Potentiation of Tumor Eradication by Adoptive Immunotherapy with T-cell Receptor Gene-Transduced T-Helper Type 1 Cells

Effects of Chemotherapy Agents on Circulating Leukocyte Populations: Potential Implications for the Success of CAR-T Cell Therapies

Simple Summary

CAR-T cell therapy is a new approach to cancer treatment that is based on manipulating a patient’s own T cells such that they become able to seek and destroy cancer cells in a highly specific manner. This approach is showing remarkable efficacy in treating some types of blood cancers but so far has been much less effective against solid cancers. Here, we review the diverse effects of chemotherapy agents on circulating leukocyte populations and find that, despite some negative effects over the short term, chemotherapy can favourably modulate the immune systems of cancer patients over the longer term. Since blood is the starting material for CAR-T cell production, we propose that these effects could significantly influence the success of manufacturing, and anti-cancer activity, of CAR-T cells. Thus, if timed correctly, chemotherapy-induced changes to circulating immune cells could allow CAR-T cells to unleash more effective anti-tumour responses.

Abstract

Adoptive T-cell therapy using autologous T cells genetically modified to express cancer-specific chimeric antigen receptors (CAR) has emerged as a novel approach for cancer treatment. CAR-T cell therapy has been approved in several major jurisdictions for treating refractory or relapsed cases of B-cell precursor acute lymphoblastic leukaemia and diffuse large B-cell lymphoma. However, in solid cancer patients, several clinical studies of CAR-T cell therapy have demonstrated minimal therapeutic effects, thus encouraging interest in better integrating CAR-T cells with other treatments such as conventional cytotoxic chemotherapy. Increasing evidence shows that not only do chemotherapy drugs have tumoricidal effects, but also significantly modulate the immune system. Here, we discuss immunomodulatory effects of chemotherapy drugs on circulating leukocyte populations, including their ability to enhance cytotoxic effects and preserve the frequency of CD8⁺ T cells and to deplete immunosuppressive populations including regulatory T cells and myeloid-derived suppressor cells. By modulating the abundance and phenotype of leukocytes in the blood (the ‘raw material’ for CAR-T cell manufacturing), we propose that prior chemotherapy could facilitate production of the most effective CAR-T cell products. Further research is required to directly test this concept and identify strategies for the optimal integration of CAR-T cell therapies with cytotoxic chemotherapy for solid cancers.

T-cell-receptor cross-recognition and strategies to select safe T-cell receptors for clinical translation

Adoptive transfer of T-cell-receptor (TCR)-transduced T cells has shown promising results for cancer treatment, but has also produced severe immunotoxicities caused by on-target as well as off-target TCR recognition. Off-target toxicities are related to the ability of a single T cell to cross-recognize and respond to several different peptide–major histocompatibility complex (pMHC) antigens; a property that is essential for providing broad antigenic coverage despite a confined number of unique TCRs in the human body. However, this degeneracy makes it incredibly difficult to account for the range of targets that any TCR might recognize, which represents a major challenge for the clinical development of therapeutic TCRs. The prospect of using affinity-optimized TCRs has been impeded due to observations that affinity enhancement might alter the specificity of a TCR, thereby increasing the risk that it will cross-recognize endogenous tissue. Strategies for selecting safe TCRs for the clinic have included functional assessment after individual incubations with tissue-derived primary cells or with peptides substituted with single amino acids. However, these strategies have not been able to predict cross-recognition sufficiently, leading to fatal cross-reactivity in clinical trials. Novel technologies have emerged that enable extensive characterization of the exact interaction points of a TCR with pMHC, which provides a foundation from which to make predictions of the cross-recognition potential of individual TCRs. This review describes current advances in strategies for dissecting the molecular interaction points of TCRs, focusing on their potential as tools for predicting cross-recognition of TCRs in clinical development.

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T-cell-receptor (TCR) degeneracy plays a fundamental role in the capacity of our immune systems to recognize foreign antigens.

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TCR cross-reactivity provides an inherent risk in TCR–gene transfer cell therapies.

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Advances in description of TCR cross-recognition can guide the selection process for TCRs into clinical use.

Plasmodium parasite as an effective hepatocellular carcinoma antigen glypican-3 delivery vector

We have previously demonstrated that malaria parasite infection has an anti-tumor effect in a mouse model. This research aimed to investigate the possibility of using Plasmodium parasite as a novel vaccine vector for hepatocellular carcinoma (HCC) immunotherapy. We constructed a Plasmodium yoelii 17XNL strain (P.y) expressing murine glypican-3 (GPC3) protein (P.y-GPC3), and examined its therapeutic potency in a murine Hepa1-6-induced hepatoma model that highly expressed GPC3 protein. The prerequisites for invoking a CD8+ T cell response were assessed after P.y-based immunization, which included obviously increased concentrations of T helper cell type 1 (Th1)-associated cytokines, such as IL-2, IFN-γ and TNF-α, in serum and preferential expansion of the CD8α+ dendritic cell (DC) subset with higher expression of CD80 and CD86 molecules. Compared with uninfected and wild-type P.y-infected mice, a significant GPC3-specific cytotoxic T lymphocyte (CTL) response was detected in P.y-GPC3 vaccinated mice. Furthermore, P.y-GPC3-based vaccination dramatically inhibited Hepa1-6-induced tumor growth in the implanted HCC and prolonged the survival of tumor-bearing mice. We concluded that a Plasmodium-based vector is highly efficient in inducing tumor antigen-specific T cell-mediated immunity and protection against tumor cells. More broadly, this strategy supported our hypothesis that Plasmodium parasites, as novel therapeutic antigen vectors, may be applicable to tumor immunotherapy for patients with HCC.

IL-2 and Beyond in Cancer Immunotherapy

The development of the T- and natural killer (NK) cell growth factor IL-2 has been a sentinel force ushering in the era of immunotherapy in cancer. With the advent of clinical grade recombinant IL-2 in the mid-1980s, oncologists could for the first time directly manipulate lymphocyte populations with systemic therapy. By itself, recombinant IL-2 can induce clinical responses in up to 15% of patients with metastatic cancer or renal cell carcinoma. When administered with adoptively transferred tumor-reactive lymphocytes, IL-2 promotes T cell engraftment and response rates of up to 50% in metastatic melanoma patients. Importantly, these IL-2-driven responses can yield complete and durable responses in a subset of patients. However, the use of IL-2 is limited by toxicity and concern of the expansion of T regulatory cells. To overcome these limitations and improve response rates, other T cell growth factors, including IL-15 and modified forms of IL-2, are in clinical development. Administering T cell growth factors in combination with other agents, such as immune checkpoint pathway inhibitors, may also improve efficacy. In this study, we review the development of T- and NK cell growth factors and highlight current combinatorial approaches based on these reagents.

