Highly efficient gene transfer in naive human T cells with a murine leukemia virus-based vector

Interleukin-7 permits Th1/Tc1 maturation and promotes ex vivo expansion of cord blood T cells: a critical step toward adoptive immunotherapy after cord blood transplantation

Donor leukocyte infusions (DLI) in the allogeneic hematopoietic transplant setting can provide a clinically relevant boost of immunity to reduce opportunistic infections and to increase graft-versus-leukemia activity. Despite significant advances in applicability, DLI has not been available for single-unit recipients of unrelated cord blood transplant. Ex vivo expansion of cord blood T cells can be achieved with interleukin (IL)-2 and CD3/CD28 costimulatory beads. However, significant apoptosis occurs in proliferating T cells, diminishing the yield and skewing the CD4/CD8 ratio in the T-cell population, jeopardizing the potential efficacy of DLI. In this study, we show that interleukin (IL)-7 not only reduces apoptosis of activated T lymphocytes and enhances their proliferation but also promotes functional maturation, leading to secretion of IFN-gamma and other key cytokines. Recognizing that infused T lymphocytes will need to meet microbial antigens in secondary lymphoid organs to generate effectors, we also show that expansion with IL-7 promotes the preservation of a polyclonal broad T-cell receptor repertoire and a surface phenotype that favors lymph node homing. Expanded lymphocytes lack alloreactivity against recipient and other allogeneic cells, indicating a favorable safety profile from graft-versus-host disease. Nevertheless, expanded T cells can be primed subsequently against lymphoid and myeloid leukemia cells to generate tumor-specific cytotoxic T cells. Taken together, our findings offer a major step in fulfilling critical numerical and biological requirements to quickly generate a DLI product ex vivo using a negligible fraction of a cord blood graft that provides a flexible adoptive immunotherapy platform for both children and adults.

In vivo persistence of genetically modified T cells generated ex vivo using the fibronectin CH296 stimulation method

Recombinant human fibronectin fragment (FN-CH296, RetroNectin) has been widely used for retroviral gene therapy to enhance gene transfer efficiency. Based on the observation that immobilized FN-CH296 together with anti-CD3 monoclonal antibodies (anti-CD3) enhanced cell proliferation while conserving the naive phenotype of T cells, we used FN-CH296 costimulation to generate engineered T cells. For comparison, human peripheral blood mononuclear cells were stimulated under three kinds of conditions including anti-CD3 only, anti-CD3 and anti-CD28 monoclonal antibodies conjugated with beads (anti-CD3/anti-CD28) and immobilized FN-CH296 together with anti-CD3 (anti-CD3/FN-CH296); all three treatments were followed by retroviral gene transfer. Of all the stimulation methods, the one involving anti-CD3/FN-CH296 produced the most cell expansion with conservation of the naive phenotype. Engineered T cells were transplanted into NOD/SCID (non-obese diabetic/severe combined immunodeficient) mice, and all the mice were killed 14 days later. Transplanted T cells were detected in all the mice; however, mice injected with anti-CD3/FN-CH296-stimulated T cells showed higher transgene expression in organs than mice injected with anti-CD3-stimulated cells. These results demonstrate that the anti-CD3/FN-CH296 stimulation can be an efficient way to generate large numbers of genetically modified T cells that can provide higher and longer lasting levels of transgene expression in vivo and that are suitable for adoptive T-cell transfer therapy.

An in vivo assay for retrovirally transduced human peripheral T lymphocytes using nonobese diabetic/severe combined immunodeficiency mice

OBJECTIVE

Availability of a mouse model to analyze human peripheral lymphocytes genetically modified with retroviral vectors would be useful in T-cell-directed gene transfer studies. To address this issue, we assessed the ability of nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice to maintain such cells in their peripheral blood.

