover, CB-iNK T cells facilitated the expansion of antigen-specific donor T cells when co-activated. Lastly, CB-iNK T cells promoted xenograft engraftment in a humanized murine model. Mechanistically, we demonstrated that NRP1, highly expressed on NKT10 subset, inhibited Th1 cytokine production by iNK T cells leading to Th2 functional polarization. Therefore, NKT10-enriched CB-iNK T cells maintain a prototypical multi-functionality and are suitable candidate as off the shelf cell therapy to prevent GVHD and relapse, and to promote donor immune-reconstitution in ASCT.