Generation Of Virus-Specific Cytotoxic T Lymphocytes (CTLS) Resistant to the Immunosuppressive Drug Tacrolimus (FK506)

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The immunogenicity of virus-derived 2A sequences in immunocompetent individuals

Genetic engineering of T cells for adoptive immunotherapy in cancer patients has shown significant promise. To ensure optimal antitumor activity and safety, the simultaneous expression of multiple genes is frequently required, and short viral-derived 2A sequences are increasingly preferred for this purpose. Concerns exist, however, that these virus-derived sequences may induce unwanted immune responses, and thus diminish persistence of the gene-modified cells after adoptive transfer. Whereas such responses were absent in immunocompromised recipients, potential immunogenicity in immunocompetent individuals remains a concern. We now address whether ex vivo T cell responses can be elicited against the most widely used 2A sequences (2A-Thosea asigna virus (TAV) or 2A-equine rhinitis virus (ERAV), specifically) in immunocompetent individuals. We used a potent ex vivo culture system previously validated to induce T cell responses even against weakly immunogenic antigens. Of the sixteen donors tested, only five released very low levels of interferon-γ in response to 2A-TAV peptide mixtures (single peptide specificity in three donors, adjacent self-antigen peptide specificity in one donor and nonspecific reactivity in one donor). None of them produced cytotoxic activity or responded to 2A-ERAV. These results suggest that exposure to viral-derived 2A sequences is unlikely to produce unwanted T cell responses in immunocompetent individuals and further supports their continued use for studies of human gene therapy

Robust and cost effective expansion of human regulatory T cells highly functional in a xenograft model of graft-versus-host disease

The low frequency of naturally occurring regulatory T cells (nTregs) in peripheral blood and the suboptimal protocols available for their ex vivo expansion limit the development of clinical trials based on the adoptive transfer of these cells. We have, therefore, generated a simplified, robust and cost-effective platform for the large-scale expansion of nTregs using a gas permeable static culture flask (G-Rex) in compliance with Good Manufacturing Practice. More than 109 putative Tregs co-expressing CD25 and CD4 molecules (92±5%) and FoxP3 (69±19%) were obtained within 21 days of culture. Expanded Tregs showed potent regulatory activity in vitro (80±13% inhibition of CD8+ cell division) and in vivo (suppression or delay of graft-versus-host disease in a xenograft mouse model) indicating that the cost-effective and simplified production of nTregs we propose will facilitate the implementation of clinical trials based on their adoptive transfer

Engineering CD19-specific T lymphocytes with interleukin-15 and a suicide gene to enhance their anti-lymphoma/leukemia effects and safety

T lymphocytes expressing a chimeric antigen receptor (CAR) targeting the CD19 antigen (CAR.19) may be of value for the therapy of B-cell malignancies. Because the in vivo survival, expansion and anti-lymphoma activity of CAR.19 T + cells remain suboptimal even when the CAR contains a CD28 costimulatory endodomain, we generated a novel construct that also incorporates the interleukin-15 (IL-15) gene and an inducible caspase-9-based suicide gene (iC9/CAR.19/IL-15). We found that compared with CAR.19 T + cells, iC9/CAR.19/IL-15 T cells had: (1) greater numeric expansion upon antigen stimulation (10-fold greater expansion in vitro, and 3-to 15-fold greater expansion in vivo) and reduced cell death rate (Annexin-V/7-AAD cells 106% for iC9/CAR.19/IL-15 T + cells and 3219% for CAR.19 T + cells); (2) reduced expression of the programmed death 1 (PD-1) receptor upon antigen stimulation (PD-1 cells 15% for iC9/CAR.19/IL-15 T + cells versus 40% for CAR.19 T + cells); and (3) improved antitumor effects in vivo (from 4.7-to 5.4-fold reduced tumor growth). In addition, iC9/CAR.19/IL-15 T + cells were efficiently eliminated upon pharmacologic activation of the suicide gene. In summary, this strategy safely increases the anti-lymphoma/leukemia effects of CAR.19-redirected T lymphocytes and may be a useful approach for treatment of patients with B-cell malignancies

Selective elimination of a chemoresistant side population of B-CLL cells by cytotoxic T lymphocytes in subjects receiving an autologous hCD40L/IL-2 tumor vaccine

