Lymphopenia and interleukin-2 therapy alter homeostasis of CD4+CD25+ regulatory T cells

Cytokines as Adjuvants for Vaccine and Cellular Therapies for Cancer

PROBLEM STATEMENT: The development of a potent vaccine that can help treat tumors resistant to conventional cytotoxic therapies remains elusive. While part of the problem may be that trials have focused on patients with bulky residual disease, the desire to maximize responses to the vaccine remains. APPROACH: The gamma(c) family of cytokines offer a unique opportunity to support the expansion and effector potential of vaccine-responding T-cells, as well as stimulate other effectors, such as natural killer (NK) cells, to become activated. RESULTS: Combining vaccines with cytokines seems logical but can bring unwanted toxicity, as has been observed with interleukin (IL)-2. In addition, the nonspecific activation or expansion of unwanted cell subsets, such as regulatory T-cells, can contribute to global immunosuppression and limit vaccine responses. The development of IL-7 and IL-21 for the clinic offers the promise of enhancing anti-tumor responses but with far less systemic toxicity and no expansion of regulatory T cells. Preclinical studies demonstrate that IL-15 could also improve T-cell, and especially NK-cell, responses as well. CONCLUSIONS/RECOMMENDATIONS: Future work should expand the use of vaccines with IL-7, IL-21 and hopefully IL-15 in high-risk patients, and consider treatment while in a state of minimal residual disease to maximize benefit. Identifying tumors that can signal through gamma(c) cytokines will also be essential so that induction of relapse will be avoided.

FOXP3 expression accurately defines the population of intratumoral regulatory T cells that selectively accumulate in metastatic melanoma lesions

Regulatory T (T(reg)) cells are often found in human tumors; however, their functional characteristics have been difficult to evaluate due to low cell numbers and the inability to adequately distinguish between activated and T(reg) cell populations. Using a novel approach, we examined the intracellular cytokine production capacity of tumor-infiltrating T cells in the single-cell suspensions of enzymatically digested tumors to differentiate T(reg) cells from effector T cells. Similar to T(reg) cells in the peripheral blood of healthy individuals, tumor-infiltrating FOXP3(+)CD4 T cells, unlike FOXP3(-) T cells, were unable to produce IL-2 and IFN-gamma upon ex vivo stimulation, indicating that FOXP3 expression is a valid biological marker for human T(reg) cells even in the tumor microenvironment. Accordingly, we enumerated FOXP3(+)CD4 T(reg) cells in intratumoral and peritumoral sections of metastatic melanoma tumors and found a significant increase in proportion of FOXP3(+)CD4 T(reg) cells in the intratumoral compared with peritumoral areas. Moreover, their frequencies were 3- to 5-fold higher in tumors than in peripheral blood from the same patients or healthy donors, respectively. These findings demonstrate that the tumor-infiltrating CD4 T(reg) cell population is accurately depicted by FOXP3 expression, they selectively accumulate in tumors, and their frequency in peripheral blood does not properly reflect tumor microenvironment.

Suppression of murine allergic airway disease by IL-2:anti-IL-2 monoclonal antibody-induced regulatory T cells

Regulatory T cells (Treg) play a decisive role in many diseases including asthma and allergen-induced lung inflammation. However, little progress has been made developing new therapeutic strategies for pulmonary disorders. In the current study we demonstrate that cytokine:antibody complexes of IL-2 and anti-IL-2 mAb reduce the severity of allergen-induced inflammation in the lung by expanding Tregs in vivo. Unlike rIL-2 or anti-IL-2 mAb treatment alone, IL-2:anti-IL-2 complexes dampened airway inflammation and eosinophilia while suppressing IL-5 and eotaxin-1 production. Mucus production, airway hyperresponsiveness to methacholine, and parenchymal tissue inflammation were also dramatically reduced following IL-2:anti-IL-2 treatment. The suppression in allergic airway disease was associated with a marked expansion of Tregs (IL-10(+)CD4(+)CD25(+) and Foxp3(+)CD4(+)CD25(+)) in the tissues, with a corresponding decrease in effector T cell responses. The ability of IL-2:anti-IL-2 complexes to suppress airway inflammation was dependent on Treg-derived IL-10, as IL-10(+/+), but not IL-10(-/-) Tregs, were capable of mediating the suppression. Furthermore, a therapeutic protocol using a model of established airway allergy highlighted the ability of IL-2:anti-IL-2 complexes to expand Tregs and prevent successive airway inflammation and airway hyperresponsiveness. This study suggests that endogenous Treg therapy may be a useful tool to combat the rising incidence of allergic airway disease.

Immune reconstitution and implications for immunotherapy following haematopoietic stem cell transplantation

Recovery of a fully functional immune system is a slow and often incomplete process following allogeneic stem cell transplantation. While innate immunity reconstitutes quickly, adaptive B- and especially T-cell lymphopoeisis may be compromised for years following transplantation. In large part, these immune system deficits are due to the decrease, or even absence, of thymopoiesis following transplantation. Thereby, T-cell reconstitution initially relies upon expansion of mature donor T cells; a proliferation driven by high cytokine levels and the presence of allo-reactive antigens. This peripheral mechanism of T-cell generation may have important clinical consequences. By expanding tumouricidal T cells, it may provide a venue to enhance T-cellular immunotherapy following transplantation. Alternatively, decreased thymic function may impair long-term anti-tumour immunity and increase the likelihood of graft-versus-host disease.

