Total lymphoid irradiation nonmyeloablative preconditioning enriches for IL-4-producing CD4+-TNK cells and skews differentiation of immunocompetent donor CD4+ cells

In vivo antitumor function of tumor antigen-specific CTLs generated in the presence of OX40 co-stimulation in vitro

Adoptive cell transfer (ACT) is an emerging and promising cancer immunotherapy that has been improved through various approaches. Here, we described the distinctive characteristics and functions of tumor Ag-specific effector CD8⁺ T-cells, co-cultured with a tumor-specific peptide and a stimulatory anti-OX40 antibody, before being used for ACT therapy in tumor-bearing mouse recipients. Splenic T-cells were obtained from wild-type FVB/N mice that had been injected with a HER2/neu (neu)-expressing tumor and a neu-vaccine. The cells were then incubated for 7 days in vitro with a major histocompatibility complex (MHC) class I peptide derived from neu, in the presence or absence of an agonistic anti-OX40 monoclonal antibody, before CD8⁺ T cells were isolated for use in ACT therapy. The proliferative ability of OX40-driven tumor Ag-specific effector CD8⁺ T-cells in vitro was less than that of non-OX40-driven tumor Ag-specific effector CD8⁺ T-cells, but they expressed significantly more early T-cell differentiation markers, such as CD27, CD62L and CCR7, and significantly higher levels of Bcl-2, an anti-apoptotic protein. These OX40-driven tumor Ag-specific effector CD8⁺ T-cells, when transferred into tumor-bearing recipients, demonstrated potent proliferation capability and successfully eradicated the established tumor. In addition, these cells exhibited long-term antitumor function, and appeared to be established as memory T-cells. Our findings suggest a possible in vitro approach for improving the efficacy of ACT, which is simple, requires only a small amount of modulator, and can potentially avoid several toxicities associated with co-stimulation in vivo.

Helper T-cell differentiation in graft-versus-host disease after allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an effective therapeutic option for many malignant diseases. However, the efficacy of allo-HSCT is limited by the occurrence of destructive graft-versus-host disease (GVHD). Since allogeneic T cells are the driving force in the development of GVHD, their activation, proliferation, and differentiation are key factors to understanding GVHD pathogenesis. This review focuses on one critical aspect: the differentiation and function of helper T (Th) cells in acute GVHD. We first summarize well-established subsets including Th1, Th2, Th17, and T-regulatory cells; their flexibility, plasticity, and epigenetic modification; and newly identified subsets including Th9, Th22, and T follicular helper cells. Next, we extensively discuss preclinical findings of Th-cell lineages in GVHD: the networks of transcription factors involved in differentiation, the cytokine and signaling requirements for development, the reciprocal differentiation features, and the regulation of microRNAs on T-cell differentiation. Finally, we briefly summarize the recent findings on the roles of T-cell subsets in clinical GVHD and ongoing strategies to modify T-cell differentiation for controlling GVHD in patients. We believe further exploration and understanding of the immunobiology of T-cell differentiation in GVHD will expand therapeutic options for the continuing success of allo-HSCT.

Recipient myeloid-derived immunomodulatory cells induce PD-1 ligand-dependent donor CD4+Foxp3+ regulatory T cell proliferation and donor-recipient immune tolerance after murine nonmyeloablative bone marrow transplantation

We showed previously that nonmyeloablative total lymphoid irradiation/rabbit anti-thymocyte serum (TLI/ATS) conditioning facilitates potent donor-recipient immune tolerance following bone marrow transplantation (BMT) across MHC barriers via recipient invariant NKT (iNKT) cell-derived IL-4-dependent expansion of donor Foxp3(+) naturally occurring regulatory T cells (nTregs). In this study, we report a more specific mechanism. Wild-type (WT) BALB/c (H-2(d)) hosts were administered TLI/ATS and BMT from WT or STAT6(-/-) C57BL/6 (H-2(b)) donors. Following STAT6(-/-) BMT, donor nTregs demonstrated no loss of proliferation in vivo, indicating that an IL-4-responsive population in the recipient, rather than the donor, drives donor nTreg proliferation. In graft-versus-host disease (GVHD) target organs, three recipient CD11b(+) cell subsets (Gr-1(high)CD11c(-), Gr-1(int)CD11c(-), and Gr-1(low)CD11c(+)) were enriched early after TLI/ATS + BMT versus total body irradiation/ATS + BMT. Gr-1(low)CD11c(+) cells induced potent H-2K(b+)CD4(+)Foxp3(+) nTreg proliferation in vitro in 72-h MLRs. Gr-1(low)CD11c(+) cells were reduced significantly in STAT6(-/-) and iNKT cell-deficient Jα18(-/-) BALB/c recipients after TLI/ATS + BMT. Depletion of CD11b(+) cells resulted in severe acute GVHD, and adoptive transfer of WT Gr-1(low)CD11c(+) cells to Jα18(-/-) BALB/c recipients of TLI/ATS + BMT restored day-6 donor Foxp3(+) nTreg proliferation and protection from CD8 effector T cell-mediated GVHD. Blockade of programmed death ligand 1 and 2, but not CD40, TGF-β signaling, arginase 1, or iNOS, inhibited nTreg proliferation in cocultures of recipient-derived Gr-1(low)CD11c(+) cells with donor nTregs. Through iNKT-dependent Th2 polarization, myeloid-derived immunomodulatory dendritic cells are expanded after nonmyeloablative TLI/ATS conditioning and allogeneic BMT, induce PD-1 ligand-dependent donor nTreg proliferation, and maintain potent graft-versus-host immune tolerance.

