Tracking ex vivo-expanded CD4+CD25+ and CD8+CD25+ regulatory T cells after infusion to prevent donor lymphocyte infusion-induced lethal acute graft-versus-host disease

[Increased suppressor activity of transformed ex vivo regulatory T-cells in comparison with unstimulated cells of the same donor]

Regulatory T-cells CD4⁺CD25⁺FoxP3⁺CD127low (Tregs) play a key role in the maintenance of tolerance to auto antigens, inhibit function of effector T and B lymphocytes, and provide a balance between effector and regulatory arms of immunity. Patients with autoimmune diseases have decreased Treg numbers and impaired suppressive activity. Transformed ex vivo autologous Tregs could restore destroyed balance of the immune system. We developed a method for Treg precursor cell cultivation. Following the method, we were able to grown up 300-400 million of Tregs cells from 50 ml of peripheral blood during a week. Transformed ex vivo Tregs are 90-95% CD4⁺CD25⁺FoxP3⁺CD127low and have increased expression of transcription genes FoxP3 and Helios. Transformed ex vivo Tregs have increased demethylation of FoxP3 promoter and activated genes of proliferation markers Cycline B1, Ki67 and LGALS 1. Transformed ex vivo Tregs have increased suppressive activity and up to 80-90% these cells secrete cytokines TNFα и IFNγ. Our data suggest transformed ex vivo autologous Tregs have genetic, immunophenotypic and functional characteristics for regulatory T-cells and further can be used for adoptive immunotherapy autoimmune diseases and inhibition of transplantation immunity.

Donor-Specific Regulatory T Cells Acquired from Tolerant Mice Bearing Cardiac Allograft Promote Mixed Chimerism and Prolong Intestinal Allograft Survival

The induction of donor-specific transplant tolerance has always been a central problem for small bowel transplantation (SBT), which is thought to be the best therapy for end-stage bowel failure. With the development of new tolerance-inducing strategies, mixed chimerism induced by co-stimulation blockade has become most potent for tolerance of allografts, such as skin, kidney, and heart. However, a lack of clinically available co-stimulation blockers has hindered efficient application in humans. Furthermore, unlike those for other types of solid organ transplantation, strategies to induce robust mixed chimerism for intestinal allografts have not been fully developed. To improve current mixed chimerism induction protocols for future clinical application, we developed a new protocol using donor-specific regulatory T (Treg) cells from mice with heart allograft tolerance, immunosuppressive drugs which could be used clinically and low doses of irradiation. Our results demonstrated that donor-specific Treg cells acquired from tolerant mice after in vitro expansion generate stable chimerism and lead to acceptance of intestinal allograft. Increased intragraft Treg cells and clonal deletion contribute to the development of SBT tolerance.

The Immunosuppressant Protosappanin A Promotes Dendritic Cell-Mediated Expansion of Alloantigen-Specific Tregs and Prolongs Allograft Survival in Rats

Protosappanin A (PrA), an immunosuppressive ingredient of the medicinal herb Caesalpinia sappan L, prolongs heart allograft survival in rats, possibly by impairing the function of antigen-presenting cells (APCs). We examined the effects of PrA on the maturation and function of dendritic cells (DCs), a potent class of APCs, and the downstream cell–cell and intracellular signaling pathways mediating the immunosuppressive activity of PrA. PrA inhibited LPS-stimulated maturation of Wistar rat DCs in vitro as reflected by reduced expression of costimulatory molecules (CD80 and CD86) and reduced expression of TLR4 and NF-κB, two critical signaling components for antigen recognition. PrA also enhanced the release of IL-10 and decreased the release of IL-12 from DCs, but had no effect on the production of TGF-ß. In mixed cultures, Wistar DCs pretreated with PrA impaired the proliferation of Sprague Dawley (SD) rat T cells while promoting the expansion of SD rat CD4⁺CD25⁺ regulatory T cells (Tregs). Both oral PrA treatment and infusion of PrA-pretreated Wistar DCs prolonged cardiac allograft survival (Wistar donor, SD recipient) and expanded recipient CD4⁺CD25⁺Foxp3⁺ Tregs. Donor spleen cells, but not spleen cells from a third rat strain (DA), supported the expansion of recipient CD4⁺CD25⁺Foxp3⁺ Tregs and suppressed recipient T cell proliferation. We conclude that PrA triggers a tolerogenic state in DCs that allows for the induction of alloantigen-specific Tregs and the suppression of allograft rejection in vivo.

