Search

Autologous, patient-specific, monocyte-derived dendritic cell (MoDC) vaccines have been successfully applied in the clinical studies so far. However, the routine application of this strategy has been hampered by the difficulties in generating sufficient numbers of DC and the poor DC vaccine quality because of pathology or prior treatment received by the patients. The immunotherapeutic potential of other subsets of DC has not been thoroughly investigated because of their rarity in tissues and difficulties associated with their ex vivo generation. The high expansion and differentiation potential of CD34 hematopoietic progenitor cells (HPC), isolated from umbilical cord blood (UCB), into different DC subsets make them an attractive alternative DC source for cancer immunotherapy. Therefore, the aim of this study was to generate a large number of different DC subsets from CD34 HPC and evaluate their functionality in comparison with MoDC. Our culture protocol generated a clinically relevant number of mature CD1a myeloid DC and CD207 Langerhans cells (LC)-like DC subsets from CD34 HPC with >95% purity. Both DC subsets exhibited a cytokine profile that favors cytotoxic T-cell responses. Furthermore, UCB-DC and UCB-LC demonstrated superior induction of proliferation of both allogeneic as well as viral antigen-specific CD8 T cells, both in vitro and in vivo. Additional studies revealed that UCC-DC and UCB-LC can efficiently expand minor histocompatibility antigen (MiHA) HA-1-specific cytotoxic T cells in the peripheral blood of leukemia patients and prime MiHA HA-1-specific and HA-2-specific cytotoxic T cells in vitro. These preclinical findings support the pharmaceutical development of the described culture protocol for clinical evaluation.

Allogeneic stem cell transplantation (alloSCT) can be curative for hemato-oncology patients due to effective graft-versus-tumor immunity. However, relapse remains the major cause of treatment failure, emphasizing the need for adjuvant immunotherapies. In this regard, post-transplantation dendritic cell (DC) vaccination is a highly interesting strategy to boost graft-versus-tumor responses. Previously, we developed a clinically applicable protocol for simultaneous large-scale generation of end-stage blood DC subsets from donor-derived CD34+ stem cells, including conventional type 1 and 2 DCs (cDC1s and cDC2s), and plasmacytoid DCs (pDCs). In addition, the total cultured end-product (DC-complete vaccine), also contains non-end-stage-DCs (i.e. non-DCs). In this study, we aimed to dissect the phenotypic identity of these non-DCs and their potential immune modulatory functions on the potency of cDCs and pDCs in stimulating tumor-reactive CD8+ T and NK cell responses, in order to obtain rationale for clinical translation of our DC-complete vaccine. The non-DC compartment was heterogeneous and comprised of myeloid progenitors and (immature) granulocyte- and monocyte-like cells. Importantly, non-DCs potentiated toll-like receptor-induced DC maturation, as reflected by increased expression of co-stimulatory molecules and enhanced cDC-derived IL-12 and pDC-derived IFN-α production. Additionally, antigen-specific CD8+ T cells effectively expanded upon DC-complete vaccination in vitro and in vivo. This effect was strongly augmented by non-DCs in an antigen-independent manner. Moreover, non-DCs did not impair in vitro DC-mediated NK cell activation, degranulation nor cytotoxicity. Notably, in vivo i.p. DC-complete vaccination activated i.v. injected NK cells. Together, these data demonstrate that the non-DC compartment potentiates DC-mediated activation and expansion of antigen-specific CD8+ T cells and do not impair NK cell responses in vitro and in vivo. This underscores the rationale for further clinical translation of our CD34+-derived DC-complete vaccine in hemato-oncology patients post alloSCT. [ABSTRACT FROM AUTHOR]

Effective T-cell therapy against cancer is dependent on the formation of long-lived, stem cell-like T cells with the ability to self-renew and differentiate into potent effector cells. Here, we investigated the in vivo existence of stem cell-like antigen-specific T cells in allogeneic stem cell transplantation (allo-SCT) patients and their ex vivo generation for additive treatment posttransplant. Early after allo-SCT, CD8+ stem cell memory T cells targeting minor histocompatibility antigens (MiHAs) expressed by recipient tumor cells were not detectable, emphasizing the need for improved additive MiHA-specific T-cell therapy. Importantly, MiHA-specific CD8+ T cells with an early CCR7+CD62L+CD45RO+CD27+CD28+CD95+ memory-like phenotype and gene signature could be expanded from naive precursors by inhibiting Akt signaling during ex vivo priming and expansion. This resulted in a MiHA-specific CD8+ T-cell population containing a high proportion of stem cell-like T cells compared with terminal differentiated effector T cells in control cultures. Importantly, these Akt-inhibited MiHA-specific CD8+ T cells showed a superior expansion capacity in vitro and in immunodeficient mice and induced a superior antitumor effect in intrafemural multiple myeloma-bearing mice. These findings provide a rationale for clinical exploitation of ex vivo-generated Akt-inhibited MiHA-specific CD8+ T cells in additive immunotherapy to prevent or treat relapse in allo-SCT patients. [ABSTRACT FROM AUTHOR]

Natural killer (NK) cell-based adoptive immunotherapy is an attractive adjuvant treatment option for patients with acute myeloid leukemia. Recently, we reported a clinical-grade, cytokine-based culture method for the generation of NK cells from umbilical cord blood (UCB) CD34+ hematopoietic progenitor cells with high yield, purity and in vitro functionality. The present study was designed to evaluate the in vivo anti-leukemic potential of UCB-NK cells generated with our GMP-compliant culture system in terms of biodistribution, survival and cytolytic activity following adoptive transfer in immunodeficient NOD/SCID/IL2Rgnull mice. Using single photon emission computed tomography, we first demonstrated active migration of UCB-NK cells to bone marrow, spleen and liver within 24 h after infusion. Analysis of the chemokine receptor expression profile of UCB-NK cells matched in vivo findings. Particularly, a firm proportion of UCB-NK cells functionally expressed CXCR4, what could trigger BM homing in response to its ligand CXCL12. In addition, high expression of CXCR3 and CCR6 supported the capacity of UCB-NK cells to migrate to inflamed tissues via the CXCR3/CXCL10-11 and CCR6/CCL20 axis. Thereafter, we showed that low dose IL-15 mediates efficient survival, expansion and maturation of UCB-NK cells in vivo. Most importantly, we demonstrate that a single UCB-NK cell infusion combined with supportive IL-15 administration efficiently inhibited growth of human leukemia cells implanted in the femur of mice, resulting in significant prolongation of mice survival. These preclinical studies strongly support the therapeutic potential of ex vivo-generated UCB-NK cells in the treatment of myeloid leukemia after immunosuppressive chemotherapy. [ABSTRACT FROM AUTHOR]