MATERIALS AND METHODS

Human peripheral lymphocytes stimulated with recombinant human interleukin-2 (rhIL-2) and anti-CD3 and CD28 antibodies were transduced with the enhanced green fluorescent protein (EGFP) gene using the retroviral vector GCsap(MSCV) and then transplanted into NOD/SCID mice at 1 x 10(8) cells per mouse.

RESULTS

Transplanted human peripheral lymphocytes survived and expressed EGFP in the mice over the 6- to 8-week posttransplant period without any signs of graft-vs-host disease. Of importance was that these cells remained at the G(0)/G(1) stage and again proliferated in response to cytokines when cultured in vitro. Interestingly, the mice in which the transduced T lymphocytes remained at the resting stage clearly elucidated the superiority of the murine stem cell virus (MSCV) LTR to maintain the transgene expression by nonproliferating T lymphocytes over the Moloney murine leukemia virus (MoMLV)- and myeloproliferative sarcoma virus (MPSV)-derived LTRs, which was obscure in in vitro culture where the transduced lymphocytes was being stimulated with rhIL-2.

CONCLUSIONS

The mouse model and GCsap(MSCV) vector described herein comprise a simple and reliable in vivo assay system for studies of gene and cell therapies employing human peripheral lymphocytes.

Functional and phenotypic variations in human T cells subjected to retroviral-mediated gene transfer

The insertion of suicide genes in donor T lymphocytes constitutes the basis of new approaches aiming at the treatment of the graft-versus-host disease (GVHD), a frequent complication in recipients of allogeneic haematopoietic grafts. In this study we investigated the impact that the ex vivo manipulation required for the retroviral transduction of T cells had on the functionality and differentiation of these cells. Compared to fresh T cells, samples that had been subjected to standard activation (1 microg/ml of both anti-CD3i and anti-CD28i MoAbs) followed by transduction with vectors encoding for the HSV-tk and tNGFR genes maintained the proliferative response to an allogeneic stimulus. These cells, however, had a significantly lower cytotoxic response to allogeneic cells compared to fresh samples. When the concentration of anti-CD3i was reduced to up to 1000-fold (1 ng/ml), similar T-cell transductions were obtained, while the cytotoxicity of the ex vivo manipulated samples was significantly recovered, when assessed either at 7 or 14 days of culture. In all instances, a similar functionality was observed in transduced samples not subjected to immunomagnetic cell sorting, compared to purified fractions enriched in NGFR(+) and NFGR(-) cells. The analysis of CD45RA and CCR7 markers in samples transduced under standard stimulatory conditions showed a differentiation of fresh CD8(+) CD45RA(+)/CCR7(+) naive cells to cells having a predominant central CD45RA(-)/CCR7(+) and effector CD45RA(-)/CCR7(-) memory phenotype. However, when samples were activated with low doses of anti-CD3i, a significant population of naive cells became apparent. Although activation with high doses of anti-CD3i/anti-CD28i resulted in a similar phenotype in both NGFR(+) and NFGR(-) populations, the naive population observed in samples activated with low concentrations of anti-CD3i was almost restricted to the NGFR(-) population. These results show that reducing the stimulation mediated by anti-CD3i in protocols of T-cell retroviral gene transfer significantly helps to preserve the cytotoxic capacity of these cells to allogeneic cells, without affecting the susceptibility of these cells to the retroviral vector. In addition, we observed that modulating the activation of transduced T cells implies the generation of changes in the differentiation of CD8(+) cells, although we could not establish a direct relationship between the CD45RA/CCR7 phenotype of these cells and their cytotoxic reactivity to an allogeneic stimulus.