Bladder cancer-associated cancer-testis antigen-derived long peptides encompassing both CTL and promiscuous HLA class II-restricted Th cell epitopes induced CD4+ T cells expressing converged T-cell receptor genes in vitro

DEP domain containing 1 (DEPDC1) and M-phase phosphoprotein 1 (MPHOSPH1) are human cancer testis antigens that are frequently overexpressed in urinary bladder cancer. In a phase I/II clinical trial, a DEPDC1- and MPHOSPH1-derived short peptide vaccine demonstrated promising efficacy in preventing bladder cancer recurrence. Here, we aimed to identify long peptides (LPs) derived from DEPDC1 and MPHOSPH1 that induced both T-helper (Th) cells and tumor-reactive cytotoxic T lymphocytes (CTLs). Stimulation of peripheral blood mononuclear cells (PBMCs) from healthy donors with the synthetic DEPDC1- and MPHOSPH1-LPs predicted to bind to promiscuous human leukocyte antigen (HLA) class II molecules by a computer algorithm induced specific CD4⁺ T cells as revealed by interferon-γ enzyme-linked immunospot assays. Three of six LPs encompassed HLA-A2- or -A24-restricted CTL epitopes or both, and all six LPs stimulated DEPDC1- or MPHOSPH1-specific Th cells restricted by promiscuous and frequently observed HLA class II molecules in the Japanese population. Some LPs are naturally processed from the proteins in DCs, and the capacity of these LPs to cross-prime CTLs was confirmed in vivo using HLA-A2 or -A24 transgenic mice. The LP-specific and HLA class II-restricted T-cell responses were also observed in PBMCs from patients with bladder cancer. Repeated stimulation of PBMCs with DEPDC1-LPs and MPHOSPH1-LPs yielded clonal Th cells expressing specific T-cell receptor (TCR)-α and β genes. These DEPDC1- or MPHOSPH1-derived LPs may have applications in immunotherapy in patients with bladder cancer, and the TCR genes identified may be useful for monitoring of Th cells specific to LPs in vivo.

The present status and future prospects of peptide-based cancer vaccines

Tumor cells commonly express several antigens, such as tumor-associated antigens (TAAs) or mutation-derived antigens (neoantigens), that can be regarded as foreign antigens and elicit anti-tumor immune responses in cancer patients. Various TAAs or neoantigens expressed in cancer cells have been identified and utilized as targets for cancer vaccines. One approach to elicit tumor-specific immune responses is termed peptide-based cancer vaccination; it involves administrating TAAs or neoantigen-derived peptide for treatment of cancers. There have been several forms of peptide-based cancer vaccines depending on which effector cells, such as CTLs or CD4(+) T-helper cells, are targeted to be activated. Many phase I and II clinical trials of peptide-based cancer vaccines using TAA-derived CTL epitopes, T-helper cell epitopes or dendritic cells loaded with TAA-derived peptides for various malignant tumors have been conducted and provide clinical benefits in a small fraction of patients. Nowadays, to improve the efficiency of peptide-based cancer vaccines, combination immunotherapy of peptide-based cancer vaccines with the immune-checkpoint blockade therapies using mAbs specific for CTLA-4, programmed cell death 1 (PD-1), or PD-1 ligand 1 (PD-L1) have been developed for clinical application. Furthermore, along with the recent technological progress in genetic and bioinformatic analysis, it has become easier to identify neoantigens from individual cancer patients. It is expected that peptide-based cancer vaccines targeting neoantigens as a personalized cancer immunotherapy will be developed.

An oncofetal antigen, IMP-3-derived long peptides induce immune responses of both helper T cells and CTLs

Insulin-like growth factor II mRNA-binding protein 3 (IMP-3), an oncofetal antigen identified using genome-wide cDNA microarray analyses, is overexpressed in several malignancies. IMP-3-derived cytotoxic T lymphocyte (CTL) epitopes have been used for peptide-based immunotherapies against various cancers. In addition to CTLs, induction of tumor-associated antigen (TAA)-specific helper T (Th) cells is crucial for establishment of effective antitumor immunity. In this study, we aimed to identify IMP-3-derived long peptides (IMP-3-LPs) carrying CTL and promiscuous Th-cell epitopes for use in cancer immunotherapy. IMP-3-derived Th-cell epitopes that bind to multiple HLA-class II molecules were predicted by in silico analysis, and their immunogenicity was determined by utilizing human T cells. We identified two highly immunogenic IMP-3-LPs presented by multiple HLA-class II molecules. One of the IMP-3-LPs encompassed two CTL epitopes that have been used for peptide-vaccine immunotherapy in ongoing clinical trials. IMP-3-LPs-specific Th cells responded to autologous dendritic cells (DCs) loaded with the recombinant IMP-3 proteins, suggesting that these s (LPs) can be naturally processed and presented. The IMP-3-LPs and specific Th cells augmented the expansion of IMP-3-specific CTLs, which was further enhanced by programmed cell death-1 (PD-1) blockade. In addition, IMP-3-LP encapsulated in liposomes was efficiently cross-presented in vitro, and this LP successfully cross-primed CTLs in HLA-A2 transgenic mice (Tgm) in vivo. Furthermore, one of the IMP-3-LPs induced IMP-3-specific Th cells from peripheral blood mononuclear cells (PBMCs) of head-and-neck malignant tumor (HNMT) patients. These findings suggest the potential usefulness of IMP-3-LPs in propagating both Th cells and CTLs and may have implications for IMP-3-LPs-based cancer immunotherapy.

T-cell receptor gene therapy--ready to go viral?

T lymphocytes can be redirected to recognize a tumor target and harnessed to combat cancer by genetic introduction of T-cell receptors of a defined specificity. This approach has recently mediated encouraging clinical responses in patients with cancers previously regarded as incurable. However, despite the great promise, T-cell receptor gene therapy still faces a multitude of obstacles. Identification of epitopes that enable effective targeting of all the cells in a heterogeneous tumor while sparing normal tissues remains perhaps the most demanding challenge. Experience from clinical trials has revealed the dangers associated with T-cell receptor gene therapy and highlighted the need for reliable preclinical methods to identify potentially hazardous recognition of both intended and unintended epitopes in healthy tissues. Procedures for manufacturing large and highly potent T-cell populations can be optimized to enhance their antitumor efficacy. Here, we review the current knowledge gained from preclinical models and clinical trials using adoptive transfer of T-cell receptor-engineered T lymphocytes, discuss the major challenges involved and highlight potential strategies to increase the safety and efficacy to make T-cell receptor gene therapy a standard-of-care for large patient groups.

Identification of glypican-3-derived long peptides activating both CD8+ and CD4+ T cells; prolonged overall survival in cancer patients with Th cell response

In a recent phase I clinical trial, a vaccine consisting of glypican-3 (GPC3)-derived CTL epitopes was found to be safe and induced measurable immune and clinical responses in patients with hepatocellular carcinoma (HCC). The aim of this study was to identify GPC3-derived long peptides (GPC3-LPs) carrying promiscuous HLA class II-restricted T helper (Th) cell epitopes. Using a computer algorithm, we predicted GPC3-LPs that can bind to promiscuous HLA class II molecules. Their antigenicity for induction of specific CD4⁺ T cells in healthy donors or patients with HCC, before and after vaccination with GPC3-SPs, was proven by IFNγ enzyme-linked immunospot assays. Natural processing of these epitopes was confirmed by the immune response of helper T cells to dendritic cells (DCs) loaded with GPC3 proteins. Cross-presentation capacity was assessed in vitro using human DCs and LPs encapsulated in liposomes and in vivo in HLA-A2 transgenic mice (Tgm). All five LPs could induce Th1 cells and were presented by several frequently occurring HLA class II molecules in vitro. Four of them were likely to be naturally processed. One of the LPs encapsulated in liposomes was well cross-presented in vitro; it cross-primed CTLs in HLA-A2 Tgm. LP-specific and HLA class II-restricted CD4⁺ T-cell responses were observed in 14 of 20 HCC patients vaccinated with GPC3-SPs. Repeated vaccinations enhanced GPC3-LP-specific responses in 8 of 13 patients with HCC. Moreover, the presence of the specific Th cell was correlated with prolonged overall survival (OS). GPC3-LPs can be useful for cancer immunotherapy.