Phosphoantigen-activated V gamma 2V delta 2 T cells antagonize IL-2-induced CD4+CD25+Foxp3+ T regulatory cells in mycobacterial infection

Although Foxp3(+) T regulatory cells (Tregs) are well documented for their ability to suppress various immune cells, T-cell subsets capable of counteracting Tregs have not been demonstrated. Here, we assessed phosphoantigen-activated Vgamma2Vdelta2 T cells for the ability to interplay with Tregs in the context of mycobacterial infection. A short-term IL-2 treatment regimen induced marked expansion of CD4(+)CD25(+)Foxp3(+) T cells and subsequent suppression of mycobacterium-driven increases in numbers of Vgamma2Vdelta2 T cells. Surprisingly, activation of Vgamma2Vdelta2 T cells by adding phosphoantigen Picostim to the IL-2 treatment regimen down-regulated IL-2-induced expansion of CD4(+)CD25(+)Foxp3(+) T cells. Consistently, in vitro activation of Vgamma2Vdelta2 T cells by phosphoantigen plus IL-2 down-regulated IL-2-induced expansion of CD4(+)CD25(+)Foxp3(+) T cells. Interestingly, anti-IFN-gamma-neutralizing antibody, not anti-TGF-beta or anti-IL-4, reduced the ability of activated Vgamma2Vdelta2 T cells to down-regulate Tregs, suggesting that autocrine IFN-gamma and its network contributed to Vgamma2Vdelta2 T cells' antagonizing effects. Furthermore, activation of Vgamma2Vdelta2 T cells by Picostim plus IL-2 treatment appeared to reverse Treg-driven suppression of immune responses of phosphoantigen-specific IFNgamma(+) or perforin(+) Vgamma2Vdelta2 T cells and PPD-specific IFNgamma(+)alphabeta T cells. Thus, phos-phoantigen activation of Vgamma2Vdelta2 T cells antagonizes IL-2-induced expansion of Tregs and subsequent suppression of Ag-specific antimicrobial T-cell responses in mycobacterial infection.

Development of regulatory T cells requires IL-7Ralpha stimulation by IL-7 or TSLP

Interleukin-7 (IL-7), a cytokine produced by stromal cells, is required for thymic development and peripheral homeostasis of most major subsets of T cells. We examined whether regulatory T (Treg) cells also required the IL-7 pathway by analyzing IL-7Ralpha(-/-) mice. We observed a striking reduction in cells with the Treg surface phenotype (CD4, CD25, GITR (glucocorticoid-induced tumor necrosis factor [TNF]-like receptor), CD45RB, CD62L, CD103) or intracellular markers (cytotoxic T-lymphocyte-associated antigen-4, CTLA-4, and forkhead box transcription factor 3, Foxp3). Foxp3 transcripts were virtually absent in IL-7Ralpha(-/-) lymphoid tissues, and no Treg cell suppressive activity could be detected. There are 2 known ligands for IL-7Ralpha: IL-7 itself and thymic stromal lymphopoietin (TSLP). Surprisingly, mice deficient in IL-7 or the other chain of the TSLP receptor (TSLPR) developed relatively normal numbers of Treg cells. Combined deletion of IL-7 and TSLP receptor greatly reduced Treg cell development in the thymus but was not required for survival of mature peripheral Treg cells. We conclude that Treg cells, like other T cells, require signals from the IL-7 receptor, but unlike other T cells, do not require IL-7 itself because of at least partially overlapping actions of IL-7 and TSLP for development of Treg cells.

Immune modulation and chronic graft-versus-host disease

As more and more patients undergoing allogeneic hematopoietic SCT (HSCT) survive the early post-transplant period, the number of individuals at risk for chronic GVHD has grown. Treatment for established cGVHD remains unsatisfactory. No experimental agent has demonstrated superiority to steroids alone in a randomized clinical trial. Distinguishing chronic from acute graft-versus-host disease is a major issue. The importance of achieving clarity in cGVHD diagnosis is critical as efforts are undertaken to understand its pathogenesis and to design definitive trials that can target prevention and/or treatment. Immune tolerance to self-antigens may be broken in cGVHD, giving rise to the autoimmune manifestations of the disorder. Recent attention has focused on CD4+CD25 regulatory T cells and their relationship to cGVHD. Significant enthusiasm has emerged for manipulating Treg either ex vivo or in vivo for clinical benefit. Another immunomodulatory approach to cGVHD might be the targeting of B lymphocytes and the antibodies they produce. As efforts continue to devise strategies to treat and prevent chronic GVHD, it is important to acknowledge the link between cGVHD and freedom from relapse, at least for certain malignancies.

Safety and immunologic response of a viral vaccine to prostate-specific antigen in combination with radiation therapy when metronomic-dose interleukin 2 is used as an adjuvant

PURPOSE

We have previously reported on the safety and immunologic response of a poxvirus-based vaccine encoding prostate-specific antigen (PSA) used in combination with radiation therapy in patients with localized prostate cancer. We hypothesized that a "metronomic" dose of interleukin 2 (IL-2) as a biological adjuvant would cause less toxicity while maintaining immunologic response.

EXPERIMENTAL DESIGN

Eighteen patients with localized prostate cancer were treated in a single-arm trial using previously established doses of vaccine and radiation therapy. The vaccine used was a recombinant vaccinia virus engineered to encode PSA admixed with a recombinant vaccinia encoding the costimulatory molecule B7.1, followed by booster vaccinations with a recombinant fowlpox vector expressing PSA. Patients received a total of eight planned vaccination cycles, once every 4 weeks, with granulocyte-macrophage colony-stimulating factor given on days 1 to 4 and interleukin 2 (IL-2) at a dose of 0.6 MIU/M2 given from days 8 to 21 after each vaccination. Definitive external beam radiation therapy was initiated after the third vaccination cycle. Patients were evaluated for safety and immunologic response. Toxicity and immunologic activity were compared with the previously reported regimen containing a higher dose of IL-2.

RESULTS

Seventeen of 18 patients received all eight cycles of vaccine with IL-2. Five of eight HLA-A2+ patients evaluated had an increase in PSA-specific T cells of > or =3-fold. Toxicities were generally mild, with only seven vaccination cycles of 140 given resulting in grade 3 toxicities possibly attributable to IL-2.

CONCLUSIONS

Metronomic-dose IL-2 in combination with vaccine and radiation therapy is safe, can induce prostate-specific immune responses, and has immunologic activity similar to low-dose IL-2, with markedly reduced toxicities.

A pilot study of consolidative immunotherapy in patients with high-risk pediatric sarcomas

PURPOSE

Patients with metastatic or recurrent Ewing's sarcoma family of tumors and alveolar rhabdomyosarcoma have <25% 5-year survival in most studies. This study administered a novel immunotherapy regimen aimed at consolidating remission in these patients.

