Initial depletion of regulatory T cells: the missing solution to preserve the immune functions of T lymphocytes designed for cell therapy

Rational combinations of in vivo cancer antigen priming and adoptive T-cell therapy mobilize immune and clinical responses in terminal cancers

PURPOSE

It is now recognized that solid tumors encroach on the host's immune microenvironment to favor its own proliferation. Strategies to enhance the specificity of the endogenous T-cell population against tumors have been met with limited clinical success. We aimed to devise a two-tier protocol coupling in vivo whole antigen priming with ex vivo cellular expansion to clinically evaluate survival in patients following re-infusion of primed, autologous T cells, thereby determining treatment efficacy.

EXPERIMENTAL DESIGN

Treatment commenced with the acquisition of whole tumor antigens from tumor cell lines corresponding with patients' primary malignancy. Lysate mixture was inoculated intradermally, while peripheral blood mononuclear cells (PBMCs) were periodically extracted via phlebotomy and expanded in culture ex vivo for re-infusion. Post-treatment tumor-specific T-cell response and cytotoxicity was confirmed via Elispot and real-time cell analyzing (RTCA) assay. Serum cytokine levels and cytotoxicity scores were evaluated for associations with survival status and duration.

RESULTS

There was a significant increase in cytotoxicity exhibited by T cells measured using both Elispot and RTCA following treatment. Correlation analysis determined significant association between higher post-treatment cytotoxicity scores and survival status (R = 0.52, p = 0.0028) as well as longer survival duration in months (R = 0.59, p = 0.005).

CONCLUSIONS

Our treatment protocol successfully demonstrated significant correlation between tumor-associated antigen-specific immune response and objective prolongation of survival. Whole-cell cancer antigen priming and adoptive T-cell therapy is, therefore, a highly feasible clinical model which can be easily replicated to positively influence outcome in end-stage malignancy.

Modelling T cell proliferation: Dynamics heterogeneity depending on cell differentiation, age, and genetic background

Cell proliferation is the common characteristic of all biological systems. The immune system insures the maintenance of body integrity on the basis of a continuous production of diversified T lymphocytes in the thymus. This involves processes of proliferation, differentiation, selection, death and migration of lymphocytes to peripheral tissues, where proliferation also occurs upon antigen recognition. Quantification of cell proliferation dynamics requires specific experimental methods and mathematical modelling. Here, we assess the impact of genetics and aging on the immune system by investigating the dynamics of proliferation of T lymphocytes across their differentiation through thymus and spleen in mice. Our investigation is based on single-cell multicolour flow cytometry analysis revealing the active incorporation of a thymidine analogue during S phase after pulse-chase-pulse experiments in vivo, versus cell DNA content. A generic mathematical model of state transition simulates through Ordinary Differential Equations (ODEs) the evolution of single cell behaviour during various durations of labelling. It allows us to fit our data, to deduce proliferation rates and estimate cell cycle durations in sub-populations. Our model is simple and flexible and is validated with other durations of pulse/chase experiments. Our results reveal that T cell proliferation is highly heterogeneous but with a specific “signature” that depends upon genetic origins, is specific to cell differentiation stages in thymus and spleen and is altered with age. In conclusion, our model allows us to infer proliferation rates and cell cycle phase durations from complex experimental 5-ethynyl-2'-deoxyuridine (EdU) data, revealing T cell proliferation heterogeneity and specific signatures.

We assess the impact of genetics and aging on immune system dynamics by investigating the dynamics of proliferation of T lymphocytes across their differentiation through thymus and spleen in mice. Understanding cell proliferation dynamics requires specific experimental methods and mathematical modelling. Our investigation is based upon single-cell multicolour flow cytometry analysis thereby revealing the active incorporation in DNA of a thymidine analogue during S phase after pulse-chase experiments in vivo, versus cell DNA content. A generic mathematical model that simulates the evolution of single cell behaviour during the experiment allows us to fit our data, to deduce proliferation rates and mean cell cycle phase durations in sub-populations. This reveals that T cell proliferation is constrained by genetic influences, declines with age, and is specific to cell differentiation stage, revealing a specific “signature” of cell proliferation. Our model is simple and flexible and can be used with other pulse/chase experiments.

