Therapy with cultured T cells: principles revisited

Bidirectional crosstalk between therapeutic cancer vaccines and the tumor microenvironment: Beyond tumor antigens

Immunotherapy has rejuvenated cancer therapy, especially after anti-PD-(L)1 came onto the scene. Among the many therapeutic options, therapeutic cancer vaccines are one of the most essential players. Although great progress has been made in research on tumor antigen vaccines, few phase III trials have shown clinical benefits. One of the reasons lies in obstruction from the tumor microenvironment (TME). Meanwhile, the therapeutic cancer vaccine reshapes the TME in an ambivalent way, leading to immune stimulation or immune escape. In this review, we summarize recent progress on the interaction between therapeutic cancer vaccines and the TME. With respect to vaccine resistance, innate immunosuppressive TME components and acquired resistance caused by vaccination are both involved. Understanding the underlying mechanism of this crosstalk provides insight into the treatment of cancer by directly targeting the TME or synergizing with other therapeutics.

The microbiome restrains melanoma bone growth by promoting intestinal NK and Th1 cell homing to bone

Bone metastases are frequent complications of malignant melanoma leading to reduced quality of life and significant morbidity. Regulation of immune cells by the gut microbiome influences cancer progression, but the role of the microbiome in tumor growth in bone is unknown. Using intracardiac or intratibial injections of B16-F10 melanoma cells into mice, we showed that gut microbiome depletion by broad-spectrum antibiotics accelerated intraosseous tumor growth and osteolysis. Microbiome depletion blunted melanoma-induced expansion of intestinal NK cells and Th1 cells and their migration from the gut to tumor-bearing bones. Demonstrating the functional relevance of immune cell trafficking from the gut to the bone marrow (BM) in bone metastasis, blockade of S1P-mediated intestinal egress of NK and Th1 cells, or inhibition of their CXCR3/CXCL9-mediated influx into the BM, prevented the expansion of BM NK and Th1 cells and accelerated tumor growth and osteolysis. Using a mouse model, this study revealed mechanisms of microbiota-mediated gut-bone crosstalk that are relevant to the immunological restraint of melanoma metastasis and tumor growth in bone. Microbiome modifications induced by antibiotics might have negative clinical consequences in patients with melanoma.

Advances in Allogeneic Cancer Cell Therapy and Future Perspectives on “Off-the-Shelf” T Cell Therapy Using iPSC Technology and Gene Editing

The concept of allogeneic cell therapy was first presented over 60 years ago with hematopoietic stem cell transplantation. However, complications such as graft versus host disease (GVHD) and regimen-related toxicities remained as major obstacles. To maximize the effect of graft versus leukemia, while minimizing the effect of GVHD, donor lymphocyte infusion was utilized. This idea, which was used against viral infections, postulated that adoptive transfer of virus-specific cytotoxic T lymphocytes could reconstitute specific immunity and eliminate virus infected cells and led to the idea of banking third party cytotoxic T cells (CTLs). T cell exhaustion sometimes became a problem and difficulty arose in creating robust CTLs. However, the introduction of induced pluripotent stem cells (iPSCs) lessens such problems, and by using iPSC technology, unlimited numbers of allogeneic rejuvenated CTLs with robust and proliferative cytotoxic activity can be created. Despite this revolutionary concept, several concerns still exist, such as immunorejection by recipient cells and safety issues of gene editing. In this review, we describe approaches to a feasible “off-the-shelf” therapy that can be distributed rapidly worldwide. We also offer perspectives on the future of allogeneic cell cancer immunotherapy.

Regression of Breast Cancer Metastases Following Treatment with Irradiated SV-BR-1-GM, a GM-CSF Overexpressing Breast Cancer Cell Line: Intellectual Property and Immune Markers of Response

BACKGROUND

SV-BR-1-GM, derived from a patient with grade 2 (moderately differentiated) breast cancer, is a GM-CSF-secreting breast cancer cell line with properties of antigen-presenting cells. SV-BR-1-GM and next-generation versions are covered by several pending and granted patents.

METHODS

We report findings from an open-label phase I, single-arm pilot study with irradiated SV-BR-1-GM cells in 3 breast and 1 ovarian cancer subjects. Inoculations were preceded by lowdose intravenous cyclophosphamide and followed by interferon-alpha2b injections into the SVBR- 1-GM inoculation sites. We assessed both cellular and humoral immune responses, and measured expression levels of SV-BR-1-GM HLA alleles.

RESULTS

Treatment was generally safe and well tolerated. Immune responses were elicited universally. Overall survival was more than 33 months for three of the four patients. As previously reported, one patient had prompt regression of metastases in lung, breast, and soft tissue. Following cessation of treatment, the patient relapsed widely, including in the brain. Upon retreatment, rapid tumor response was again seen, including complete regression of brain metastases. Consistent with a role of Class II HLA in contributing to SV-BR-1-GM's mechanism of action, this patient allele-matched SV-BR-1-GM at the HLA-DRB1 and HLA-DRB3 loci. We are in the process of developing next-generation SV-BR-1-GM, expressing patient-specific HLAs. Patent applications were filed in various jurisdictions. Thus far, one is granted, in Japan.

CONCLUSION

A whole-cell immunotherapy regimen with SV-BR-1-GM cells induced regression of metastatic breast cancer. We develop intellectual property based on SV-BR-1-GM's predicted mechanism of action to develop additional whole-cell immunotherapies for cancer patients.

'Off-the-shelf' immunotherapy with iPSC-derived rejuvenated cytotoxic T lymphocytes

Adoptive T-cell therapy to target and kill tumor cells shows promise and induces durable remissions in selected malignancies. However, for most cancers, clinical utility is limited. Cytotoxic T lymphocytes continuously exposed to viral or tumor antigens, with long-term expansion, may become unable to proliferate ("exhausted"). To exploit fully rejuvenated induced pluripotent stem cell (iPSC)-derived antigen-specific cytotoxic T lymphocytes is a potentially powerful approach. We review recent progress in engineering iPSC-derived T cells and prospects for clinical translation. We also describe the importance of introducing a suicide gene safeguard system into adoptive T-cell therapy, including iPSC-derived T-cell therapy, to protect from unexpected events in first-in-humans clinical trials.

A phase I dose escalation trial of MAGE-A3- and HPV16-specific peptide immunomodulatory vaccines in patients with recurrent/metastatic (RM) squamous cell carcinoma of the head and neck (SCCHN)

BACKGROUND

We conducted a phase I dose escalation study to evaluate the safety and immunologic response to peptide immunomodulatory vaccines GL-0810 (HPV16) and GL-0817 (MAGE-A3) in HPV16 and MAGE-A3-positive RM-SCCHN patients, respectively.

METHODS

Three dose levels (500, 1,000, and 1,500 µg) of GL-0810 or GL-0817 with adjuvants Montanide (1.2 ml) and GM-CSF (100 µg/m2) were administered subcutaneously q2 weeks for a total of four vaccinations in HPV16 and MAGE-A3-positive RM-SCCHN patients, respectively.