EXPERIMENTAL DESIGN

Fifty-two patients with translocation positive, recurrent, or metastatic Ewing's sarcoma family of tumors or alveolar rhabdomyosarcoma underwent prechemotherapy cell harvest via apheresis for potential receipt of immunotherapy. Following completion of standard multimodal therapy, 30 patients ultimately initiated immunotherapy and were sequentially assigned to three cohorts. All cohorts received autologous T cells, influenza vaccinations, and dendritic cells pulsed with peptides derived from tumor-specific translocation breakpoints and E7, a peptide known to bind HLA-A2. Cohort 1 received moderate-dose recombinant human interleukin-2 (rhIL-2), cohort 2 received low-dose rhIL-2, and cohort 3 did not receive rhIL-2.

RESULTS

All immunotherapy recipients generated influenza-specific immune responses, whereas immune responses to the translocation breakpoint peptides occurred in 39%, and only 25% of HLA-A2(+) patients developed E7-specific responses. Toxicity was minimal. Intention-to-treat analysis revealed a 31% 5-year overall survival for all patients apheresed (median potential follow-up 7.3 years) with a 43% 5-year overall survival for patients initiating immunotherapy.

CONCLUSIONS

Consolidative immunotherapy is a scientifically based and clinically practical approach for integrating immunotherapy into a multimodal regimen for chemoresponsive cancer. Patients receiving immunotherapy experienced minimal toxicity and favorable survival. The robust influenza immune responses observed suggest that postchemotherapy immune incompetence will not fundamentally limit this approach. Future studies will seek to increase efficacy by using more immunogenic antigens and more potent dendritic cells.

Tumor destruction using electrochemotherapy followed by CpG oligodeoxynucleotide injection induces distant tumor responses

PURPOSE

Electrochemotherapy (ECT) is an effective local therapy of human cutaneous cancers but has no effect on distant untreated tumors. We addressed whether tumor-associated antigens released after ECT could induce an efficient systemic immunity when associated with an appropriate immunoadjuvant.

METHODS AND RESULTS

We first studied the nature of the cellular recruitment and the expression of various toll-like receptors (TLRs) in tumors treated by ECT. We found that ECT induced a massive recruitment of CD11c and CD11b positive cells in the tumors and a strong increase of TLR9 expression. We then tested antitumor effects of the combination: ECT followed by TLR-9 ligands, CpG oligodeoxynucleotides (CpG ODN), in three murine tumor models. We found that this combination triggered both potent local synergistic antitumor effects, on the ipsi-lateral ECT-treated tumor, and more interestingly, a systemic antitumor response on the contra-lateral untreated tumor, in the three models. The systemic protection was T-cell dependent as it was not observed in nude littermates. The combination induced tumor-specific T cell effectors in the tumor-draining lymph nodes and in the spleen which secreted significantly more gamma-interferon upon activation than with ECT or CpG ODN alone.

CONCLUSIONS

Our data show that ECT and CpG ODN synergize and induce a significant increase of the local effect and a systemic T-dependent antitumor response. Such combination constitutes a potential innovative vaccination strategy using in situ tumor-associated antigens that could eventually be translated into the clinic.

Characterizing and optimizing immune responses to leukaemia antigens after allogeneic stem cell transplantation

Allogeneic stem cell transplantation remains a curative treatment for haematological malignancies resistant to other treatment approaches through the unique graft-versus-leukaemia effect (GvL). However, the lack of specificity of this response results in the targeting of normal tissue, and the morbidity and mortality associated with graft-versus-host disease (GvHD). Further improvements in exploiting the GvL effect to prevent relapse in high-risk leukaemias while minimizing toxicity have focused on the use of targeted anti-leukaemic immunotherapy. These strategies include the use of vaccines against minor histocompatibility antigens (HA-1, HA-2 and H-Y) and leukaemia-specific antigens (proteinase 3, Wilms' tumour 1 and BCR-ABL), and the adoptive transfer of leukaemia-specific T cells. The unique post-transplant milieu, which is characterized by lymphopenia, regulatory T-cell depletion and the release of growth factors, offers the opportunity to promote the expansion of engrafted T cells and enhance the specific GvL response. Techniques to reduce regulatory T-cell control over T-cell responses to leukaemia antigens could further enhance GvL reactivity. Finally, these approaches to increase GvL effects would be facilitated by transplant approaches to deplete GvHD alloresponses selectively while preserving GvL reactivity.

Adoptive cell therapy for patients with melanoma, using tumor-infiltrating lymphocytes genetically engineered to secrete interleukin-2

Adoptive cell transfer of tumor-infiltrating lymphocytes (TILs) after lymphodepletion mediates regression in 50% of patients with metastatic melanoma. In vivo persistence and telomere length of the transferred cells correlate with antitumor response. In an attempt to prolong the in vivo survival of the transferred cells, TILs were genetically engineered to produce interleukin (IL)-2. In vitro, these transduced TILs secreted IL-2 while retaining tumor specificity and exhibited prolonged survival after IL-2 withdrawal. In a phase I/II clinical trial, seven evaluable patients received transduced TILs and one patient experienced a partial response associated with in vivo persistence of IL-2-transduced TILs in circulating lymphocytes. An additional five patients received transduced TILs in conjunction with IL-2 administration. Persistence of IL-2-transduced TILs was observed in three patients, including one partial responder. The transgene DNA as well as vector-derived IL2 mRNA could be detected for 4 months in responding patients. The low response rate in this trial was possibly due to a reduction in telomere length in cells as a result of prolonged in vitro culture. In this study, insertion of the IL-2 gene into antitumor TILs increased their ability to survive after IL-2 withdrawal in vitro but did not increase their in vivo persistence or clinical effectiveness.

CD4+CD25high T cell numbers are enriched in the peripheral blood of patients with rheumatoid arthritis

Accumulating evidences support that CD4(+)CD25(high) T regulatory (Treg) cells play an essential role in controlling and preventing autoimmunity. Paradoxically, RA patients have elevated numbers of circulating CD4(+)CD25(high) T cells, however, the inflammation is still ongoing. Further identification of these CD4(+)CD25(high) T cells may contribute to a better understanding of underlying mechanisms. We show here that these CD4(+)CD25(high) T cells were composed of CD4(+)CD25(high)FoxP3(+) Treg cells and activated CD4(+)CD25(high)FoxP3(-) effector cells. Moreover, there were significantly more Treg cells and effector T cells expressing GITR, and more monocytes expressing GITR-L. Thus, although RA patients have elevated numbers of CD4(+)CD25(high) T cells, the suppressive function is not increased, because of the increased number of activated effector T cells. In addition, the GITR-GITR-L system was activated in RA patients, which might lead to diminish suppressive activity of Treg cells and/or lead to resistance of activated effector T cells to suppression by Treg cells, thus, contributing to the ongoing inflammation in RA patients.

