Toward improved immunocompetence of adoptively transferred CD8+ T cells

CpG-mediated augmentation of CD8+ T-cell responses in mice is attenuated by a water-in-oil emulsion (Montanide ISA-51) but enhanced by an oil-in-water emulsion (IDRI SE)

Adjuvants are a key component in enhancing immunogenicity of vaccines and play a vital role in facilitating the induction of the correct type of immunity required for each vaccine to be optimally efficacious. Several different adjuvants are found in licensed vaccines, and many others are in pre-clinical or clinical testing. Agonists for TLRs are potent activators of the innate immune system and some, such as CpG (TLR9 agonist), are particularly good for promoting cellular immunity because of the induction of Th1 cytokines. Emulsions that have both delivery and adjuvant properties are classified as water-in-oil (W/O) or oil-in-water (O/W) formulations. The W/O emulsion Montanide ISA-51, often combined with CpG, has been widely tested in cancer vaccine clinical trials. Squalene-based O/W emulsions are in licensed influenza vaccines, and T-cell responses have been assessed pre-clinically. No clinical study has compared the two types of emulsions, and the continued use of W/O with CpG in cancer vaccines may be because the lack of single adjuvant controls has masked the interference issue. These findings may have important implications for the development of vaccines where T-cell immunity is considered essential, such as those for cancer and chronic infections. Using particulate (hepatitis B surface antigen) and soluble protein (ovalbumin) antigen, we show in mice that a W/O emulsion (ISA-51) abrogates CpG-mediated augmentation of CD8(+) T-cell responses, whereas a squalene-based O/W emulsion significantly enhanced them.

Impact of T cell selection methods in the success of clinical adoptive immunotherapy

Chemotherapy and/or radiotherapy regular regimens used for conditioning of recipients of hematopoietic stem cell transplantation (SCT) induce a period of transient profound immunosuppression. The onset of a competent immunological response, such as the appearance of viral-specific T cells, is associated with a lower incidence of viral infections after haematopoietic transplantation. The rapid development of immunodominant peptide virus screening together with advances in the design of genetic and non-genetic viral- and tumoural-specific cellular selection strategies have opened new strategies for cellular immunotherapy in oncologic recipients who are highly sensitive to viral infections. However, the rapid development of cellular immunotherapy in SCT has disclosed the role of the T cell selection method in the modulation of functional cell activity and of in vivo secondary effects triggered following immunotherapy.

Ex vivo generation of highly purified and activated natural killer cells from human peripheral blood

Adoptive immunotherapy using natural killer (NK) cells has been a promising treatment for intractable malignancies; however, there remain a number of difficulties with respect to the shortage and limited anticancer potency of the effector cells. We here established a simple feeder-free method to generate purified (>90%) and highly activated NK cells from human peripheral blood-derived mononuclear cells (PBMCs). Among the several parameters, we found that CD3 depletion, high-dose interleukin (IL)-2, and use of a specific culture medium were sufficient to obtain highly purified, expanded (∼200-fold) and activated CD3(-)/CD56(+) NK cells from PBMCs, which we designated zenithal-NK (Z-NK) cells. Almost all Z-NK cells expressed the lymphocyte-activated marker CD69 and showed dramatically high expression of activation receptors (i.e., NKG2D), interferon-γ, perforin, and granzyme B. Importantly, only 2 hours of reaction at an effector/target ratio of 1:1 was sufficient to kill almost all K562 cells, and the antitumor activity was also replicated in tumor-bearing mice in vivo. Cytolysis was specific for various tumor cells, but not for normal cells, irrespective of MHC class I expression. These findings strongly indicate that Z-NK cells are purified, expanded, and near-fully activated human NK cells and warrant further investigation in a clinical setting.