The suppressive function of human CD8(+) iTregs is inhibited by IL-1β and TNFα

CD8(+) Tregs display an immunoregulatory activity and may play an essential role in the immunopathology of several diseases. Therefore, their therapeutic potential is exquisite and further studies on their differentiation and function are essential. The aim of this study was to evaluate the role of the innate immune system in CD8(+) iTreg differentiation and function. Naive human CD8(+) CD25(-) CD45RA(+) T cells were cultured in Treg-inducing conditions with or without IL-1β, TNFα or monocyte-derived dendritic cells (DCs). The differentiation of CD8(+) CD127(-) CD25(hi) FoxP3(hi) -induced Tregs (CD8(+) iTregs) is dependent on TGF-β1 and IL-2, which had synergistic effect upon their differentiation. CD8(+) iTregs were also induced in a coculture with allogeneic mature DCs (mDCs). The CD8(+) iTregs suppressive function was confirmed, which was diminished in the presence of IL-1β and TNFα. The IL-1β-prevented suppressive function was associated with reduced secretion of IL-10 and IFNγ, whereas the presence of TNFα did not affect their secretion. Furthermore, the presence of TNFα reduced IL-10 and TGF-β1 secretion by CD8(+) iTregs, whereas only IL-10 secretion was decreased by IL-1β. Together, these results suggest that IL-1β and TNFα prevent IL-2- and TGF-β1-driven CD8(+) iTregs suppressive function in human T cells. Such pro-inflammatory innate immune response possibly mediates its negative tolerogenic effect through reduced IFNγ-, IL-10- and TGF-β1-driven mechanism.

Immunotherapy of multiple myeloma: the start of a long and tortuous journey

The field of tumor immunotherapy is still in its infancy. It is becoming clear that the human immune response is the result of highly complex, continuously evolving interactions between cells of the adaptive and innate arms of the immune system, the internal and external environments, and normal and abnormal cells (e.g., myeloma plasma cells). Despite the considerable advances in our knowledge over the past 30 years, we have still only scratched the surface of the immune system's interaction with malignant diseases such as myeloma and to date, this has not translated into significantly better outcomes for patients with this disease. This review will summarize our current knowledge of the fundamental immunology of myeloma, review immunotherapy trials reported to date and discuss whether, in light of the current information, immunotherapy of multiple myeloma is an achievable goal.

Current progress in the development of a cell-based vaccine for the immunotherapy of acute myeloid leukemia

Evidence that immunological control contributes to the elimination of residual leukemia has emerged from allogeneic hematopoietic stem cell transplantation. This review assesses the current understanding of immunobiology of acute myeloid leukemia and how dendritic cells and T cells may be harnessed using in vitro and in vivo priming techniques. Preclinical and clinical dendritic cell vaccine trials reported to date are considered and the prospects for immunotherapy with dendritic cell-based vaccine constructs evaluated.

IL-7 inhibits tumor growth by promoting T cell-mediated antitumor immunity in Meth A model

Immune suppression is well documented during tumor progression, which includes loss of effect of T cells and expansion of T regulatory (Treg) cells. IL-7 plays a key role in the proliferation, survival and homeostasis of T cells and displays a potent antitumor activity in vivo. In the present study, we investigated the antitumor effect of IL-7 in Meth A model. IL-7 inhibited tumor growth and prolonged the survival of tumor-bearing mice with corresponding increases in the frequency of CD4 and CD8 T cells, Th1 (CD4(+)IFN-γ(+)), Tc1 (CD8(+)IFN-γ(+)) and T cells cytolytic activity against Meth A cells. Neutralization of CD4 or CD8 T cells reversed the antitumor benefit of IL-7. Furthermore, IL-7 decreased regulatory T Foxp3 as well as cells suppressive activity with a reciprocal increase in SMAD7. In addition, we observed an increase of the serum concentrations of IL-6 and IFN-γ, and a significant decrease of TGF-β and IL-10 after IL-7 treatment. Taken together, these results indicate that IL-7 augments T cell-mediated antitumor immunity and improves the effect of antitumor in Meth A model.

The innovative evolution of cancer gene and cellular therapies

We provide an overview of the latest developments in cancer gene therapy--from the bench to early-stage clinical trials. We describe the most recent work of worldwide teams including experienced scientists and clinicians, reflecting the recent emergence of gene therapy from the 'Valley of Death'. The treatment efficacy of clinical gene therapy has now been shown in a number of diseases including cancer and we are observing a renewed interest by big pharmaceutical and biotechnology companies most obviously demonstrated by Amgen's acquisition of Biovex for up to USD$1 billion. There is an opportunity to be cautiously hopeful regarding the future of gene therapy in the clinic and we review here some of the most recent progress in the field.