Identification of promiscuous KIF20A long peptides bearing both CD4+ and CD8+ T-cell epitopes: KIF20A-specific CD4+ T-cell immunity in patients with malignant tumor

PURPOSE

To identify long peptides (LP) derived from a novel tumor-associated antigen (TAA), kinesin family member 20A (KIF20A), which induce tumor-specific T-helper type 1 (TH1) cells and CTLs.

EXPERIMENTAL DESIGN

We combined information from a recently developed computer algorithm predicting HLA class II-binding peptides with KIF20A-derived CTL-epitope sequences presented by HLA-A2 (A*02:01) or HLA-A24 (A*24:02) to select candidate promiscuous TH1-cell epitopes containing CTL epitopes. Peripheral blood mononuclear cells (PBMC) derived from healthy donors or patients with head-and-neck malignant tumor (HNMT) were used to study the immunogenicity of KIF20A-LPs, and the in vitro cross-priming potential of KIF20A-LPs bearing CTL epitopes. We used HLA-A24 transgenic mice to address whether vaccination with KIF20A-LP induces efficient cross-priming of CTLs in vivo. The TH1-cell response to KIF20A-LPs in HNMT patients receiving immunotherapy with TAA-derived CTL-epitope peptides was analyzed using IFN-γ enzyme-linked immunospot assays.

RESULTS

We identified promiscuous KIF20A-LPs bearing naturally processed epitopes recognized by CD4(+) T cells and CTLs. KIF20A-specific CTLs were induced by vaccination with a KIF20A-LP in vivo. KIF20A expression was detected in 55% of HNMT by immunohistochemistry, and significant frequencies of KIF20A-specific TH1 cell responses were detected after short-term in vitro stimulation of PBMCs with KIF20A-LPs in 50% of HNMT patients, but not in healthy donors. Furthermore, these responses were associated with KIF20A expression in HNMT tissues.

CONCLUSIONS

These are the first results showing the presence of KIF20A-specific TH1 cell responses in HNMT patients and underline the possible utility of KIF20A-LPs for propagation of TH1 cells and CTLs.

Deregulated systemic IL-10/IL-12 balance in advanced and poor prognosis paediatric soft tissue sarcomas

CONTEXT

The roles of interleukin 10 (IL-10) and IL-12 in regulation of cancer growth and Th1/Th2 immune responses towards cancer are unclear.

OBJECTIVE

To establish the prognostic significance of serum IL-10 and IL-12 in paediatric soft tissue sarcomas (STS).

MATERIALS AND METHODS

ELISA determinations of cytokines were performed as pre-treatment in 59 children with STS and 30 healthy controls.

RESULTS

Elevated IL-10 and decreased IL-12 serum levels correlated with advanced disease, poor response to chemotherapy and poor outcome. IL-10 ≥ 9.5 pg/ml, IL-12 ≤ 65 pg/ml and lymph nodes involvement independently predicted poor overall survival (OS) in multivariate Cox analysis.

CONCLUSION

Serum IL-10/IL-12 balance determination may facilitate to assess risk groups and prognosis in childhood STS.

Immunotherapeutic approaches to improve graft-versus-tumor effect and reduce graft-versus-host disease

The therapeutic efficacy of allogeneic stem cell transplantation is mainly based on the alloreactive immune response of the graft against the host. However, the graft-versus-host process can be viewed as a double-edged sword since it is responsible for both the beneficial graft-versus-tumor effect and the deleterious graft-versus-host disease. During the last two decades, intensive research has been focused on the development of novel immunotherapeutic methods aimed to dissociate graft-versus-host disease from graft-versus-tumor effect. A brief description of these efforts is discussed in this review.

Cytotoxic chemotherapy and CD4+ effector T cells: an emerging alliance for durable antitumor effects

Standard cytotoxic chemotherapy can initially achieve high response rates, but relapses often occur in patients and represent a severe clinical problem. As increasing numbers of chemotherapeutic agents are found to have immunostimulatory effects, there is a growing interest to combine chemotherapy and immunotherapy for synergistic antitumor effects and improved clinical benefits. Findings from recent studies suggest that highly activated, polyfunctional CD4+ effector T cells have tremendous potential in strengthening and sustaining the overall host antitumor immunity in the postchemotherapy window. This review focuses on the latest progresses regarding the impact of chemotherapy on CD4+ T-cell phenotype and function and discusses the prospect of exploiting CD4+ T cells to control tumor progression and prevent relapse after chemotherapy.

T-cell receptor gene therapy: critical parameters for clinical success

T-cell receptor (TCR) gene therapy aims to induce immune reactivity against tumors by introducing genes encoding a tumor-reactive TCR into patient T cells. This approach has been extensively tested in preclinical mouse models, and initial clinical trials have demonstrated the feasibility and potential of TCR gene therapy as a cancer treatment. However, data obtained from preclinical and clinical studies suggest that both the therapeutic efficacy and the safety of TCR gene therapy can be and needs to be further enhanced. This review highlights those strategies that can be followed to develop TCR gene therapy into a clinically relevant treatment option for cancer patients.

1α,25-Dihydroxyvitamin D3 and all-trans retinoic acid synergistically inhibit the differentiation and expansion of Th17 cells

1α,25-Dihydroxyvitamin D(3) (1,25D3), the active form of vitamin D(3), is an immunoregulatory hormone with beneficial effects on Th1 cell-mediated inflammatory diseases. Although IL-17-producing CD4(+) T helper (Th17) cells have been recently identified as novel effector cells, the immunomodulating effects of 1,25D3 on Th17 cells have not been well defined. We confirmed here that 1,25D3 inhibited the generation of Th17 cells in vitro. Interestingly, 1,25D3 synergistically suppressed the generation of Th17 cells by the combination with all-trans retinoic acid (ATRA). 1,25D3 and ATRA suppressed the development of allergen-induced contact hypersensitivity (CHS) in a mouse ear swelling model. In addition, we found that 1,25D3 and ATRA significantly inhibited the development of human Th17 cells from both naïve and memory human CD4(+) T cells. 1,25D3 and ATRA effectively suppressed mRNA expressions of IL-1R1, IL-21R, IL-23R, RORC, and AHR in human T cells. ATRA further suppressed IL-6R, whereas 1,25D3 did not. Finally, we found that 1,25D3 and ATRA remarkably blocked IL-22 as well as IL-17 mRNA expression in human memory CD4(+) T cells. Thus, we initially reveal that 1,25D3 and ATRA have synergistic effects on the generation of Th17 cells, suggesting that the combination with ATRA would provide a promising novel therapy for Th17 cell-related immune diseases including skin inflammation.

Generation of multi-functional antigen-specific human T-cells by lentiviral TCR gene transfer

T-cell receptor (TCR) gene transfer is an attractive strategy to generate antigen-specific T-cells for adoptive immunotherapy of cancer and chronic viral infection. However, current TCR gene transfer protocols trigger T-cell differentiation into terminally differentiated effector cells, which likely have reduced ability to mediate disease protection in vivo. We have developed a lentiviral gene transfer strategy to generate TCR-transduced human T-cells without promoting T-cell differentiation. We found that a combination of interleukin-15 (IL15) and IL21 facilitated lentiviral TCR gene transfer into non-proliferating T-cells. The transduced T-cells showed redirection of antigen specificity and produced IL2, IFNgamma and TNFalpha in a peptide-dependent manner. A significantly higher proportion of the IL15/IL21-stimulated T-cells were multi-functional and able to simultaneously produce all three cytokines (P<0.01), compared with TCR-transduced T-cells generated by conventional anti-CD3 plus IL2 stimulation, which primarily secreted only one cytokine. Similarly, IL15/IL21 maintained high levels of CD62L and CD28 expression in transduced T-cells, whereas anti-CD3 plus IL2 accelerated the loss of CD62L/CD28 expression. The data demonstrate that the combination of lentiviral TCR gene transfer together with IL15/IL21 stimulation can efficiently redirect the antigen specificity of resting primary human T-cells and generate multi-functional T-cells.