RESULTS

Nine and seven patients were enrolled in the HPV16 and MAGE-A3 cohorts, respectively. No dose-limiting toxicities were observed, and toxicity was predominantly local and grade 1 (erythema, pain, and itching at the injection site). In those patients who received all four vaccinations, 80 % (4/5) of the HPV16 cohort and 67 % (4/6) of the MAGE-A3 cohort developed antigen-specific T cell and antibody responses to the vaccine. Significant concordance between T cell and antibody responses was observed for both groups. No clear dose-response correlation was seen. All patients progressed by RECIST at first repeat imaging, except for one patient in the MAGE-A3 500 µg cohort who had stable disease for 10.5 months. The median PFS and OS for the MAGE-A3 cohorts were 79 and 183 days, respectively, and for the HPV16 cohort 80 and 196 days, respectively.

CONCLUSIONS

GL-0810 and GL-0817 were well tolerated in patients with RM-SCCHN with T cell and antibody responses observed in the majority of patients who received all four vaccinations.

Vaccine immunotherapy in breast cancer treatment: promising, but still early

Cancer vaccine-based immunotherapy should potentiate immunosurveillance function, preventing and protecting against growing tumors. Tumor cells usually activate the immune system, including T lymphocytes and natural killer cells, which are able to eliminate the transformed cells. Immunosubversion mechanisms related to tumor cells antigenic immunoediting induces mechanisms of tolerance and immunoescape. This condition impairs not only host-generated immunosurveillance, but also attempts to harness the immune response for therapeutic purposes. Most trials evaluating breast cancer vaccines have been carried out in patients in the metastatic and adjuvant setting. The aim of this review is to analyze the activity of vaccination strategies in current clinical trials. We summarize the differential approaches, protein-based and cell-based vaccines, focusing on vaccines targeting HER2/neu protein. Another focus of the review is to provide the reader with future challenges in the field, taking into account both the immunological and clinical aspects to better target the goal.

Adoptive T cell transfer for cancer immunotherapy in the era of synthetic biology

Adoptive T cell transfer for cancer and chronic infection is an emerging field that shows promise in recent trials. Synthetic-biology-based engineering of T lymphocytes to express high-affinity antigen receptors can overcome immune tolerance, which has been a major limitation of immunotherapy-based strategies. Advances in cell engineering and culture approaches to enable efficient gene transfer and ex vivo cell expansion have facilitated broader evaluation of this technology, moving adoptive transfer from a "boutique" application to the cusp of a mainstream technology. The major challenge currently facing the field is to increase the specificity of engineered T cells for tumors, because targeting shared antigens has the potential to lead to on-target off-tumor toxicities, as observed in recent trials. As the field of adoptive transfer technology matures, the major engineering challenge is the development of automated cell culture systems, so that the approach can extend beyond specialized academic centers and become widely available.

Passive immunotherapeutic strategies for the treatment of malignant gliomas

This review provides historical and recent perspectives related to passive immunotherapy for high-grade gliomas. The authors discuss approaches that use lymphokine-activated killer cells, cytotoxic T lymphocytes, and monoclonal antibodies.

Identification of immunologic biomarkers associated with clinical response after immune-based therapy for cancer

The identification of immunologic biomarkers associated with clinical response after immune intervention for cancer is an area of intensive investigation. The field would benefit from a more systemic and directed approach for biomarker identification and evaluation. Lessons can be learned from other fields, such as cancer diagnostics, as to how to develop response-associated biomarkers. Studies in both human in vitro models as well as murine models of cancer can significantly inform and streamline the choice of candidates. Adoptive T-cell therapy is an interesting model for exploring potential immunologic surrogates that may predict clinical response. Most likely the clinical effectiveness of immune-based treatments will be predicted by panels of markers rather than single assays of a specific immune effector cell.

T cell growth control using hapten-specific antibody/interleukin-2 receptor chimera

IL-2 is a cytokine that is essential for the expansion and survival of activated T cells. Although adoptive transfer of tumor-specific T cells with IL-2 is one of strategies for cancer immunotherapy, it is essential to replace IL-2 that exerts severe side effects in vivo. To solve this problem, we propose to use an antibody/IL-2R chimera, which can transduce a growth signal in response to a cognate antigen. We constructed two chimeras, in which ScFv of anti-fluorescein antibody was tethered to extracellular D2 domain of erythropoietin receptor and transmembrane/cytoplasmic domains of IL-2Rbeta or gamma chain. When the chimeras were co-expressed in IL-3-dependent pro-B cell line Ba/F3 and IL-2-dependent T cell line CTLL-2, gene-modified cells were selectively expanded in the absence of IL-3 and IL-2, respectively, by adding fluorescein-conjugated BSA (BSA-FL) as a cognate antigen. Growth assay revealed that the cells with the chimeras transduced a growth signal in a BSA-FL dose-dependent manner. Furthermore, STAT3, STAT5, ERK1/2 and Akt, which are hallmarks for IL-2R signaling, were all activated by the chimeras in CTLL-2 transfectant. We also demonstrated that the chimeras were functional in murine primary T cells. These results demonstrate that the antibody/IL-2R chimeras could substantially mimic the wild-type IL-2R and could specifically expand gene-modified T cells in the presence of the cognate antigen.

Loss of T cell-mediated antitumor immunity after construct-specific downregulation of retrovirally encoded T-cell receptor expression in vivo

Adoptive T-cell therapy is clinically efficacious in the treatment of select cancers. However, it is often difficult to obtain adequate numbers of tumor-specific T cells for therapy. One method for overcoming this limitation is to generate tumor-specific T cells by retrovirally mediated T-cell-receptor (TCR) gene transfer. However, despite instances of therapeutic success, major obstacles remain, including attaining the survival of retrovirally modified T cells in vivo as well as inducing long-term and multi-gene retroviral expression. Using a murine model of adoptively transferred retrovirally modified CD8(+) T cells, where antitumor immunity was dependent on sustained, multigene expression, we found that in vitro assays are poor indicators of in vivo efficacy. Despite persisting for over 9 months in a nonlymphopenic environment, genetically modified T cells exhibited discordant retrovirally mediated gene expression in vivo not readily evident from initial in vitro assays. In particular, one of the two TCR subunit genes necessary for antigen specificity was selectively lost in vivo. As this discordant gene expression was associated with the loss of antitumor immunity, consideration of these findings may provide guidance in the design, evaluation and application of retroviral vectors for use in the treatment of cancer and other human disease.

