HLA molecular mismatches and induced donor-specific tolerance in combined living donor kidney and hematopoietic stem cell transplantation.

Introduction: We investigated the potential role of HLA molecular mismatches (MM) in achieving stable chimerism, allowing for donor-specific tolerance in patients undergoing combined living donor kidney and hematopoietic stem cell transplantation (HSCT).

Methods: All patients with available DNA samples (N=32) who participated in a phase 2 clinical trial (NCT00498160) where they received an HLA mismatched co-transplantation of living donor kidney and facilitating cell-enriched HSCT were included in this study. High-resolution HLA genotyping data were used to calculate HLA amino acid mismatches (AAMM), Eplet MM, three-dimensional electrostatic mismatch scores (EMS-3D), PIRCHE scores, HLA-DPB1 T-cell epitope group MM, HLA-B leader sequence MM, and KIR ligands MM between the donor and recipient in both directions.

Immune tolerance via FCR001 cell therapy compared with maintenance immunosuppression for kidney transplantation: Real-world evidence analysis of safety and efficacy.

While kidney transplantation (KTx) has traditionally required lifelong immunosuppression, an investigational stem cell therapy, FCR001, has been demonstrated to induce tolerance and eliminate the need for immunosuppression through the establishment of persistent mixed chimerism in a phase 2 clinical study. Real-world evidence (RWE) methods were employed to compare the safety and efficacy of non-myeloablative conditioning with FCR001 with standard of care [SOC] immunosuppression in a retrospective single-center analysis of outcomes among propensity score matched living-donor KTx receiving SOC (n = 144) or FCR001 (n = 36). Among the FCR001 recipients, 26 (72%) developed persistent chimerism allowing durable elimination of all immunosuppression.

Evaluation of Immunocompetence and Biomarkers of Tolerance in Chimeric and Immunosuppression-free Kidney Allograft Recipients.

Background: Thirty-seven patients have received a living-donor kidney transplant in a phase 2 study designed to induce tolerance with facilitated allogeneic hematopoietic stem cell transplant. The study protocol is based on tolerogenic CD8 + /T-cell receptor - facilitating cells (FCR001; also including hematopoietic stem cells and αβ-T-cell receptor + T cells) and low-dose, nonmyeloablative conditioning. Persistent chimerism allowing full immunosuppression (IS) withdrawal was achieved in 26 patients (time off IS 36-123 mo).

FL/GCSF/AMD3100-mobilized Hematopoietic Stem Cells Induce Mixed Chimerism With Nonmyeloablative Conditioning and Transplantation Tolerance.

Background: Mobilization of hematopoietic stem cells (HSCs) has become the preferred approach for HSC transplantation. AMD3100, a competitive inhibitor of C-X-C motif chemokine receptor-4, has been found to be a rapid mobilizing agent. The present study evaluated approaches to optimize the product collected.

Facilitating cells: role in inducing transplantation tolerance.

Purpose Of Review: This review discusses the role and mechanisms by which facilitating cells promote stem cell engraftment and induce tolerance in HLA-disparate kidney transplant recipients.

Recent Finding: Facilitating cells in both mice and human are heterogeneous, consisting of several subpopulations. They have been shown to enhance stem cell engraftment in allogeneic recipients.

Fms-Like Tyrosine Kinase 3-Ligand Contributes to the Development and Function of the Subpopulation of CD8α Plasmacytoid Precursor Dendritic Cells in CD8 /TCR Facilitating Cells.

Facilitating cells (FC) are a CD8 TCR bone marrow subpopulation that enhance engraftment of purified hematopoietic stem cells (HSC) and induce antigen-specific CD4 CD25 FoxP3 regulatory T cell (Treg) in vivo. The major subpopulation in FC resembles plasmacytoid precursor dendritic cells (p-preDC) both phenotypically and functionally. Here, we report that the number of FC was significantly reduced in Fms-like tyrosine kinase 3-ligand-knockout (Flt3-L-KO) mice.

Tolerance induction in HLA disparate living donor kidney transplantation by facilitating cell-enriched donor stem cell Infusion: The importance of durable chimerism.