In vitro-expanded CD4(+)CD25(high)Foxp3(+) regulatory T cells controls corneal allograft rejection

AIMS

Natural CD4(+)CD25(+) regulatory cells (nTregs) have been implicated in maintaining peripheral immune tolerance. This study aims to test whether immunotherapy using in vitro-expanded Treg (iTregs) could suppress allograft rejection in corneal transplantation model.

METHODS

Natural CD4(+)CD25(+) T cells were freshly purified from naïve mice and expanded in vitro by culturing with anti-CD3/CD28-coated Dynabeads, interleukin (IL)-2 and transforming growth factor (TGF-β1). Suppression ability of iTregs was assayed by co-culturing with CD4(+)CD25(-) T cells (Teff) in vitro and by targeting corneal allograft rejection in vivo. Tracking of iTreg after adoptive transfer in vivo were examined by CFSE labeling.

RESULTS

Natural Treg cells were expanded by culturing with anti-CD3/CD28-coated Dynabeads in the presence of IL-2 and TGF-β1. Compared with nTregs, iTregs had similar expression of CD62L, and PD- L1, lower expression of CD69, higher levels of PD-1, CD25, and Foxp3. iTreg cells exerted stronger suppression function than natural Treg cells when cocultured with CD4(+)CD25(-) T cells in vitro and prevented fully MHC-mismatched corneal allograft rejection. Survival of iTreg cells could suppress alloimmune reaction and most prone to migrate to graft draining LNs and spleens. Moreover, maintaining CD25 expression on iTregs was indicative for preservation of allosuppression.

CONCLUSION

Therapeutic use of in vitro-expanded CD4(+)CD25(+) T cells may be a effective and safe tool for controlling allograft rejection and may help induce allograft tolerance.

Prevention of allograft rejection by amplification of Foxp3(+)CD4(+)CD25(+) regulatory T cells

CD4(+)CD25(+) T cells were identified originally as potent suppressors of autoimmunity and were later termed "natural regulatory T cells" or nTreg cells. Subsequently, a transcription factor called forkhead box protein 3 (Foxp3) was identified to be a critical regulator for Treg differentiation and function. Foxp3(+)CD4(+)CD25(+) Treg cells have been increasingly documented to suppress allograft rejection and to mediate allograft tolerance in transplantation. In this article, the authors review current approaches for amplification of allo-specific Foxp3(+)CD4(+)CD25(+) Treg cells for prevention of allograft rejection and induction of allo-specific transplant tolerance.

Ex vivo-expanded natural CD4+CD25+ regulatory T cells synergize with host T-cell depletion to promote long-term survival of allografts