Selective expansion of genetically modified T cells using an antibody/interleukin-2 receptor chimera

Although adoptive transfer of tumor-specific T cells is a plausible approach for cancer immunotherapy, the therapeutic application was hampered due to severe side effects caused by administration of high-dose interleukin (IL)-2, which was used for long-lasting maintenance of tumor-specific T cells in vivo. To solve this problem, here we propose to use an antibody/IL-2 receptor chimera, which can transduce a growth signal in response to a cognate antigen. As a model system, V(H) or V(L) region of anti-hen egg lysozyme (HEL) antibody HyHEL-10 was tethered to extracellular D2 domain of erythropoietin receptor and transmembrane/cytoplasmic domains of IL-2 receptor beta or gamma chain. When the pairs of chimeric receptors (V(H)-IL-2Rbeta and V(L)-IL-2Rgamma, or V(H)-IL-2Rgamma and V(L)-IL-2Rbeta) were expressed in IL-3-dependent pro-B cell line Ba/F3 and IL-2-dependent T cell line CTLL-2, the cognate antigen HEL induced selective expansion of gene-modified cells in the absence of IL-3 and IL-2, respectively. Growth assay revealed that the combination of V(H)-IL-2Rbeta and V(L)-IL-2Rgamma transduced a more stringent HEL-dependent growth signal, indicating some conformational effects of the chimeras. Furthermore, STAT3, STAT5 and ERK1/2, which are hallmarks for IL-2R signaling, were all activated by the antibody/IL-2R chimeras. These results clearly demonstrate that the antibody/IL-2R chimeras could substantially mimic the wild-type IL-2R signaling, suggesting the potential application in expansion of gene-modified T cells.

Use of ultraviolet-light irradiated multiple myeloma cells as immunogens to generate tumor-specific cytolytic T lymphocytes

Background

As the eradication of tumor cells in vivo is most efficiently performed by cytolytic T lymphocytes (CTL), various methods for priming tumor-reactive lymphocytes have been developed. In this study, a method of priming CTLs with ultraviolet (UV)-irradiated tumor cells, which results in termination of tumor cell proliferation, apoptosis, as well as upregulation of heat shock proteins (HSP) expression is described.

Methods

Peripheral blood mononuclear cells (PBMC) were primed weekly with UV-irradiated or mitomycin-treated RPMI 8226 multiple myeloma cells. Following three rounds of stimulation over 21 days, the lymphocytes from the mixed culture conditions were analyzed for anti-MM cell reactivity.

Results

By day 10 of cultures, PBMCs primed using UV-irradiated tumor cells demonstrated a higher percentage of activated CD8+/CD4- T lymphocytes than non-primed PBMCs or PBMCs primed using mitomycin-treated MM cells. Cytotoxicity assays revealed that primed PBMCs were markedly more effective (p < 0.01) than non-primed PBMCs in killing RPMI 8226 MM cells. Surface expression of glucose regulated protein 94 (Grp94/Gp96) and Grp78 were both found to be induced in UV-treated MM cells.

Conclusion

Since, HSP-associated peptides are known to mediate tumor rejection; these data suggest that immune-mediated eradication of MM cells could be elicited via a UV-induced HSP process. The finding that the addition of 17-allylamide-17-demethoxygeldanamycin (17AAG, an inhibitor of HSP 90-peptide interactions) resulted in decreased CTL-induced cytotoxicity supported this hypothesis. Our study, therefore, provides the framework for the development of anti-tumor CTL cellular vaccines for treating MM using UV-irradiated tumor cells as immunogens.

Cysteine cathepsins: regulators of antitumour immune response

Cysteine cathepsins are lysosomal cysteine proteases that are involved in a number of important biological processes, including intracellular protein turnover, propeptide and hormone processing, apoptosis, bone remodelling and reproduction. In cancer, the cathepsins have been linked to extracellular matrix remodelling and to the promotion of tumour cell motility, invasion, angiogenesis and metastasis, resulting in poor outcome of cancer patients; however, cysteine cathepsins are also involved at different levels of the innate and adaptive immune responses. Their best known role in this aspect is their contribution to major histocompatibility complex class II antigen presentation, the processing of progranzymes into proteolytically active forms, cytotoxic lymphocyte self-protection, cytokine and growth factor degradation and, finally, the induction of cytokine expression and modulation of integrin function. This review is focused on the role of cysteine cathepsins in the antitumour immune response and the evaluation of their pro- and anticancer behaviours during the regulation of these processes.

A novel approach to generate host antitumor T cells: adoptive immunotherapy by T cells maturing in xenogeneic thymus

Mouse or human T cells developing in xenogeneic porcine thymus are functional. With efficient peripheral repopulation of mouse T cells by grafting fetal pig thymus (FP THY), B6 nude mice were immunized with inactivated syngeneic melanoma, B16 cells. Splenocytes from B16-immunized FP THY-grafted B6 nude mice efficiently killed B16, but not EL4 target cells in cytotoxicity assays in vitro. Adoptive transfer of splenocytes from B16-immunizd FP THY-grafted B6 nude mice to B16-bearing B6 mice significantly prolonged recipient survival and inhibited B16 solid tumor growth when B16 cells were injected IV or SC, respectively, compared with the identical controls. Splenocytes from nonimmunized FP THY-grafted B6 nude mice failed to protect B6 mice from B16-induced mortality. The present data have demonstrated that mouse T cells maturing in xenogeneic thymus have the ability to kill syngeneic tumor cells. This study may offer a novel resource to produce host antitumor T cells for adoptive immunotherapy of tumor patients.

Accumulation in tumor tissue of adoptively transferred T cells: A comparison between intravenous and intraperitoneal injection

Accumulation of T cells at the tumor is essential in cancer immunotherapy based on adoptive transfer of tumor-specific T cells. To gain further insight into the accumulation process and to evaluate the effect of using different routes of cell transfer, we investigated the accumulation of ovalbumin-specific CD8+ T cells (OT-I) injected either intravenously (IV) or intraperitoneally (IP) into mice carrying a subcutaneous tumor of the ovalbumin-expressing melanoma cell line B16-OVA. Maximal accumulation of the adoptively transferred cells in tumor tissue was observed 5 days after injection, irrespective of the injection route. The route of injection affected neither the total number of adoptively transferred cells found in tumor tissue nor the kinetics of this accumulation. In the spleen, however, the accumulation of adoptively transferred cells was clearly dependent on the injection route. IP injections resulted in a large number of adoptively transferred cells in the spleen on all days analyzed. In comparison, IV injection resulted in significantly fewer adoptively transferred cells in the spleen, and this number decreased over time. The route of injection affected neither the activation status of the adoptively transferred T cells that accumulated at the tumor site, nor the ability of these cells to control tumor growth. Two cell populations, SIINFEKL-tetramer(Low)(Tet(Low))CD69+ CD25+ and Tet(high)CD69- CD25-, were present in tumor samples, whereas only Tet(High)CD69- CD25- cells accumulated in the spleen. In tumors, IV injection resulted in a higher fraction of adoptively transferred cells with an activated phenotype (Tet(Low)CD69+ CD25+) compared with IP injection.

