CTLA4-Ig-modified dendritic cells inhibit lymphocyte-mediated alloimmune responses and prolong the islet graft survival in mice

Myeloid-derived suppressor cells promote allograft survival by suppressing regulatory T cell dysfunction in high-risk corneal transplantation

Highly inflamed and neovascularized corneal graft beds are known as high-risk (HR) environments for transplant survival. One of the primary factors leading to this rejection is reduction in the suppressive function of regulatory T cells (Treg). Our results show that myeloid-derived suppressor cells (MDSC) counteract interleukin-6-mediated Treg dysfunction by expressing interleukin-10. Additionally, MDSC maintain forkhead box P3 stability and their ability to suppress IFN-γ+ Th1 cells. Administering MDSC to HR corneal transplant recipients demonstrates prolonged graft survival via promotion of Treg while concurrently suppressing IFN-γ+ Th1 cells. Moreover, MDSC-mediated donor-specific immune tolerance leads to long-term corneal graft survival as evidenced by the higher survival rate or delayed survival of a second-party C57BL/7 (B6) graft compared to those of third-party C3H grafts observed in contralateral low-risk or HR corneal transplantation of BALB/c recipient mice, respectively. Our study provides compelling preliminary evidence demonstrating the effectiveness of MDSC in preventing Treg dysfunction, significantly improving graft survival in HR corneal transplantation, and showing promising potential for immune tolerance induction.

The emerging role of regulatory cell-based therapy in autoimmune disease

Autoimmune disease, caused by unwanted immune responses to self-antigens, affects millions of people each year and poses a great social and economic burden to individuals and communities. In the course of autoimmune disorders, including rheumatoid arthritis, systemic lupus erythematosus, type 1 diabetes mellitus, and multiple sclerosis, disturbances in the balance between the immune response against harmful agents and tolerance towards self-antigens lead to an immune response against self-tissues. In recent years, various regulatory immune cells have been identified. Disruptions in the quality, quantity, and function of these cells have been implicated in autoimmune disease development. Therefore, targeting or engineering these cells is a promising therapeutic for different autoimmune diseases. Regulatory T cells, regulatory B cells, regulatory dendritic cells, myeloid suppressor cells, and some subsets of innate lymphoid cells are arising as important players among this class of cells. Here, we review the roles of each suppressive cell type in the immune system during homeostasis and in the development of autoimmunity. Moreover, we discuss the current and future therapeutic potential of each one of these cell types for autoimmune diseases.

Myd88 knockdown with RNA interference induces in vitro immune hyporesponsiveness in dendritic cells from rhesus monkeys

Immature dendritic cells (imDCs) are activated and mature to initiate an adaptive immune response, resulting in allograft rejection and transplantation failure. Myeloid differentiation factor 88 (Myd88) is a key factor in the Toll-like receptor (TLR) signaling pathway. Here, we investigated the effect of Myd88 silencing on DC function and immune response. CD34 + cells were isolated from the bone marrow of rhesus monkeys by the immunomagnetic bead method and then infected with an adenovirus expressing Myd88-specific short hairpin RNA (sh-Myd88). sh-NC (nontargeting negative control)- or sh-Myd88-infected DCs were treated with lipopolysaccharide (LPS) for another 48 h to induce DCS maturation. The maturation of DCs was identified by immunofluorescence staining for MHCII, CD80, and CD86. DC apoptosis was examined using Annexin V/PI staining. DC-related cytokine levels (IFN-γ and IL-12) were assessed by ELISA. A mixed lymphocyte reaction (MLR) was performed to test the effect of Myd88-silenced DCs on T lymphocytes in vitro. The results showed that compared with control or sh-NC-infected DCs, Myd88-silenced DCs had lower MHCII, CD80, CD86, and DC-related cytokine (IFN-γ and IL-12) levels. Myd88 did not affect the apoptosis of DCs. MLR demonstrated that Myd88 silencing could effectively block LPS-activated T cell proliferation in vitro. These data were consistent with the characteristics of tolerogenic DCs. In conclusion, our data indicated that Myd88 silencing could inhibit the maturation of imDCs and alleviate immune rejection, which provides a reference for immune tolerance in clinical liver transplantation.