Dendritic cells control CD4+CD25+ Treg cell suppressor function in vitro through juxtacrine delivery of IL-2

CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) restrict inflammatory responses to self and nonself. Aberrant Treg activity is pathologic: Insufficient Treg activity is implicated in autoimmunity, allergy, and graft-versus-host-disease; overabundant activity is implicated in chronic infection and cancer. Tregs require IL-2 for their expansion and acquisition/execution of suppressor function; however, because Tregs cannot produce IL-2, they depend on IL-2 from an exogenous source. Until now, that IL-2 source had not been established. We asked whether dendritic cells (DCs) could supply IL-2 to Tregs and, if so, what was required for that delivery. We used flow cytometry, IL-2 ELISPOT, RT-qPCR, and IL-2 promoter-driven reporter assays to measure intracytoplasmic IL-2, secreted protein, IL-2 message and IL-2 promoter activity in bone marrow-derived (BMDC) and splenic DCs. We examined conjugate formation between Tregs, conventional CD4(+) cells, and IL-2-expressing DCs. We measured Treg levels of CD25, Foxp3, and suppressor function after co-culture with IL-2 sufficient and IL-2(-/-) DCs. We generated IL-2-mCherry-expressing DCs and used epifluorescence microscopy and flow cytometry to track IL-2 transfer to Tregs and test requirements for transfer. Between 0.7 to 2.4% of DCs constitutively produced IL-2 and diverted IL-2 secretion to Tregs by preferentially forming conjugates with them. Uptake of DC IL-2 by Tregs required cell-cell contact and CD25. Tregs increased levels of CD25 and Foxp3 from baseline and showed greater suppressor function when co-cultured with IL-2-sufficient DCs, but not when co-cultured with IL-2(-/-) DCs. Exogenous IL-2, added in excess of 500 U/ml to co-cultures with IL-2(-/-) DCs, restored Treg suppressor function. These data support a model of juxtacrine delivery of IL-2 from DCs to Tregs and suggest that a subset of DCs modulates Treg function through controlled, spatial delivery of IL-2. Knowledge of how DCs regulate Tregs should be integrated into the design of interventions intended to alter Treg function.

Total lymphoid irradiation in heart transplantation: long-term efficacy and survival--an 18-year experience

BACKGROUND

Total lymphoid irradiation (TLI) has been used in transplantation for over 20 years and is currently used in a number of major heart transplant centers as a secondary therapy for recalcitrant recurrent rejection or rejection with hemodynamic compromise. The purpose of this study is to evaluate the long-term risks and efficacy of TLI in the treatment of rejection.

METHODS

Between 1990 and 1996, 73 adult patients (from 211 adult transplant recipients) received TLI for recurrent rejection (71%), rejection with hemodynamic compromise (25%), and rejection with vasculitis (4%). The treatment consisted of 80 cGy twice per week for 5 weeks. Fifty-five patients received at least 80% of the full dose (>640 cGy). Follow-up ended December 31, 2007, comprising a total 18 year experience.

RESULTS

Patients treated with TLI exhibited a short-term decrease in hazard for rejection in the first 12 months posttransplantation (relative risk, 0.36) but exhibited increased cumulative rejection over the long term. There were no differences in the rates of infection, allograft coronary disease, or malignancy, but seven patients developed myelodysplasia or acute myelogenous leukemia, four of those being the rare but uniformly fatal acute megakaryocytic leukemia type 7.