Persistent antigen at vaccination sites induces tumor-specific CD8⁺ T cell sequestration, dysfunction and deletion

To understand why cancer vaccine-induced T cells often fail to eradicate tumors, we studied immune responses in mice vaccinated with gp100 melanoma peptide in incomplete Freund’s adjuvant (IFA), commonly used in clinical cancer vaccine trials. Peptide/IFA vaccination primed tumor-specific CD8⁺ T cells, which accumulated not in tumors but at the persisting, antigen-rich vaccination site. Once there, primed T cells became dysfunctional and underwent antigen-driven, Interferon-γ (IFN-γ) and Fas ligand (FasL)-mediated apoptosis, resulting in hyporesponsiveness to subsequent vaccination. Provision of anti-CD40 antibody, Toll-like receptor 7 (TLR7) agonist and interleukin-2 (IL-2) reduced T cell apoptosis but did not prevent vaccination site sequestration. A non-persisting vaccine formulation shifted T cell localization towards tumors, inducing superior anti-tumor activity while reducing systemic T cell dysfunction and promoting memory formation. Persisting peptide/IFA vaccine depots can induce specific T cell sequestration, dysfunction and deletion at vaccination sites; short-lived formulations may overcome these limitations and result in greater therapeutic efficacy of peptide-based cancer vaccines.

Viral-specific adoptive immunotherapy after allo-SCT: the role of multimer-based selection strategies

Recipients of hematopoietic SCT undergo a period of profound immunosuppression due to the chemotherapy and/or radiotherapy used for the conditioning and to the graft versus host reaction. SCT patients are highly susceptible to the development of viral infections such as CMV or EBV. The achievement of a competent immunological response, such as viral-specific T cells, is associated with a lower incidence of viral infections. Methods for direct identification of antigen-specific T cells have been based on the functional characteristics of these T cells. Techniques such as proliferation and ELISPOT assays, intracellular cytokine staining and IFN-γ capture have been used to quantitate and obtain viral-specific T cells. Multimers are composed of several MHC molecules loaded with immunodominant peptides joined to a fluorescent molecule, which signal can be quantified by a flow cytometer. Multimer technology together with recent advances in flow cytometry, have facilitated the monitoring and selection of antigen-specific T cells without the need for in vitro cultures and manipulation. This has resulted in a better characterization of the function and phenotype of the different subpopulations of T cells involved in the immune recovery post allogeneic SCT. It is becoming a distinct possibility to isolate individual antigen-specific T cells, without long-term culture techniques, and potentially use them as adoptive immunotherapy in the SCT setting.

Ex vivo interleukin-12-priming during CD8(+) T cell activation dramatically improves adoptive T cell transfer antitumor efficacy in a lymphodepleted host

BACKGROUND

Clinical application of adoptive T cell therapy has been hindered by an inability to generate adequate numbers of nontolerized, functionally active, tumor-specific T cells, which can persist in vivo. In order to address this, we evaluated the impact of interleukin (IL)-12 signaling during tumor-specific CD8(+) T cell priming in terms of persistence and antitumor efficacy using an established B16 melanoma tumor adoptive therapy model.

STUDY DESIGN

B6 mice were injected subcutaneously with B16 melanoma tumor cells. On day 12 of tumor growth, mice were preconditioned with cyclophosphamide (4mg dose, intraperitoneally), and 1 day later were treated by adoptive transfer of tumor-specific pmel-1 CD8(+) T cells primed ex vivo 3 days earlier with both IL-12 and antigen (hGP100(25-33) peptide) or antigen only. Tumors were measured biweekly, and infused donor T cells were analyzed for persistence, localization to the tumor, phenotype, and effector function.

RESULTS

Adoptive transfer of tumor-specific CD8(+) T cells primed with IL-12 was significantly more effective in reducing tumor burden in mice preconditioned with cyclophosphamide compared with transfer of T cells primed without IL-12. This enhanced antitumor response was associated with increased frequencies of infused T cells in the periphery and tumor as well as elevated expression of effector molecules including granzyme B and interferon-γ (IFNγ).

CONCLUSIONS

Our findings demonstrate that ex vivo priming of tumor-specific CD8(+) T cells with IL-12 dramatically improves their in vivo persistence and therapeutic ability on transfer to tumor-bearing mice. These findings can be directly applied as novel clinical trial strategies.