Translating the concept of suppressor/regulatory T cells to clinical applications

The in vivo expansion of suppressor/regulatory T cells (Tregs) is a desirable event in autoimmunity and transplantation. Here we summarize the general rules involved in antigen recognition by T cells and describe Tregs and their requirements, discussing different levels of immune intervention.

Adoptive T cell therapy of solid cancers

The development of immune-based approaches for the treatment of cancer has been actively investigated for many years. One strategy that has emerged as a potentially effective strategy for the treatment of aggressive established malignancies is adoptive T cell therapy. The power of this approach has been repeatedly observed in preclinical animal models. However, moving from homogeneous animal models to the heterogeneous human clinical setting has been very difficult. It is only in recent times that we have been able to pinpoint the problems of the clinical translation of adoptive T cell therapy. Some of the major problems are sources of tumor-specific T cells, ex vivo expansion, persistence, and anti-tumor activity. This review overviews the nature of these problems and some of the emerging solutions.

A Phase I Study of the Optimized Cryptic Peptide TERT572Y in Patients with Advanced Malignancies

OBJECTIVE

It was the aim of this study to evaluate the safety of the optimized cryptic peptide TERT(572Y) in pretreated patients with advanced cancer.

METHODS

Nineteen patients with progressive and chemotherapy-refractory tumors received escalated doses (2-6 mg) of 2 subcutaneous injections of the optimized TERT(572Y) peptide followed by 4 subcutaneous injections of the native TERT(572) peptide every 3 weeks. Both TERT peptides were coinjected with adjuvant Montanide ISA51. Toxicity was evaluated every 3 weeks and peptide-specific CD8+ cells were detected by flow cytometry using TERT(572Y) tetramers.

RESULTS

Fourteen out of 19 patients completed the vaccination program. No grade III/IV toxicity was observed. Grade I anemia was observed in 4 patients and local skin reaction at the injection site in 11 patients. Other nonhematologic toxicities were mild, and no late toxicity was observed after a median postvaccination follow-up period of 10.7 months. There was no dose-limiting toxicity. Peripheral blood TERT(572Y)-specific CD8+ lymphocytes were detected in 13 out of 14 evaluable patients after 2 injections with the optimized TERT(572Y) peptide. There was no complete or partial response, but 4 patients (21%) with persistent TERT(572Y)-specific CD8+ experienced stable disease for a median of 10.5 months.

CONCLUSION

TERT(572Y) peptide vaccine is well tolerated and effective in eliciting specific TERT(572Y) CD8+ lymphocytes in pretreated cancer patients, demonstrating that cryptic peptides could be used in cancer immunotherapy.

Breast cancer vaccines: a clinical reality or fairy tale?

The characterization of tumor antigens recognized by immune effector cells has opened the perspective of developing therapeutic vaccines in the field of breast cancer. The potential advantages of the vaccines are: (i) the induction of a robust immune response against tumors that are spontaneously weekly immunogenic; (ii) the tumor specificity for some antigens; (iii) the good tolerance and safety profile and (iv) the long-term immune memory, critical to prevent efficiently tumor recurrence. Most trials evaluating breast cancer vaccines have been carried out in patients with extended metastatic breast cancer, characterized by aggressive tumors, resistant to standard cytotoxic treatments, so that clinical efficacy was difficult to achieve. However, some significant immune responses against tumor antigens induced upon vaccinations were recorded. The aim of this review is to analyze the activity of vaccination strategies in current clinical trials. Data of clinical activity have been observed by using vaccines targeting HER2/neu protein, human telomerase reverse transcriptase, carcinoembryonic antigen and carbohydrate antigen given after stem cell rescue. The review discusses possible future directions for vaccine development and applications in the adjuvant setting.

Tumor antigen-specific T helper cells in cancer immunity and immunotherapy

Historically, cancer-directed immune-based therapies have focused on eliciting a cytotoxic T cell (CTL) response, primarily due to the fact that CTL can directly kill tumors. In addition, many putative tumor antigens are intracellular proteins, and CTL respond to peptides presented in the context of MHC class I which are most often derived from intracellular proteins. Recently, increasing importance is being given to the stimulation of a CD4+ T helper cell (Th) response in cancer immunotherapy. Th cells are central to the development of an immune response by activating antigen-specific effector cells and recruiting cells of the innate immune system such as macrophages and mast cells. Two predominant Th cell subtypes exist, Th1 and Th2. Th1 cells, characterized by secretion of IFN-gamma and TNF-alpha, are primarily responsible for activating and regulating the development and persistence of CTL. In addition, Th1 cells activate antigen-presenting cells (APC) and induce limited production of the type of antibodies that can enhance the uptake of infected cells or tumor cells into APC. Th2 cells favor a predominantly humoral response. Particularly important during Th differentiation is the cytokine environment at the site of antigen deposition or in the local lymph node. Th1 commitment relies on the local production of IL-12, and Th2 development is promoted by IL-4 in the absence of IL-12. Specifically modulating the Th1 cell response against a tumor antigen may lead to effective immune-based therapies. Th1 cells are already widely implicated in the tissue-specific destruction that occurs during the pathogenesis of autoimmune diseases, such as diabetes mellitus and multiple sclerosis. Th1 cells directly kill tumor cells via release of cytokines that activate death receptors on the tumor cell surface. We now know that cross-priming of the tumor-specific response by potent APC is a major mechanism of the developing endogenous immune response; therefore, even intracellular proteins can be presented in the context of MHC class II. Indeed, recent studies demonstrate the importance of cross-priming in eliciting CTL. Many vaccine strategies aim to stimulate the Th response specific for a tumor antigen. Early clinical trials have shown that focus on the Th effector arm of the immune system can result in significant levels of both antigen-specific Th cells and CTL, the generation of long lasting immunity, and a Th1 phenotype resulting in the development of epitope spreading.

Ex Vivo Expansion of Human Umbilical Cord Blood-Derived T-Lymphocytes with Homologous Cord Blood Plasma

This study was designed to establish a more effective and safe culture system for adoptive immunotherapy by investigating the use of homologous cord blood plasma (HCBP) instead of fetal bovine serum (FBS), which has various limitations including ethical problems for the ex vivo expansion of human umbilical T lymphocytes. Fresh human umbilical mononuclear cell fractions were isolated by Ficoll-Hypaque density centrifugation. Nonadherent mononuclear cell fractions were cultured with anti-CD3 antibody (5 microg/ml), IL-2 (175 U/ml), and either 10% FBS or 10% HCBP. On day 8, the cellular proliferation rate and cell surface markers were assessed. There was no significant difference in proliferation when human umbilical cord blood T lymphocytes were grown in medium supplemented with FBS or HCBP (p > 0.05). In medium containing FBS, the proportion of CD3(+)CD4(+) (markers for helper T cell), CD3(+)CD8(+) (cytotoxic T cell), CD3(+)CD25(+) (activated T cell), CD3(+)CD38(+) (immature T cell), and CD3(+)CD45RO(+) (memory T cell) cells was significantly increased (p < 0.05), whereas proportion of CD3(+)CD45RA(+) (naive T cell) and CD16(+)CD56(+) (NK cell) cells was significantly decreased (p < 0.05). In HCBP supplemented medium, the proportion of CD3(+)CD8(+), CD3(+)CD25(+), CD3(+)CD45RA(+), and CD3(+)CD45RO(+) cells was significantly increased (p < 0.05). The proportion of CD3(+)CD4(+), CD3(+)CD45RO(+) and CD3(+)CD38(+) cells was significantly higher, but proportion of CD3(+)CD45RA(+) and CD3(+)CD8(+) cells was significantly lower in FBS compared with HCBP supplemented medium (p < 0.05). Our results support the feasibility of ex vivo expansion of human umbilical cord blood T lymphocytes in medium supplemented with HCBP for future adoptive cellular immunotherapy.