CONCLUSIONS

Patients treated with TLI seemed to experience a reduction in the early hazard for rejection, but long-term outcomes indicate that such patients continued to accumulate more rejection and rejection-death events, likely because these patients were overall at much higher risk for rejection than the other patient groups. We observed minimal long-term complications, except for the unique occurrence of myelodysplasia and acute megakaryocytic leukemia type 7.

Novel treatment concepts for graft-versus-host disease

Acute and chronic graft-versus-host disease (GVHD) are potentially lethal complications after stem cell transplantation (SCT). Steroids are the appropriate first-line treatment for both. However, if patients do not adequately benefit from steroid therapy, mortality is high and standardized treatment algorithms are lacking. This is mainly because of limited data from prospective, randomized clinical trials. In addition, most of the available treatment options only induce clinical benefits in a limited proportion of patients. Thus, there is an urgent clinical need to develop more potent immunosuppressive treatment strategies for patients suffering from acute or chronic steroid-refractory GVHD while maintaining the graft versus tumor effect to avoid a potential rise in relapse-related mortality. The increasing knowledge about host- as well as donor-derived variables favoring GVHD development and the increasing armamentarium of immune-modulatory agents entering preclinical and clinical research will probably allow more effective treatment of GVHD in the future. This review describes novel developments in the treatment of steroid-refractory GVHD, with a special focus on the rationale behind promising pharmacologic compounds or up-coming cellular therapies.

Dendritic cell recovery post-lymphodepletion: a potential mechanism for anti-cancer adoptive T cell therapy and vaccination

Adoptive transfer of autologous tumor-reactive T cells holds promise as a cancer immunotherapy. In this approach, T cells are harvested from a tumor-bearing host, expanded in vitro and infused back to the same host. Conditioning of the recipient host with a lymphodepletion regimen of chemotherapy or radiotherapy before adoptive T cell transfer has been shown to substantially improve survival and anti-tumor responses of the transferred cells. These effects are further enhanced when the adoptive T cell transfer is followed by vaccination with tumor antigens in combination with a potent immune adjuvant. Although significant progress has been made toward an understanding of the reasons underlying the beneficial effects of lymphodepletion to T cell adoptive therapy, the precise mechanisms remain poorly understood. Recent studies, including ours, would indicate a more central role for antigen presenting cells, in particular dendritic cells. Unraveling the exact role of these important cells in mediation of the beneficial effects of lymphodepletion could provide novel pathways toward the rational design of more effective anti-cancer immunotherapy. This article focuses on how the frequency, phenotype, and functions of dendritic cells are altered during the lymphopenic and recovery phases post-induction of lymphodepletion, and how they affect the anti-tumor responses of adoptively transferred T cells.

Nonmyeloablative conditioning with total lymphoid irradiation and antithymocyte globulin: an update

PURPOSE OF REVIEW

The immune modulatory effects of total lymphoid irradiation (TLI) for graft-versus-host disease (GVHD) protection and transplantation tolerance following allogeneic bone marrow and organ transplantation have been studied for years in animal models. In preclinical models nonmyeloablative TLI conditioning alters residual host T cell subsets to favor regulatory natural killer T cells that suppress GVHD and prevent organ allograft rejection. These preclinical models have been recently adapted to human transplantation.

RECENT FINDINGS

Patients receiving allogeneic hematopoietic cell transplantation for hematological malignancies conditioned with TLI and depletive T cell antibodies showed sustained donor chimerism, a reduced incidence of acute GVHD yet retained graft antitumor activity. As in the preclinical models, nonmyeloablative TLI conditioning significantly altered residual host T cell subsets favoring natural killer T cells, and the low incidence of GVHD was associated with increased IL-4 secretion by chimeric donor T cells. The TLI regimen used in cancer patients was modified to determine conditions for stable mixed chimerism and tolerance induction following combined hematopoietic cell and kidney transplantation.

SUMMARY

This review summarizes the evolution of the preclinical TLI protocols and their recent translation to clinical trials, and discusses the mechanisms involved in protection from GVHD and the induction of tolerance following mixed chimerism.

Total lymphoid irradiation for graft-versus-host disease protection

PURPOSE

The immunosuppressive effects of total lymphoid irradiation (TLI) for protection against graft-versus-host disease (GvHD) after allogeneic bone marrow transplantation have been studied for years in animal models. In preclinical models of bone marrow transplantation non-myeloablative TLI conditioning protects against GvHD by skewing host T-cell subsets to favor regulatory natural killer T cells that suppress GvHD by polarizing donor T cells towards secretion of non-inflammatory cytokines such as IL-4. These preclinical models have recently been adapted to human transplantation.