Local Immunomodulatory Strategies to Prevent Allo-Rejection in Transplantation of Insulin-Producing Cells

Islet transplantation has shown promise as a curative therapy for type 1 diabetes (T1D). However, the side effects of systemic immunosuppression and limited long-term viability of engrafted islets, together with the scarcity of donor organs, highlight an urgent need for the development of new, improved, and safer cell-replacement strategies. Induction of local immunotolerance to prevent allo-rejection against islets and stem cell derived β cells has the potential to improve graft function and broaden the applicability of cellular therapy while minimizing adverse effects of systemic immunosuppression. In this mini review, recent developments in non-encapsulation, local immunomodulatory approaches for T1D cell replacement therapies, including islet/β cell modification, immunomodulatory biomaterial platforms, and co-transplantation of immunomodulatory cells are discussed. Key advantages and remaining challenges in translating such technologies to clinical settings are identified. Although many of the studies discussed are preliminary, the growing interest in the field has led to the exploration of new combinatorial strategies involving cellular engineering, immunotherapy, and novel biomaterials. Such interdisciplinary research will undoubtedly accelerate the development of therapies that can benefit the whole T1D population.

Cellular Mechanisms of Rejection of Optic and Sciatic Nerve Transplants: An Observational Study

Background.

Organ transplantation is a standard therapeutic strategy for irreversible organ damage, but the utility of nerve transplantation remains generally unexplored, despite its potential benefit to a large patient population. Here, we aimed to establish a feasible preclinical mouse model for understanding the cellular mechanisms behind the rejection of peripheral and optic nerves.

Methods.

We performed syngenic and allogenic transplantation of optic and sciatic nerves in mice by inserting the nerve grafts inside the kidney capsule, and we assessed the allografts for signs of rejection through 14 d following transplantation. Then, we assessed the efficacy of CTLA4 Ig, Rapamycin, and anti-CD3 antibody in suppressing immune cell infiltration of the nerve allografts.

Results.

By 3 d posttransplantation, both sciatic and optic nerves transplanted from BALB/c mice into C57BL/6J recipients contained immune cell infiltrates, which included more CD11b⁺ macrophages than CD3⁺ T cells or B220⁺ B cells. Ex vivo immunogenicity assays demonstrated that sciatic nerves demonstrated higher alloreactivity in comparison with optic nerves. Interestingly, optic nerves contained higher populations of anti-inflammatory PD-L1⁺ cells than sciatic nerves. Treatment with anti-CD3 antibody reduced immune cell infiltrates in the optic nerve allograft, but exerted no significant effect in the sciatic nerve allograft.

Conclusions.

These findings establish the feasibility of a preclinical allogenic nerve transplantation model and provide the basis for future testing of directed, high-intensity immunosuppression in these mice.

CTLA4-Ig (abatacept): a promising investigational drug for use in type 1 diabetes

Introduction: Type 1 diabetes (T1D) is an autoimmune disease that results from the destruction of insulin-producing beta cells in the pancreas; it leads to the under or nonproduction of insulin. T1D is associated with numerous life-threatening micro- and macro-vascular complications and early deaths, hence the development of preventative strategies is a priority for research.Areas covered: The authors outline the drawbacks of available treatments for T1D and assess the three key strategies for prevention, including immunomodulatory therapies which hold the most potential. This article examines CTLA4-Ig and its efficacy and safety profiles. Finally, the pharmacokinetic parameters and pharmacodynamic markers of abatacept are shown in vivo and in clinical trials, guiding dosage regimen recommendations for future investigational studies.Expert opinion: Immunomodulation is one of the promising strategies for decelerating the progression of beta-cell destruction after the onset of T1D. It holds the advantage of specific immune modulation without systemic general immunosuppression. Preclinical and clinical studies have yielded promising data on the use of CTLA4-Ig in T1D. Variations in response to CTLA4-Ig might be partially explained by the existence of multiple T1D subtypes with varying baseline innate inflammatory/regulatory bias and the rate of C-peptide decline.