Human CD90 identifies Th17/Tc17 T cell subsets that are depleted in HIV-infected patients

By revisiting CD90, a GPI-anchored glycoprotein, we show that CD90 is expressed by a subset of CD4(+) and CD8(+) human T cells. CD4(+)CD90(+) cells share similarities with Th17 cells because they express the Th17-specific transcription factor RORC2 and produce IL-17A. CD4(+)CD90(+) cells are activated memory T cells that express the gut mucosal markers CCR6, CD161, and the α(4) and β(7) integrins. Compared with CD90-depleted CCR6(+) memory Th17 cells, CD4(+)CD90(+) cells express higher levels of IL-22 and proinflammatory cytokines (IL-6, TNF-α and GM-CSF), but they produce lower levels of IL-21 and no IL-9. Analyses of CD8(+)CD90(+) cells reveal that they express RORC2 and are able to produce higher levels of IL-17A, IL-22, and CCL20 compared with CD90-depleted CD8(+) cells. These data show that CD90 identifies Th17 and Tc17 cells with a peculiar cytokine profile. Studies of circulating CD90(+) cells in HIV patients show that CD90(+) cells are decreased with an imbalance of the CD4(+)CD90(+)/regulatory T cell ratio in nontreated patients compared with treated patients and healthy donors. Overall, human CD90 identifies a subset of Th17 and Tc17 cells within CD4(+) and CD8(+) T cells, respectively, which are depleted during HIV infection.

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.

Ex vivo expansion protocol for human tumor specific T cells for adoptive T cell therapy

Adoptive T cell therapy is a promising treatment strategy for patients with different types of cancer. The methods used for generation of high numbers of tumor specific T cells usually require long-term ex vivo culture, which frequently lead to generation of terminally differentiated effector cells, demonstrating low persistence in vivo. Therefore, optimization of protocols for generation of T cells for adoptive cell therapy is warranted. The aim of this work was to develop a protocol for expansion of antigen-specific T cells using Dynabeads CD3/CD28 to obtain T cells expressing markers important for in vivo persistence and survival. To achieve high numbers of antigen-specific T cells following expansion, we have tested the effect of depleting regulatory T cells using Dynabeads CD25 and including a pre-stimulation step with peptide prior to the non-specific expansion with Dynabeads. Our data demonstrate that virus- and tumor specific T cells can be expanded to high numbers using Dynabeads CD3/CD28 following optimization of the culture conditions. The expansion protocol presented here results in enrichment of antigen-specific CD8(+) T cells with an early/intermediate memory phenotype. This is observed even when the antigen-specific CD8(+) T cells demonstrated a terminal effector phenotype prior to expansion. This protocol thus results in expanded T cells with a phenotypic profile which may increase the chance of retaining long-term persistence following adoptive transfer. Based on these data we have developed a cGMP protocol for expansion of tumor specific T cells for adoptive T cell therapy.

Inhibition of phosphoinositide 3-kinase ameliorates dextran sodium sulfate-induced colitis in mice

The critical role of phosphoinositide 3-kinase gamma (PI3Kgamma) in inflammatory cell activation and recruitment makes it an attractive target for immunomodulatory therapy. 5-Quinoxilin-6-methylene-1,3-thiazolidine-2,4-dione (AS605240), a potent PI3Kgamma inhibitor, has been reported to ameliorate chronic inflammatory disorders including rheumatoid arthritis, systemic lupus erythematosus, and atherosclerosis. However, its in vivo effect on intestinal inflammation remains unknown. Here we evaluated the protective and therapeutic potentials of AS605240 in mice with dextran sodium sulfate (DSS)-induced acute and chronic colitis. Our results showed that AS605240 improved survival rate, disease activity index, and histological damage score in mice administered DSS in both preventive and therapeutic studies. AS605240 treatment also significantly inhibited the increase in myeloperoxidase levels, macrophage infiltration, and CD4(+) T-cell number in the colon of DSS-fed mice. The DSS-induced overproduction of colonic proinflammatory cytokines including interleukin (IL)-1beta, tumor necrosis factor-alpha, and interferon-gamma was significantly suppressed in mice undergoing AS605240 therapy, whereas colonic anti-inflammatory cytokines such as IL-4 were up-regulated. The down-regulation of the phospho-Akt level in immunological cells from the inflamed colon tissue and spleen of AS605240-treated mice was detected both by immunohistochemical analysis and Western blotting. These findings demonstrate that AS605240 may represent a promising novel agent for the treatment of inflammatory bowel disease by suppressing leukocyte infiltration as well as by immunoregulating the imbalance between proinflammatory and anti-inflammatory cytokines.