RECENT FINDINGS

Patients receiving allogeneic hematopoietic cell transplantation for hematological malignancies conditioned with TLI and depletive T-cell antibodies showed sustained donor chimerism, a reduced incidence of acute GvHD yet retained anti-tumor activity. As in the preclinical models, the low incidence of GvHD is associated with increased IL-4 secretion by chimeric donor T cells.

SUMMARY

This review summarizes the evolution of the preclinical TLI protocols and their recent translation to clinical trials, and discusses the mechanisms involved in protection from GvHD and the induction of tolerance following mixed chimerism.

Host natural killer T cells induce an interleukin-4-dependent expansion of donor CD4+CD25+Foxp3+ T regulatory cells that protects against graft-versus-host disease

Although CD4(+)CD25(+) T cells (T regulatory cells [Tregs]) and natural killer T cells (NKT cells) each protect against graft-versus-host disease (GVHD), interactions between these 2 regulatory cell populations after allogeneic bone marrow transplantation (BMT) have not been studied. We show that host NKT cells can induce an in vivo expansion of donor Tregs that prevents lethal GVHD in mice after conditioning with fractionated lymphoid irradiation (TLI) and anti-T-cell antibodies, a regimen that models human GVHD-protective nonmyeloablative protocols using TLI and antithymocyte globulin (ATG), followed by allogeneic hematopoietic cell transplantation (HCT). GVHD protection was lost in NKT-cell-deficient Jalpha18(-/-) hosts and interleukin-4 (IL-4)(-/-) hosts, or when the donor transplant was Treg depleted. Add-back of donor Tregs or wild-type host NKT cells restored GVHD protection. Donor Treg proliferation was lost in IL-4(-/-) hosts or when IL-4(-/-) mice were used as the source of NKT cells for adoptive transfer, indicating that host NKT cell augmentation of donor Treg proliferation after TLI/antithymocyte serum is IL-4 dependent. Our results demonstrate that host NKT cells and donor Tregs can act synergistically after BMT, and provide a mechanism by which strategies designed to preserve host regulatory cells can augment in vivo donor Treg expansion to regulate GVHD after allogeneic HCT.

Adoptive immunotherapy for cancer: building on success

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

Downstream of Tyrosine Kinases-1 and Src Homology 2-Containing Inositol 5′-Phosphatase Are Required for Regulation of CD4+CD25+ T Cell Development

The adaptor protein, downstream of tyrosine kinases-1 (Dok-1), and the phosphatase SHIP are both tyrosine phosphorylated in response to T cell stimulation. However, a function for these molecules in T cell development has not been defined. To clarify the role of Dok-1 and SHIP in T cell development in vivo, we compared the T cell phenotype of wild-type, Dok-1 knockout (KO), SHIP KO, and Dok-1/SHIP double-knockout (DKO) mice. Dok-1/SHIP DKO mice were runted and had a shorter life span compared with either Dok-1 KO or SHIP KO mice. Thymocyte numbers from Dok-1/SHIP DKO mice were reduced by 90%. Surface expression of both CD25 and CD69 was elevated on freshly isolated splenic CD4(+) T cells from SHIP KO and Dok-1/SHIP DKO, suggesting these cells were constitutively activated. However, these T cells did not proliferate or produce IL-2 after stimulation. Interestingly, the CD4(+) T cells from SHIP KO and Dok-1/SHIP DKO mice produced higher levels of TGF-beta, expressed Foxp3, and inhibited IL-2 production by CD3-stimulated CD4(+)CD25(-) T cells in vitro. These findings suggest Dok-1 and SHIP function in pathways that influence regulatory T cell development.

Potential Role of Natural Killer Cell Receptor-Expressing Cells in Immunotherapy for Leukemia

Natural killer cell receptor (NKR)-expressing cells have cytolytic activity against leukemic cells, and solid tumor cells escape from T-cell recognition because of the low expression levels of class I HLA molecules in both allogeneic and autologous settings. This characteristic feature of NK cell recognition of target cells in contrast with that of T-cells provides a strategy to overcome tolerance in the tumor-bearing host. Furthermore, inhibitory NKR-expressing cells may have cytolytic activity and immunoregulatory functions. Several methods can be used to expand NKR-expressing cells for adoptive immunotherapy for leukemia and other malignant diseases. We review recent developments in the biology and clinical application of NKR-expressing cells, such as NK cells, lymphokine-activated killer cells, cytokine-induced killer cells, NKT cells, and other NKR-expressing cells.