Effects of Adoptive Transfer of Tolerogenic Dendritic Cells on Allograft Survival in Organ Transplantation Models: An Overview of Systematic Reviews

Objective. To dissect the efficacy of Tol-DC therapy with or without IS in multiple animal models of transplantation. Methods and Results. PubMed, Medline, Embase, and the Cochrane Library were searched for reviews published up to April 2015. Six systematic reviews and a total of 61 articles were finally included. Data were grouped by organ transplantation models and applied to meta-analysis. Our meta-analysis shows that Tol-DC therapy successfully prolonged allograft survival to varying extents in all except the islet transplantation models and with IS drugs further prolonged the survival of heart, skin, and islet allografts in mice, but not of heart allografts in rats. Compared with IS drugs alone, Tol-DC therapy with IS extended islet allograft survival in rats but failed to influence the survival of skin, small intestine, and heart allografts in rats or of heart and skin allografts in mice. Conclusion. Tol-DC therapy significantly prolonged multiple allograft survival and further prolonged survival with IS. However, standardized protocols for modification of Tol-DC should be established before its application in clinic.

Tolerogenic Dendritic Cells for Regulatory T Cell Induction in Man

Dendritic cells (DCs) are highly specialized professional antigen-presenting cells that regulate immune responses, maintaining the balance between tolerance and immunity. Mechanisms via which they can promote central and peripheral tolerance include clonal deletion, the inhibition of memory T cell responses, T cell anergy, and induction of regulatory T cells (Tregs). These properties have led to the analysis of human tolerogenic DCs as a therapeutic strategy for the induction or re-establishment of tolerance. In recent years, numerous protocols for the generation of human tolerogenic DCs have been developed and their tolerogenic mechanisms, including induction of Tregs, are relatively well understood. Phase I trials have been conducted in autoimmune disease, with results that emphasize the feasibility and safety of treatments with tolerogenic DCs. Therefore, the scientific rationale for the use of tolerogenic DCs therapy in the fields of transplantation medicine and allergic and autoimmune diseases is strong. This review will give an overview on efforts and protocols to generate human tolerogenic DCs with focus on IL-10-modulated DCs as inducers of Tregs and discuss their clinical applications and challenges faced in further developing this form of immunotherapy.

Regulatory dendritic cell therapy: from rodents to clinical application

Dendritic cells (DC) are highly-specialized, bone marrow-derived antigen-presenting cells that induce or regulate innate and adaptive immunity. Regulatory or "tolerogenic" DC play a crucial role in maintaining self tolerance in the healthy steady-state. These regulatory innate immune cells subvert naïve or memory T cell responses by various mechanisms. Regulatory DC (DCreg) also exhibit the ability to induce or restore T cell tolerance in many animal models of autoimmune disease or transplant rejection. There is also evidence that adoptive transfer of DCreg can regulate T cell responses in non-human primates and humans. Important insights gained from in vitro studies and animal models have led recently to the development of clinical grade human DCreg, with potential to treat autoimmune disease or enhance transplant survival while reducing patient dependency on immunosuppressive drugs. Phase I trials have been conducted in type-1 diabetes and rheumatoid arthritis, with results that emphasize the feasibility and safety of DCreg therapy. This mini-review will outline how observations made using animal models have been translated into human use, and discuss the challenges faced in further developing this form of regulatory immune cell therapy in the fields of autoimmunity and transplantation.

Alternative immunomodulatory strategies for xenotransplantation: CD80/CD86-CTLA4 pathway-modified immature dendritic cells promote xenograft survival

Background

Xenotransplantation is a promising approach to circumventing the current organ shortage. However, T-cell-dependent anti-xenoresponses are a major challenge to successful xenografts. Given the advantages of the use of CTLA4-Ig in the survival of allografts, the purpose of the study was to investigate the therapeutic potential of CTLA4-IgG4 modified immature dendritic cells (imDCs) in the prevention of islets xenograft rejection.

Methods

CTLA4-IgG4 was constructed by the fusion of the extracellular regions of porcine CTLA4 to human the hIgG4 Fc region. The imDCs were induced and cultured from porcine peripheral blood mononuclear cells (PBMC). The CTLA4-IgG4 modified imDCs were delivered via the portal vein to the liver of diabetic mice (insulin-dependent diabetes mellitus) before islet xenografting, and mCTLA4-Ig was administered intravenously after xenotransplantation.

Results

The xenograft survival of mice receiving unmodified imDCs was approximately 30 days. However, following administration of CTLA4-IgG4 modified imDCs before grafting and mCTLA4-Ig after grafting, xenografts survived for more than 100 days. Flow cytometric analysis showed that the CD4⁺CD25⁺Foxp3⁺ Treg population was increased in spleens. The efficacy of donor CTLA4-IgG4 modified imDCs correlated partially with the amplification of Tregs.

