Mitomycin-C-treated peripheral blood mononuclear cells (PBMCs) prolong allograft survival in composite tissue allotransplantation

Induction of Long-Lasting Regulatory B Lymphocytes by Modified Immune Cells in Kidney Transplant Recipients

BACKGROUND

We recently demonstrated that donor-derived modified immune cells (MICs)-PBMCs that acquire immunosuppressive properties after a brief treatment-induced specific immunosuppression against the allogeneic donor when administered before kidney transplantation. We found up to a 68-fold increase in CD19 + CD24 hi CD38 hi transitional B lymphocytes compared with transplanted controls.

METHODS

Ten patients from a phase 1 clinical trial who had received MIC infusions before kidney transplantation were followed to post-transplant day 1080.

RESULTS

Patients treated with MICs had a favorable clinical course, showing no donor-specific human leukocyte antigen antibodies or acute rejections. The four patients who had received the highest dose of MICs 7 days before surgery and were on reduced immunosuppressive therapy showed an absence of in vitro lymphocyte reactivity against stimulatory donor blood cells, whereas reactivity against third party cells was preserved. In these patients, numbers of transitional B lymphocytes were 75-fold and seven-fold higher than in 12 long-term survivors on minimal immunosuppression and four operationally tolerant patients, respectively ( P <0.001 for both). In addition, we found significantly higher numbers of other regulatory B lymphocyte subsets and a gene expression signature suggestive of operational tolerance in three of four patients. In MIC-treated patients, in vitro lymphocyte reactivity against donor blood cells was restored after B lymphocyte depletion, suggesting a direct pathophysiologic role of regulatory B lymphocytes in donor-specific unresponsiveness.

CONCLUSIONS

These results indicate that donor-specific immunosuppression after MIC infusion is long-lasting and associated with a striking increase in regulatory B lymphocytes. Donor-derived MICs appear to be an immunoregulatory cell population that when administered to recipients before transplantation, may exert a beneficial effect on kidney transplants.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

MIC Cell Therapy for Individualized Immunosuppression in Living Donor Kidney Transplant Recipients (TOL-1), NCT02560220.

A novel phosphocholine-mimetic inhibits a pro-inflammatory conformational change in C-reactive protein

C-reactive protein (CRP) is an early-stage acute phase protein and highly upregulated in response to inflammatory reactions. We recently identified a novel mechanism that leads to a conformational change from the native, functionally relatively inert, pentameric CRP (pCRP) structure to a pentameric CRP intermediate (pCRP*) and ultimately to the monomeric CRP (mCRP) form, both exhibiting highly pro-inflammatory effects. This transition in the inflammatory profile of CRP is mediated by binding of pCRP to activated/damaged cell membranes via exposed phosphocholine lipid head groups. We designed a tool compound as a low molecular weight CRP inhibitor using the structure of phosphocholine as a template. X-ray crystallography revealed specific binding to the phosphocholine binding pockets of pCRP. We provide in vitro and in vivo proof-of-concept data demonstrating that the low molecular weight tool compound inhibits CRP-driven exacerbation of local inflammatory responses, while potentially preserving pathogen-defense functions of CRP. The inhibition of the conformational change generating pro-inflammatory CRP isoforms via phosphocholine-mimicking compounds represents a promising, potentially broadly applicable anti-inflammatory therapy.

Individualised immunosuppression with intravenously administered donor-derived modified immune cells compared with standard of care in living donor kidney transplantation (TOL-2 Study): protocol for a multicentre, open-label, phase II, randomised controlled trial

INTRODUCTION

Donor-derived modified immune cells (MIC) induced long-term specific immunosuppression against the allogeneic donor in preclinical models of transplantation. In a phase I clinical trial (TOL-1 Study), MIC treatment resulted in a cellular phenotype that was directly and indirectly suppressive to the recipient's immune system allowing for reduction of conventional immunosuppressive therapy. Here, we describe a protocol for a randomised controlled, multicentre phase-IIb clinical trial of individualised immunosuppression with intravenously administered donor MIC compared with standard-of-care (SoC) in living donor kidney transplantation (TOL-2 Study).