Reprogramming T lymphocytes for melanoma adoptive immunotherapy by T-cell receptor gene transfer with lentiviral vectors

T-cell receptor (TCR) gene transfer for cancer immunotherapy is limited by the availability of large numbers of tumor-specific T cells. TCR alpha and beta chains were isolated from a highly lytic HLA-A2-restricted cytotoxic T lymphocyte (CTL) clone recognizing the melanoma-associated Melan-A/MART-1 antigen and inserted into a lentiviral vector carrying a bidirectional promoter capable of robust and coordinated expression of the two transgenes. Lentiviral vector-based gene delivery systems have shown increased transfer efficiency and transgene expression compared with the widely used gamma-retroviral vectors. This vector performed more efficiently than a gamma-retrovirus-based vector containing the same expression cassette, resulting in a T-cell population with 60% to 80% of transgenic TCR expression with mainly CD8(+) intermediate effector phenotype. Transgenic T cells specifically produced cytokine in response to and killed antigen-expressing melanoma cells, retained an overlapping functional avidity in comparison with the TCR donor CTL clone, and exerted significant therapeutic effects in vivo upon adoptive transfer in melanoma-bearing severe combined immunodeficient mice. Optical imaging showed their accumulation in the tumor site. Overall, our results indicate that lentiviral vectors represent a valid tool for stable and high-intensity expression of transgenic TCR and support clinical exploitation of this approach for therapeutic application.

Combination immunotherapy with radiation and CpG-based tumor vaccination for the eradication of radio- and immuno-resistant lung carcinoma cells

Unmethylated cytosine-phosphorothioate-guanine containing oligodeoxynucleotides (CpG-ODN) is known as a ligand of toll-like receptor 9 (TLR9), which selectively activates type-1 immunity. We have already reported that the vaccination of tumor-bearing mice with liposome-CpG coencapsulated with model-tumor antigen, ovalbumin (OVA) (CpG + OVA-liposome) caused complete cure of the mice bearing OVA-expressing EG-7 lymphoma cells. However, the same therapy was not effective to eradicate Lewis lung carcinoma (LLC)-OVA-carcinoma. To overcome the refractoriness of LLC-OVA, we tried the combination therapy of radiation with CpG-based tumor vaccination. When LLC-OVA-carcinoma intradermally (i.d.) injected into C57BL/6 became palpable (7-8 mm), the mice were irradiated twice with a dose of 14 Gy at intervals of 24 h. After the second radiation, CpG + OVA-liposome was i.d. administered near the draining lymph node (DLN) of the tumor mass. The tumor growth of mice treated with radiation plus CpG + OVA-liposome was greatly inhibited and approximately 60% of mice treated were completely cured. Moreover, the combined therapy with radiation and CpG + OVA-liposome allowed the augmented induction of OVA-tetramer(+) LLC-OVA-specific cytotoxic T lymphocyte (CTL) in DLN of tumor-bearing mice. These results indicate that the combined therapy of radiation with CpG-based tumor vaccine is a useful strategy to eradicate intractable carcinoma.

Pre-treatment serum levels of interleukin-10, interleukin-12 and their ratio predict response to therapy and probability of event-free and overall survival in childhood soft tissue sarcomas, Hodgkin's lymphomas and acute lymphoblastic leukemias

OBJECTIVES

Deregulated serum IL-10, IL-12 and their reciprocal balance have been stated in malignancies of adults. In children with cancer the issue has not been investigated so far.

DESIGN AND METHODS

To determine the diagnostic and prognostic roles of pre-treatment serum levels of IL-10 (Th2 cytokine), IL-12 (Th1) and their ratios (measured by the IL-10 and IL-12p70 ELISA kits; Endogen) in 91 children with soft tissue sarcomas (STS), Hodgkin's lymphomas (HL) and acute lymphoblastic leukemias (ALL).

RESULTS

Median IL-10 and IL-12 levels were significantly higher in cancer patients than in healthy controls. Increased IL-10 indicated presence of general symptoms in HL and high risk group in ALL. Elevated IL-10 and IL-10/IL-12 ratios and decreased IL-12 correlated with poor-risk histology in STS, poor response to therapy, relapse and death from cancer. Multivariate analysis identified IL-10/IL-12 ratio>0.14 and IL-12<40 pg/mL as significant predictors for shorter EFS and OS, respectively.

CONCLUSION

Pre-treatment serum levels of IL-10, IL-12 and IL-10/IL-12 balance in children with STS, HL and ALL may be of value as additional prognostic tools to predict the response to therapy and probability of EFS and OS.

Identification of novel helper epitopes of MAGE-A4 tumour antigen: useful tool for the propagation of Th1 cells

MAGE-A4 has been considered as an attractive cancer-testis (CT) antigen for tumour immunotherapy. It has been well accepted that T-helper type 1 (Th1) cell-dominant immunity is critical for the successful induction of antitumour immunity in a tumour-bearing host. The adoptive Th1 cell therapy has been shown to be an attractive strategy for inducing tumour eradication in mouse systems. However, Th1-cell therapy using human tumour-specific Th1 cells, which were expanded from peripheral blood mononuclear cells (PBMCs) in a clinically useful protocol, has never been performed. Here, we first identified MAGE-A4-derived promiscuous helper epitope, peptide (MAGE-A4 280-299), bound to both HLA-DPB1(*)0501 and DRB1(*)1403. Using the peptide, we established a suitable protocol for the propagation of MAGE-A4-specific Th1 cells in vitro. Culture of CD4(+) T cells with IFN-gamma-treated PBMC-derived adherent cells in the presence of helper epitope peptide resulted in a great expansion of MAGE-A4-reactive Th cells producing IFN-gamma , but not IL-4. Moreover, it was shown that ligation of MAGE-A4-reactive Th1 cells with the cognate peptide caused the production of IFN-gamma and IL-2. Thus, our identified MAGE-A4 helper epitope peptide will become a good tool for the propagation of tumour-specific Th1 cells applicable to adoptive immunotherapy of human cancer.

Adoptive immunotherapy of disseminated leukemia with TCR-transduced, CD8+ T cells expressing a known endogenous TCR

Adoptive T-cell immunotherapy has shown promise in the treatment of human malignancies, but the challenge of isolating T cells with high avidity for tumor antigens in each patient has limited application of this approach. The transfer into T cells of T-cell receptor (TCR) genes encoding high-affinity TCRs recognizing defined tumor-associated antigens can potentially circumvent this obstacle. Using a well-characterized murine model of adoptive T-cell immunotherapy for widely disseminated leukemia, we demonstrate that TCR gene-modified T cells can cure mice of disseminated tumor. One goal of such adoptive therapy is to establish a persistent memory response to prevent recurrence; however, long-term function of transferred TCR-transduced T cells is limited due to reduced expression of the introduced TCR in vivo in quiescent resting T cells. However, by introducing the TCR into a cell with a known endogenous specificity, activation of these T cells by stimulation through the endogenous TCR can be used to increase expression of the introduced TCR, potentially providing a strategy to increase the total number of tumor-reactive T cells in the host and restore more potent antitumor activity.