Diphtheria toxin-murine granulocyte-macrophage colony-stimulating factor–induced hepatotoxicity is mediated by Kupffer cells

DT388GMCSF, a fusion toxin composed of the NH2-terminal region of diphtheria toxin (DT) fused to human granulocyte-macrophage colony-stimulating factor (GMCSF) has shown efficacy in the treatment of acute myeloid leukemia. However, the primary dose-limiting side effect is liver toxicity. We have reproduced liver toxicity in rats using the rodent cell-tropic DT-murine GMCSF (DT390mGMCSF). Serum aspartate aminotransferase and alanine aminotransferase were elevated 15- and 4-fold, respectively, in DT390mGMCSF-treated rats relative to controls. Histologic analysis revealed hepatocyte swelling; however, this did not lead to hepatic necrosis or overt histopathologic changes in the liver. Immunohistochemical staining showed apoptotic cells in the sinusoids, and depletion of cells expressing the monocyte/macrophage markers, ED1 and ED2, indicating that Kupffer cells (KC) are targets of DT390mGMCSF. In contrast, sinusoidal endothelial cells seemed intact. In vitro, DT390mGMCSF was directly cytotoxic to primary KC but not hepatocytes. Two related fusion toxins, DT388GMCSF, which targets the human GMCSF receptor, and DT390mIL-3, which targets the rodent IL-3 receptor, induced a less than 2-fold elevation in serum transaminases and did not deplete KC in vivo. In addition, DTU2mGMCSF, a modified form of DT390mGMCSF with enhanced tumor cell specificity, was not hepatotoxic and was significantly less toxic to KC in vivo and in vitro. These results show that DT390mGMCSF causes liver toxicity by targeting KC, and establish a model for studying how this leads to hepatocyte injury. Furthermore, alternative fusion toxins with potentially reduced hepatotoxicity are presented.

Use of adenoviruses encoding CD40L or IL-2 against B cell lymphoma

Some B cell lymphomas lack important costimulatory properties that could prevent them from being used as cell based vaccines. Infection of A20 B lymphoma cells with a replication-defective adenovirus encoding murine (m) CD40L, but not mIL-2, produces an antigen presentation phenotype with upregulation of MHC Class I/II, induction of B7-1/2 molecules and production of MIL-12 and MIP-1alpha. Subcutaneous vaccination with irradiated Ad-mCD40L-infected- or Ad-mIL-2-infected-A20 cells generated A20-specific CD8+ T cell responses and cross reactive A20 Ig antibodies. Only vaccination with Ad-mCD40L-infected A20 cells produced a significant delay in tumor growth and long-term survival (p = 0.0039). Stronger protective immunity to A20 challenge was generated by intravenous priming with A20 cells infected with Ad-mCD40L, Ad-mIL-2 or their combination followed by a boost immunization with A20 cells activated with syngeneic fibroblasts expressing CD40L. Compared to Ad-LacZ-infected A20 priming, the combination priming was most effective followed by Ad-mCD40L and Ad-mIL-2 (p = 0.0027, p = 0.0027, p = 0.0163 respectively). Significant A20-specific CD8+ T cell-mediated cytotoxicity was only demonstrated in splenocytes from these groups of vaccinated animals. By contrast, ELISPOT assay of splenocytes from all A20 prime/boosted vaccinated groups demonstrated increases in gamma-interferon release by T cells elicited by in vitro stimulation either with A20 cells or another syngeneic 2PK-3 lymphoma, indicating the presence of cross reactive immunity. Similarly anti-A20 immunoglobulin antibodies generated after vaccination were not necessarily A20 idiotype-specific. Direct therapy of pre-established tumors was achieved with the combination of Ad-mCD40L and Ad-mIL-2 given at Days 4 and 8 at the tumor site with a significant long-term survival of 85% of tumor-bearing mice (p = 0.0001). Our study strongly supports the use of Ad-CD40L and Ad-IL-2 combination therapy for the treatment of patients with B cell lymphoma.

The Mortimer M. Bortin lecture

The graft-versus-leukemia effect of allogeneic blood or marrow transplantation is a dramatic example of the power of the immune system to eradicate malignant disease. In this personal essay, adapted from the inaugural Mortimer M. Bortin Lecture presented at the 2004 Tandem BMT Meetings, the author recounts early efforts by Bortin and others to manipulate the graft-versus-leukemia effect and separate it from the potentially fatal complications of graft-versus-host disease.

IL-12 enhances the generation of tumour antigen-specific Th1 CD4 T cells during ex vivo expansion

CD4+ T cells are essential for the immune response against cancer. Vaccination against cancer will likely only be effective at preventing growth of micrometastatic disease while adoptive T cell therapy will be better suited for eradication of bulky pre-existing disease (Knutson et al. Expert Opin Biol Ther 2002; 2:55-66). Problems with the use of adoptive T cell therapy include lack of CD4+ T cell help, low frequency of antigen-specific T cells, and lack of effective ex vivo expansion techniques. In this study, we focused on improving ex vivo expansion of CD4+ T helper cells. The effects of IL-12, along with IL-2, on the ex vivo generation of HER-2/neu antigen-specific T cells were examined. Patients were immunized with a peptide-based vaccine that contained a helper epitope, p776-790, derived from the intracellular domain of HER-2/neu. While T cell immunity to p776-790, assessed by proliferation assays, could be readily measured in short-term cultures, cell line generation by multiple in vitro stimulation with peptide and IL-2 as the only added cytokine resulted in loss of antigen-specific proliferation. The inclusion of IL-12, along with IL-2, restored antigen-specific proliferation in a dose-dependent fashion. The resulting p776-790-specific T cells responded readily to antigen by proliferating and producing type I cytokines (IFN-gamma and TNF-alpha). The increased proliferative response of the cultures was due in part to an increase in the number of HER-2/neu-specific T cells. These results suggest that IL-12 is an important cytokine for ex vivo recovery and maintenance of antigen-specific CD4+ T lymphocytes that would otherwise be lost by using IL-2 alone in combination with antigen. Furthermore, these results have important implications for ex vivo expansion of CD4+ T cell for use in anti-tumour adoptive immunotherapy.