The HTLV receptor is an early T-cell activation marker whose expression requires de novo protein synthesis

The human T-cell leukemia virus type 1 (HTLV) is the first isolated human retrovirus, but its receptor has yet to be identified, in part due to its ubiquitous expression. Here we report that quiescent CD4 and CD8 T lymphocytes do not express this receptor, as monitored with a soluble receptor-binding domain derived from the HTLV envelope. However, HTLV receptor is an early activation marker in neonatal and adult T lymphocytes, detected as early as 4 hours following T-cell-receptor (TCR) stimulation. This induced surface expression of the HTLV receptor requires de novo protein synthesis and results in a wide distribution on the surface of activated lymphocytes. Moreover, the distribution of the HTLV receptor is independent of TCR/CD3-capped membrane structures, as observed by confocal immunofluorescence microscopy. To determine whether HTLV receptor up-regulation specifically requires TCR-mediated signals or, alternatively, is dependent on more generalized cell cycle entry/proliferation signals, its expression was monitored in interleukin 7 (IL-7)-stimulated neonatal and adult T cells. Neonatal, but not adult, lymphocytes proliferate in response to IL-7 and HTLV receptor expression is restricted to the former population. Thus, HTLV receptor expression appears to be an early marker of cell cycle entry. Up-regulation of the HTLV receptor, via signals transmitted through the IL-7 cytokine receptor as well as the TCR, is likely to contribute to the mother-to-infant transmission and spreading of HTLV-1.

Immunologic potential of donor lymphocytes expressing a suicide gene for early immune reconstitution after hematopoietic T-cell-depleted stem cell transplantation

We have previously shown that the infusion of donor lymphocytes expressing the herpes simplex virus thymidine kinase (HSV-tk) gene is an efficient tool for controlling graft-versus-host disease (GVHD) while preserving the graft-versus-leukemia (GVL) effect. In addition to the GVL effect, the administration of donor HSV-tk(+) cells could have a clinical impact in promoting immune reconstitution after T-cell-depleted stem cell transplantation (SCT). To explore this hypothesis, we have investigated whether in vitro polyclonal activation, retroviral transduction, immunoselection, and expansion affect the immune competence of donor T cells. We have observed that, after appropriate in vitro manipulation, T cells specific for antigens relevant in the context of SCT are preserved in terms of frequency, expression of T-cell receptor, proliferation, cytokine secretion, and lytic activity. A reduction in the frequency of allospecific T-cell precursors is observed after prolonged T-cell culture, suggesting that cell manipulation protocols involving a short culture time and high transduction efficiency are needed. Finally, the long-term persistence of HSV-tk(+) cells was observed in a patient treated in the GVL clinical trial, and a reversion of the phenotype of HSV-tk(+) cells from CD45RO(+) to CD45RA(+) was documented more than 2 years after the infusion. Based on all this evidence, we propose a clinical study of preemptive infusions of donor HSV-tk(+) T cells after SCT from haploidentical donors to provide early immune reconstitution against infection and potential immune protection against disease recurrence.

Modalities of interleukin-7-induced human immunodeficiency virus permissiveness in quiescent T lymphocytes

The metabolic and cell cycle status of primary T lymphocytes conditions their susceptibility to human immunodeficiency virus (HIV) and HIV-derived vectors. While in fully quiescent T lymphocytes the reverse transcription and nuclear import of these retroelements are impaired, leading to an abortive infection, various stimuli can induce a state of virus permissiveness. Here, we studied the modalities by which interleukin-7 (IL-7), an important controller of T-cell homeostasis, exerts this effect. IL-7-exposed cord blood T lymphocytes proliferated and were efficiently transduced by HIV-derived vectors. In contrast, similarly treated adult peripheral blood (PB) T lymphocytes failed to divide, and only a subset of these cells became infectible. HIV-resistant and -sensitive subsets of IL-7-treated PB T lymphocytes differed in cell cycle status but not in naïve, memory, or activation phenotypes. Nuclear factor of activated T cells was not induced by IL-7, and cyclosporine did not prevent HIV-mediated gene transfer. Furthermore, the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin blocked IL-7-induced cell survival and Bcl-2 synthesis but had no effect on the acquisition of HIV susceptibility, suggesting that IL-7-induced HIV type 1 permissiveness is not mediated by the PI-3 K pathway and that, perhaps, the Jak/STAT5 pathway, the other known mediator of IL-7-triggered signaling in T cells, governs this process.