Modulation of the TCR stimulation strength can render human activated CD4+ T cells suppressive

In this study, we explored the potential of human naive CD4(+) T cells to acquire regulatory properties upon stimulation. We demonstrated that, in vitro, pre-activated naive CD4(+)CD25(-)CD45RA(+) T cells could become anergic and suppressive CD4(+)CD25(+) T cells upon lower intensity TCR stimulation. These CD4(+)CD25(+) T cells generated in vitro potently suppress the proliferation of allogenic CD4(+)CD25(-) T cells independently of cytokines and in a contact-dependent manner. Our data indicate that expression of Foxp3 is not necessary to induce the suppressive T cell activity. We demonstrate that these CD4(+)CD25(+) T cells are unresponsive upon re-stimulation and that their suppressive activity is transient. However, we showed that the anergy and the suppressive function could be reversed by increasing the stimulus and their level of activation. We concluded from our data that these anergy and suppressive activities are related to a fine tuning of TCR activation threshold.

IL-7 and IL-15 allow the generation of suicide gene–modified alloreactive self-renewing central memory human T lymphocytes

Long-term clinical remissions of leukemia, after allogeneic hematopoietic stem cell transplantation, depend on alloreactive memory T cells able to self-renew and differentiate into antileukemia effectors. This is counterbalanced by detrimental graft-versus-host disease (GVHD). Induction of a selective suicide in donor T cells is a current gene therapy approach to abrogate GVHD. Unfortunately, genetic modification reduces alloreactivity of lymphocytes. This associates with an effector memory (TEM) phenotype of gene-modified lymphocytes and may limit antileukemia effect. We hypothesized that alloreactivity of gene-modified lymphocytes segregates with the central memory (TCM) phenotype. To this, we generated suicide gene–modified TCM lymphocytes with a retroviral vector after CD28 costimulation and culture with IL-2, IL-7, or a combination of IL-7 and IL-15. In vitro, suicide gene–modified TCM cells self-renewed upon alloantigen stimulation and resisted activation-induced cell death. In a humanized mouse model, only suicide gene–modified T cells cultured with IL-7 and IL-15 persisted, differentiated in TEM cells, and were as potent as unmanipulated lymphocytes in causing GVHD. GVHD was halted through the activation of the suicide gene machinery. These results warrant the use of suicide gene–modified TCM cells cultured with IL-7 and IL-15 for the safe exploitation of the alloreactive response against cancer.

Effects of targeted deletion of cannabinoid receptors CB1 and CB2 on immune competence and sensitivity to immune modulation by Delta9-tetrahydrocannabinol

The role of cannabinoid receptors, CB1 and CB2, in immune competence and modulation by Delta9-tetrahydrocannabinol (Delta9-THC) was investigated in CB1(-/-)/CB2(-/-) mice. Immunofluorescence analysis of splenic leukocytes showed no significant differences in the percentage of T cell subsets, B cells, or macrophages between wild-type and CB1(-/-)/CB2(-/-) mice. Lymphoproliferative control responses to PHA, phorbol ester plus ionomycin, or LPS and sensitivity to suppression by Delta9-THC showed no profound differences between the two genotypes, although some differences were observed in control baseline responses. Likewise, similar control responses and sensitivity to Delta9-THC were observed in mixed lymphocyte responses (MLR) and in IL-2 and IFN-gamma production in both genotypes. Conversely, humoral immune responses showed a markedly different profile of activity. Delta9-THC suppressed the in vivo T cell-dependent, anti-sheep RBC (anti-sRBC) IgM antibody-forming cell (AFC) response in wild-type but not in CB1(-/-)/CB2(-/-) mice, and the in vitro anti-sRBC IgM response in CB1(-/-)/CB2(-/-) splenocytes was too low to rigorously assess CB1/CB2 involvement in modulation by Delta9-THC. Conversely, comparable in vitro IgM AFC control responses to LPS and CD40 ligand (CD40L) activation were observed in the two genotypes. Interestingly, LPS-induced IgM responses were refractory to suppression by Delta9-THC, regardless of genotype, and CD40L-induced IgM responses were only suppressed by Delta9-THC in wild-type but not in CB1(-/-)/CB2(-/-) B cells. Collectively, we demonstrate differential involvement of CB1 and/or CB2 in immune modulation by Delta9-THC and in some control responses. Moreover, CB1/CB2 involvement was observed in humoral responses requiring CD40-initiated signaling for suppression by Delta9-THC.