Retroviral Immunotoxin Gene Therapy of Leukemia in Mice Using Leukemia-Specific T Cells Transduced with an Interleukin-3/Bax Fusion Protein Gene

In past studies, we showed that T cells transduced with retroviral diphtheria immunotoxin (IT) target genes could serve as vehicles for delivering IT to tumors in vivo. We took advantage of the observation that antigen-specific T cells are able to penetrate tumors to design an approach delivering combined cellular and humoral therapy directly to the tumor site. To improve tumor specificity, we selected interleukin (IL)-3 as a ligand because its receptor is selectively overexpressed on myeloid leukemia progenitors. Because Bcl-2 family proteins show structural similarity to diphtheria toxin (DT), we constructed a unique retroviral IT using Bax, a proapoptotic member of the Bcl-2 family, in place of DT. Bax was chosen because several studies showed that its transduction induces lethal apoptosis in different cancers. The retroviral construct for gene therapy included IL-3 positioned downstream of its 80 amino acid leader, and permitted cotranslational protein synthesis of hybrid IL-3/human Bax fusion protein. Other vectors were constructed with IL-3 fused to DT or Pseudomonas exotoxin. Retroviral vectors were used to transiently transduce C8, a CD4(+) T cell clone that specifically recognized FBL-3, a lethal myeloid leukemia. Supernatants collected from transduced cells showed proapoptotic activity and selectively inhibited FBL-3 cells in vitro. Intraperitoneal injection of transduced but not nontransduced C8 into mice with subcutaneous tumors or systemic cancer significantly inhibited tumor growth. These results indicate that retroviral IT made with IL-3 and various toxic proteins may be useful in patients with acute myelogenous leukemia (AML). Furthermore, the Bax construct may be particularly useful as a nonimmunogenic substitute for bacterial toxins in retIT.

Future directions in the management of ovarian cancer

As investigators at the bench define the oncogenic pathways involved in ovarian cancer growth and invasion, clinical scientists will develop therapies to target these important pathways. The approach to the treatment of ovarian cancer will change to focus on strategies designed to eliminate minimal residual disease after primary therapy and in this way cure the disease. Concepts of consolidation after standard adjuvant chemotherapy and maintenance regimens will start to be evaluated for clinical efficacy. In addition, the focus on recurrent disease may change from repeated cytotoxic approaches to regimens chosen to prevent invasion or the development of drug resistance, changing the approach to ovarian cancer recurrence to a treatment plan of managing a chronic, but not imminently terminal, disease.

Immunologic principles and immunotherapeutic approaches in ovarian cancer

Ovarian cancer is an immunogenic tumor, and numerous antigens have been identified in recent years. Several of these antigens are important in regulating tumor growth and may be ideal targets for the development of immune-based strategies. In the absence of immunologic intervention, tumors evade the immune system by several mechanisms, most notably tolerance and immunosuppression. As understanding of the immune response improves, strategies are being designed to circumvent T-cell tolerance to self-antigens through modulation of APC function. In addition, techniques are being developed to identify reverse ovarian cancer-induced immune evasion tactics. The type of the immune-based therapy to apply varies with disease burden. It is hoped that discoveries at the bench along with lessons learned in prior clinical trials soon will allow clinicians to develop rationally based immunologic strategies to treat and prevent ovarian cancer.

Immunotherapy of glioblastoma multiforme

Glioblastoma multiforme is immunogenic and several glioblastoma multiforme-related antigens have now been identified. In addition, the immunologic characteristics of the tumor microenvironment that may affect tumor growth are becoming increasingly understood. The type of immune-based approach selected to treat glioblastoma multiforme will depend on the tumor burden. For minimal disease states, active vaccination may be useful for generating adequate protection from relapse. However, for more advanced stage disease states, more rigorous strategies may need to be applied, such as adoptive T-cell therapy, antibody therapy or a combination of different techniques. The immunosuppressive environment observed during advanced malignancy may need to be reversed for improved efficacy of immune-based therapies.

Adoptive immunotherapy for malignant glioma

Despite remarkable advancements in imaging modalities and treatment options available to patients diagnosed with malignant brain tumors, the prognosis for those with high-grade lesions remains poor. The imprecise mechanisms of currently available treatments to manage these tumors do not spare damage to the normal surrounding brain and often result in major cognitive and motor deficits. Immunotherapy holds the promise of offering a potent, yet targeted, treatment to patients with brain tumors, with the potential to eradicate the malignant tumor cells without damaging normal tissues. The T cells of the immune system are uniquely capable of recognizing the altered protein expression patterns within tumor cells and mediating their destruction through a variety of effector mechanisms. Adoptive T-cell therapy is an attempt to harness and amplify the tumor-eradicating capacity of a patients' own T cells and then return these effectors to the patient in such a state that they effectively eliminate residual tumor. Although this approach is not new to the field of tumor immunology, new advancements in our understanding of T-cell activation and function and breakthroughs in tumor antigen discovery hold great promise for the translation of this modality into a clinical success.

Human papillomavirus therapy for the prevention and treatment of cervical cancer

Cervical carcinoma is associated with human papillomavirus infection. Proliferation of cancer cells depends on the continual expression of the E6 and E7 viral oncogenes. This article includes treatment strategies that can interfere with expression or function of the proteins and immunotherapeutic approaches that can eliminate cells that express E6 and E7 proteins.

Low oxygen tension enhances the stimulation and proliferation of human T lymphocytes in the presence of IL-2

BACKGROUND

Optimization of the culture environment for the ex vivo expansion of T cells is crucial for obtaining the large doses of cells needed for cellular immunotherapy. O2 tension is a key parameter that impacts the proliferation and quality of the expanded T cells.

METHODS

Peripheral blood mononuclear cells were stimulated with either PHA or an anti-CD3 monoclonal antibody under 5% (low) or 20% (high) O2 atmospheres. After stimulation, cells were cultured in the presence of IL-2 under either low or high O2 conditions.

RESULTS

T cells stimulated and grown under 5% O2 exhibited higher proliferation rates and a mean (n = 11) of 5.8-fold greater total expansion over T cells grown under 20% O2. Stimulation under 5% O2 produced a lasting proliferative effect even after a switch to 20% O2. Examination of apoptosis by the flow cytometry-based TUNEL assay showed a mean (n = 9) of 2.9-fold greater percentage of apoptotic cells under 20% O(2). Flow-cytometric analysis of the IL-2 receptor (CD25) showed that the normal downregulation kinetics - following stimulation-induced CD25 upregulation - were slowed under 5% O(2), such that the 5% O2 cultures had a greater number of CD25+ cells, and those CD25+ cells expressed an average (n = 6) of 41% higher levels of CD25 receptor per cell. No significant O2 tension effects were observed on other surface antigens (CD3, CD28, and CD62L) examined. The key metabolic parameters, specific glucose uptake rate, q(glu), and specific lactate production rate, q(lac), were both increased by a mean (n = 5) of 47% under 5% O2.