The anti-tumour activity of allogeneic cytokine-induced killer cells in patients who relapse after allogeneic transplant for haematological malignancies

We performed a Phase I/II clinical trial to study the feasibility, toxicity and efficacy of allogeneic cytokine-induced killer (CIK) cell expansion, and treatment for patients with haematological malignancies who relapsed after allogeneic haemopoietic SCT (allo-HSCT). Allogeneic CIK cells were successfully generated for a total of 24 patients, including those from patients' own leukapheresis products in 5 patients who had no access to further donor cells. The median CD3(+) T-cell expansion was 9.33 (1.3-38.97) fold, and CD3(+)CD56(+) natural killer (NK)-like T-cell expansion was 27.77 (2.59-438.93) fold. A total of 55 infusions were done for 16 patients who had either failed or progressed after initial response to various individualized chemotherapy regimens and donor lymphocyte infusion (DLI), at doses ranging from 10 to 200 million CD3(+) cells/kg. Response attributable to CIK cell infusion was observed in five patients. These included two with ALL, two with Hodgkin's disease (HD) and one with AML, and two of whom had a response sustained for more than 2 years. Acute GVHD occurred in three and was easily treatable. This study provides some evidence suggestive of the efficacy of allogeneic CIK cells even after failure of DLI in some cases.

Safety analysis of ex vivo-expanded NK and NK-like T cells administered to cancer patients: a phase I clinical study

The chimeric state after allogeneic hematopoietic stem cell transplantation provides a platform for adoptive immunotherapy using donor-derived immune cells. The major risk with donor lymphocyte infusions (DLIs) is the development of graft-versus-host disease (GvHD). Development of new DLI products with antitumor reactivity and reduced GvHD risk represents a challenging task in cancer immunotherapy. Although natural killer (NK) and NK-like T cells are promising owing to their antitumor activity, their low concentrations in peripheral blood mononuclear cells reduces their utility in DLIs. We have recently developed a system that allows expansion of clinical-grade NK and NK-like T cells in large numbers. In this study, the safety of donor-derived long-term ex vivo-expanded human NK and NK-like T cells given as DLIs was investigated as immunotherapy for cancer in five patients following allogeneic stem cell infusion. Infusion of the cells was safe whether administered alone or with IL-2 subcutaneously. No signs of acute GvHD were observed. One patient with hepatocellular carcinoma showed markedly decreased serum alpha-fetoprotein levels following cell infusions. These findings suggest that the use of ex vivo-expanded NK and NK-like T cells is safe and appears an attractive approach for further clinical evaluation in cancer patients.

Toll-like receptor agonists: are they good adjuvants?

Therapeutic immunization leading to cancer regression remains a significant challenge. Successful immunization requires activation of adaptive immunity, including tumor specific CD4 T cells and CD8 T cells. Generally, the activation of T cells is compromised in patients with cancer because of immune suppression, loss of tumor antigen expression, and dysfunction of antigen-presenting cells. Antigen-presenting cells such as dendritic cells (DCs) are key for the induction of adaptive antitumor immune responses. Recently, attention has focused on novel adjuvants that enhance dendritic cell function and their ability to prime T cells. Agonists that target toll-like receptors are being used clinically either alone or in combination with tumor antigens and showing initial success both in terms of enhancing immune responses and eliciting antitumor activity. This review summarizes the application of these adjuvants to treat cancer and the potential for boosting responses in vivo.

Monitoring immune responses after glioma vaccine immunotherapy

Immunotherapy provides the ideal candidate of therapeutic attack against malignant gliomas because it allows for targeting of cancer cells without the potential for nonspecific toxicity. This is important when glial tumor cells spread far through normal brain tissue. Current vaccine therapies are in clinical trials and are showing beneficial responses. Given that the inflammatory response may make serial radiographic imaging more difficult to interpret, newer methodologies of immunomonitoring must be developed to assess the biologic efficacy of these immunotherapies. This article reviews methods of monitoring the immune system after vaccination against malignant gliomas. Improvements in immunomonitoring should lead to an increase in the efficiency of identifying viable avenues of therapeutic research, and assess the efficacy of those currently employed.

Characterization of the class I-restricted gp100 melanoma peptide-stimulated primary immune response in tumor-free vaccine-draining lymph nodes and peripheral blood

PURPOSE

The aim of this study was to characterize the primary gp100(209-2M)-specific T-cell response in vaccine-draining, metastases-free lymph nodes and peripheral blood of peptide-vaccinated stage I to III melanoma patients.