Interface hepatitis is associated with a high incidence of late graft fibrosis in a group of tightly monitored pediatric orthotopic liver transplantation patients

Chronic graft dysfunction, manifesting with elevated liver enzymes and histological features of interface hepatitis (IH), is being increasingly recognized as a long-term problem after liver transplantation. The aim of this study was to characterize our group of post-orthotopic liver transplantation (OLT) patients with respect to clinical, laboratory, and histological signs of IH. A retrospective study of charts and liver biopsy specimens from patients transplanted between 1986 and 1999 was used. Histological features of IH were found in 29/119 patients at a median interval of 23.9 months (95% confidence interval -28.2 to 52.6) after OLT. All patients with IH had risk factors for chronic rejection, such as steroid-resistant rejection, acute rejection later than 3 months post-OLT, female receiver of male graft, or pretransplant cytomegalovirus (CMV)-positive serology with a CMV-negative donor liver. None of the 29 had features favoring a diagnosis of de novo autoimmune hepatitis, but 4 had isolated hypergammaglobulinemia, and 4 had non-organ-specific autoantibodies without hyperimmunoglobulin G. Sixteen of 29 patients also had features of chronic rejection, such as foam cell arteriopathy, loss of bile ducts, or pericentral fibrosis. After abnormal biopsy, all but 1 patient were switched to tacrolimus. During a median follow-up of 12 years, death occurred in 5, retransplantation occurred in 7, and definite cirrhosis occurred in 4. In conclusion, IH was detected in 24.4% of our patients and was associated with a high degree of fibrosis development. Most likely, IH represents a form of chronic rejection directed against periportal hepatocytes.

Understanding and harnessing the graft-versus-leukaemia effect

The graft-versus-leukaemia (GVL) effect is a central component of the stem cell allograft's ability to cure haematological malignancies. The GVL effect is mediated by donor-derived natural killer cells and T lymphocytes, which have distinct mechanisms of recognizing and targeting the recipient's malignant cells. After transplantation the cytokine milieu is favourable to the early establishment of a GVL effect, but the need to prevent graft-versus-host disease limits the full potential of this process. Clinical studies have identified some critical components of the transplant preparation, donor selection, stem cell source (peripheral blood versus bone marrow) and post-transplant management that can be manipulated to optimize the GVL effect. However, further developments focusing on the selective depletion of unwanted alloreactivity with preservation of GVL effects, and the use of vaccines or the adoptive transfer of leukaemia-specific lymphocytes, will be required to enhance the GVL effect to reliably eradicate more resistant leukaemias.

Administration of rhIL-7 in humans increases in vivo TCR repertoire diversity by preferential expansion of naive T cell subsets

Interleukin-7 (IL-7) is a homeostatic cytokine for resting T cells with increasing serum and tissue levels during T cell depletion. In preclinical studies, IL-7 therapy exerts marked stimulating effects on T cell immune reconstitution in mice and primates. First-in-human clinical studies of recombinant human IL-7 (rhIL-7) provided the opportunity to investigate the effects of IL-7 therapy on lymphocytes in vivo. rhIL-7 induced in vivo T cell cycling, bcl-2 up-regulation, and a sustained increase in peripheral blood CD4⁺ and CD8⁺ T cells. This T cell expansion caused a significant broadening of circulating T cell receptor (TCR) repertoire diversity independent of the subjects' age as naive T cells, including recent thymic emigrants (RTEs), expanded preferentially, whereas the proportions of regulatory T (T reg) cells and senescent CD8⁺ effectors diminished. The resulting composition of the circulating T cell pool more closely resembled that seen earlier in life. This profile, distinctive among cytokines under clinical development, suggests that rhIL-7 therapy could enhance and broaden immune responses, particularly in individuals with limited naive T cells and diminished TCR repertoire diversity, as occurs after physiological (age), pathological (human immunodeficiency virus), or iatrogenic (chemotherapy) lymphocyte depletion.

Dendritic cell therapy in combination with interferon-alpha for the treatment of metastatic renal cell carcinoma

OBJECTIVES

To evaluate the safety and efficacy of dendritic cell (DC) therapy in combination with interferon-alpha (IFN-alpha) in patients with advanced renal cell carcinoma.

METHODS

Seven patients, with progressive disease following IFN-alpha and interleukin (IL)-2 treatment, were treated with monocyte-derived DC (Mo-DC) and IFN-alpha between February 2004 and September 2006. They received Mo-DC once a week for 5 weeks and then every 2 weeks either intradermally or intratumorally. IFN-alpha (5-6 million U) was subcutaneously administered three times a week. Tumor size was evaluated by computed tomography scans before and after the 5th and 10th DC vaccination. A delayed-type hypersensitivity test was performed after the 4th and 5th DC administration for immunological monitoring.

RESULTS

Five patients had stable disease while the remaining two patients had progressive disease following 4 months of vaccination. In six patients the time to progression was prolonged in comparison with the previous cytokine treatment. Six patients showed delayed-type hypersensitivity after the 4th or 5th immunization. Three patients developed high fever following DC immunization. Treatment was associated with transient flu-like symptoms.

CONCLUSIONS

Our data indicate that DC therapy combined with IFN-alpha is safe and has the potential for prolonging the time to progression in patients with advanced renal cell carcinoma.

The biology of interleukin-2

Much data support an essential role for interleukin (IL)-2 in immune tolerance. This idea is much different from the early paradigm in which IL-2 is central for protective immune responses. This change in thinking occurred when a T regulatory cell defect was shown to be responsible for the lethal autoimmunity associated with IL-2/IL-2R deficiency. This realization allowed investigators to explore immune responses in IL-2-nonresponsive mice rendered autoimmune-free. Such studies established that IL-2 sometimes contributes to optimal primary immune responses, but it is not mandatory. Emerging findings, however, suggest an essential role for IL-2 in immune memory. Here, the current understanding of the dual role of IL-2 in maintaining tolerance and contributing to immunity in vivo is reviewed with some emphasis on T regulatory cell production and homeostasis. Also discussed are implications of this new appreciation concerning the immunobiology of IL-2 with respect to targeting IL-2 or its receptor in immunotherapy.

