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Background The Wilms tumor antigen 1 (WT1) is over-expressed in a vast majority of adult and childhood acute leukemia and myelodysplastic syndromes, being lowly or transiently expressed in normal tissues and hematopoietic stem cells (HSCs). A number of HLA-restricted WT1 epitopes are immunogenic, allowing the in vitro induction of WT1-specific cytotoxic T lymphocytes (CTLs) from patients and healthy donors. Aim The aim of the study was to investigate the feasibility of producing WT1-specific CTLs suitable for somatic cell therapy to prevent or treat relapse in children with acute myeloid or lymphoblastic leukemia given haploidentical HSC transplantation (haplo-HSCT). Methods For WT1-specific CTL production, donor-derived either peripheral blood mononuclear cells (PBMCs) or CD8+ lymphocytes were stimulated with WT1 peptide-loaded donor dendritic cells in the presence of interleukin (IL)-7 and IL-12. Effector cells were re-stimulated once with irradiated donor PBMCs pulsed with WT1-peptides, and then expanded in an antigen-independent way. Results WT1-specific CTLs, displaying high-level cytotoxicity against patients’ leukemia blasts and negligible activity against patients’ non-malignant cells, were obtained from both PBMCs and CD8+ lymphocytes. WT1-specific CTLs obtained from PBMCs showed a better expansion capacity and better anti-leukemia activity than those obtained from CD8+ lymphocytes, even though the difference was not statistically significant. In CTLs derived from PBMCs, both CD8+ and CD4+ subpopulations displayed strong anti-leukemia cytotoxic activity. Discussion Results of this pre-clinical study pave the way to a somatic cell therapy approach aimed at preventing or treating relapse in children given haplo-HSCT for WT1-positive leukemia.

Background aims. Adoptive T-cell therapy with tumor-specifi c T cells has emerged as a potentially useful approach for treating patients with advanced malignancies. We have demonstrated previously the feasibility of obtaining large numbers of autologous anti-tumor-specifi c cytotoxic T lymphocytes (CTL) generated by stimulation of patients ’ peripheral blood mononuclear cells with dendritic cells pulsed with apoptotic tumor cells. Methods . Six patients with progressing metastatic solid tumors (one renal cell carcinoma, two ovarian cancers, two extraosseous peripheral neuroectodermal tumors, one soft tissue sarcoma) not eligible for conventional therapies were treated with adoptive immunotherapy. Anti-tumor CTL, proven to be reactive in vitro against patient tumor cells, but not against normal cells, were infused following lymphodepleting chemotherapy administered to favor T-cell proliferation in vivo. Results . Patients received a median of nine CTL infusions (range 2 – 19). The median number of CTL administered per infusion was 11 10 8 (range 1 – 55 10 8 ). No patient experienced acute or late adverse events related to CTL infusion, even when large numbers of cells were given. Post-infusion laboratory investigations demonstrated an increase in the frequency of circulating anti-tumor T-cells and, in patients with a longer follow-up receiving two CTL infusions/year, a stabilization of these values. Conclusions. Our study demonstrates that autologous ex vivo -generated anti-tumor CTL can be administered safely in patients with advanced solid tumors and can improve the immunologic reactivity of recipients against tumor. These preliminary results provide a rationale for evaluating the clinical effi cacy of this immunotherapeutic approach in phase I/II studies.

Aims and background Adoptive immunotherapy can be a therapeutic option to treat cancer patients with advanced-stage disease refractory to conventional therapies. Methods and study design We used T-cell therapy with autologous antitumor cytotoxic T lymphocytes (CTLs) in a patient with metastatic renal cell carcinoma. Autologous antitumor CTLs obtained by stimulating CD8-enriched cells with dendritic cells pulsed with irradiated apoptotic tumor cells and expanded in vitro were transfused on days +14 and +28 following chemotherapy and every 2 to 4 months thereafter. Results and Conclusions Treatment with high doses of antitumor CTLs proved to be safe and induced immunological responses and long-lasting clinical benefit in our patient.