Foxp3(+)CD4(+)CD25(+) natural regulatory T (nT(reg)) cells have been shown in immunodeficient mice to suppress allograft rejection after adoptive cotransfer. We hypothesized that immunotherapy using ex vivo-expanded nT(reg) could suppress allograft rejection in wild-type mice. Donor alloantigen (alloAg) specificity of naive splenic nT(reg) was enriched in vitro by culturing with anti-CD3/CD28-coated Dynabeads plus bone marrow-derived dendritic cells (BM-DC) in the presence of interleukin (IL)-2 or IL-2 plus transforming growth factor (TGF)-beta. On average, 96.2% fresh CD4(+)CD25(+) nT(reg) were intracellular Foxp3(+). By d+20 in culture, 6.4% nT(reg) were Foxp3(+) following expansion with IL-2 alone, and 14.4% or 19.7% nT(reg) were Foxp3(+) when expanded with IL-2 plus 0.5 or 2.5 ng/mL TGF-beta, respectively. In vitro, alloAg-enriched, TGF-beta/IL-2-conditioned nT(reg) exerted stronger donor alloAg-specific suppression than cells with IL-2 alone in mixed lymphocyte reaction (MLR) assays. In vivo, alloAg-enriched, TGF-beta/IL-2-conditioned nT(reg) expressed high-level Foxp3 following infusion, effectively overcame acute rejection and induced long-term survival of donor but not third-party heart allografts in peritransplant host T-cell-depleted mice. Long-term surviving allografts were noted to possess Foxp3(+) graft-infiltrating cells of exogenous and endogenous origins. In conjunction with transient host T-cell depletion, therapeutic use of ex vivo-expanded nT(reg) may be a practical means of preventing acute allograft rejection.

Bone Marrow Transplantation

Hematopoietic transplantation is increasingly being used as treatment for a variety of severe diseases. Data from International Registries indicate that more than 25,000 transplants are performed every year in Europe, and a similar number in the United States (US) (Copelan 2006; Gratwohl et al. 2007). The objectives of this procedure are: (1) to replace hematopoiesis affected by a severe and irreversible disorder, (2) to rescue the patient from intense marrow toxicity induced by high-dose chemotherapy and/or radiation, and (3) to use a fraction of cells contained in the graft as anti-tumor immunotherapy. Of note, one or more of these objectives may be pursued in a particular situation; for example, in a patient with acute leukemia, transplantation aims to replace the neoplastic hematopoiesis by administering high-dose cytotoxic therapy and taking advantage of the graft-versus-leukemia effect of donor T-lymphocytes from the graft. In contrast, in aplastic anemia the only goal of the procedure is to restore an adequate hematopoiesis.

Characterization of in vitro antimurine thymocyte globulin-induced regulatory T cells that inhibit graft-versus-host disease in vivo

Antithymocyte/antilymphocyte globulins are polyclonal antihuman T-cell antibodies used clinically to treat acute transplant rejection. These reagents deplete T cells, but a rabbit antihuman thymocyte globulin has also been shown to induce regulatory T cells in vitro. To examine whether antithymocyte globulin-induced regulatory cells might be functional in vivo, we generated a corresponding rabbit antimurine thymocyte globulin (mATG) and tested its ability to induce regulatory cells in vitro and whether those cells can inhibit acute graft-versus-host disease (GVHD) in vivo upon adoptive transfer. In vitro, mATG induces a population of CD4(+)CD25(+) T cells that express several cell surface molecules representative of regulatory T cells. These cells do not express Foxp3 at either the protein or mRNA level, but do show suppressive function both in vitro and in vivo when adoptively transferred into a model of GVHD. These results demonstrate that in a murine system, antithymocyte globulin induces cells with suppressive activity that also function in vivo to protect against acute GVHD. Thus, in both murine and human systems, antithymocyte globulins not only deplete T cells, but also appear to generate regulatory cells. The in vitro generation of regulatory cells by anti-thymocyte globulins could provide ad-ditional therapeutic modalities for immune-mediated disease.

Immune tolerance: mechanisms and application in clinical transplantation

The achievement of immune tolerance, a state of specific unresponsiveness to the donor graft, has the potential to overcome the current major limitations to progress in organ transplantation, namely late graft loss, organ shortage and the toxicities of chronic nonspecific immumnosuppressive therapy. Advances in our understanding of immunological processes, mechanisms of rejection and tolerance have led to encouraging developments in animal models, which are just beginning to be translated into clinical pilot studies. These advances are reviewed here and the appropriate timing for clinical trials is discussed.