EXPERIMENTAL DESIGN

After two or three gp100(209-2M) vaccinations, sentinel lymph nodes that drained both the primary tumor and adjacent vaccine sites were excised concomitant with wide excision of the tumor. Comparative 7-color flow cytometry phenotype analysis was done on gp100 tetramer-positive CD8(+) T cells from sentinel lymph nodes, closely proximate time-related peripheral blood mononuclear cells (PBMC) collected 2 to 4 weeks after sentinel lymph node excision, and on PBMC collected 6 months later after 7 or 11 more immunizations. Lymph node and peripheral blood T cells were tested for proliferative response, functional avidity, and tumor cell-induced CD107 mobilization.

RESULTS

The frequencies of gp100-specific CD8(+) T cells from time-related PBMC and sentinel lymph nodes were comparable and were similar to those reported for virus-specific memory T cells. Their respective in vitro proliferation responses were also equivalent but statistically higher than proliferation responses of peripheral blood T cells collected after completion of the entire vaccine regimen. By contrast, functional avidity and CD107 responses were significantly higher in circulating T cells. Sentinel lymph node-derived, gp100-specific CD8(+) T cells predominantly expressed central and effector memory phenotype signatures, whereas there were higher frequencies of effector T cells in the peripheral blood.

CONCLUSION

Priming immunization with gp100(209-2M) without coadministration of CD4(+) helper T cell-restricted antigens induced the effective expansion of peptide-specific central and effector memory CD8(+) T cells with high proliferation potential in vaccine-draining lymph nodes of stage I to III melanoma patients. Lymph node memory T cells gave rise to circulating gp100-specific effector T cells exhibiting increased functional maturation.

Phenotype and functional characterization of long-term gp100-specific memory CD8+ T cells in disease-free melanoma patients before and after boosting immunization

PURPOSE

Effective cancer vaccines must both drive a strong CTL response and sustain long-term memory T cells capable of rapid recall responses to tumor antigens. We sought to characterize the phenotype and function of gp100 peptide-specific memory CD8+ T cells in melanoma patients after primary gp100(209-2M) immunization and assess the anamnestic response to boosting immunization.

EXPERIMENTAL DESIGN

Eight-color flow cytometry analysis of gp100-specific CD8+ T cells was done on peripheral blood mononuclear cells collected shortly after the primary vaccine regimen, 12 to 24 months after primary vaccination, and after boosting immunization. The anamnestic response was assessed by comparing the frequency of circulating gp100-specific T cells before and after boosting. Gp100 peptide-induced in vitro functional avidity and proliferation responses and melanoma-stimulated T-cell CD107 mobilization were compared for cells from all three time points for multiple patients.

RESULTS

The frequency of circulating gp100-specific memory CD8+ T cells was comparable with cytomegalovirus-specific and FLU-specific T cells in the same patients, and the cells exhibited anamnestic proliferation after boosting. Their phenotypes were not unique, and individual patients exhibited one of two distinct phenotype signatures that were homologous to either cytomegalovirus-specific or FLU-specific memory T cells. Gp100-specific memory T cells showed some properties of competent memory T cells, such as heightened in vitro peptide-stimulated proliferation and increase in central memory (TCM) differentiation when compared with T-cell responses measured after the primary vaccine regimen. However, they did not acquire enhanced functional avidity usually associated with competent memory T-cell maturation.

CONCLUSIONS

Although vaccination with class I-restricted melanoma peptides alone can break tolerance to self-tumor antigens, it did not induce fully competent memory CD8+ T cells--even in disease-free patients. Data presented suggest other vaccine strategies will be required to induce functionally robust long-term memory T cells.

Characterization of the recognition and functional heterogeneity exhibited by cytokine-induced killer cell subsets against acute myeloid leukaemia target cell