Chemotherapeutic drugs may be used to enhance the killing efficacy of human tumor antigen peptide-specific CTLs

The effects of anticancer chemotherapy on antigen-specific cytotoxic T lymphocytes (CTLs) are mostly unknown. We tested the effects of cytotoxic drugs such as 5-fluorouracil, gemcitabine, and oxaliplatin on the functional activity of antigen-specific CTL cultures derived from the peripheral blood mononuclear cells of human donors. We found that a biweekly drug-exposure of human HLA-A(*)02.01+ CTLs derived from bulk cultures led to completely different effects if occurring early (day second) or late (day thirteenth) after the in vitro stimulations with the cognate peptides. In the first case, there was a significant CTL inhibition, whereas in the second, there was a marked enhancement of the antigen-specific cytolytic activity. Results of immunocytofluorimetric studies and CTL/natural killer inhibition assays suggested that the latter effect could be related to a more selective drug-mediated inhibition of cohabitant T regulatory (reg) cells. These results were translated in an in vivo therapeutic mouse model where humanized HLA-A(*)02.01 transgenic mice inoculated with EL-4/humanized HLA-A(*)02.01 transgenic mice showed a prolonged survival and the greatest rate of cure when receiving a combined treatment with a thymidylate synthase-specific peptide vaccine and a multidrug chemotherapy regimen administered late after immunization. Tumor samples derived from this group of mice showed a reduced expression of the target thymidylate synthase antigen, a marked reduction of T(reg)s, and a noteworthy infiltration of C8+ T cells. These results may have clinical implications for the design of new translational anticancer regimens aimed at combining chemotherapy and immunotherapy.

Integration of B cells and CD8+ T in the protective regulation of systemic epithelial inflammation

Mechanisms that control abnormal CD4(+) T cell-mediated tissue damage are a significant factor in averting and resolving chronic inflammatory epithelial diseases. B cells can promote such immunoregulation, and this is thought to involve interaction with MHC II- or CD1-restricted regulatory T cells. The purpose of this study is to genetically define the interacting cells targeted by protective B cells, and to elucidate their regulatory mechanisms in CD4(+) T cell inflammation. Transfer of G alpha i2-/- CD3(+) T cells into lymphopenic mice causes a dose-dependent multi-organ inflammatory disease including the skin, intestine, and lungs. Disease activity is associated with elevated levels of serum TNF-alpha and IFN-gamma, and an activated IL-17 producing CD4(+) T cell population. Mesenteric node B cells from wild type mice suppress disease activity, serum cytokine expression, and levels of CD4(+) T cells producing TNF-alpha IFN-gamma, and IL-17. The protective function of B cells requires genetic sufficiency of IL-10, MHC I and TAP1. Regulatory B cells induce the expansion and activation of CD8(+) T cells, which is correlated with disease protection. These results demonstrate that CD8(+) T cells can ameliorate lymphopenic systemic inflammatory disease, through peptide/MHC I-dependent B cell interaction.

Adoptive transfer of T(reg) depleted autologous T cells in advanced renal cell carcinoma

PURPOSE

CD4(+)CD25(+) regulatory T (T(reg)) cells are present in increased numbers in patients with advanced cancer and CD25(+) T cell depletion potentiates tumour immunity in animal models. The aim of this study was to assess the feasibility and safety of adoptive transfer of CD25(+) depleted autologous T cells in patients with advanced renal cell carcinoma and to examine resulting changes in lymphocyte subsets.

PATIENTS AND METHODS

Six patients with advanced renal cell carcinoma underwent leukapheresis followed by conditioning chemotherapy with cyclophosphamide and fludarabine. The autologous leukapheresis product was depleted of CD25(+) cells using CliniMACS System then re-infused into the patient.

RESULTS

Efficient CD25(+) depletion from all leukapheresis products was achieved and 0.55-5.87 x 10(7)/kg CD3(+) cells were re-infused. Chemotherapy related haematological toxicity was observed, but blood counts recovered in all patients allowing discharge after a mean inpatient stay of 21 days. One patient subsequently developed a rapidly progressive neurological syndrome. A transient reduction in CD25(+) subset was noted in the peripheral blood of 5 out of 6 patients with evidence of increased T cell responses to PHA in 4 out of 6 patients. One patient showed increased specific proliferative responses to the tumour associated antigen h5T4 coinciding with the nadir of T(reg) cells.

CONCLUSIONS

Given the transient nature of the reduction in CD25(+) subset and the observed toxicity there is a need to explore further strategies to improve the safety and efficacy of this approach. Nevertheless, the results provide proof of concept in potentiation of tumour antigen T cell responses when T(reg) cell levels are depleted.

Autoimmunity in common variable immunodeficiency

BACKGROUND

Autoimmunity has been increasingly recognized as a major issue in patients with common variable immunodeficiency (CVID), the most common symptomatic primary immunodeficiency in adulthood. Different authors report high prevalences of autoimmune diseases in CVID, and several mechanisms have been proposed to explain this apparent paradox. Genetic predisposition, under current surveillance, innate and adaptive immunity deficiencies leading to persistent/recurrent infections, variable degrees of immune dysregulation, and possible failure in central and peripheral mechanisms of tolerance induction or maintenance may all contribute to increased autoimmunity.

CONCLUSIONS

Data on the clinical/immunological profile of affected patients and treatment are available mostly concerning autoimmune cytopenias, the most common autoimmune diseases in CVID. Treatment is based on conventional alternatives, in association with short experience with new agents, including rituximab and infliximab. Benefits of early immunoglobulin substitutive treatment and hypothetical premature predictors of autoimmunity are discussed as potential improvements to CVID patients' follow-up.