Antiviral gene therapy

This chapter describes the major gene therapeutic approaches for viral infections. The vast majority of published approaches target severe chronic viral infections such as hepatitis B or C and HIV infection. Two basic gene therapy strategies are introduced here. The first involves the expression of a protein or an RNA that inhibits viral replication by targeting crucial steps of the viral life cycle or by interfering with a cellular factor required for virus replication. The major limitation of this approach is that primary levels of gene modification have generally not been sufficient to reduce the availability of target cells permissive for virus replication to a level that significantly decreases overall viral load. Thus, investigators have banked on the expectation that gene-protected cells have a sufficient selective advantage to accumulate and gain prevalence over time, a prediction that so far could not be confirmed in clinical trials. In vivo levels of gene modification can be improved, however, by introducing an additional selectable marker. In addition, a secreted antiviral gene product that exerts a bystander effect could significantly reduce overall virus replication despite relatively low levels of gene modification. In addition to these direct antiviral approaches, several strategies have been developed that employ or aim to enhance host immune responses. The innate immune response has been enhanced, for example, by the in vivo expression of interferons. Alternatively, T cells can be grafted with recombinant receptors to boost adaptive virus-specific immunity. These approaches are especially promising for chronic virus infection, where natural immune responses are evidently not sufficient to effectively control virus replication.

Potent tumor-specific protection ignited by adoptively transferred CD4+ T cells

Administration of anti-CD25 mAb before an aggressive murine breast tumor inoculation provoked effective antitumor immunity. Compared with CD4(+) T cells purified from anti-CD25 mAb-pretreated mice that did not reject tumor, CD4(+) T cells purified from anti-CD25 mAb-pretreated mice that rejected tumor stimulated by dendritic cells (DCs) produced more IFN-gamma and IL-2, and less IL-17 in vitro, and ignited protective antitumor immunity in vivo in an adoptive transfer model. Tumor Ag-loaded DCs activated naive CD8(+) T cells in the presence of these CD4(+) T cells in vitro. Tumor Ag and adoptively transferred CD4(+) T cells were both required for inducing a long-term tumor-specific IFN-gamma-producing cellular response and potent protective antitumor activity. Although adoptively transferred CD4(+) T cells ignited effective tumor-specific antitumor immunity in wild-type mice, they failed to do so in endogenous NK cell-depleted, Gr-1(+) cell-depleted, CD40(-/-), CD11c(+) DC-depleted, B cell(-/-), CD8(+) T cell-depleted, or IFN-gamma(-/-) mice. Collectively, the data suggest that adoptively transferred CD4(+) T cells orchestrate both endogenous innate and adaptive immunity to generate effective tumor-specific long-term protective antitumor immunity. The data also demonstrate the pivotal role of endogenous DCs in the tumor-specific protection ignited by adoptively transferred CD4(+) T cells. Thus, these findings highlight the importance of adoptively transferred CD4(+) T cells, as well as host immune components, in generating effective tumor-specific long-term antitumor activity.

Dual T cell receptor expressing CD8+ T cells with tumor- and self-specificity can inhibit tumor growth without causing severe autoimmunity

The engineering of Ag-specific T cells by expression of TCR genes is a convenient method for adoptive T cell immunotherapy. A potential problem is the TCR gene transfer into self-reactive T cells that survived tolerance mechanisms. We have developed an experimental system with T cells that express two TCRs with defined Ag-specificities, one recognizing a tumor-specific Ag (LCMV-gp(33)), the other recognizing a self-Ag in the pancreas (OVA). By using tumor cells expressing high and low amounts of Ag and mice expressing high and low levels of self-Ag in the pancreas (RIP-OVA-Hi and RIP-OVA-Lo), we show that 1) tumor rejection requires high amount of tumor Ag, 2) severe autoimmunity requires high amount of self-Ag, and 3) if Ag expression on tumor cells is sufficient and low in the pancreas, successful adoptive T cell therapy can be obtained in the absence of severe autoimmunity. These results are shown with T cells from dual TCR transgenic mice or T cells that were redirected by TCR gene transfer. Our data demonstrate that the approach of adoptively transferring TCR redirected T cells can be effective without severe side effects, even when high numbers of T cells with self-reactivity were transferred.

Adoptive T-cell therapy as a therapeutic option for chronic hepatitis B

The human hepatitis B virus is a small, enveloped and non-cytopathic virus, with a very narrow host range and a strong liver tropism causing acute and chronic liver disease. Although a well-tolerated vaccine is available, more than 350 million people are chronically infected worldwide. Available therapies for chronic hepatitis B only rarely eliminate the virus. Although new antivirals are being developed, long-term treatment is required, which may be limited by the selection of resistant viruses. Therefore, immunotherapies are investigated as an approach to eliminate persistently infected cells. Besides therapeutic vaccination, adoptive T-cell therapy is an interesting option, which is discussed in this review.

T-cell receptor gene therapy for cancer: the progress to date and future objectives

In the last decade research has begun into the use of T-cell receptor (TCR) gene therapy as a means to control and eradicate malignancies. There is now a large body of evidence to demonstrate that through the use of this technology one can redirect T-cell antigen specificity to produce both cytotoxic and helper T cells, which are functionally competent both in vitro and in vivo and show promising antitumour effects in humans. This review focuses on the means by which TCR gene transfer is achieved and the recent advances to modify the TCRs and vector delivery systems which aim to enhance the efficiency and safety of TCR gene transfer protocols.

Gene transfer of human TCR in primary murine T cells is improved by pseudo-typing with amphotropic and ecotropic envelopes

BACKGROUND

T cell receptor (TCR) gene therapy represents an attractive anti-cancer treatment but requires further optimization of its efficacy and safety in clinically relevant models, such as those using a tumor antigen and TCR of human origin. Currently, however, there is no consensus as to what protocol is most optimal for retroviral human TCR gene transfer into primary murine T cells, most notably with respect to virus pseudo-type.

METHODS

Primary murine T cells were transduced, expanded and subsequently tested for transgene expression, proliferation and antigen-specific function. To this end, murine leukemia virus (MLV) retroviruses were produced upon transfection of various packaging cells with genes encoding either green fluorescent protein (GFP) or TCRalphabeta specific for human melanoma antigen gp100(280-288) and the helper elements GAG/POL and ENV. Next to viral pseudotyping, the following parameters were studied: T cell densities; T cell activation; the amounts of IL-2 and the source of serum used to supplement medium.

RESULTS

The pseudo-type of virus produced by packaging cells critically determines T cell transduction efficiencies. In fact, MLV-A and MLV-E pseudo-typed viruses derived from a co-culture of Phoenix-A and 293T cells resulted in T cell transduction efficiencies that were two-fold higher than those based on retroviruses expressing either VSV-G, GALV, MLV-A or MLV-E envelopes. In addition, T cell densities during transduction were inversely related to transduction efficiencies. Further optimization resulted in transduction efficiencies of over 90% for GFP, and 68% for both a murine and a human (i.e. murinized) TCR. Importantly, TCR-transduced T cells proliferate (i.e. showing a log increase in cell number in a few days) and show antigen-specific function.