The polyclonal cytokine-induced killer (CIK) cells exhibit potent cytotoxicity against a variety of tumour cells including autologous and allogeneic acute myeloid leukaemic (AML) targets. At maturity, three lymphocyte subsets: CD3(-) CD56(+), CD3(+) CD56(-) and CD3(+) CD56(+), constitute the bulk of the CIK cell culture. The CD3(-) CD56(+) subset behaves like classical natural killer (NK) cells where cytotoxicity is potentiated by blocking the human leucocyte antigen Class I molecules in the AML targets. Both the CD3(+) CD56(+) and CD3(+) CD56(-) subsets, though known to kill autologous and allogeneic targets to a comparable degree and therefore non-major histocompatibility complex (MHC)-restricted, nevertheless require the presence of the MHC molecule on the target, which interacts with their CD3-T-cell receptor complex. Although CIK cells are often termed 'NK-like' T cells, we have demonstrated that the well-characterized NK receptors KIR, NKG2C/E, NKG2D and DNAM-1 are not involved in the process of AML recognition for the CD3(+) CD56(-) and CD3(+) CD56(+) subsets. The CD3(+) CD56(+) and CD3(+) CD56(-) subsets express a polyclonal and comparable TCRVbeta repertoire in a Gaussian distribution. The CD3(+) CD56(+) subset kills AML targets more efficiently than its CD3(+) CD56(-) counterpart because of the presence of a higher proportion of CD8(+) cells. The CD3(+) CD56(+) subset comprise more terminally differentiated late effector T cells that bear the CD27(+) CD28(-) or CD27(-) CD28(-) phenotype, with a higher granzyme A content. In comparison, the phenotype of the CD3(+) CD56(-) subset is consistent with early effector T cells that are CD27(+) CD28(+) and CD62L(+), known to be less cytotoxic but possess greater proliferative potential.

Translational research in melanoma

Current treatment of malignant melanoma exemplifies not only the need for translational research but also many of the challenges of moving from bench to bedside. Melanoma remains unique among solid tumors in that its treatment primarily is surgical. Radiation is of limited benefit, and chemotherapy has been disappointing in both the adjuvant and metastatic settings. This leaves clinicians with few options for reducing the chance of recurrence after surgery and for treating unresectable disease. With this in mind, there has been a fervent attempt to identify novel approaches to melanoma therapy and translate them into clinical use.

Tumor microenvironment and immune escape

This article describes the multiple escape mechanisms used by tumor cells to avoid T-cell-mediated recognition and destruction. The discussion focuses on escape mechanisms that may result from changes at the level of TA-specific cytotoxic T lymphocytes and tumor cells in the tumor microenvironment. Specifically, we discuss the negative impact of regulatory T cells and T-cell apoptosis on the tumor antigen-specific cytotoxic T lymphocyte response. We also discuss changes in the expression of histocompatibility antigens by tumor cells, which may affect tumor cell-immune cell interactions.

Brain microenvironment promotes the final functional maturation of tumor-specific effector CD8+ T cells

During the priming phase of an antitumor immune response, CD8(+) T cells undergo a program of differentiation driven by professional APCs in secondary lymphoid organs. This leads to clonal expansion and acquisition both of effector functions and a specific adhesion molecule pattern. Whether this program can be reshaped during the effector phase to adapt to the effector site microenvironment is unknown. We investigated this in murine brain tumor models using adoptive transfer of tumor-specific CD8(+) T cells, and in spontaneous immune responses of patients with malignant glioma. Our data show proliferation of Ag-experienced tumor-specific T cells within the brain parenchyma. Moreover, CD8(+) T cells further differentiated in the brain, exhibiting enhanced IFN-gamma and granzyme B expression and induction of alpha(E)(CD103)beta(7) integrin. This unexpected integrin expression identified a subpopulation of CD8(+) T cells conditioned by the brain microenvironment and also had functional consequences: alpha(E)(CD103)beta(7)-expressing CD8(+) T cells had enhanced retention in the brain. These findings were further investigated for CD8(+) T cells infiltrating human malignant glioma; CD8(+) T cells expressed alpha(E)(CD103)beta(7) integrin and granzyme B as in the murine models. Overall, our data indicate that the effector site plays an active role in shaping the effector phase of tumor immunity. The potential for local expansion and functional reprogramming should be considered when optimizing future immunotherapies for regional tumor control.