Experimental and clinical approaches for optimization of the graft-versus-leukemia effect

The goal of allogeneic (allo)-hematopoietic stem-cell transplantation (HSCT) in the treatment of hematologic malignancies is to harness the graft-versus-leukemia (GVL) effect, while minimizing the risk of graft-versus-host disease (GVHD). Allo-HSCT research has focused on the GVL target antigens and effector mechanisms, and on potential approaches to exploit GVL independently of GVHD. Donor lymphocyte infusion (DLI) achieves the most powerful anti-leukemic responses, and this approach is often used in combination with nonmyeloablative transplant regimens to optimize GVL and reduce GVHD. Serial, dose-escalating, and CD8(+) T-cell-depleted DLI have been introduced into clinical practice, while other variants of DLI have so far been explored only in animal models. The role of naturally occurring regulatory T cells in transplantation tolerance is being increasingly acknowledged, and murine studies indicate the potential ability of T cells to regulate GVHD while maintaining GVL. Experimental and clinical studies have demonstrated the importance of host-type chimerism, particularly for antigen-presenting cells, in determining the occurrence of DLI-induced GVL. Murine studies could assist in the development of clinical strategies targeted at antigen-presenting cells. Clinical studies exploiting natural killer-cell-mediated antitumor reactivity in the context of killer inhibitory receptor-ligand-mismatched allo-HSCT have provided promising results.

Correlation of the CD4+CD25highT-regulatory cells in recipients and their corresponding donors to acute GVHD

Graft-versus-host disease continues to be a major life-threatening complication after allogeneic hematopoietic stem cells transplantation (aHSCT). The relationship of acute GVHD (aGVHD) with the levels of peripheral CD4(+)CD25(high) T cells in patients after aHSCT and in their corresponding donors is not fully investigated. We examined the levels of CD4(+)CD25(high) T cells in patients after aHSCT and in their corresponding donors, and analyzed the relationship of CD4(+)CD25(high) T cells to the incidence and prognosis of aGVHD. The recipients with normal or high CD4(+)CD25(high) T cells (three of eight, 37.5%) had no or mild aGVHD (grade I), and all survived during the follow-up period. In striking contrast, the recipients with lower or no CD4(+)CD25(high) T cells suffered from greater than grade II aGVHD (four of four, 100%), and all died within 1-year post-aHSCT. Moreover, the number of CD4(+)CD25(high) T cells in recipients correlated significantly with that of their corresponding donors. The CD4(+)CD25(high) T cells from the recipients and their corresponding donors expressed high levels of Foxp3, and effectively suppressed the proliferation of CD4(+)CD25(-) responder T cells. This study suggests that human Treg cells may play an important role in aGVHD, as has been seen in murine models. The levels of peripheral CD4(+)CD25(high) T cells in recipients and donors could be helpful for predicting of the onset and outcome of aGVHD.

Targeting Acute Allograft Rejection by Immunotherapy With Ex Vivo-Expanded Natural CD4+CD25+ Regulatory T Cells

BACKGROUND

Natural CD4CD25 regulatory T (Treg) cells have been implicated in suppressing alloreactivity in vitro and in vivo. We hypothesized that immunotherapy using ex vivo-expanded natural Treg could prevent acute allograft rejection in mice.

METHODS

Natural CD4+ CD25+ Treg were freshly purified from naive mice via automated magnetic cell sorter and expanded ex vivo by anti-CD3/CD28 monoclonal antibody (mAb)-coated Dynabeads. Suppression was assayed in vitro by mixed lymphocyte reaction and in vivo by targeting cardiac allograft rejection. Survival of Treg or effector T (Teff) cells after adoptive transfer in vivo was tracked by flow cytometry and all allografts were examined by histology and immunohistochemistry.