CD4+ T-cell recognition of human 5T4 oncofoetal antigen: implications for initial depletion of CD25+ T cells

BACKGROUND

The human 5T4 (h5T4) oncofoetal antigen is expressed by a wide variety of human carcinomas including colorectal, ovarian, gastric and renal, but rarely on normal tissues. Its restricted expression on tumour tissues as well as its association with tumour progression and bad prognosis has driven the development of a MVA-based vaccine (TroVax) which has been tested in several early phase clinical trials and these studies have led to the start of a phase III trial in renal cell carcinoma patients. We have recently shown that CD8(+) T cells recognizing h5T4 can be generated in the absence of CD4(+) T cells from peripheral blood lymphocytes of human healthy individuals.

RESULTS

We report the existence and expansion of human CD4(+) T cells against h5T4 by stimulation with autologous monocyte-derived dendritic cells infected with a replication defective adenovirus encoding the h5T4 cDNA (Ad-h5T4). The h5T4-specific T-cell responses in normal individuals are enhanced by initial depletion of CD25(+) cells (putative T regulatory cells) prior to the in vitro stimulation. We have identified a novel h5T4-derived 15-mer peptide recognized by CD4(+) T cells in HLA-DR4 positive healthy individuals. Interestingly, CD4(+) T cells spontaneously recognizing a different 5T4 epitope restricted by HLA-DR were identified in tumour-infiltrating lymphocytes isolated from a regressing renal cell carcinoma lung metastasis.

CONCLUSION

Our data show that CD4(+) T cells recognizing h5T4 can be expanded and detected in healthy individuals and a renal cell carcinoma patient. Such h5T4-specific CD4(+) T cells boosted or induced by vaccination could act to modulate both cell or antibody mediated anti-tumour responses.

Regulatory T-cell expansion and function do not account for the impaired alloreactivity of ex vivo-expanded T cells

CD3- and CD28-activated T cells expanded for 12 days ex vivo to produce suicide gene-modified T cells are hyporesponsive to alloantigens. To investigate whether this impaired alloreactivity is a result of preferential expansion of regulatory T (Treg) cells, we compared peripheral blood mononuclear cells (PBMC) activated with CD3 and CD28 antibodies co-immobilized on beads and expanded for 12 days with interleukin (IL)-2 (Co(CD3/CD28) cells) to the respective unactivated PBMC in terms of proliferation, cytokine production, and expression of Treg markers [cytotoxic T-lymphocyte antigen 4 (CTLA4), glucocorticoid-induced tumour necrosis factor receptor (GITR) and forkhead box P3 (FoxP3)] after allostimulation. Alloreactive cells were identified by carboxyfluoresceine succinimidyl ester staining dilution. Alloreactive cells in Co(CD3/CD28) cells had a lower proliferative response and a lower potential for IL-2 and interferon-gamma secretion than did those in PBMC, demonstrating a functional impairment of alloreactive cells during ex vivo expansion. Expression of Treg markers transiently increased during ex vivo expansion and was unaffected by depletion of CD25(+) cells (containing Treg cells) before ex vivo PBMC expansion. Such prior CD25(+) depletion did not restore the alloreactivity of Co(CD3/CD28) cells. After allostimulation, expression of Treg markers was restricted to proliferative (alloreactive) cells among PBMC or Co(CD3/CD28) cells. Lastly, CD4(+) CD25(+) cells purified from Co(CD3/CD28) cells lacked suppressive activity when used as a third party, in contrast to CD4(+) CD25(+) cells purified from PBMC. In conclusion, the impaired alloreactivity of T cells expanded ex vivo is not a result of preferential Treg cell expansion and/or enhanced suppressive Treg activity.