CD4+ CD25+ FOXP3+ regulatory T cells increase de novo in kidney transplant patients after immunodepletion with Campath-1H

Campath-1H (Alemtuzumab) is an effective immunodepletion agent used in renal transplantation. To evaluate its influence on T lymphocytes during repletion, we analyzed peripheral blood from Campath-1H-treated renal allograft recipients for the presence of FOXP3(+) regulatory T (Treg) cells. Flow cytometry demonstrated that CD4(+)CD25(+)FOXP3(+) lymphocytes increased significantly within the CD4(+) T-cell population, skewing Treg/Teff (T effector) ratios for up to several years. In contrast, Treg levels in patients treated with anti-CD25 (Basiliximab) and maintained on CsA demonstrated a sustained decrease. The increase in Tregs in Campath-1H treated patients developed independent of maintenance immunosuppression. Importantly, the increase in Tregs was not fully explained by their homeostatic proliferation, increased thymic output, or Treg sparing, suggesting de novo generation/expansion. Consistent with this, in vitro stimulation of PBMCs with Campath-1H, with or without anti-CD3, activation led to an increase in CD4(+)CD25(+)FOXP3(+) cells that had suppressive capabilities. Together, these data suggest that Campath-1H promotes an increase in peripheral Tregs and may act as an intrinsic generator of Tregs in vivo.

Escape from suppression: tumor-specific effector cells outcompete regulatory T cells following stem-cell transplantation

Immune reconstitution of autologous hematopoietic stem-cell transplant recipients with the progeny of mature T cells in the graft leads to profound changes in the emerging functional T-cell repertoire. In the steady state, the host is frequently tolerant to tumor antigens, reflecting dominant suppression of naive and effector T cells by regulatory T cells (T(regs)). We examined the relative frequency and function of these 3 components within the tumor-specific T-cell compartment during immune reconstitution. Grafts from tumor-bearing donors exerted a significant antitumor effect in irradiated, syngeneic tumor-bearing recipients. This was associated with dramatic clonal expansion and interferon-gamma (IFNgamma) production by previously tolerant tumor-specific T cells. While donor-derived T(regs) expanded in recipients, they did not inhibit the antigen-driven expansion of effector T cells in the early posttransplantation period. Indeed, the repopulation of tumor-specific effector T cells significantly exceeded that of T(regs), the expansion of which was limited by IL-2 availability. Although the intrinsic suppressive capacity of T(regs) remained intact, their diminished frequency was insufficient to suppress effector cell function. These findings provide an explanation for the reversal of tolerance leading to tumor rejection in transplant recipients and likely contribute to the efficacy of adoptive T-cell therapies in lymphopenic hosts.

Effect of low-dose IL-2 immunotherapy on frequency and phenotype of regulatory T cells and NK cells in HIV/HCV-coinfected patients

We evaluated the effect of low-dose IL-2 therapy (daily 1.2 MIU/m(2), subcutaneously) on the number and phenotype of regulatory T cells (T(regs)) and natural killer (NK) cells in HIV/HCV-coinfected patients taking antiretroviral therapy. The frequency and phenotype of circulating T(regs) (defined as CD3(+) CD4(+) CD25(high) or CD3(+) CD4(+) FOXP3(+)) and NK cells (CD3(-) CD16(+)/CD56(+)) were evaluated at baseline and after 12 weeks of treatment. The expression of CD25, CTLA-4, and granzymes A and B by CD4(+) FOXP3(+) cells, as well as the expression of KIR receptors (NKB1, CD158a, and NKAT2) on NK cells, was evaluated. Low doses of IL-2 resulted in the augmented frequency and absolute number of T(regs) in coinfected individuals. FOXP3 levels per cell as well as augmented CD25 and CTLA-4 expression by T(regs) suggested that IL-2 may lead to both expansion and activation of T(regs), although changes in the proportion of CD4(+) FOXP3(+) cells were not associated with changes in HCV viral load and CD4(+) cells between baseline and week 12. NK cell frequency also increased after IL-2 therapy. Interestingly, the pattern of expression of KIR receptors was changed by IL-2 treatment, since the frequency of NK cells expressing NKB1 augmented whereas the frequency of NK expressing CD158a and NKAT2 decreased.

A phase I study of ultra low dose interleukin-2 and stem cell factor in patients with HIV infection or HIV and cancer

PURPOSE

Ultra low doses of interleukin-2 (IL-2) can activate the high-affinity IL-2 receptor constitutively expressed on CD56(bright) natural killer (NK) cells, the CD34+ NK cell precursor, and CD4+ CD25+ regulatory T cells (Tregs) in vivo. We have previously shown synergy between IL-2 and stem cell factor (SCF) in the generation of CD56(bright) NK cells from CD34+ hemopoietic progenitor cells in vitro and showed synergistic NK cell expansion in an in vivo preclinical model. To determine the safety, toxicity, and immune modulation of this combination of cytokines in vivo, we conducted a first-in-man phase I study.

EXPERIMENTAL DESIGN

A phase I dose escalation study was conducted using IL-2 at 900,000 or 650,000 IU/m2/d for 8 weeks with 5 or 10 microg/kg/d of SCF given thrice a week for 8 weeks in patients with HIV infection and/or cancer.

RESULTS

Ten of 13 patients completed therapy; four experienced the dose-limiting toxicities of grade 3 fatigue or urticaria. The maximum tolerated doses of IL-2 and SCF in combination is 650,000 IU/m2/d of IL-2 and 5 microg/kg/d thrice a week of SCF. NK cells were expanded over 2-fold on therapy; Tregs were expanded nearly 6-fold from baseline.

CONCLUSIONS

Administration of IL-2 with SCF is safe and well tolerated and leads to expansion of lymphocyte subsets in patients with HIV or HIV and cancer; however, the changes in NK cell and Treg expansion seen with this cytokine combination were no different than those seen with a similar dose of IL-2 alone.