DISCUSSION

Beyond the physiological significance, improved T-cell proliferation under 5% O2 would allow for decreased culture times in expanding T cells for cellular immunotherapies. Evidence of increased IL-2R expression and reduced apoptosis levels under 5% O2 may help explain this phenomenon.

Tissue distribution of target antigen has a decisive influence on the outcome of adoptive cancer immunotherapy

Adoptive transfer of allogeneic T cells has unmatched efficacy to eradicate leukemic cells. We therefore sought to evaluate in kinetic terms interactions between T cells and allogeneic leukemic cells. T cells primed against the model B6(dom1) minor histocompatibility antigen were adoptively transferred in irradiated B10 (B6(dom1)-positive) and congenic B10.H7(b) (B6(dom1)-negative) recipients, some of which were also injected with EL4 leukemia/lymphoma cells (B6(dom1)-positive). A key finding was that the tissue distribution of the target epitope dramatically influenced the outcome of adoptive cancer immunotherapy. Widespread expression of B6(dom1) in B10 recipients induced apoptosis and dysfunction of antigen-specific T cells. Furthermore, in leukemic B10 and B10.H7(b) hosts, a massive accumulation of effector/memory B6(dom1)-specific T cells was detected in the bone marrow, the main site of EL4 cell growth. The accumulation of effector/memory cells in recipient bone marrow was EL4 dependent, and its kinetics was different from that observed in recipient spleen. We conclude that strategies must be devised to prevent apoptosis of adoptively transferred T cells confronted with a high antigen load and that local monitoring of the immune response at the site of tumor growth may be mandatory for a meaningful assessment of the efficacy of adoptive immunotherapy.

Systemic administration of IL-15 augments the antigen-specific primary CD8+ T cell response following vaccination with peptide-pulsed dendritic cells

The systemic administration of IL-2 can act as a potent adjuvant for T cell-directed vaccine strategies. However, not only is the administration of IL-2 potentially toxic, but recent evidence suggests that it may also paradoxically limit the duration and magnitude of the cytotoxic T cell response. A recently identified cytokine, IL-15, shares many properties with IL-2 and may provide a preferential means of augmenting T cell-directed vaccine responses. Although well characterized in vitro, there are few data on the ability of IL-15 to augment T cell-mediated responses in vivo. We therefore evaluated the ability of systemic IL-15 to function as a T cell adjuvant in a murine vaccine model. To establish a population of easily identifiable Ag-responsive T cells, naive CD8(+) (OT-1) T cells were first adoptively transferred into mice. Vaccination with peptide-pulsed dendritic cells induced a modest expansion of OT-1 T cells. The addition of systemic IL-15 for 7 days following vaccination resulted in a significant increase in the expansion of responding T cells in the PBL, spleen, and lymph nodes. Importantly, the responding T cells were cytotoxic and maintained a Tc1-biased phenotype. We did not observe either enhanced resistance to activation-induced cell death or preferential generation of memory T cells as a result of treatment with IL-15 compared with IL-2. These studies show for the first time that IL-15 is capable of augmenting the primary CD8(+) T cell response to vaccination and contribute to the basis for future experiments exploring the clinical role of IL-15.

Low oxygen tension and autologous plasma enhance T-cell proliferation and CD49d expression density in serum-free media

BACKGROUND

As cellular immunotherapy with ex vivo expanded cells becomes more widely used to treat a variety of illnesses, optimization of culture parameters, to maximize cell production and function, is essential for continued success. The effects of reduced oxygen tension and autologous plasma on T-cell expansion, receptor expression, apoptosis, and cytolytic activity in serum-free media were investigated.

METHODS

PBMCs derived from whole blood samples were activated with anti-CD3 and anti-CD28 MAb in serum-free (AIM V) medium containing IL-2, and maintained at 5% and 20% oxygen tension. In some cases cultures were supplemented with 2% autologous plasma.

RESULTS

Low oxygen enhanced T-cell expansion 13- and 4.8-fold in serum-free and plasma-supplemented media, respectively. Autologous plasma also had a beneficial effect on T-cell cultures. Plasma-supplemented cultures expanded 74-fold more than serum-free cultures at low oxygen tension, and 43-fold more at high oxygen tension. Several samples expanded very poorly under serum-free conditions, and reasonable cell numbers were obtained only from plasma-supplemented cultures. CD49d expression density increased 3-fold to 4-fold in cultures supplemented with plasma. In contrast to our previous findings in serum-containing media, IL-2 receptor expression kinetics were unaffected by oxygen tension. No effects caused by oxygen tension or autologous plasma on expression of other surface antigens (CD4, CD8, CD44, CD95) were observed.

DISCUSSION

Low oxygen tension and autologous plasma greatly increase expansion of T cells, thereby decreasing the time needed for production of cells for prophylaxis. Increased CD49d expression density may translate into improved migration and cytotoxicity.

Opposing effects of IL-2 in tumor immunotherapy: promoting CD8 T cell growth and inducing apoptosis

Tumors often induce specific CTL responses, but these are usually ineffective at eliminating the growing tumor. The T cell growth factor IL-2 has potential for expanding and prolonging CTL responses, and there is considerable interest in using this cytokine in combination with other immunotherapeutic agents that target T cell responses. Using adoptive transfer of OT-I CD8 T cells specific for OVA(257-264) peptide, and E.G7 tumor cells transfected with OVA, we have examined the effects of IL-2 on the generation and maintenance of a CTL response to the tumor. Administration of IL-2 during the initial phase of the response, clonal expansion, and development of effector function, had no effect on the number of CTL generated or the control of tumor growth. In contrast, a short 2-day time course of low-dose IL-2 at the peak of clonal expansion or at later times resulted in prolonged and expanded responses by the OT-I CTL, with concomitant decrease in tumor load and extension of survival. However, when IL-2 administration was more prolonged, as is often the case in clinical trials, the therapeutic benefit was lost due to elimination of the tumor-specific CTL, at least in part through induction of apoptosis. These results demonstrate that use of IL-2 for tumor immunotherapy is very much a double-edged sword and strongly suggest that more limited time and dose regimens may substantially improve its clinical efficacy when it is used in conjunction with approaches that target CTL responses.