Conclusions

These results confirm that selective inhibition of the direct and indirect pathways of T-cell activation by donor CTLA4-IgG4 modified imDCs and receptor CTLA4-Ig is a highly effective strategy to promote survival of xenografts.

Adoptive infusion of tolerogenic dendritic cells prolongs the survival of pancreatic islet allografts: a systematic review of 13 mouse and rat studies

Objective

The first Phase I study of autologous tolerogenic dendritic cells (Tol-DCs) in Type 1 diabetes (T1D) patients was recently completed. Pancreatic islet transplantation is an effective therapy for T1D, and infusion of Tol-DCs can control diabetes development while promoting graft survival. In this study, we aim to systematically review islet allograft survival following infusion of Tol-DCs induced by different methods, to better understand the mechanisms that mediate this process.

Methods

We searched PubMed and Embase (from inception to February 29^th, 2012) for relevant publications. Data were extracted and quality was assessed by two independent reviewers. We semiquantitatively analyzed the effects of Tol-DCs on islet allograft survival using mixed leukocyte reaction, Th1/Th2 differentiation, Treg induction, and cytotoxic T lymphocyte activity as mechanisms related-outcomes. We discussed the results with respect to possible mechanisms that promote survival.

Results

Thirteen articles were included. The effects of Tol-DCs induced by five methods on allograft survival were different. Survival by each method was prolonged as follows: allopeptide-pulsed Tol-DCs (42.14±44 days), drug intervention (39 days), mesenchymal stem cell induction (23 days), genetic modification (8.99±4.75 days), and other derivation (2.61±6.98 days). The results indicate that Tol-DC dose and injection influenced graft survival. Single-dose injections of 10⁴ Tol-DCs were the most effective for allograft survival, and multiple injections were not superior. Tol-DCs were also synergistic with immunosuppressive drugs or costimulation inhibitors. Possible mechanisms include donor specific T cell hyporesponsiveness, Th2 differentiation, Treg induction, cytotoxicity against allograft reduction, and chimerism induction.

Conclusions

Tol-DCs induced by five methods prolong MHC mismatched islet allograft survival to different degrees, but allopeptide-pulsed host DCs perform the best. Immunosuppressive or costimulatory blockade are synergistic with Tol-DC on graft survival. Multiple injections are not superior to single injection. Yet more rigorously designed studies with larger sample sizes are still needed in future.

Effect of combined OX40Ig and CTLA4Ig gene local transfer on allograft rejection and the underlying mechanisms

BACKGROUND

OX40Ig and CTLA4Ig fusion proteins have been suggested to induce immune tolerance and prevent rejection in allografts. The present study aims to investigate and compare the effects of ex vivo combined OX40Ig and CTLA4Ig lentivirus-mediated gene transfer on the long-term survival of the graft, as well as potential underlying mechanisms.

METHODS

We ex vivo transferred Brown Norway rats' superficial groin free flap with lentivirus vectors expressing OX40Ig or CTLA4Ig, or OX40Ig and CTLA4Ig combined, and transplanted the free flaps to Lewis rats. Short-course rapamycin was administered after transfection and transplantation. RT-PCR and Western blot were employed to evaluate expression of OX40Ig and CTLA4Ig. We assessed the survival time of the grafts and the degree of acute graft rejection after indicated treatment. Mixed lymphocyte reaction, flow cytometry, and ELISA were also used to evaluate systemic immune reactions.

RESULTS

Ex vivo transfer of OX40Ig or CTLA4Ig lentivirus vectors led to local expression of corresponding mRNA and proteins in the donor flap without affecting other organs of the recipient. The graft survival time was significantly expanded and rejection was markedly attenuated after transfection. Mixed lymphocyte reaction, flow cytometry (CD4(+) and CD8(+) T lymphocyte proportions), and serum ELISA analysis (IL-2, IFN-γ, IL-4, and IL-10) also showed decreased immune response following transfection. Combined OX40Ig and CTLA4Ig transfer exerted superior effect on improving graft survival and preventing graft rejection, inhibiting the immune response and decreasing the production of proinflammatory cytokines, compared with singular transfer of either OX40Ig or CTLA4Ig.

CONCLUSION

Combined ex vivo transfer of OX40Ig and CTLA4Ig lentivirus vectors provided superior benefits on long-term survival and restoration of the graft through inhibiting immune response and decreasing the production of proinflammatory cytokines.