METHODS AND ANALYSIS

Sixty-three living donor kidney transplant recipients from six German transplant centres are randomised 2:1 to treatment with MIC (MIC group, N=42) or no treatment with MIC (control arm, N=21). MIC are manufactured from donor peripheral blood mononuclear cells under Good Manufacturing Practice conditions. The primary objective of this trial is to determine the efficacy of MIC treatment together with reduced conventional immunosuppressive therapy in terms of achieving an operational tolerance-like phenotype compared with SoC 12 months after MIC administration. Key secondary endpoints are the number of patient-relevant infections as well as a composite of biopsy-proven acute rejection, graft loss, graft dysfunction or death. Immunosuppressive therapy of MIC-treated patients is reduced during follow-up under an extended immunological monitoring including human leucocyte antigen-antibody testing, and determination of lymphocyte subsets, for example, regulatory B lymphocytes (Breg) and antidonor T cell response. A Data Safety Monitoring Board has been established to allow an independent assessment of safety and efficacy.

ETHICS AND DISSEMINATION

Ethical approval has been provided by the Ethics Committee of the Medical Faculty of the University of Heidelberg, Heidelberg, Germany (AFmu-580/2021, 17 March 2022) and from the Federal Institute for Vaccines and Biomedicines, Paul-Ehrlich-Institute, Langen, Germany (Vorlage-Nr. 4586/02, 21 March 2022). Written informed consent will be obtained from all patients and respective donors prior to enrolment in the study. The results from the TOL-2 Study will be published in peer-reviewed medical journals and will be presented at symposia and scientific meetings.

TRIAL REGISTRATION NUMBER

NCT05365672.

A systematic review of immunomodulatory strategies used in skin-containing preclinical vascularized composite allotransplant models

BACKGROUND

Acute rejection remains a vexing problem in vascularized composite allotransplantation (VCA). Available immunosuppressive regimens are successful at minimizing alloimmune response and allowing VCA in humans. However, repeated rejection episodes are common, and systemic side effects of the current standard regimen (Tacrolimus, MMF, Prednisone) are dose limiting. Novel immunomodulatory approaches to improve allograft acceptance and minimize systemic toxicity are continuously explored in preclinical models. We aimed to systematically summarize past and current approaches to help guide future research in this complex field.

METHODS

We conducted a systematic review of manuscripts listed in the MEDLINE and PubMed databases. For inclusion, articles had to primarily investigate the effect of a therapeutic approach on prolonging the survival of a skin-containing preclinical VCA model. Non-VCA studies, human trials, anatomical and feasibility studies, and articles written in a language other than English were excluded. We followed the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines.

RESULTS

The search retrieved 980 articles of which 112 articles were ultimately included. The majority of investigations used a rat model. An orthotopic hind limb VCA model was used in 53% of the studies. Cell and drug-based approaches were investigated 58 and 52 times, respectively. We provide a comprehensive review of immunomodulatory strategies used in VCA preclinical research over a timeframe of 44 years.

CONCLUSION

We identify a transition from anatomically non-specific to anatomical models mimicking clinical needs. As limb transplants have been most frequently performed, preclinical research focused on using the hind limb model. We also identify a transition from drug-based suppression therapies to cell-based immunomodulation strategies.

Phase I trial of donor-derived modified immune cell infusion in kidney transplantation

BACKGROUNDPreclinical experiments have shown that donor blood cells, modified in vitro by an alkylating agent (modified immune cells [MICs]), induced long-term specific immunosuppression against the allogeneic donor.METHODSIn this phase I trial, patients received either 1.5 × 106 MICs per kg BW on day -2 (n = 3, group A), or 1.5 × 108 MICs per kg BW on day -2 (n = 3, group B) or day -7 (n = 4, group C) before living donor kidney transplantation in addition to post-transplantation immunosuppression. The primary outcome measure was the frequency of adverse events (AEs) until day 30 (study phase) with follow-up out to day 360.RESULTSMIC infusions were extremely well tolerated. During the study phase, 10 treated patients experienced a total of 69 AEs that were unlikely to be related or not related to MIC infusion. No donor-specific human leukocyte antigen Abs or rejection episodes were noted, even though the patients received up to 1.3 × 1010 donor mononuclear cells before transplantation. Group C patients with low immunosuppression during follow-up showed no in vitro reactivity against stimulatory donor blood cells on day 360, whereas reactivity against third-party cells was still preserved. Frequencies of CD19+CD24hiCD38hi transitional B lymphocytes (Bregs) increased from a median of 6% before MIC infusion to 20% on day 180, which was 19- and 68-fold higher, respectively, than in 2 independent cohorts of transplanted controls. The majority of Bregs produced the immunosuppressive cytokine IL-10. MIC-treated patients showed the Immune Tolerance Network operational tolerance signature.CONCLUSIONMIC administration was safe and could be a future tool for the targeted induction of tolerogenic Bregs.TRIAL REGISTRATIONEudraCT number: 2014-002086-30; ClinicalTrials.gov identifier: NCT02560220.FUNDINGFederal Ministry for Economic Affairs and Technology, Berlin, Germany, and TolerogenixX GmbH, Heidelberg, Germany.