Successful solid organ transplantation currently requires the life-long use of medications to suppress the immune system in order to prevent transplant rejection. Drug-based immunosuppression significantly increases the risk of infection and cancer, as well as being very costly. Development of new therapies to minimize or eliminate entirely the need for anti-rejection drugs is of great interest to the transplant community.

Intragraft Molecular Pathways Associated with Tolerance Induction in Renal Transplantation.

The modern immunosuppression regimen has greatly improved short-term allograft outcomes but not long-term allograft survival. Complications associated with immunosuppression, specifically nephrotoxicity and infection risk, significantly affect graft and patient survival. Inducing and understanding pathways underlying clinical tolerance after transplantation are, therefore, necessary.

Leukocyte iNOS is required for inflammation and pathological remodeling in ischemic heart failure.

In the failing heart, iNOS is expressed by both macrophages and cardiomyocytes. We hypothesized that inflammatory cell-localized iNOS exacerbates left ventricular (LV) remodeling. Wild-type (WT) C57BL/6 mice underwent total body irradiation and reconstitution with bone marrow from iNOS mice (iNOSc) or WT mice (WTc).

Delayed Donor Bone Marrow Infusion Induces Liver Transplant Tolerance.

Background: Nonmyeloablative conditioning followed by donor bone marrow infusion (BMI) to induce tolerance has not been robustly tested in liver transplantation (LT) and may be unsafe at the time of LT. We hypothesized T cell-depleted BMI is effective in inducing tolerance when delayed after LT, resulting in potentially safer future clinical applications.

Methods: Nonimmunosuppressed syngeneic (Lewis to Lewis) and allogeneic (ACI to Lewis) rat LT transplants were initially performed as controls.

A Critical Role for TGF-β/Fc and Nonlytic IL-2/Fc Fusion Proteins in Promoting Chimerism and Donor-Specific Tolerance.

Background: Immunoglobulin-cytokine fusion molecules have been shown to be the new generation of immunomodulating agents in transplantation tolerance induction. In the present study, we tested whether immunoregulatory cytokine fusion proteins of IL-10/Fc, TGF-β/Fc, or IL-2/Fc would enhance allogeneic bone marrow cell (BMC) engraftment and promote tolerance induction.

Methods: B6 (H2) mice were conditioned with anti-CD154 (MR1) and rapamycin (Rapa) plus 100 cGy total body irradiation (MR1/Rapa/100 cGy) and transplanted with allogeneic B10.

Facilitating cells: Translation of hematopoietic chimerism to achieve clinical tolerance.

For over 50 y the association between hematopoietic chimerism and tolerance has been recognized. This originated with the brilliant observation by Dr. Ray Owen that freemartin cattle twins that shared a common placental blood supply were red blood cell chimeras, which led to the discovery that hematopoietic chimerism resulted in actively acquired tolerance.

Immune reconstitution/immunocompetence in recipients of kidney plus hematopoietic stem/facilitating cell transplants.

Nineteen subjects have more than 18 months' follow-up in a phase IIb tolerance protocol in HLA-mismatched recipients of living donor kidney plus facilitating cell enriched hematopoietic stem cell allografts (FCRx). Reduced intensity conditioning preceded a kidney allograft, followed the next day by FCRx. Twelve have achieved stable donor chimerism and have been successfully taken off immunosuppression (IS).

Facilitating cells in tolerance induction for kidney transplantation.

Purpose Of Review: To describe the clinical outcomes and science behind a CD8/TCR facilitating cell-based hematopoietic stem cell transplant approach (termed FCRx) to induce tolerance to renal allografts without graft-versus-host disease (GVHD) and avoidance of long-term immunosuppressant drugs in living donor kidney transplant recipients.

Recent Findings: Successful solid organ transplantation currently requires the life-long use of medications to suppress the immune system to prevent transplant rejection. Drug-based immunosuppression significantly increases the risk of infection and cancer, as well as being very costly.

DOCK2 is critical for CD8(+) TCR(-) graft facilitating cells to enhance engraftment of hematopoietic stem and progenitor cells.

CD8(+) TCR(-) graft facilitating cells (FCs) enhance engraftment of hematopoietic stem cells (HSCs) in allogeneic and syngeneic recipients. The mechanisms by which FCs promote HSC engraftment and tolerance induction have not been fully elucidated. Here, we provide data to support a critical role for dedicator of cytokinesis 2 (DOCK2) in multiple aspects of FCs function.