Effective proliferation of human regulatory T cells requires a strong costimulatory CD28 signal that cannot be substituted by IL-2

The strength of immune repression by regulatory T (Treg) cells is thought to depend on the efficiency of Treg cell activation. The stimuli and their individual strength required to activate resting human Treg cells, however, have so far not been elucidated in detail. We reveal here that induction of proliferation of human CD4(+)C25(+) Treg cells requires an extraordinary strong CD28 costimulatory signal in addition to TCR/CD3 engagement. CD28 costimulation, noteworthy, cannot be substituted by IL-2 to induce proliferation of Treg cells, which is in contrast to CD4(+)CD25(-) T cells. IL-2, in contrast, prevents spontaneous apoptosis of Treg cells, but does not initiate their amplification. IL-2 and CD28 costimulation clearly exhibit disparate effects on Treg cells which are in contrast to those on CD4(+)CD25(-) T cells. Moreover, the prerequisites for Treg cell proliferation differ strikingly from those for effector T cells, implying a balanced orchestration in initiating and limiting a T cell immune response. In addition, data are of relevance for the design of therapeutic strategies involving IL-2 administration and CD28 costimulation.

CD158K/KIR3DL2 transcript detection in lesional skin of patients with erythroderma is a tool for the diagnosis of Sézary syndrome

The distinction between Sézary syndrome (SS) and benign erythrodermic inflammatory diseases (EID) is difficult to make both clinically and on skin biopsies, since histomorphology can provide nonspecific results. New markers of circulating malignant Sézary cells have been recently described, especially CD158k/KIR3DL2 and T-plastin, but it has not been yet determined whether they could help in the diagnosis of erythroderma in skin samples. In this study, 13 frozen skin specimens from 10 SS patients and 26 from EID were analyzed for CD158k/KIR3DL2 expression using immunohistochemistry with AZ158 mAb, which also recognizes the monomeric CD158e/KIR3DL1 receptor. Although positive in all SS samples, immunohistochemistry appeared to not reliably discriminate between SS and EID. Therefore in all samples disclosing a significant staining with AZ158 mAb, CD158k/KIR3DL2, CD158e/KIR3DL1 and T-plastin mRNA expression were analyzed on the same skin specimen using conventional and/or quantitative real-time reverse transcription (RT)-PCR. Interestingly, only CD158k/KIR3DL2 transcripts were found to be significantly overexpressed in skin biopsies from patients with SS (P<0.0001), including when normalization to CD3 expression was achieved (P=0.0003). In light of these findings, CD158k/KIR3DL2 transcripts appear to be a unique molecular marker of SS in skin samples, allowing differential diagnosis with benign EID in routine practice.

Inducible caspase 9 suicide gene to improve the safety of allodepleted T cells after haploidentical stem cell transplantation

Addback of donor T cells following T cell-depleted stem cell transplantation (SCT) can accelerate immune reconstitution and be effective against relapsed malignancy. After haploidentical SCT, a high risk of graft-versus-host disease (GVHD) essentially precludes this option, unless the T cells are first depleted of alloreactive precursor cells. Even then, the risks of severe GVHD remain significant. To increase the safety of the approach and thereby permit administration of larger T cell doses, we used a suicide gene, inducible caspase 9 (iCasp9), to transduce allodepleted T cells, permitting their destruction should administration have adverse effects. We made a retroviral vector encoding iCasp9 and a selectable marker (truncated CD19). Even after allodepletion (using anti-CD25 immunotoxin), donor T cells could be efficiently transduced, expanded, and subsequently enriched by CD19 immunomagnetic selection to >90% purity. These engineered cells retained antiviral specificity and functionality, and contained a subset with regulatory phenotype and function. Activating iCasp9 with a small-molecule dimerizer rapidly produced >90% apoptosis. Although transgene expression was downregulated in quiescent T cells, iCasp9 remained an efficient suicide gene, as expression was rapidly upregulated in activated (alloreactive) T cells. We have demonstrated the clinical feasibility of this approach after haploidentical transplantation by scaling up production using clinical grade materials.

Tumor Antigen–Specific T-Cell Expansion Is Greatly Facilitated by In vivo Priming

PURPOSE

Adoptive T-cell therapy is a promising strategy for the treatment of patients with established tumors but is often limited to specific cancers where tumor-infiltrating lymphocytes, the source of T cells for ex vivo culture, can be obtained. In this study, we evaluated the feasibility of expanding HER-2/neu-specific T cells derived from peripheral blood ex vivo following in vivo priming with a HER-2/neu peptide vaccine.