[Immunosuppressive effect of mitomycin C-treated peripheral mononuclear blood cells (MICs) in vascularised composite allotransplantation]

BACKGROUND

Vascularized Composite Allotransplantation (VCA) enables the restoration of complex tissue defects. Since the first successful hand and face transplants were performed, clinical and experimental research has consistently improved immunosuppressive therapies. The incubation of peripheral blood mononuclear cells (PBMCs) with mitomycin C (MMC) results in immunomodulatory cells (MICs). In previous studies, the systemic application of MICs on the day of allogeneic hind limb transplantation led to a significant immunosuppression in rats. The aim of this study is to further investigate the optimal point in time of MIC application in a complex VCA model.

MATERIAL AND METHODS

In six groups, 60 allogeneic hind limb transplantations were performed. Fully mismatched rats were used as hind limb donors [Lewis (LEW)] and recipients [Brown-Norway (BN)]. Group A received donor-derived MICs seven days preoperatively. Group B received no immunosuppression; group C received untreated PBMCs seven days prior to transplantation. Animals in group D received cell culture media, whereas group E was treated with a standard immunosuppression consisting of tacrolimus and prednisolone. In group F, syngeneic hind limb transplantations (BN→BN) were performed. Transplant rejection was assessed clinically and histologically.

RESULTS

Group A showed a significantly earlier onset of allograft rejection after 3.5 ± 0.2 days (p < 0.01) when compared with control groups B, C and D (5.5 ± 0.7, 5.3 ± 0.7 und 5.7 ± 0.5). Groups E and F showedno allograft rejection.

CONCLUSION

This study shows that the time of application determines the immunomodulatory effects of MICs. Whereas the systemic application of MICs on the day of transplantation led to a significant immunosuppression in previous studies, this study demonstrates that preoperative injections of MICs lead to an acceleration of allotransplant rejection. Follow-up studies are necessary to investigate further modifications of application time as well as dose-effect relations and cell characteristics of these potential immunosuppressive cells.

Regulatory B cells in transplantation: roadmaps to clinic

Over the last two decades, an additional and important role for B cells has been established in immune regulation. Preclinical studies demonstrate that regulatory B cells (Breg) can prolong allograft survival in animal models and induce regulatory T cells. Operationally tolerant human kidney transplant recipients demonstrate B-cell-associated gene signatures of immune tolerance, and novel therapeutic agents can induce Bregs in phase I clinical trials in transplantation. Our rapidly expanding appreciation of this novel B-cell subtype has made the road to clinical application a reality. Here, we outline several translational pathways by which Bregs could soon be introduced to the transplant clinic.

The combination of mitomycin-induced blood cells with a temporary treatment of ciclosporin A prolongs allograft survival in vascularized composite allotransplantation

BACKGROUND

Vascularized composite allotransplantation (VCA) is a rapidly expanding field of transplantation and provides a potential treatment for complex tissue defects. Peripheral blood mononuclear cells (PBMCs) shortly incubated with the antibiotic and chemotherapeutic agent mitomycin C (MMC) can suppress allogeneic T cell response and control allograft rejection in various organ transplantation models. MMC-incubated PBMCs (MICs) are currently being tested in a phase I clinical trial in kidney transplant patients. Previous studies with MICs in a complex VCA model showed the immunomodulatory potential of these cells. The aim of this study is to optimize and evaluate the use of MICs in combination with a standard immunosuppressive drug in VCA.

METHODS

Fully mismatched rats were used as hind limb donors [Lewis (RT1¹)] and recipients [Brown-Norway (RT1ⁿ)]. Sixty allogeneic hind limb transplantations were performed in six groups. Group A received donor-derived MICs combined with a temporary ciclosporin A (CsA) treatment. Group B received MICs in combination with a temporarily administered reduced dose of CsA. Group C served as a control and received a standard CsA dose temporarily without an additional administration of MICs, whereas Group D was solely medicated with a reduced CsA dose. Group E received no immunosuppressive therapy, neither CsA nor MICs. Group F was given a continuous standard immunosuppressive regimen consisting of CsA and prednisolone. The endpoint of the study was the onset of allograft rejection which was assessed clinically and histologically.

RESULTS

In group A and B, the rejection-free interval of the allograft was significantly prolonged to an average of 23.1 ± 1.7 and 24.7 ± 1.8 days compared to the corresponding control groups (p < 0.01). Rejection in groups C, D, and E was noted after 14.3 ± 1.1, 7.8 ± 0.7, and 6.9 ± 0.6 days. No rejection occurred in control group F during the follow-up period of 100 days. No adverse events have been noted.