We demonstrated in previous studies that interleukin (IL) -2 supports in vitro cell proliferation of donor-derived cytotoxic T lymphocyte (CTL) lines directed against different types of leukemia blasts. The aim of this study was to compare the capacity of IL-15 with that of IL-2 in supporting the proliferation and cytotoxic activity of antileukemia CTL cultures, and their influence on T-cell memory compartment differentiation. Antileukemia CTL lines were generated using donor-derived dendritic cells pulsed with apoptotic leukemia blasts, in the presence of IL-12 and IL-7, during the primary culture, and expanded through 2 rounds of leukemia-specific stimulation and 1 round of antigen-independent expansion, each supplemented with either IL-2 or IL-15. Both IL-2-supplemented (IL-2-CTLs) and IL-15-supplemented (IL-15-CTLs) lines contained predominant numbers of CD45RA/CCR7 effector memory (TEM) and CD45RA/CCR7 (TEMRA+) T cells. Significantly higher numbers (P

Although the graft-versus-leukemia effect of allogeneic bone marrow transplantation (BMT) is of paramount importance in the maintenance of disease remission, the role played by the autologous T-cell response in antitumor immune surveillance is less defined. We evaluated the emergence of antileukemia cytotoxic T-lymphocyte precursors (CTLp's) and the correlation of this phenomenon with maintenance of hematologic remission in 16 children with acute myeloid leukemia (AML), treated with either chemotherapy alone (5 patients) or with autologous BMT (A-BMT, 11 patients). Antileukemia CTLp's were detectable in 8 patients in remission after induction chemotherapy; none of them subsequently had a relapse. Of the 8 patients who did not show detectable CTLp frequency while in remission after induction chemotherapy, 7 subsequently experienced leukemia relapse. In patients undergoing A-BMT, molecular fingerprinting of the TCR-Vβ repertoire, performed on antileukemia lines, demonstrated that selected antileukemia T-cell clonotypes, detectable in bone marrow before transplantation, survived ex vivo pharmacologic purging and were found in the recipient after A-BMT. These data provide evidence for an active role of autologous T cells in the maintenance of hematologic remission and also suggest that quantification of antileukemia CTLp frequency may be a useful tool to identify patients at high risk for relapse, thus potentially benefiting from an allogeneic antitumor effect.

In previous studies, we showed the possibility of expanding in vitro polyclonal CTL lines directed against patient leukemia cells using effector cells derived from both HLA-matched and HLA-mismatched hematopoietic stem cell donors. Some CTL lines, especially those derived from an HLA-disparate donor, displayed residual alloreactivity against patient nonmalignant cells. In this study, we evaluated the possibility of separating in vitro CTLs with selective graft-versus-leukemia (GVL) activity from those potentially involved in the development of graft-versus-host disease (GVHD) through single T-cell cloning of antileukemia polyclonal CTL lines. We showed that CTLs that were expanded from a single T-cell clone (TCC), able to selectively kill leukemia blasts and devoid of alloreactivity towards nonmalignant cells, can be obtained from antileukemia alloreactive polyclonal CTL lines. TCCs expressed a wide repertoire of different T-cell receptor (TCR)-Vβ families, mainly produced IFNγ and interleukin 2, irrespective of CD8 or CD4 phenotype, and could be extensively expanded in vitro without losing their peculiar functional features. The feasibility of our approach for in vitro separation of GVL from GVH reaction opens perspectives for using TCCs, which are selectively reactive towards leukemia blasts, for antileukemia adoptive immune therapy approaches after hematopoietic stem cell transplantation, in particular from HLA-mismatched donors. (Cancer Res 2006; 66(14): 7310-6)