T cell immune reconstitution following lymphodepletion

T cell reconstitution following lymphopenia from chemotherapy or stem cell transplant is often slow and incompetent, contributing to the development of infectious diseases, relapse, and graft-versus-host disease. This is due to the fact that de novo T cell production is impaired following cytoreductive regimens. T cells can be generated from two pathways: (1) thymus derived through active thymopoiesis and (2) peripherally expanded clones through homeostatic proliferation. During recovery from lymphopenia, the thymic pathway is commonly compromised in adults and T cells rely upon peripheral expansion to restore T cell numbers. This homeostatic proliferation exploits the high cytokine levels following lymphopenia to rapidly generate T cells in the periphery. Moreover, this early peripheral expansion of T cells can also be driven by exogenous antigen. This results in loss of T cell repertoire diversity and may predispose to auto- or allo-immunity. Alternatively, the high homeostatic proliferation following lymphopenia may facilitate expansion of anti-tumor immunity. Murine and human studies have provided insight into the cytokine and cellular regulators of these two pathways of T cell generation and the disparate portraits of T cell immunity created through robust thymopoiesis or peripheral expansion following lymphopenia. This insight has permitted the manipulation of the immune system to maximize anti-tumor immunity through lymphopenia and led to an appreciation of mechanisms that underlie graft versus host disease.

Host-derived interleukin-18 differentially impacts regulatory and conventional T cell expansion during acute graft-versus-host disease

Interleukin (IL)-18 stimulates T helper 1 (Th1) and Th2-mediated immune responses, and has been shown to modulate acute graft-versus-host disease (aGVHD). It is still unknown whether increased IL-18 levels during aGVHD are of host or donor origin, and how the absence of IL-18 has an impact on migration and expansion of conventional CD4(+)CD25(-)(Tconv) and CD4(+)CD25(+) regulatory (Treg) T cells in vivo. By utilizing IL-18 gene-deficient donor versus recipient animals we found that the major cytokine production during the early phase of aGVHD induction was recipient derived, whereas donor hematopoietic cells contributed significantly less. By generating IL-18(-/-) luciferase transgenic mice we were able to investigate the impact of IL-18 on Tconv and Treg expansion and trafficking with in vivo bioluminescence imaging. Although migration to secondary lymphoid organs did not have a significantly impact from the absence of host IL-18, Tconv but not Treg expansion increased significantly. Absence of host IL-18 production translated into lower IFN-gamma levels in the early phase after transplantation. We conclude that host-derived IL-18 is a major factor for IFN-gamma production that may have a protective effect on CD4(+)-mediated aGVHD, but is nonessential for Treg expansion in an allogeneic environment.

Pathophysiology of acute graft-versus-host disease: recent advances

Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative therapy for many malignant and nonmalignant hematologic diseases. Donor T cells from the allografts are critical for the success of this effective therapy. Unfortunately these T cells not only recognize and attack the disease cells/tissues but also the other normal tissues of the recipient as "foreign" or "nonself" and cause severe, immune-mediated toxicity, graft-versus-host disease (GVHD). Several insights into the complex pathophysiology of GVHD have been gained from recent experimental observations, which show that acute GVHD is a consequence of interactions between both the donor and the host innate and adaptive immune systems. These insights have identified a role for a variety of cytokines, chemokines, novel T-cell subsets (naĩve, memory, regulatory, and NKT cells) and for non-T cells of both the donor and the host (antigen presenting cells, delta T cells, B cells, and NK cells) in modulating the induction, severity, and maintenance of acute GVHD. This review will focus on the immunobiology of experimental acute GVHD with an emphasis on the recent observations.

Graft-versus-leukemia effects associated with detectable Wilms tumor-1 specific T lymphocytes after allogeneic stem-cell transplantation for acute lymphoblastic leukemia

To determine whether the leukemia-associated Wilms tumor antigen (WT1) contributes to a graft-versus-leukemia (GVL) effect after allogeneic stem-cell transplantation (SCT) for acute lymphoblastic leukemia (ALL), we studied CD8(+) T-cell responses to WT1 in 10 human lymphocyte antigen (HLA)-A*0201-positive ALL patients during the early phase of immune recovery after SCT (days 30-120). Seven of 10 patients had detectable WT1 expression in their peripheral blood (PB) before SCT by quantitative reverse-transcription polymerase chain reaction. Using WT1/HLA-A*0201 tetramers and intracellular interferon-gamma (IFN-gamma) staining, WT1(+) CD8(+) T-cell responses after SCT were found only in patients with detectable WT1 expression before SCT (5 of 7 vs. 0 of 3; P < .05). To monitor the kinetics of WT1(+) CD8(+) T-cell responses and disease regression after SCT, absolute WT1(+) CD8(+) T-cell numbers and WT1 expression were studied for each time point. The emergence of WT1(+) CD8(+) T cells was associated with a decrease in WT1 expression, suggesting a WT1-driven GVL effect. Loss of WT1(+) CD8(+) T-cell responses was associated with reappearance of WT1 transcripts, consistent with a molecular relapse (P < .001). WT1(+) CD8(+) T cells had a predominantly effector-memory phenotype (CD45RO(+) CD27(-)CD57(+)) and produced IFN-gamma. Our results support the immunogenicity of WT1 after SCT for ALL and highlight the potential for WT1 vaccines to boost GVL after SCT for ALL.

Severe depletion of CD4+ CD25+ regulatory T cells from the intestinal lamina propria but not peripheral blood or lymph nodes during acute simian immunodeficiency virus infection

CD4+ CD25+ regulatory T cells (Tregs) suppress the activation and proliferation of effector lymphocytes. In human immunodeficiency virus type 1 (HIV-1) infection, Tregs play a significant role in controlling the apoptotic loss of uninfected CD4+ T cells resulting from high levels of generalized immune activation. During acute HIV-1 infection, more than 50% of CD4+ T cells are depleted from the gastrointestinal lamina propria. To elucidate the role of Tregs in HIV-1-induced depletion of CD4+ T cells in the gut-associated lymphoid tissue (GALT), we first determine the distribution of Tregs in a setting of acute infection using the simian immunodeficiency virus (SIV)/pigtailed macaque model of HIV-1 disease. CD4+ T cells from the GALT, lymph nodes, and peripheral blood were isolated from SIV-infected pigtailed macaques on days 4, 14, and 114 postinoculation. Quantitative real-time reverse transcription-PCR was used to quantitate FOXP3 copy numbers in SIV-infected and uninfected control macaques. Expression of FOXP3 in the ileal lamina propria was significantly decreased at all stages of infection compared to levels in uninfected control macaques. In addition, functional analysis of ileal CD4+ T cells from SIV-infected macaques revealed a lack of suppressive activity suggestive of the absence of Tregs in that compartment. These results indicate that Tregs are rapidly depleted in the GALT of SIV-infected macaques, defining a role for the loss of Treg-mediated suppression in early events in the pathogenesis of the disease.