CONCLUSIONS

We set up a quick and versatile method to genetically modify primary murine T cells based on transient production of TCR-positive retroviruses, and show that retroviral gene transfer of a human TCR into primary murine T cells is critically improved by viral pseudo-typing with both MLV-A and MLV-E envelopes.

WT1-specific T cell receptor gene therapy: improving TCR function in transduced T cells

Adoptive transfer of antigen-specific T lymphocytes is an attractive form of immunotherapy for haematological malignancies and cancer. The difficulty of isolating antigen-specific T lymphocytes for individual patients limits the more widespread use of adoptive T cell therapy. The demonstration that cloned T cell receptor (TCR) genes can be used to produce T lymphocyte populations of desired specificity offers new opportunities for antigen-specific T cell therapy. The first trial in humans demonstrated that TCR gene-modified T cells persisted for an extended time period and reduced tumor burden in some patients. The WT1 protein is an attractive target for immunotherapy of leukemia and solid cancer since elevated expression has been demonstrated in AML, CML, MDS and in breast, colon and ovarian cancer. In the past, we have isolated high avidity CTL specific for a WT1-derived peptide presented by HLA-A2 and cloned the TCR alpha and beta genes of a WT1-specific CTL line. The genes were inserted into retroviral vectors for transduction of human peripheral blood T lymphocytes of leukemia patients and normal donors. The treatment of leukemia-bearing NOD/SCID mice with T cells transduced with the WT1-specific TCR eliminated leukemia cells in the bone marrow of most mice, while treatment with T cells transduced with a TCR of irrelevant specificity did not diminish the leukemia burden. In order to improve the safety and efficacy of TCR gene therapy, we have developed lentiviral TCR gene transfer. In addition, we employed strategies to enhance TCR expression while avoiding TCR mis-pairing. It may be possible to generate dominant TCR constructs that can suppress the expression of the endogenous TCR on the surface of transduced T cells. The development of new TCR gene constructs holds great promise for the safe and effective delivery of TCR gene therapy for the treatment of malignancies.

Combination tumor immunotherapy with radiotherapy and Th1 cell therapy against murine lung carcinoma

Mice bearing established Lewis lung carcinoma (LLC) expressing model tumor antigen, ovalbumin (OVA) (LLC-OVA) marginally responded to local radiotherapy, but none of the mice was cured. In contrast, treatment of the tumor-bearing mice with intratumoral injection of tumor-specific T helper type 1 (Th1) cells and tumor antigen (OVA) after radiotherapy dramatically prolonged the survival days and induced complete cure of the mice at high frequency (80%). Radiation therapy combined with Th1 cells or OVA alone showed no significant therapeutic activity against LLC-OVA. Such a strong therapeutic activity was not induced by intratumoral injection of Th1 cells plus OVA. Compared with other treatment, radiation therapy combined with Th1 cells and OVA was superior to induce the generation of OVA/H-2(b) tetramer(+) tumor-specific cytotoxic T lymphocyte (CTL) with a strong cytotoxicity against LLC-OVA in draining lymph node (DLN). Moreover, the combined therapy is demonstrated to inhibit the growth of tumor mass, which grew at contralateral side. These results indicated that radiotherapy combined with Th1 cell/vaccine therapy induced a systemic antitumor immunity. These findings suggested that combination therapy with radiotherapy and Th1 cell/vaccine therapy may become a practical strategy for cancer treatment.

Monoclonal T-cell receptors: new reagents for cancer therapy

Adoptive transfer of antigen-specific T lymphocytes is an effective form of immunotherapy for persistent virus infections and cancer. A major limitation of adoptive therapy is the inability to isolate antigen-specific T lymphocytes reproducibly. The demonstration that cloned T-cell receptor (TCR) genes can be used to produce T lymphocyte populations of desired specificity offers new opportunities for antigen-specific T-cell therapy. TCR gene-modified lymphocytes display antigen-specific function in vitro, and were shown to protect against virus infection and tumor growth in animal models. A recent trial in humans demonstrated that TCR gene-modified T cells persisted in all and reduced melanoma burden in 2/15 patients. In future trials, it may be possible to use TCR gene transfer to equip helper and cytotoxic T cells with new antigen-specificity, allowing both T-cell subsets to cooperate in achieving improved clinical responses. Sequence modifications of TCR genes are being explored to enhance TCR surface expression, while minimizing the risk of pairing between introduced and endogenous TCR chains. Current T-cell transduction protocols that trigger T-cell differentiation need to be modified to generate "undifferentiated" T cells, which, upon adoptive transfer, display improved in vivo expansion and survival. Both, expression of only the introduced TCR chains and the production of naïve T cells may be possible in the future by TCR gene transfer into stem cells.

T-cell receptor gene transfer by lentiviral vectors in adoptive cell therapy

Adoptive cell therapy can be envisioned as a promising strategy for tumour immunotherapy. However, existing protocols of adoptive cell therapy still require optimisation as many factors, such as specificity, avidity, level of differentiation and amount of transferred T lymphocytes, can influence their immunocompetence and in vivo functionality. In particular, the need to reduce the in vitro expansion phase and to obtain large numbers of tumour-reactive T cells, as a favourable condition for cancer regression, make TCR gene transfer a potentially ideal tool to overcome the limits of adoptive cell therapy strategies. Here, the authors review the state-of-the-art and recent advances in TCR transfer with particular emphasis on lentiviral vector systems. Initial data from preclinical models and recent clinical trials encourage optimisation of a safe, simplified and stable transfer system. In this regard, HIV-based vectors are emerging as good alternative candidates over the most widely used oncoretroviral vectors due to their peculiar molecular features that fit the ideal conditions for donor T cell in vitro manipulation.

Redirecting T lymphocyte specificity by T cell receptor gene transfer – A new era for immunotherapy

The therapeutic efficacy of adoptively transferred cytotoxic T lymphocytes (CTL) has been demonstrated in clinical trials for the treatment of chronic myelogenous leukemia, cytomegalovirus-mediated disease, and Epstein-Barr virus-positive B cell lymphomas. It is however limited by the difficulty of generating sufficient amounts of CTLs in vitro, especially for the treatment of solid tumors. Recent gene therapy approaches, including two clinical trials, successfully apply genetic engineering of T cell specificity by T cell receptor (TCR) gene transfer. In this review we want to elucidate several principles of the redirection of T cell specificity. We cover basic aspects of retroviral gene transfer, regarding transduction efficacy and transgene expression levels. It was demonstrated that the number of TCR molecules on a T cell is important for its function. Therefore, an efficient transfer system that yields high transduction efficiency and strong and stable transgene expression is a prerequisite to achieve effector function by redirected T cells. Furthermore, we consider more recent aspects of T cell specificity engineering. These include the possibility of co-transferring coreceptors to create for example functional T helper cells by engrafting CD4(+) T cells with a MHC class I restricted TCR and the CD8 coreceptor and vice versa. Also, risks related to the adoptive transfer of TCR gene-modified T cells and possible safety mechanisms are discussed. Finally, we summarize recent findings describing transferred TCRs capable of displacing endogenous TCRs from the cell surface.