CONCLUSION

The findings of this study show that the combination of MICs with a temporary CsA treatment significantly prolongs the rejection-free interval in a complex VCA model. The combination of MICs with CsA showed no adverse events such as graft-versus-host disease. MICs, which are generated by a simple and reliable in vitro technique, represent a potential therapeutic tool for prolonging allograft survival through immunomodulation.

Cell therapy for immunosuppression after kidney transplantation

PURPOSE

To give an overview over cell therapeutic approaches to immunosuppression in clinical kidney transplantation. A focus is on myeloid suppressor cell therapy by mitomycin C-induced cells (MICs).

METHODS

Literature review with an emphasis on already existing therapies.

RESULTS

Several cell therapeutic approaches to immunosuppression and donor-specific unresponsiveness are now being tested in early phase I and phase II trials in clinical kidney transplantation. Cell products such as regulatory T cells or regulatory macrophages, or other myeloid suppressor cell therapies, may either consist of donor-specific, third-party, or autologous cell preparations. Major problems are the identification of the suppressive cell populations and their expansion to have sufficient amount of cells to achieve donor unresponsiveness (e.g., with regulatory T cells). We show a simple and safe way to establish donor unresponsiveness in living-donor kidney transplantation by MIC therapy. A phase I clinical trial is now under way to test the safety and efficacy of this cell therapeutic approach.

CONCLUSIONS

Cell therapeutic approaches to immunosuppression after kidney transplantation may revolutionize clinical transplantation in the future.

Immunosuppressive properties of mitomycin C-incubated human myeloid blood cells (MIC) in vitro

Previous animal studies showed that donor-derived blood cells treated with mitomycin C (MMC) prolong allograft survival when injected into recipients. This model was effective with whole blood, peripheral blood mononuclear cells (PBMC) (monocytes being the active cell subpopulation) or dendritic cells. In view of a potential clinical application, we study now the immunosuppressive properties of human myeloid cells in vitro. Mature dendritic cells (generated from naïve monocytes) or monocytes treated with mitomycin C do not or only weakly inhibit allogeneic T cells in vitro, whereas cells in an early differentiation state between monocytes and DC exert suppressive activity when treated with MMC. In contrast, DC generated from MMC-treated monocytes show the morphology and phenotype of early immature DC (iDC) and suppress T-cell responses. It is known that untreated monocytes injected into a recipient encounter a cytokine milieu which differentiates them to stimulatory DC. In our in vitro experiment MMC-treated monocytes cultured in a DC-maturing milieu transform themselves into suppressive early iDC. This reproduces a process which takes place when administering MMC-monocytes to a recipient. In conclusion, human MMC-DC or MMC-monocytes are not or only weakly suppressive in vitro. When MMC-monocytes are differentiated to DC the resulting cells become suppressive.

Generation of suppressive blood cells for control of allograft rejection

Our previous studies in rats showed that incubation of monocytic dendritic cells (DCs) with the chemotherapeutic drug mitomycin C (MMC) renders the cells immunosuppressive. Donor-derived MMC-DCs injected into the recipient prior to transplantation prolonged heart allograft survival. Although the generation of DCs is labour-intensive and time-consuming, peripheral blood mononuclear cells (PBMCs) can be easily harvested. In the present study, we analyse under which conditions DCs can be replaced by PBMCs and examine their mode of action. When injected into rats, MMC-incubated donor PBMCs (MICs) strongly prolonged heart allograft survival. Removal of monocytes from PBMCs completely abrogated their suppressive effect, indicating that monocytes are the active cell population. Suppression of rejection was donor-specific. The injected MICs migrated into peripheral lymphoid organs and led to an increased number of regulatory T-cells (Tregs) expressing cluster of differentiation (CD) markers CD4 and CD25 and forkhead box protein 3 (FoxP3). Tolerance could be transferred to syngeneic recipients with blood or spleen cells. Depletion of Tregs from tolerogenic cells abrogated their suppressive effect, arguing for mediation of immunosuppression by CD4⁺CD25⁺FoxP3⁺ Tregs. Donor-derived MICs also prolonged kidney allograft survival in pigs. MICs generated from donor monocytes were applied for the first time in humans in a patient suffering from therapy-resistant rejection of a haploidentical stem cell transplant. We describe, in the present paper, a simple method for in vitro generation of suppressor blood cells for potential use in clinical organ transplantation. Although the case report does not allow us to draw any conclusion about their therapeutic effectiveness, it shows that MICs can be easily generated and applied in humans.