Reconstitution of FOXP3+ regulatory T cells (Tregs) after CD25-depleted allotransplantation in elderly patients and association with acute graft-versus-host disease

Selective depletion (SD) of host-reactive donor T cells from allogeneic stem-cell transplants (SCTs) using an anti-CD25 immunotoxin (IT) is a strategy to prevent acute graft-versus-host disease (aGvHD). There is concern that concurrent removal of regulatory T cells (T(regs)) with incomplete removal of alloactivated CD25(+) T cells could increase the risk of aGvHD. We therefore measured T(regs) in the blood of 16 patients receiving a T-cell-depleted allograft together with anti-CD25-IT-treated SD lymphocytes, in 13 of their HLA-identical donors, and in 10 SD products. T(regs) were characterized by intracellular staining for forkhead box protein 3 (FOXP3) and by quantitative reverse-transcription-polymerase chain reaction (qRT-PCR) for FOXP3 gene in CD4(+) cells. Patients received a median of 1.0 x 10(8)/kg SD T cells and a stem cell product containing a median of 0.25 x 10(4)/kg residual T cells. T(regs) reconstituted promptly after SCT and underwent further expansion. Of the CD4(+) T cells in SD products, 1.5% to 4.8% were CD25(-) T(regs). Acute GvHD (>or= grade II) was restricted to 5 patients whose donors had significantly (P = .019) fewer T(regs) compared with those without clinically significant aGvHD. These results suggest that rapid T(reg) reconstitution can occur following SD allografts, either from CD25(-) T(regs) escaping depletion, or from residual CD25(-) and CD25(+) T(regs) contained in the stem-cell product that expand after transplantation and may confer additional protection against GvHD.

Interleukin-2 administration alters the CD4+FOXP3+ T-cell pool and tumor trafficking in patients with ovarian carcinoma

Interleukin (IL)-2 is used in the immunotherapy of patients with certain cancer and HIV infection. IL-2 treatment reliably results in 16% to 20% objective clinical response rate in cancer patients, with significant durability of responses in selected patients. However, the mechanisms of therapeutic activity in responding versus nonresponding patients remain poorly understood. CD4(+)CD25(+)FOXP3(+) regulatory T (Treg) cells contribute to immunosuppressive networks in human tumors. We treated 31 ovarian cancer patients with IL-2. We show that administration of IL-2 induces the proliferation of existent Treg cells in patients with ovarian cancer. The potency of Treg cell proliferation is negatively determined by the initial prevalence of Treg cells, suggesting that Treg cells are a factor for self-controlling Treg cell proliferation. After IL-2 cessation, the number of Treg cells more efficiently dropped in clinical responders than nonresponders. Furthermore, IL-2 treatment stimulates chemokine receptor CXCR4 expression on Treg cells, enables Treg cell migration toward chemokine CXCL12 in the tumor microenvironment, and may enforce Treg cell tumor accumulation. Our findings support the concept that administration of IL-2 numerically and functionally affects the Treg cell compartment. These data provide an important insight in evaluating the clinical benefit and therapeutic prediction of IL-2 treatment in patients with cancer.

Cutting edge: Th17 and regulatory T cell dynamics and the regulation by IL-2 in the tumor microenvironment

Th17 cells play an active role in inflammation and autoimmune diseases. However, the nature and regulation of Th17 in the context of tumor immunity remain unknown. In this study, we show that parallel to regulatory T (Treg) cells, IL-17(+) CD4(+) and CD8(+) T cells are kinetically induced in multiple tumor microenvironments in mice and humans. Treg cells play a crucial role in tumor immune pathogenesis and temper immune therapeutic efficacy. IL-2 is crucial for the production and function of Treg cells. We now show that IL-2 reduces IL-17(+) T cell differentiation in the tumor microenvironment accompanied with an enhanced Treg cell compartment in vitro and in vivo. Altogether, our work demonstrates a dynamic differentiation of IL-17(+) T cells in the tumor microenvironment, reveals a novel role for IL-2 in controlling the balance between IL-17(+) and Treg cells, and provides new insight of IL-17(+) T cells in tumor immune pathology and therapy.

Adoptive T cell therapy for cancer in the clinic

The transfusion of lymphocytes, referred to as adoptive T cell therapy, is being tested for the treatment of cancer and chronic infections. Adoptive T cell therapy has the potential to enhance antitumor immunity, augment vaccine efficacy, and limit graft-versus-host disease. This form of personalized medicine is now in various early- and late-stage clinical trials. These trials are currently testing strategies to infuse tumor-infiltrating lymphocytes, CTLs, Th cells, and Tregs. Improved molecular biology techniques have also increased enthusiasm and feasibility for testing genetically engineered T cells. The current status of the field and prospects for clinical translation are reviewed herein.

Immune reconstitution prevents metastatic recurrence of murine osteosarcoma

Primary tumors developing in immunocompetent hosts escape immunosurveillance by acquiring immune evasive properties. This raises the prospect that metastases derived from such tumors will also evade immunity. To investigate whether immune surveillance plays a role in preventing metastases, we studied a murine model which mimics the clinical progression of osteosarcoma: primary tumor growth in the lower extremity, amputation, minimal residual disease followed by the development of overt metastases. K7M2 implants readily escaped immune surveillance since normal BALB/c mice, T cell deficient SCID and T/NK cell deficient SCID-bg mice showed no difference in the rate of growth of primary osteosarcomas. However, both SCID and SCID-bg mice had higher rates of metastases than immunocompetent mice. Similarly, immune reconstitution following transfer of naive T cells to SCID or SCID-bg mice did not impact primary tumor growth, but significantly diminished metastatic recurrence. T cells in osteosarcoma bearing mice produced IFNgamma in response to tumor and IFNgamma production by immune reconstituting T cells was required to prevent metastases. These results demonstrate an important role for T cell based immune surveillance in preventing metastases, even when metastases develop from tumors that adeptly evade immunosurveillance. The results further suggest that T cell depleting cancer therapies may eliminate beneficial immune responses and that immune reconstitution of lymphopenic cancer patients could prevent metastatic recurrence of solid tumors.