Cyclooxygenase-2 inhibition promotes enhancement of antitumor responses by transcutaneous vaccination with cytosine-phosphate-guanosine-oligodeoxynucleotides and model tumor antigen

One of the principal goals in tumor immune prophylaxis and tumor therapy is the induction of antitumor responses by generating sufficient numbers of tumor antigen-specific helper T (Th)1 cells and cytotoxic T lymphocytes (CTLs). We have demonstrated that the administration of cytosine-phosphate-guanosine-oligodeoxynucleotide (CpG-ODN) through tape-stripped skin induced a Th1-type immune response and suggested that the skin is a potential site for vaccination. CpG-ODN induces the expression of cyclooxygenase (COX)-2, and its product prostaglandin (PG) E2 underlies an immunosuppressive network, therefore it is a simple strategy to use a COX-2 inhibitor for tumor vaccination with CpG-ODN. In this study, we examined whether a COX-2 inhibitor enhances the antitumor immune response induced by CpG-ODN with model tumor antigen, ovalbumin (OVA), applied to tape-stripped skin in mice. The COX-2 inhibitor remarkably enhanced antigen-specific Th1-type immune responses and generation of CTLs induced by transcutaneous vaccination with CpG-ODN and OVA. PGE2 and IL-10 levels in the skin were significantly decreased and production of IL-12 was enhanced. This vaccination also induces an effective antitumor immunity in tumor-challenged mice. These results suggested that transcutaneous vaccination with a COX-2 inhibitor, CpG-ODN, and tumor antigen is a very simple and cost-effective strategy for tumor vaccine and may be readily achievable.

CD8 alpha coreceptor to improve TCR gene transfer to treat melanoma: down-regulation of tumor-specific production of IL-4, IL-5, and IL-10

Therapeutic success of TCR gene transfer to treat tumors depends on the ability of redirected T cells to become activated upon tumor recognition in vivo. Help provided by tumor-specific Th1 cells is reported to relieve T cells from an anergized state and to induce tumor regression. We recently demonstrated the ability to generate melanoma-specific Th1 cells by genetic introduction of both a CD8-dependent TCR and the CD8alpha coreceptor into CD4+ T cells. In this study, we analyzed a TCR that binds Ag independently of CD8, a property generally preferred to induce tumor-specific T cell responses, and addressed the contribution of CD8alpha following introduction into TCR-transduced CD4+ T cells. To this end, primary human CD4+ T cells were gene transferred with a high-avidity TCR, and were shown not only to bind peptide/MHC class I, but also to effectively kill Ag-positive tumor cells in the absence of CD8alpha. The introduction of CD8alpha up-regulates the tumor-specific production of TNF-alpha and IL-2 to some extent, but significantly down-regulates production of IL-4, IL-5, and IL-10 in CD4+ T cells. The introduction of a mutated cysteine motif in CD8alpha, which prevents its binding to LCK and linker for activation of T cells, did not adversely affect expression and T cell cytotoxicity, but counteracted the CD8alpha-mediated down-regulation of IL-4 and IL-5, but not IL-10. In conclusion, CD8alpha down-regulates the production of major Th2-type cytokines, in part mediated by LCK and/or linker for activation of T cells, and may induce differentiation of tumor-specific Th1 cells, which makes this coreceptor an interesting candidate to improve the clinical potential of TCR gene transfer to treat cancer.

Redirection of T cells by delivering a transgenic mouse-derived MDM2 tumor antigen-specific TCR and its humanized derivative is governed by the CD8 coreceptor and affects natural human TCR expression

Retroviral transfer of T cell antigen receptor (TCR) genes selected by circumventing tolerance to broad tumor- and leukemia-associated antigens in human leukocyte antigen (HLA)-A*0201 (A2.1) transgenic (Tg) mice allows the therapeutic reprogramming of human T lymphocytes. Using a human CD8 x A2.1/Kb mouse derived TCR specific for natural peptide-A2.1 (pA2.1) complexes comprising residues 81-88 of the human homolog of the murine double-minute 2 oncoprotein, MDM2(81-88), we found that the heterodimeric CD8 alpha beta coreceptor, but not normally expressed homodimeric CD8 alpha alpha, is required for tetramer binding and functional redirection of TCR- transduced human T cells. CD8+T cells that received a humanized derivative of the MDM2 TCR bound pA2.1 tetramers only in the presence of an anti-human-CD8 anti-body and required more peptide than wild-type (WT) MDM2 TCR+T cells to mount equivalent cytotoxicity. They were, however, sufficiently effective in recognizing malignant targets including fresh leukemia cells. Most efficient expression of transduced TCR in human T lymphocytes was governed by mouse as compared to human constant (C) alphabeta domains, as demonstrated with partially humanized and murinized TCR of primary mouse and human origin, respectively. We further observed a reciprocal relationship between the level of Tg WT mouse relative to natural human TCR expression, resulting in T cells with decreased normal human cell surface TCR. In contrast, natural human TCR display remained unaffected after delivery of the humanized MDM2 TCR. These results provide important insights into the molecular basis of TCR gene therapy of malignant disease.

Generation of tumor-specific T-cell therapies

Antigen-specific tumor immunotherapy remains an attractive strategy for the treatment of malignancies. In this review we will discuss why, despite the identification of large numbers of T cell recognised tumor antigens, effective immunotherapy remains a formidable challenge. Effective strategies are needed to deal with the tolerogenic properties of many tumor antigens, and with the immunocompromised status of patients. We discuss different methods of generating tumor-specific T cells which are currently being evaluated in clinical practice, such as vaccination and adoptive transfer of tumor antigen-specific T cells. Finally, we shall discuss novel strategies in development, such as the adoptive transfer of T cell receptor (TCR) gene modified T cells to establish antigen-specific immunity in patients with leukemia and solid cancers. The transfer of validated high avidity TCRs, isolated from 'non-tolerant' repertoires or produced by in vitro affinity maturation, can serve to equip patient T cells with new anti-tumor specificities that are not naturally present in the autologous repertoire. TCR transfer into CD4(+) and CD8(+) T cells can serve to harness the function of both helper and cytotoxic T cells for tumor elimination and establishment of long-term tumor immunity.

HLA class II restricted T-cell receptor gene transfer generates CD4+ T cells with helper activity as well as cytotoxic capacity

Both cytotoxic T cells and helper T cells are important in immune responses against pathogens and malignant cells. In hematological malignancies which express HLA class II molecules, immunotherapy may be directed to HLA class II restricted antigens. We investigated whether it is possible to engineer HLA class II restricted T cells with both antigen-specific cytolytic activity and the capacity to produce high amounts of cytokines. CD4+ and CD8+ peripheral-blood-derived T cells were retrovirally transduced with the HLA class II restricted minor histocompatibility antigen dead box RNA helicase Y (DBY)-specific TCR. The TCR-transduced CD4+ T cells exerted DBY-specific cytolytic activity, produced Th0, Th1, or Th2 cytokines, and proliferated upon DBY-specific stimulation. TCR-transduced CD8+ T cells exerted cytolytic activity which equaled the level of cytolytic activity of the TCR-transferred CD4+ T cells. Cotransfer of CD4 enhanced the cytolytic activity of the TCR-transduced CD8+ T cells, but introduction of CD4 was not sufficient to generate DBY-specific CD8+ T cells with the capacity to produce high amounts of cytokines. In this study, we demonstrated the feasibility to engineer T cells with antigen-specific cytolytic activity, as well as the ability to produce significant amounts of cytokines, by TCR transfer to CD4+ T cells.