EXPERIMENTAL DESIGN

Peripheral blood mononuclear cells from cytomegalovirus (CMV)-seronegative and CMV-seropositive donors as well as HER-2/neu-positive cancer patients who had or had not been vaccinated with a HER-2/neu peptide-based vaccine was used as a source of T lymphocytes. Antigen-specific T-cell lines were generated by in vitro stimulation with antigen followed by nonspecific expansion on CD3/CD28 beads. The ability to expand antigen-specific T cells was assessed using IFN-gamma and granzyme B enzyme-linked immunosorbent spot. The phenotype of the resultant T-cell lines was evaluated by flow cytometry, including the presence of FOXP3-expressing CD4(+) T cells.

RESULTS

The frequencies of CMV-specific T cells generated from CMV(+) donors were >11-fold higher than the frequencies from CMV(-) donors (P = 0.001), with 22-fold increase of total number of CD3(+) T cells. The frequencies of HER-2/neu-specific T cells generated from the primed patients were >25-fold higher than the frequencies from unvaccinated patients (P = 0.006), with an average of a 19-fold increase of total number of CD3(+) T cells. Using peripheral blood as the source of T cells did not result in concurrent expansion of FOXP3(+)CD4(+) regulatory T cells despite the use of interleukin-2 in in vitro culture. Both CD4(+) and CD8(+) HER-2/neu-specific T cells could be expanded. The extent of ex vivo expansion correlated with the magnitude of immunity achieved during immunization (P = 0.008).

CONCLUSION

Tumor-specific T cells can be efficiently expanded from the peripheral blood ex vivo following in vivo priming with a vaccine. This approach provides an effective method to generate tumor-specific polyclonal T cells for therapeutic use that could be applied to cancer patients with any tumor type.

Quantitative assessment of human T lymphocytes in RAG2(-/-)gammac(-/-) mice: the impact of ex vivo manipulation on in vivo functionality

OBJECTIVE

Recent clinical trials of adoptive immunotherapy showed diminished reactivity of human T cells upon ex vivo manipulation. For a safe and effective clinical application of human T cells, it is necessary to improve ex vivo manipulation procedures and evaluate their impact on in vivo functionality. However, there is no preclinical model for quantitative assessment of in vivo functionality of human T cells. In this study, we investigated the feasibility of using the huPBMC- RAG2(-/-)gammac(-/-) xenogeneic mouse model. As a first example, we compared 3 different ex vivo culture conditions for human T cells.

METHODS

RAG2(-/-)gammac(-/-) mice received cultured human T cells that were stimulated via CD3 alone or costimulated via CD28 (CD3/28) and/or human 4-1BB (CD3/28/4-1BB). Engraftment levels and survival of the cells were measured. The dynamics of the human T cell phenotypes were analyzed during culture and in vivo, as well as the mechanism of the xenoresponse.

RESULTS

Engraftment potential was improved twofold for costimulation compared to CD3 alone (p < 0.001). Phenotypic analysis showed a strikingly similar pattern of development towards CD4(+) and CD8(+) effector and effector-memory cells, suggesting antigen-driven survival and expansion. All parameters used to analyze different effects on in vivo T-cell functionality, like culture condition, engraftment levels, survival of the cells over time, or xenogeneic graft-vs-host disease were absolutely independent of the distribution of the T cell population in vivo following contact with xeno-antigen.

CONCLUSION

The huPBMC-RAG2(-/-)gammac(-/-) xenogeneic transplant model is the most sensitive to date for in vivo functional evaluation of human T cells.

Lentiviral Vectors for T-cell Suicide Gene Therapy: Preservation of T-cell Effector Function After Cytokine-mediated Transduction

Retroviral transfer of the Herpes Simplex thymidine kinase (HSVTK) suicide gene to donor T cells has been used as a safety strategy against graft-versus-host disease following allogeneic stem cell transplantation. The feasibility of this strategy in human studies has been demonstrated, but a number of limitations have become apparent. Preactivation of donor lymphocytes using mitogens or monoclonal antibodies is essential for retroviral transduction, but can compromise subsequent T-cell function in vivo. We report the application of lentiviral vectors for transduction of T cells in cytokine culture, without activation through the T-cell receptor. Using vectors encoding either enhanced green fluorescent protein or a truncated CD34/mutant HSVTK fusion selection/suicide construct, we investigated the properties of T cells after gene modification. We found that following cytokine stimulation, a fraction of T cells undergoes division, and transgene expression occurred predominantly in these cells. Antiviral and alloreactive responses were preserved in these populations, and in contrast to fully activated T cells, there was minimal perturbation of regulatory T-cell numbers. We conclude that the use of interleukin-7 for lentiviral transduction offers the greatest potential for gene transfer to T cells without loss of function, and is favored for the clinical production of suicide gene modified T cells.