IL-7 differentially regulates cell cycle progression and HIV-1-based vector infection in neonatal and adult CD4+ T cells

Differences in the immunological reactivity of umbilical cord (UC) and adult peripheral blood (APB) T cells are poorly understood. Here, we show that IL-7, a cytokine involved in lymphoid homeostasis, has distinct regulatory effects on APB and UC lymphocytes. Neither naive nor memory APB CD4(+) cells proliferated in response to IL-7, whereas naive UC CD4(+) lymphocytes underwent multiple divisions. Nevertheless, both naive and memory IL-7-treated APB T cells progressed into the G(1b) phase of the cell cycle, albeit at higher levels in the latter subset. The IL-7-treated memory CD4(+) lymphocyte population was significantly more susceptible to infection with an HIV-1-derived vector than dividing CD4(+) UC lymphocytes. However, activation through the T cell receptor rendered UC lymphocytes fully susceptible to HIV-1-based vector infection. These data unveil differences between UC and APB CD4(+) T cells with regard to IL-7-mediated cell cycle progression and HIV-1-based vector infectivity. This evidence indicates that IL-7 differentially regulates lymphoid homeostasis in adults and neonates.

Lentivirus-mediated gene transfer in primary T cells is enhanced by a central DNA flap

Retroviral vectors have become the primary tool for gene delivery into hematopoietic cells, including T lymphocytes. Lentiviral vectors offer an advantage over Moloney murine leukemia virus (MuLV) vectors because of their ability to translocate across an intact nuclear membrane and integrate into the genome of nonproliferating cells. We have recently demonstrated that a central strand displacement event, controlled by the central polypurine tract (cPPT) and the central termination sequence (CTS), results in the formation of a central DNA flap which acts as a cis-determinant of HIV-1 genome nuclear import. Here, we show that insertion of this DNA determinant in a classical lentiviral vector resulted in a significantly higher level of transduction in activated T cells (51 +/- 12.7% versus 15 +/- 1.4%). CD4(+) and CD8(+) T cells were transduced at equivalent levels. Importantly, freshly isolated T cells stimulated only during the 12-h transduction period could be efficiently transduced with this new flap-containing lentiviral vector, but not with the parental lentiviral vector nor an MuLV vector. Transgene expression in the flap-containing lentiviral vector, under the control of either an internal cytomegalovirus or the elongation factor-1 alpha (EF1 alpha) promoter, was significant and expression remained elevated in resting T cells. Thus, this system allows stable expression of transgenes in T lymphocytes following a short ex vivo transduction protocol.

Retrovirus-mediated transduction of primary ZAP-70-deficient human T cells results in the selective growth advantage of gene-corrected cells: implications for gene therapy

Humans lacking the ZAP-70 protein tyrosine kinase present with an absence of CD8+ T cells and defective CD4+ T cells in the periphery. This severe combined immunodeficiency is fatal unless treated by allogeneic bone marrow transplantation. However, in the absence of suitable marrow donors, the development of alternative forms of therapy is desirable. Because lymphocytes are long-lived, it is possible that introduction of the wild-type ZAP-70 gene into CD4+ ZAP-70-deficient T cells will restore their immune function in vivo. Initial investigations evaluating the feasibility of gene therapy for ZAP-70 deficiency were performed using HTL V-I-transformed lymphocytes. Although transformation was useful in circumventing problems associated with the maintenance of ZAP-70-deficient T cells and low gene transfer levels, the presence of HTL V-I precluded any biological studies. Here, we investigated a retrovirus-mediated approach for the correction of primary T cells derived from two ZAP-70-deficient patients. Upon introduction of the wild-type ZAP-70 gene, TCR-induced MAPK activation, IL-2 secretion and proliferation were restored to approximately normal levels. Importantly, this gain-of-function was associated with a selective growth advantage of gene-corrected cells, thereby indicating the feasibility of a gene therapy-based strategy.