An Essential Role of Antigen-Presenting Cell/T-Helper Type 1 Cell-Cell Interactions in Draining Lymph Node during Complete Eradication of Class II–Negative Tumor Tissue by T-Helper Type 1 Cell Therapy

Prior studies have shown that transfer of ovalbumin (OVA)-specific T helper type 1 (Th1) cells into mice bearing MHC class II+ OVA-expressing tumor cells (A20-OVA) causes complete tumor rejection. Here we show that, although Th1 cell therapy alone was not effective against MHC class II- OVA-expressing tumor cells (EG-7), treatment of mice bearing established EG-7 tumors by i.v. transfer of Th1 cells combined with i.t. injection of the model tumor antigen OVA induced complete tumor rejection. Transferred Th1 cells enhanced the migration of tumor-infiltrating antigen-presenting cells (APC) that had processed OVA into the draining lymph node (DLN). Although transferred Th1 cells were randomly distributed in DLN, distal LN, spleen, and tumor tissue, active proliferation of Th1 cells always initiated in DLN, where Th1 cells efficiently interacted with APC that presented OVA. In parallel, OVA-tetramer+ CTLs, showing EG-7-specific cytotoxicity, were highly induced in DLN and the local tumor site. The OVA-tetramer+ CTL functioned systemically because two bilateral tumor masses were both completely rejected on treatment of one tumor. Furthermore, either active proliferation of transferred Th1 cells or generation of tetramer+ CTL was not induced in MHC class II-deficient mice and LN-deficient Aly/Aly mice. These results indicate that DLN is an indispensable organ for initiating active APC/Th1 cell interactions, which is critical for inducing complete eradication of tumor mass by tumor-specific CTL.

Elimination of human leukemia cells in NOD/SCID mice by WT1-TCR gene-transduced human T cells

Cytotoxic T lymphocytes (CTLs) specific for an HLA-A2-presented peptide epitope of the Wilms tumor antigen-1 (WT1) can selectively kill immature human leukemia progenitor and stem cells in vitro. In this study we have used retroviral gene transfer to introduce a WT1-specific T-cell receptor (TCR) into T lymphocytes obtained from patients with leukemia and from healthy donors. TCR-transduced T cells kill leukemia cells in vitro and display WT1-specific cytokine production. Intravenous injection of TCR-transduced T cells into nonobese diabetic-severe combined immunodeficiency (NOD/SCID) mice harboring human leukemia cells resulted in leukemia elimination, whereas transfer of control T cells transduced with an irrelevant TCR was ineffective. The data suggest that adoptive immunotherapy with WT1-TCR gene-modified patient T cells should be considered for the treatment of leukemia.

Gene modification strategies to induce tumor immunity

The immune system provides an attractive option for use in cancer therapy. Our increasing understanding of the molecular events important in the generation of an effective immune response presents us with the opportunity to manipulate key genes to boost the immune response against cancer. Genetic modification is being employed to enhance a range of immune processes including antigen presentation, activation of specific T cells, and localization of immune effectors to tumors. In this review, we describe how many diverse cell types, including dendritic cells, T cells, and tumor cells, are being modified with a variety of genes, including those encoding antigens, cytokines, and chemokines, in order to enhance tumor immunity.

A critical role of T cell antigen receptor-transduced MHC class I-restricted helper T cells in tumor protection

Adoptive transfer of antigen-specific CD4(+) and CD8(+) T cells is one of the most efficient forms of cancer immunotherapy. However, the isolation of antigen-specific CD4(+) T cells is limited because only few tumor-associated helper epitopes are identified. Here, we used T cell antigen receptor gene transfer to target CD4(+) T cells against an MHC class I-presented epitope of a model tumor antigen. IFN-gamma-producing CD4(+) T cells were unable to expand in vivo and to provide help for tumor rejection. In contrast, CD4(+) T cells producing high levels of IL-2 expanded in vivo, provided help for cytotoxic T lymphocyte-mediated tumor rejection, and developed T cell memory. The data demonstrate in vivo synergy between T cell antigen receptor-transduced CD4(+) and CD8(+) T cells specific for the same epitope resulting in long-term tumor protection.

Cooperation of human tumor-reactive CD4+ and CD8+ T cells after redirection of their specificity by a high-affinity p53A2.1-specific TCR

Efficient immune attack of malignant disease requires the concerted action of both CD8+ CTL and CD4+ Th cells. We used human leukocyte antigen (HLA)-A*0201 (A2.1) transgenic mice, in which the mouse CD8 molecule cannot efficiently interact with the alpha3 domain of A2.1, to generate a high-affinity, CD8-independent T cell receptor (TCR) specific for a commonly expressed, tumor-associated cytotoxic T lymphocyte (CTL) epitope derived from the human p53 tumor suppressor protein. Retroviral expression of this CD8-independent, p53-specific TCR into human T cells imparted the CD8+ T lymphocytes with broad tumor-specific CTL activity and turned CD4+ T cells into potent tumor-reactive, p53A2.1-specific Th cells. Both T cell subsets were cooperative and interacted synergistically with dendritic cell intermediates and tumor targets. The intentional redirection of both CD4+ Th cells and CD8+ CTL by the same high-affinity, CD8-independent, tumor-specific TCR could provide the basis for novel broad-spectrum cancer immunotherapeutics.

Exploiting T cell receptor genes for cancer immunotherapy

Adoptive antigen-specific immunotherapy is an attractive concept for the treatment of cancer because it does not require immunocompetence of patients, and the specificity of transferred lymphocytes can be targeted against tumour-associated antigens that are poorly immunogenic and thus fail to effectively trigger autologous T cell responses. As the isolation and in vitro expansion of antigen-specific lymphocytes is difficult, 'conventional' adoptive T cell therapy can only be carried out in specialized centres in small numbers of patients. However, T cell receptor (TCR) genes isolated from antigen-specific T cells can be exploited as generic therapeutic molecules for 'unconventional' antigen-specific immunotherapy. Retroviral TCR gene transfer into patient T cells can readily produce populations of antigen-specific lymphocytes after a single round of polyclonal T cell stimulation. TCR gene modified lymphocytes are functionally competent in vitro, and can have therapeutic efficacy in murine models in vivo. TCR gene expression is stable and modified lymphocytes can develop into memory T cells. Introduction of TCR genes into CD8(+) and CD4(+) lymphocytes provides an opportunity to use the same TCR specificity to produce antigen-specific killer and helper T lymphocytes. Thus, TCR gene therapy provides an attractive strategy to develop antigen-specific immunotherapy with autologous lymphocytes as a generic treatment option.

Reconstitution of anti-HIV effector functions of primary human CD8 T lymphocytes by transfer of HIV-specific alphabeta TCR genes

We redirected the antigen specificity of primary human CD8 T cells by retrovirus-mediated transduction of genes encoding alphabeta TCR specific to HIV-1 Pol protein. A large polyclonal population of TCR-transduced CD8 T cells showed substantial cytotoxic and cytokine production activities toward target cells either pulsed with the peptide or infected with HIV-1, and their functional activities were comparable to those of the parental CTL clone. Peptide fine-specificity and promiscuous recognition of HLA class I supertypes of the parental CTL clone were also preserved in the TCR-transduced cells. There were no signs of allogeneic responses in these cells, although hybrid TCR dimers consisting of transduced TCR and endogenous TCR were suspected to have been formed in these cells, as the effect of transgene expression on the surface expression of the desired TCR was limited. Moreover, the TCR-transduced cells showed potent inhibitory activity against HIV-1 replication in vitro, although the differential surface expression of the desired TCR resulted in differential functional avidity of individual TCR-transduced cells toward the peptide-pulsed target cells. These data suggest that the reconstitution of HIV-specific immunoreactive T cells engineered by genetic transfer of HIV-specific TCR is a potential alternative to immunotherapeutic applications against HIV infections.