Recent advances in immunosuppression and acquired immune tolerance in renal transplants

Ex vivo expansion of regulatory T cells from long-term Belatacept-treated kidney transplant patients restores their phenotype and suppressive function but not their FOXP3 TSDR demethylation status

We recently reported that Tregs from long-term Belatacept-treated kidney transplant patients displayed an altered phenotype and impaired suppressive function compared to Tregs from healthy controls. However, it remains unknown whether ex vivo expansion of Tregs from patients who underwent long-term immunosuppression may be feasible to be used in their treatment. In this work, Tregs from Belatacept-treated patients were polyclonally expanded in vitro in the presence of rapamycin and IL-2. After four weeks of expansion, Tregs from patients expressed high levels of FOXP3, CD25, CTLA-4, Helios and CCR7, and showed strong suppressive activity, even in the presence of pro-inflammatory cytokines. However, FOXP3 TSDR demethylation remained lower in expanded Tregs from Belatacept-treated patients compared to healthy control Tregs. These data suggest that ex vivo expansion of Tregs from patients undergoing long-term immunosuppression may require the use of epigenetic modifying agents to stabilize FOXP3 expression to be considered as treatment in kidney transplant patients.

Long term drug related remission may encourage drug withdrawal in patients with rheumatoid arthritis

Remission is the goal of therapy in patients with rheumatoid arthritis (RA). However, drug free remission has not been investigated adequately. Early and intensive treatment may increase the chances of successful drug free remission. Effect of long term remission while on medical therapy on the success of drug withdrawal has not been previously evaluated in RA. Long term immune suppression has been shown to have beneficial effects on relapse rates in other diseases with dysregulated immune tolerance. Therefore, drug withdrawal could be an acceptable option in RA patients in long term remission.

Thalidomide ameliorate graft chronic rejection in an allogenic kidney transplant model

Chronic T cell mediated rejection (TCMR), which is characterized by infiltration of the interstitium by T cells and macrophages, still remains a major barrier to the long-term survival of kidney transplantation. Our recent report indicated that thalidomide can attenuate graft arteriosclerosis in an aortic transplant model. In this study, we investigated the effect of thalidomide on chronic TCMR in a rat model of kidney transplantation. Fischer or Lewis kidney allografts were transplanted into Lewis recipient rats. After kidney transplantation, recipient rats were divided into 3 groups: the isograft (Iso) group, allograft (Allo) group, and thalidomide (Tha) group. Rats were sacrificed at 8 weeks after kidney transplantation, and blood and kidney samples were collected. Serum concentrations of creatinine (SCr),interleukin (IL)-2, IL-6, IL-17, and TNF-α in recipients were determined, and flow cytometry was used to detect the percentages of CD4⁺CD25⁺, CD4⁺ Foxp3⁺and CD4⁺Th17⁺ cell subsets in the peripheral blood. Grafts were procured for histopathological examination, and the expressions of α-SMA, transforming growth-β1 (TGF-β1), and VEGF in kidney grafts were investigated using Western blot. Thalidomide treatment significantly ameliorated chronic rejection, reduced renal allograft tissue damage, and decreased serum creatinine levels. Attenuation of chronic TCMR was due to the prohibited production of inflammatory cytokines, altered distribution of the CD4⁺ CD25⁺ FoxP3⁺ regulatory T (Treg) and CD4⁺ Th17⁺ cells in the peripheral blood, and decreased expression of TGF-β1, α-SMA, and VEGF in the kidney graft. These results demonstrated that thalidomide could effectively ameliorate chronic TCMR in a rat kidney transplant model.

Nanoparticles for the Induction of Antigen-Specific Immunological Tolerance

Antigen-specific immune tolerance has been a long-standing goal for immunotherapy for the treatment of autoimmune diseases and allergies and for the prevention of allograft rejection and anti-drug antibodies directed against biologic therapies. Nanoparticles have emerged as powerful tools to initiate and modulate immune responses due to their inherent capacity to target antigen-presenting cells (APCs) and deliver coordinated signals that can elicit an antigen-specific immune response. A wide range of strategies have been described to create tolerogenic nanoparticles (tNPs) that fall into three broad categories. One strategy includes tNPs that provide antigen alone to harness natural tolerogenic processes and environments, such as presentation of antigen in the absence of costimulatory signals, oral tolerance, the tolerogenic environment of the liver, and apoptotic cell death. A second strategy includes tNPs that carry antigen and simultaneously target tolerogenic receptors, such as pro-tolerogenic cytokine receptors, aryl hydrocarbon receptor, FAS receptor, and the CD22 inhibitory receptor. A third strategy includes tNPs that carry a payload of tolerogenic pharmacological agents that can “lock” APCs into a developmental or metabolic state that favors tolerogenic presentation of antigens. These diverse strategies have led to the development of tNPs that are capable of inducing antigen-specific immunological tolerance, not just immunosuppression, in animal models. These novel tNP technologies herald a promising approach to specifically prevent and treat unwanted immune reactions in humans. The first tNP, SEL-212, a biodegradable synthetic vaccine particle encapsulating rapamycin, has reached the clinic and is currently in Phase 2 clinical trials.

Mesenchymal stromal cells in clinical kidney transplantation: how tolerant can it be?

PURPOSE OF REVIEW

Progress in the improvement of short-term and long-term outcomes of kidney transplantation seems to have reached a plateau, partially due to consequences of very efficient, but nonspecific immunosuppressive drugs. In recent years, various forms of cell therapy, including the use of mesenchymal stromal cells, have been put forward as an alternative strategy for more defined therapy. It is thought that these therapies will not only allow controlled tapering of immunosuppressive medication, but might bring us also closer to the ambition of generating donor-specific immune regulation and tolerance.

RECENT FINDINGS

Different forms of alloimmunity, including direct, indirect and semi-direct alloantigen presentation have to be controlled before donor-specific immune regulation can be reached. Several mechanisms have been described how mesenchymal stromal cells can affect alloimmunity. Especially, the interaction with professional antigen presenting cells, like dendritic cells, is of critical importance.

SUMMARY

This review will discuss the current status of ongoing clinical trials with mesenchymal stromal cells in kidney transplantation and specifically concentrate on the possibilities and impossibilities of how these therapeutic strategies can contribute to control of the different forms of alloreactivity operation in organ transplantation.