Lentivirus-Induced Dendritic Cells (iDC) for Immune-Regenerative Therapies in Cancer and Stem Cell Transplantation

Abstract

Conventional dendritic cells (cDC) are ex vivo differentiated professional antigen presenting cells capable of potently stimulating naïve T cells and with vast potential for immunotherapeutic applications. The manufacture of clinical-grade cDC is relatively complex and requires several days for completion. Clinical trials showed poor trafficking of cDC from subcutaneous injection sites to lymph nodes (LN), where DC can optimally stimulate naïve lymphocytes for long-lasting memory responses. We demonstrated in mouse and human systems that a single overnight ex vivo lentiviral (LV) gene transfer into DC precursors for production of combination of cytokines and antigens was capable to induce autonomous self-differentiation of antigen-loaded DC in vitro and in vivo. These highly viable induced DC (iDC) effectively migrated from the injected skin to LN, where they effectively activated de novo antigen-specific effector memory T cells. Two iDC modalities were validated in relevant animal models and are now in clinical development: Self-differentiated Myeloid-derived Antigen-presenting-cells Reactive against Tumors co-expressing GM-CSF/IL-4/TRP2 for melanoma immunotherapy in the autologous setting (SmartDCtrp2), and Self-differentiated Myeloid-derived Lentivirus-induced against human cytomegalovirus as an allogeneic matched adoptive cell after stem cell transplantation (SmyleDCpp65). The lentiviral vector design and packaging methodology has "evolved" continuously in order to simplify and optimize function and biosafety of in vitro and in vivo genetic reprogramming of iDC. Here, we address the challenges seeking for new creations of genetically programmed iDC and integrase-defective LV vaccines for immune regeneration.

Keywords: cancer; dendritic cells; lentiviral vectors; stem cell transplantation.

Figure 1

Lentiviral vector designs that enabled the induction of monocytes into long-lived and potent induced dendritic cells (iDC). The backbones contain chimeric 5' long terminal repeats (LTR), the packaging signal (Ψ), the truncated and out-of-frame gag gene (GA), the Rev responsive element (RRE), the central polypurine and termination sequence (cPPT), the cytomegalovirus (CMV) major immediate-promoter, the mutated pre element (opre) and the self-inactivating mutation in the 3' LTR (ΔU3) as indicated (not to scale).

Figure 2

Tricistronic lentiviral vector design validated for production of SmartDCtrp2 in vivo in immune competent C57BL6 mice challenged with B16 melanoma and in vitro T cell stimulation assays using peripheral blood mononuclear cells from melanoma patients.

Figure 3

Tricistronic lentiviral vector design validated for production of donor-derived SmyleDCpp65 in vivo in humanized mice recapitulating human hematopoietic stem cell transplantation and in vitro T cell stimulation assays using peripheral blood mononuclear cells from stem cell donors.