Side-population (SP) analysis identifies precursor cells in normal and malignant tissues. Cells with this phenotype have increased resistance to many cytotoxic agents, and may represent a primary drug-resistant population in malignant diseases. To discover whether drug-resistant malignant SP cells are nonetheless sensitive to immune-mediated killing, we first established the presence of a malignant CD5+ CD19+ SP subset in the blood of 18/21 subjects with B-cell chronic lymphocytic leukemia (B-CLL). We examined the fate of these cells in six of these individuals who received autologous human CD40 ligand and interleukin-2 (hCD40L/IL-2) gene-modified tumor cells as part of a tumor vaccine study. Vaccinated patients showed an increase in B-CLL-reactive T cells followed by a corresponding decline in circulating CD5+ CD19+ SP cells. T-cell lines and clones generated from vaccinated patients specifically recognized B-CLL SP tumor cells. Elimination of SP cells is likely triggered by their increased expression of target antigens, such as receptor for hyaluronan-mediated motility (RHAMM), after stimulation of the malignant cells by hCD40L, as CD8+ RHAMM-specific T cells could be detected in the peripheral blood of immunized patients and were associated with the decline in B-CLL SP cells. Hence, malignant B cells with a primary drug-resistant phenotype can be targeted by T-cell-mediated effector activity after immunization of human subjects

Selective depletion of a minor subpopulation of B-chronic lymphocytic leukemia cells is followed by a delayed but progressive loss of bulk tumor cells and disease regression

Cancer precursor/progenitor cells may initiate and sustain the growth of tumors, but evidence for their existence in human disease is indirect, relying on their it in vitro it properties and animal models. More directly, specific elimination of these rare cells from cancer patients should produce a delayed but progressive disappearance of differentiated malignant progeny. Here, we describe selective eradication of a putative precursor population in a patient with B-cell chronic lymphocytic leukemia, followed 6 months later by a progressive loss of mature tumor cells without further treatment. This outcome supports the presence of a rare population of precursor/progenitor cells in human malignancies, and suggests benefit from their removal

Virus-specific T cells engineered to coexpress tumor-specific receptors: Persistence and antitumor activity in individuals with neuroblastoma

Cytotoxic T lymphocytes (CTLs) directed to nonviral tumor-associated antigens do not survive long term and have limited antitumor activity in vivo, in part because such tumor cells typically lack the appropriate costimulatory molecules. We therefore engineered Epstein-Barr virus (EBV)-specific CTLs to express a chimeric antigen receptor directed to the diasialoganglioside GD2, a nonviral tumor-associated antigen expressed by human neuroblastoma cells. We reasoned that these genetically engineered lymphocytes would receive optimal costimulation after engagement of their native receptors, enhancing survival and antitumor activity mediated through their chimeric receptors. Here we show in individuals with neuroblastoma that EBV-specific CTLs expressing a chimeric GD2-specific receptor indeed survive longer than T cells activated by the CD3-specific antibody OKT3 and expressing the same chimeric receptor but lacking virus specificity. Infusion of these genetically modified cells seemed safe and was associated with tumor regression or necrosis in half of the subjects tested. Hence, virus-specific CTLs can be modified to function as tumor-directed effector cells

Adverse events following infusion of T cells for adoptive immunotherapy: A 10-year experience

Background aims. The Food and Drug Administration (FDA) currently recommends at least 4 h of recipient monitoring after T cell infusions to detect early infusion reactions. Recent catastrophic reactions to 'first-in-man' biologic agents have emphasized the importance of this rule for initial studies of new products. The value of such monitoring for better established agents is less obvious. Methods. We reviewed infusion-related adverse events (AE) following administration of ex vivo-expanded T cell products (antigen-specific cytotoxic T lymphocytes, allodepleted T cells, and genetically modified T cells) on investigational new drug (IND) studies in our center. Results. From 1998 to 2008, we infused 381 T cell products to 180 recipients, enrolled on 18 studies, receiving T cells targeting malignancies or post-transplant viral infections. There were no grade 34 infusion reactions during initial monitoring or 24-h follow-up. Twenty-four mild (grade 12) AE occurred in 21 infusions either during or immediately following infusion (up to 6 h), most commonly nausea and vomiting (10/24, 41.6%), probably because of the dimethyl sulfoxide cryoprotectant, and hypotension (20.8%), attributable to diphenhydramine pre-medication. Twenty-two additional non-severe events were reported within 24 h of infusion, most commonly culture-negative fever, chills and nausea. An increased risk of adverse events was associated with age [incidence rate ratio (IRR) 0.98; 95% confidence interval (CI) 0.961.00, P 0.05], while an increased risk of immediate infusion-related events was higher in patients reporting allergies (IRR 2.72, 95% CI 1.007.40, P 0.05); sex, disease type and T cell source (allogeneic or autologous) had no effect on frequency of adverse events. Conclusions. Infusion of these T cell products was safe in the outpatient setting and associated with no severe reactions, so monitoring for 1 h after infusion is probably sufficient. As many of the AE were attributable to diphenhydramine premedication, a lower dose (0.25 mg/kg) should be selected