Lentiviral-mediated shRNA against RelB induces the generation of tolerogenic dendritic cells

OBJECTIVE

Lentiviral-mediated shRNA against RelB was used to produce tolerogenic dendritic cells from murine bone marrow derived dendritic cells (BMDCs).

METHOD

RelB expression in the BMDCs was silenced by lentivirus carrying RelB shRNA. The apoptosis rate and surface markers of DCs were assessed by flow cytometry. IL-12,IL-10,TGF-β1 secreted by DCs and DNA binding capacity of NF-κB subunits in the nucleus were measured by ELISA, independently. MLR was used to analyze the capacity of DCs to inhibit immune response.

RESULTS

RelB expression was significantly inhibited in DCs following lentiviral mediated delivery of RelB specific shRNA. The RelB shRNA-DC produced lower IL-12 and higher IL-10 than mature dendritic cells (mDCs) and silencing control DCs. There was no difference in the apoptosis rate between shRNA RelB-DCs and mDCs. The expression levels of co-stimulatory molecules (CD80, CD86 and CD83) and MHC-II class molecule were lower in the RelB shRNA-DCs than in the mDCs and silencing control DCs. In addition, RelB shRNA also inhibited the RelB DNA binding capacity but had no effect on other NF-κB subunits. The shRNA RelB-DCs can significantly inhibit mixed lymphocyte reaction (MLR) and down-regulate Th1 cytokines and prompt the production of Th2 cytokines.

CONCLUSION

Our results indicate RelB shRNA transfection of DCs can induce the immature status, and produce tolerogenic DCs.

Porcine CTLA4-Ig prolong islet xenografts in rats by downregulating the direct pathway of T-cell activation

AIM

Porcine pancreatic islets fused with pCTLA4-Ig were transplanted into diabetic rats. Xenografts survival was observed, and the underlying immunological rejection mechanisms were investigated.

METHODS

Control porcine islets, empty vector (Adv-GFP)-transfected, and gene-modified porcine islets were transplanted into the renal capsule of diabetic rats. The survival rates of the xenografts were observed. Changes in serum levels of IL-4 and γ-IFN in the recipients were assessed.

RESULTS

The survival time of xenografts in the gene-modified porcine islets group was 34.50 ± 4.14 days, which was longer than those in the control group (34.50 ± 4.14 days vs. 7.43 ± 1.72 days and 7.22 ± 1.72 days; P < 0.01). Changes in the serum levels of IL-4 and γ-IFN between the groups of rats post-transplantation indicated the differentiation bias of T helper cells.

CONCLUSIONS

The donor-originated pCTLA-IgG4 fusion protein inhibits the direct pathway of recipient T-cell priming, which might prolong xenograft survival.

Tolerogenic dendritic cells and their potential applications

Dendritic cells (DCs) play a pivotal role in regulating the balance between immunity and tolerance of the immune system. Recent advancements in DC biology and techniques for manipulating the function of these cells have shown their immense therapeutic potential for treating a variety of immune disorders. Theoretically, antigen-specific tolerogenic DCs can be generated in vitro and delivered to patients to correct the dysfunctional immune responses that attack their own tissues or over-react to innocuous foreign antigens. However, DCs are a heterogeneous population of cells with differences in cell surface makers, differentiation pathways and functions. Studies are needed to examine which subset of DCs can be used for what type of applications. Furthermore, most of the information on tolerogenic DCs has been obtained from animal models and translational studies are needed to examine how a DC therapeutic strategy can be implemented clinically to modulate immunity.

Development of dendritic cell-based immunotherapy for autoimmunity

Dendritic cells are professional antigen-presenting cells that maintain immune tolerance to self-antigens by deleting or controlling the pathogenicity of auto-reactive T-cells. Dendritic cell-based immunotherapies show great promise for the restoration of tolerance in autoimmune disease. Dendritic cells can be modified ex vivo to induce stable tolerogenic function and be used as cellular 'vaccines' or they can be targeted in vivo with sophisticated antigen delivery systems. Tolerogenic dendritic cells induce antigen-specific T-cell tolerance in vivo and have therapeutic effects in animal models of autoimmunity. The current challenge is to bring tolerogenic dendritic cell therapy to the clinic.