Stimulation of Host NKT Cells by Synthetic Glycolipid Regulates Acute Graft-versus-Host Disease by Inducing Th2 Polarization of Donor T Cells

NKT cells are a unique immunoregulatory T cell population that produces large amounts of cytokines. We have investigated whether stimulation of host NKT cells could modulate acute graft-vs-host disease (GVHD) in mice. Injection of the synthetic NKT cell ligand alpha-galactosylceramide (alpha-GalCer) to recipient mice on day 0 following allogeneic bone marrow transplantation promoted Th2 polarization of donor T cells and a dramatic reduction of serum TNF-alpha, a critical mediator of GVHD. A single injection of alpha-GalCer to recipient mice significantly reduced morbidity and mortality of GVHD. However, the same treatment was unable to confer protection against GVHD in NKT cell-deficient CD1d knockout (CD1d(-/-)) or IL-4(-/-) recipient mice or when STAT6(-/-) mice were used as donors, indicating the critical role of host NKT cells, host production of IL-4, and Th2 cytokine responses mediated by donor T cells on the protective effects of alpha-GalCer against GVHD. Thus, stimulation of host NKT cells through administration of NKT ligand can regulate acute GVHD by inducing Th2 polarization of donor T cells via STAT6-dependent mechanisms and might represent a novel strategy for prevention of acute GVHD.

Immunoregulatory Cells for Transplantation Tolerance and Graft-versus-Leukemia Effect

Various immunoregulatory cells that inhibit graft-versus-host disease (GVHD) and induce the graft-versus-leukemia (GVL) effect are found after allogeneic hematopoietic stem cell transplantation. These cells comprise CD4+CD25+ regulatory T-cells, regulatory dendritic cells (rDCs), gamma(delta) T-cells, natural killer (NK) T-cells, and NK cells and T-cells with inhibitory NK receptors. Although the first 4 types of cells effectively inhibit GVHD in animal models, with rDCs showing an inhibitory effect on GVHD in humans as well, the GVL effect was observed only in rDCs. Additional analyses are required to determine whether these cells can inhibit GVHD and exert the GVL effect in humans. In contrast, NK cells and T-cells with inhibitory NK receptors have been shown in humans to possess a suppressive activity against GVHD while preserving the GVL effect. These results indicate that immunoregulatory cells may be used to modulate GVHD and the GVL effect in clinical settings.

Host conditioning with total lymphoid irradiation and antithymocyte globulin prevents graft-versus-host disease: the role of CD1-reactive natural killer T cells

Our previous studies in mice showed that the nonmyeloablative conditioning regimen of fractionated irradiation of the lymphoid tissues (total lymphoid irradiation; TLI) and depletive anti-T-cell antibodies (anti-thymocyte serum) markedly increased the percentage of regulatory DX5+ and natural killer 1.1+ T cells in the mouse spleen, and prevented acute lethal graft-versus-host disease (GVHD) in BALB/c mice (H-2(d)) following the transplantation of bone marrow (BM) and peripheral blood mononuclear cells (PBMC) from C57BL/6 (H-2(b)) donors. The object of the current study was to determine whether the TLI and anti-thymocyte serum regimen protected natural killer T-cell deficient CD1(-/-) BALB/c mice against GVHD after BM and PBMC transplantation from C57BL/6 donors, and whether a similar conditioning regimen of TLI and anti-thymocyte globulin (ATG) can prevent GVHD in Lewis rat (RT1(l)) hosts after BM and PBMC transplantation from ACI rat (RT1(a)) donors. The experimental results in mice showed that, although wild-type BALB/c hosts are protected in association with a marked increase in CD1- reactive T cells expressing the invariant TCR identified with a CD1 tetramer reagent; CD1(-/-) BALB/c hosts are not. Studies of chimeric donor cells in mice protected from GVHD showed donor T-cell polarization to a Th2 cytokine pattern. Results in rats showed that approximately 1000 fold more donor PBMC cells were required to induce a similar incidence of lethal GVHD in TLI and ATG conditioned hosts as compared with hosts conditioned with single-dose total-body irradiation or total-body irradiation and ATG. Surviving TLI and ATG conditioned rat hosts were complete chimeras. In conclusion, the TLI and ATG/anti-thymocyte serum conditioning regimen protects against GVHD in rats and mice, and regulatory natural killer T cells are required for protection.