Objective Studies of memory T cells transferred with the graft are relevant to better understand the early immune reconstitution of patients given autologous bone marrow transplantation (A-BMT). A critical question is whether memory T cells resident in bone marrow (BM) of patients with hematological malignancies are resistant to either pretransplant chemotherapy or ex vivo pharmacological purging. Patients and methods To address these issues, we evaluated the frequency of tetanus-toxoid (TT)-specific proliferating T-cell precursors (TT-PTCp) in BM and peripheral blood (PB) of eight patients with acute myeloid leukemia (AML) given A-BMT after in vitro purging of BM with mafosfamide. Patients were studied at the time of BM harvesting and five of them also after A-BMT. Results The range of TT-PTCp frequencies found after A-BMT were comparable with those observed in PB and in BM at the time of harvesting and did not differ significantly from those of eight age-matched healthy subjects who donated BM for a human leukocyte antigen-identical sibling. TT-PTCp frequencies in BM, studied before and after ex vivo purging, appeared not to be affected by incubation with mafosfamide. We also compared the T-cell receptor (TCR)-Vβ-repertoire usage of TT-specific T-cell lines (TT-TCL) in BM of patients at the time of harvesting and in their PB 2 months after transplantation. The same TCR-clonotypes were detected in TT-TCL at time of harvesting and after A-BMT. Conclusion These data indicate that BM-resident memory T cells of patients with AML are resistant to both pretransplant chemotherapy and ex vivo pharmacological purging and may contribute to immune reconstitution after A-BMT.

Patients undergoing allogeneic cord blood transplantation (CBT) benefit from a low risk of graft-versus-host disease (GVHD), but there are still concerns that they be able to recover an effective immune capacity early after transplantation. We investigated the ability to develop in vitro T-lymphocyte-mediated immune response toward human cytomegalovirus and Candida albicans antigens, early and late after transplantation, in children given cord blood transplants from either an HLA-identical sibling or an unrelated donor. Proliferative capacity and frequency of antigen-specific T cells were evaluated; antigen-specific CD4+ T-cell clones were also generated and characterized for T-cell receptor repertoire diversity, cytokine phenotype, and their origin (either from donor or patient). We found that the majority of recipients can develop a specific response to viral or fungal antigens already early after transplantation. Antigen-specific T-cell clones of both donor and recipient origin contributed to the reconstitution of immune response. Antigen-specific T lymphocytes of recipient origin were detected in patients receiving a transplant from a relative, after a chemotherapy-based conditioning regimen, and who did not have GVHD. Our results document, at a clonal level, that after CBT recovery of either polyclonal or pauciclonal T-cell response toward widespread pathogens is prompt, with some patients benefiting from a contribution of recipient-derived cells. (Blood. 2004;103:4322-4329)

Allogeneic cord blood transplantation (CBT), especially from unrelated donors, is being increasingly used for treating paediatric patients with both malignant and non-malignant disorders. Recent clinical and experimental evidence suggests that human cord blood mononuclear cells (CBMC) may acquire in utero a state of tolerance towards non-inherited maternal antigens (NIMA). In order to better define this phenomenon, we measured, by means of a limiting dilution assay (LDA), the frequency of NIMA-specific CTL precursors (CTLp) in cord blood samples obtained from 13 healthy neonates. The immunophenotype of the effector cells recovered from LDA was also analysed. Data concerning both CTLp frequency and phenotype of effector cells were compared with those obtained stimulating CBMC with cells of paternal origin (NIPA) and adult PBMC with allogeneic targets. Results showed that cytotoxic cells directed towards cells of maternal origin could be detected in all cord blood samples tested. Phenotype analysis demonstrated that NIPA elicit the expansion of CD3+/CD8bright T cells, a phenotype associated with alloreactive CTL. By contrast, NIMA preferentially stimulated the expansion of CD3-/CD8dim+ cells, a phenotype associated with NK cells, which are known to be able, in certain clinical conditions, to kill allogeneic haematopoietic cells without causing GVHD. Thus, our results indicate that, when evaluated in a limiting dilution condition, NIMA-reactive cord blood cells are detectable and a preferential expansion of NK cells is observed.