The Regulatory/Cytotoxic Graft-Infiltrating T Cells Differentiate Renal Allograft Borderline Change From Acute Rejection

The interpretation of cellular infiltrate from renal transplant recipients with borderline (BL) changes is still a challenging problem. To analyze the immune phenotype of such infiltrate, we quantified the mRNA expression of Foxp3 and interleukinL-10 and granzyme B (GB) in 15 kidney biopsies with BL changes. Controls were patients presenting type IA acute rejection and nonrejecting patients. Only levels of GB mRNA correlated significantly with response to antirejection therapy. Levels of Foxp3 mRNA in BL changes were intermediate between type IA acute rejection and nonrejecting controls. To determine the balance of alloagressive to graft-protecting T cells, we quantified the Foxp3/GB ratio. BL changes T cells infiltrate expressed a significantly higher Foxp3/GB ratio than that in IA acute rejection. These results suggest that T cell infiltrate from BL change exhibit a tolerogenic rather than a cytotoxic phenotype.

Rapid and massive expansion of cord blood-derived cytokine-induced killer cells: an innovative proposal for the treatment of leukemia relapse after cord blood transplantation

We have used a standardized 21-day expansion protocol to produce cytokine-induced killer (CIK) cells starting from very small amounts of nucleated cells (approximately 15 x 10(6) cells) isolated from cord blood. Mononuclear cells are stimulated with anti CD3 (OKT3) and IFNgamma and then expanded with IL-2. Moreover, we show that washouts of cord blood units bags (at the end of the infusion) may be sufficient to yield almost 500 x 10(6) CIK by the same expansion protocol. CIK cells show strong cytotoxic activity against a variety of tumor target cell lines including B and T lymphomas and myeloid leukemias. More importantly, expanded cord blood-derived CIK cells are cytotoxic against fresh leukemic blasts and express perforin, granzyme and NKG2D molecule at high levels. The same in vitro protocol has already been used to expand CIK cells from peripheral blood of adult donors under GMP conditions and therefore these observations open up the possibility of imagining a future clinical application of leukemia relapse following cord blood transplantation with CIK cells obtained from the same cord blood unit.

9th American Society of Gene Therapy annual meeting

The American Society of Gene Therapy, under the presidency of Mark Kay, held its annual meeting in Baltimore, MD, USA this year. This meeting was well received by academics and industry alike in order to promote research, development and application of gene therapy. Exchange of information, promotion of education and development of clinical translation have been the main aims of this society. On face value, the meeting seems to highlight that gene-based treatment is coming of age. Many drawbacks of gene-based treatments were discussed at this meeting with an intense vigour. Immunology has been the major hurdle in restricting the full realisation of gene therapy in the clinical arena. In summary, the field of gene therapy has progressed from its infancy stage of trying to get it to work, to another stage where attempts are being made to overcome the problems associated with its application, in particular, in relation to human immune responses to the vector and the transgene. This progress should be celebrated and not treated as a failure of this form of therapy, as to make this progress is indeed an achievement for any form of therapy.

Phase I/II study of vaccination with dendritic-like leukaemia cells for the immunotherapy of acute myeloid leukaemia

Twenty-two patients with acute myeloid leukaemia were recruited into a phase I/II clinical trial investigating the vaccination of patients in complete remission (CR) with autologous dendritic-like leukaemia cells (DLLC). At trial entry, leukaemia cells were harvested and tested for their ability to undergo cytokine-induced dendritic cell differentiation. Patients were then treated with intensive chemotherapy. Five patients achieved both CR and had leukaemia cells that successfully underwent differentiation and therefore proceeded to vaccination. Four escalating doses of DLLC were administered weekly by subcutaneous injection. Vaccination was generally well tolerated although one patient developed extensive eczema and an increased antinuclear factor titre possibly indicating induction of autoimmunity. Development of anti-leukaemic T-cell responses was assessed by enzyme-linked immunospot analysis of gamma-interferon secreting T lymphocytes and by human leucocyte antigen tetramer analysis for WT1-specific T cells. Increases in anti-leukaemic T-cell responses were demonstrated in four patients, but only two of the five remained in remission more than 12 months postvaccination. The study has demonstrated that generation of DLLC is feasible in only a subgroup of patients and is currently neither broadly applicable or clinically effective.