RESULTS

By day nine in culture, 26.6+/-5.3-fold of expansion was achieved by co-culture of fresh natural Treg with anti-CD3/CD28 mAb-coated Dynabeads and interleukin-2. Ex vivo-expanded Treg exerted stronger suppression than fresh ones towards alloantigens in vitro and prevented CD4 Teff-mediated but only delayed CD4+/CD8+ Teff-mediated heart allograft rejection in Rag-/- mice. Long-term surviving allografts showed no signs of acute or chronic rejection with graft-infiltrating Treg expressing CD25 and FoxP3. Infused Treg persisted and expanded long-term in vivo and trafficked through the peripheral lymphoid tissues. CD25 expression was dynamic in vivo: maintained CD25 expression on Treg was indicative for the preservation of allosuppression, while significantly enhanced CD25 expression on CD4+ effector T cells was most likely associated with T-cell expansion and graft rejection.

CONCLUSIONS

Therapeutic use of ex vivo-expanded natural CD4+ CD25+ Treg may be a feasible and nontoxic modality for controlling allograft rejection or perhaps inducing allograft tolerance.

The role of CD4+CD25hi regulatory T cells in the physiopathogeny of graft-versus-host disease

Donor T cells present within hematopoietic stem cell transplants promote engraftment, contribute to T-cell reconstitution and provide an antileukemic effect. However, they are also responsible for the life-threatening graft-versus-host disease. The subpopulation of CD4+CD25hi regulatory T cells, initially identified as crucial players in the regulation of autoimmune processes, might also play a role in the control of alloreactivity. Experimental studies in mice indicate that donor regulatory T cells indeed control alloreactive responses and reduce graft-versus-host disease. Recent clinical reports also suggest that higher numbers of CD4+CD25hi cells within the transplant or in the blood of grafted patients might be associated with reduced graft-versus-host disease. Hence, these cells are attractive immunoregulatory candidates to prevent graft-versus-host disease in humans.

Regulatory T cells in graft-versus-host disease

Alloreactive T cells present in a bone marrow transplant are responsible for graft-vs-host disease, but their depletion is associated with impaired engraftment, immunosuppression, and loss of the graft-vs-leukemia effect. The subpopulation of CD4(+)CD25(+) immunoregulatory T cells was first identified based on its crucial role in the control of autoimmune processes, but they also play a role in alloreactive responses. Moreover, these cells could be used to develop innovative strategies in the field of transplantation and particularly to prevent graft-vs-host disease. Indeed, high numbers of CD4(+)CD25(+) immunoregulatory T cells can modulate graft-vs-host disease if administered at the same time as allogeneic hematopoietic stem cell transplantation in mice. This review discusses various important issues regarding the possible use of CD4(+)CD25(+) immunoregulatory T cells to modulate alloreactivity in hematopoietic stem cell transplantation.

Attenuation of murine lysosomal storage disease by allogeneic neonatal bone marrow transplantation using costimulatory blockade and donor lymphocyte infusion without myeloablation

Treatment of nonmalignant childhood disorders by bone marrow transplantation (BMT) is limited by toxicity from preparatory regimens and immune consequences associated with engraftment of allogeneic donor cells. Using costimulatory blockade (anti-CD40L mAb and CTLA-4Ig) combined with high-dose BMT in nonablated neonates, we obtained engraftment and established tolerance using both partially MHC mismatched (H2g7 into H2b) and fully mismatched BM (H2s into H2b). Recipients were mucopolysaccharidosis type VII (MPS VII) mice with lysosomal storage disease in order to assess therapeutic outcome. Recipients treated with donor lymphocyte infusion (DLI) amplified microchimerism to full donor. Recipients without DLI maintained long-term engraftment, tolerance, and had extended life spans. DLI increased donor cell mediated replacement of beta-glucuronidase (GUSB) activity in all tissues and maintained clearance of lysosomes better than in non-DLI-treated mice. DLI amplification of partially mismatched BM and fully mismatched BM caused late onset chronic GvHD in 56% and 100% of recipients, respectively.