Antitumor activity of cytotoxic T lymphocytes engineered to target vascular endothelial growth factor receptors

The demonstration that angiogenesis is required for the growth of solid tumors has fueled an intense interest in the development of new therapeutic strategies that target the tumor vasculature. Here we report the development of an immune-based antiangiogenic strategy that is based on the generation of T lymphocytes that possess a killing specificity for cells expressing vascular endothelial growth factor receptors (VEGFRs). To target VEGFR-expressing cells, recombinant retroviral vectors were generated that encoded a chimeric T cell receptor comprised of VEGF sequences linked to intracellular signaling sequences derived from the zeta chain of the T cell receptor. After transduction of primary murine CD8 lymphocytes by such vectors, the transduced cells were shown to possess an efficient killing specificity for cells expressing the VEGF receptor, Flk-1, as measured by in vitro cytotoxicity assays. After adoptive transfer into tumor-bearing mice, the genetically modified cytotoxic T lymphocytes strongly inhibited the growth of a variety of syngeneic murine tumors and human tumor xenografts. An increased effect on in vivo tumor growth inhibition was seen when this therapy was combined with the systemic administration of TNP-470, a conventional angiogenesis inhibitor. The utilization of the immune system to target angiogenic markers expressed on tumor vasculature may prove to be a powerful means for controlling tumor growth.

Ex vivo expansion of functional T lymphocytes from HIV-infected individuals

This study was designed to define the conditions for expansion of functional T lymphocytes from human immunodeficiency virus (HIV)-infected subjects, with the ultimate goal of using these cells for immunotherapy. The most appropriate culture conditions for good T cell proliferation included stimulation with anti-CD3 and anti-CD28 coated microspheres, and propagation in Aim V serum-free media with 20 U/ml interleukin-2 (IL-2), supplemented with decreasing concentrations of serum for the initial 8 days. Under these conditions, a 14-day culture period yielded approximately a 10,000-fold expansion of T lymphocytes from HIV-infected donors. The cultured cells comprised approximately 15% CD4+ cells and 70% CD8+ cells. These cells retained functional capacity as assessed by cytotoxicity towards HIV proteins, and production of IL-2 and interferon-gamma (IFN-gamma). Viral replication within the culture system was controlled, but not eliminated, without the requirement for antiviral agents. These culture conditions were demonstrated to be suitable for larger scale expansion of cells in hollow fibre bioreactors. This methodology provides a suitable means of producing large quantities of functional T cells for use in autologous immunotherapy protocols.

Adoptive T-cell therapy for the treatment of solid tumours

Solid tumours can be eradicated by infusion of large amounts of tumour-specific T-cells in animal models. The successes seen in preclinical models, however, have not been adequately translated to human disease due, in part, to the inability to expand tumour antigen-specific T-cells ex vivo. Polyclonality and retention of antigen-specificity are two important properties of infused T-cells that are necessary for successful eradication of tumours. Investigators are beginning to evaluate the impact of attempting to reconstitute full T-cell immunity representing both major T-cell subsets, cytolytic T-cells and T-helper (Th) cells. One of the more important and often overlooked steps of successful adoptive T-cell therapy is the ex vivo expansion conditions, which can dramatically alter the phenotype of the T-cell. A number of cytokines and other soluble activation factors that have been characterised over the last decade are now available to supplement in vitro antigen presentation and IL-2. Newer molecular techniques have been developed and are aimed at genetically altering the characteristics of T-cells including their antigen-specificity and growth in vivo. In addition, advanced imaging techniques, such as positron emission tomography (PET), are being implemented in order to better define the in vivo function of ex vivo expanded tumour-specific T-cells.

Tumor-infiltrating macrophages induce apoptosis in activated CD8(+) T cells by a mechanism requiring cell contact and mediated by both the cell-associated form of TNF and nitric oxide

We have investigated the ability of different cells present in murine tumors to induce apoptosis of activated CD8(+) T cells in vitro. Tumor cells do not induce apoptosis of T cells; however, macrophages that infiltrate tumors are potent inducers of apoptosis. Tumor macrophages express cell surface-associated TNF, TNF type I (CD120a) and II (CD120b) receptors, and, upon contact with T cells which induces release of IFN-gamma from T cells, secrete nitric oxide. Killing of T cells in vitro is blocked by Abs to IFN-gamma, TNF, CD120a, or CD120b, or N-methyl-L-arginine. In concert with that finding, tumor macrophages isolated from either TNF type I or type II receptor -/- mice are not proapoptotic and do not produce nitric oxide upon contact with activated T cells. Control macrophages do not express TNF receptors or release nitric oxide. Tumor cells or tumor-derived macrophages do not express FasL, and blocking Abs to either Fas or FasL have no effect on macrophage-mediated T cell killing. These results demonstrate that macrophages which infiltrate tumors are highly proapoptotic and may be responsible for elimination of activated antitumor T cells within the tumor bed.

Regression of extensive pulmonary metastases in mice by adoptive transfer of antigen-specific CD8(+) CTL reactive against tumor cells expressing a naturally occurring rejection epitope

In this study, we developed a mouse model of adoptive immunotherapy reflecting immune recognition of syngeneic tumor cells naturally expressing an endogenous rejection Ag. Specifically, in a pulmonary metastases model, we examined the potency and maintenance of an antitumor CD8(+) CTL response in vivo, as well as its effectiveness against an "extensive" tumor burden. The approach taken was to first generate tumor-specific CTL from mice challenged with the CMS4 sarcoma coadministered with anti-CTLA4 mAb, which has been shown to facilitate the induction of Ag-specific T cell responses in vivo. An H-2L(d)-restricted nonamer peptide, derived from an endogenous murine leukemia provirus was identified as a CMS4-reactive CTL epitope based upon the following: CTL cross-recognition of another syngeneic tumor cell line (CT26 colon carcinoma) previously characterized to express that gene product; sensitization of Ag-negative lymphoblasts or P815 targets with the peptide; and by cold target inhibition assays. In vivo, the adoptive transfer of CMS4-reactive CTL (> or =1 x 10(6)) resulted in nearly the complete regression of 3-day established lung metastases. Furthermore, mice that rejected CMS4 following a single adoptive transfer of CTL displayed antitumor activity to a rechallenge 45 days later, not only in the lung, but also at a s.c. distal site. Lastly, the adoptive transfer of CTL to mice harboring extensive pulmonary metastases (> 150 nodules) led to a substantial reduction in tumor burden. Overall, these data suggest that the adoptive transfer of tumor-specific CTL may have therapeutic potential for malignancies that proliferate in or metastasize to the lung.

IL-2 during in vitro priming promotes subsequent engraftment and successful adoptive tumor immunotherapy by persistent memory phenotypic CD8(+) T cells

Adoptive T cell tumor immunotherapy potentially consists of two protective components by the transferred effector cells, the immediate immune response and the subsequent development of memory T cells. The extent by which adoptively transferred CD8(+) CTL are destined to become memory T cells is ambiguous as most studies focus on the acute effects on tumor shortly following adoptive transfer. In this study we show that a substantial fraction of the input CTL develop into memory cells that reject a s.c. tumor challenge. The use of exogenous IL-2 or a combination of IL-2 and IL-4, but not solely IL-4, during the ex vivo culture for the CTL inoculation was necessary for efficient development of CD8(+) memory T cells. Thus, an important component of adoptive immunotherapy using CTL is the production of CD8(+) Ag-specific memory cells which is primarily favored by IL-2 receptor signaling during ex vivo generation of the effector CTL.