Induction of Circulating Tumor-reactive CD8+ T Cells After Vaccination of Melanoma Patients With the gp100209-2M Peptide

Patients with stage I-III melanoma were vaccinated with the modified HLA-A2-binding gp100(209-2M)-peptide after complete surgical resection of their primary lesion and sentinel node biopsy. Cytoplasmic interferon-gamma production by freshly thawed peripheral blood mononuclear cells (direct ex vivo analysis) or by peripheral blood mononuclear cells subjected to 1 cycle of in vitro sensitization with peptide, interleukin-2, and interleukin-15 was measured following restimulation with the modified and native gp100 peptides, and also A2gp100 melanoma cell lines. Peptide-reactive and tumor-reactive T cells were detected in 79% and 66% of selected patients, respectively. Patients could be classified into 3 groups according to their vaccine-elicited T-cell responses. One group of patients responded only to the modified peptide used for immunization, whereas another group of patients reacted to both the modified and native gp100 peptides, but not to naturally processed gp100 antigen on melanoma cells. In the third group of patients, circulating CD8 T cells recognized A2gp100 melanoma cell lines and also both the modified and native peptides. T cells with a low functional avidity, which were capable of lysing tumor cells only if tumor cells were first pulsed by the exogenous administration of native gp100(209-217) peptide were identified in most patients. These results indicate that vaccination with a modified gp100 peptide induced a heterogeneous group of gp100-specific T cells with a spectrum of functional avidities; however, high avidity, tumor-reactive T cells were detected in the majority of patients.

Engineered CD8+ cytotoxic T cells with fiber-modified adenovirus-mediated TNF-alpha gene transfection counteract immunosuppressive interleukin-10-secreting lung metastasis and solid tumors

T-cell suppression derived from tumor-secreted immunosuppressive interleukin (IL)-10 becomes a major barrier to CD8+ T-cell immunotherapy of tumors. Tumor necrosis factor-alpha (TNF-alpha) is a multifunctional cytokine capable of activating T and dendritic cells (DCs) and counteracting IL-10-mediated DC inhibition and regulatory T-cell-mediated immune suppression. In this study, we constructed a recombinant adenovirus (MF)AdVTNF with fiber-gene modified by RGD insertion into the viral knob's H1 loop and a melanoma cell line B16(OVA/IL-10) engineered to express ovalbumin (OVA) and to secrete IL-10 (2.2 ng/ml/10(6) cells/24 h). We transfected OVA-specific CD8+ T cells with (MF)AdVTNF, and found a fivefold increase in transgene human TNF-alpha secretion (4.3 ng/ml/10(6) cells/24 h) by the engineered CD8+ T(TNF) cells transfected with (MF)AdVTNF, compared to that (0.8 ng/ml/10(6) cells/24 h) by CD8+ T cells transfected with the original AdVTNF without viral fiber modification. The engineered CD8+ T(TNF) cells exhibited enhanced cytotoxicity and elongated survival in vivo after adoptive transfer. TNF-alpha derived from both the donor CD8+ T cells and the host cells plays an important role in donor CD8+ T-cell survival in vivo after adoptive transfer. We also demonstrated that the transfected B16(OVA/IL-10) tumor cells secreting IL-10 are more resistant to in vivo CD8+ T-cell therapy than the original B16(OVA) tumor cells without IL-10 expression. Interestingly, the engineered CD8+ T(TNF) cells secreting transgene-coded TNF-alpha, but not the control CD8+ T(control) cells without any transgene expression eradicated IL-10-secreting 12-day lung micrometastasis in all 10/10 mice and IL-10-secreting solid tumors ( approximately 5 mm in diameter) in 6/10 mice. Transfer of the engineered CD8+ T(TNF) cells further induced both donor- and host-derived memory CD8+ T cells, leading to a stronger long-term antitumor immunity against the IL-10-secreting B16(OVA/IL-10) tumor cell challenges. Therefore, CD8+ T cells engineered to secrete TNF-alpha may be useful when designing strategies for adoptive T-cell therapy of solid tumors.

Adoptive immunotherapy for cancer: building on success

Adoptive cell transfer after host preconditioning by lymphodepletion represents an important advance in cancer immunotherapy. Here, we describe how a lymphopaenic environment enables tumour-reactive T cells to destroy large burdens of metastatic tumour and how the state of differentiation of the adoptively transferred T cells can affect the outcome of treatment. We also discuss how the translation of these new findings might further improve the efficacy of adoptive cell transfer through the use of vaccines, haematopoietic-stem-cell transplantation, modified preconditioning regimens, and alternative methods for the generation and selection of the T cells to be transferred.