Graft-versus-Leukemia and Graft-versus-Host Reactions after Donor Lymphocyte Infusion Are Initiated by Host-Type Antigen-Presenting Cells and Regulated by Regulatory T Cells in Early and Long-Term Chimeras

Regulatory T (T(reg)) cells and host antigen-presenting cells (APCs) have been implicated in graft-versus-host disease (GVHD) and the graft-versus-leukemia (GVL) effect after donor lymphocyte infusion (DLI), but their relative contributions remain unclear in early versus long-term complete donor or mixed murine allogeneic hematopoietic stem cell (HSC) chimeras. We have previously demonstrated that donor HSC-derived Thy1(+) T(reg) cells, consisting primarily of CD4(+)CD25(+) cells, play an important role in the suppression of graft-versus-host (GVH) reactivity when DLI is given to complete donor chimeras 28 days after HSC transplantation. Data presented here demonstrate that protection against GVHD exerted by Thy1(+) T(reg) cells is less evident with time and eventually is not required in long-term complete donor chimeras because of an absence of host-type APCs to activate alloreactive T cells. Lethal GVHD was observed when Thy1(+) T(reg) cells were depleted from complete donor chimeras given by DLI at day 28, 35, or 42; however, T(reg) cell depletion and DLI at day 70 no longer induced GVHD-associated mortality. Moreover, the failure of DLI to induce GVHD with T(reg) depletion correlated with a loss of the DLI-induced GVL effect in long-term (day 100) complete donor chimeras. In contrast to the results from complete donor chimeras, GVL reactivity in day 100 mixed chimeras was robust after DLI. Loss of a DLI-induced GVL effect in long-term complete donor chimeras was attributed to the absence of host APCs because the infusion of exogenous host-type dendritic cells partially restored both DLI-induced GVL and GVH reactions in day 100 complete donor chimeras. The GVL and GVH reactions restored by infusion of host dendritic cells in day 100 complete donor chimeras were at least partially regulated by T(reg) cells because transient depletion of CD25(+) cells increased both the GVL effect and the severity of GVHD after DLI. Taken together, these data suggest that T(reg) cells can regulate DLI-induced GVL and GVH reactions in both early and long-term complete donor chimeras, and a state of mixed chimerism is superior to complete donor chimerism because host-type APCs facilitate a DLI-induced GVL effect without severe GVHD.

Tolerance induction by third-party "off-the-shelf" CD4+CD25+ Treg cells

OBJECTIVE

Recent reports have shown that donor or host CD4(+)CD25(+) Treg cells can be used to control GVHD or graft rejection following allogeneic BMT in mice. In the present study we investigated the potential of third-party Treg cells compared to donor-type cells to facilitate BM allografting.

METHODS

Graft rejection is assessed in a mouse model of T cell-mediated BM allograft rejection. Lethally irradiated C3H mice are transplanted at day 2 after irradiation with T cell-depleted Balb/Nude BM. Graft rejection is induced by purified host-type T cells infused one day prior to BMT. Cells tested for their facilitating activity are added to the T cell-depleted BM allograft.

RESULTS

Naïve or ex vivo-expanded third-party Treg cells can effectively enhance engraftment of T cell-depleted BM allografts, exhibiting reactivity in vitro and in vivo similar to that found for donor-type Treg cells.

CONCLUSION

The use of third-party Treg cells in contrast to donor-type cells could allow advanced preparation of a large bank of Treg cells (off-the-shelf), with all the appropriate quality controls required for cell therapy.

CD4+CD25+ Regulatory T Cells and Graft-Versus-Host Disease

Peripheral suppression of autoreactive T cells by specialized T-cell populations is one of several mechanisms ensuring self-tolerance within the adaptive immune system. Thymus-derived CD4+CD25+ T cells expressing the transcriptional repressor FOXP3 mediate such immunoregulatory functions and are pivotal for the prevention of autoimmunity. As peripheral tolerance induction is a prerequisite for successful treatment outcome after allogeneic hematopoietic stem cell transplantation (HSCT), the role of CD4+CD25+ T cells in transplantation models and clinical trials is now under investigation in many laboratories. Here we summarize recent results regarding protection from graft-versus-host disease (GVHD) by adoptively transferred CD4+CD25+ T cells in mice and discuss early findings from clinical studies in HSCT.