The need for inducing tolerance in vascularized composite allotransplantation.

Successful hand and face transplantation in the last decade has firmly established the field of vascularized composite allotransplantation (VCA). The experience in VCA has thus far been very similar to solid organ transplantation in terms of the morbidity associated with long-term immunosuppression. The unique immunological features of VCA such as split tolerance and resistance to chronic rejection are being investigated.

Simultaneous bone marrow and composite tissue transplantation in rats treated with nonmyeloablative conditioning promotes tolerance.

Background: Approaches to safely induce tolerance in vascularized composite allotransplantation (VCA) with chimerism through bone marrow transplantation (BMT) are currently being pursued. However, VCA was historically performed sequentially after donor chimerism was established. Delayed VCA is not clinically applicable due to the time constraints associated with procurement from deceased donors.

Tolerance induction in HLA disparate living donor kidney transplantation by donor stem cell infusion: durable chimerism predicts outcome.

Background: We recently reported that durable chimerism can be safely established in mismatched kidney recipients through nonmyeloablative conditioning followed by infusion of a facilitating cell (FC)-based hematopoietic stem cell transplantation termed FCRx. Here we provide intermediate-term follow-up on this phase II trial.

Methods: Fifteen human leukocyte antigen-mismatched living donor renal transplant recipients underwent low-intensity conditioning (fludarabine, cyclophosphamide, 200 cGy TBI), received a living donor kidney transplant on day 0, then infusion of cryopreserved FCRx on day +1.

A critical role for the TLR4/TRIF pathway in allogeneic hematopoietic cell rejection by innate immune cells.

We show for the first time that signaling through the TLR4/TRIF pathway plays a critical role in allogeneic bone marrow cell (BMC) rejection. This appears to be unique to BMCs as organ allografts are rejected mainly via MyD88 signaling. Using T- or T-/B-cell-deficient mice, we found that BMC allorejection occurred early before T-cell activation and was T- and B-cell independent, suggesting an effector role for innate immune cells in BMC rejection.

A clinically feasible approach to induce delayed tolerance in recipients of prior kidney or vascularized composite allotransplants.

Background: Mixed chimerism induces donor-specific tolerance to kidney and vascularized composite allotransplants (VCA). However, simultaneous kidney or VCA and bone marrow transplantation (BMT) is problematic because of the combined risk and time required for conditioning. Here, we developed a delayed tolerance induction strategy with mixed chimerism through BMT in prior kidney or VCA recipients.

Novel regulatory therapies for prevention of Graft-versus-host disease.

Graft-versus-host disease is one of the major transplant-related complications in allogeneic hematopoietic stem cell transplantation. Continued efforts have been made to prevent the occurrence of severe graft-versus-host disease by eliminating or suppressing donor-derived effector T cells. Conventional immunosuppression does not adequately prevent graft-versus-host disease, especially in mismatched transplants.

Chimerism and tolerance without GVHD or engraftment syndrome in HLA-mismatched combined kidney and hematopoietic stem cell transplantation.

The toxicity of chronic immunosuppressive agents required for organ transplant maintenance has prompted investigators to pursue approaches to induce immune tolerance. We developed an approach using a bioengineered mobilized cellular product enriched for hematopoietic stem cells (HSCs) and tolerogenic graft facilitating cells (FCs) combined with nonmyeloablative conditioning; this approach resulted in engraftment, durable chimerism, and tolerance induction in recipients with highly mismatched related and unrelated donors. Eight recipients of human leukocyte antigen (HLA)-mismatched kidney and FC/HSC transplants underwent conditioning with fludarabine, 200-centigray total body irradiation, and cyclophosphamide followed by posttransplant immunosuppression with tacrolimus and mycophenolate mofetil.

Identification of inducible nitric oxide synthase in peripheral blood cells as a mediator of myocardial ischemia/reperfusion injury.

Although the late phase of ischemic preconditioning is known to be mediated by increased inducible nitric oxide synthase (iNOS) activity, controversy persists regarding the role of iNOS in ischemia/reperfusion (I/R) injury and, specifically, whether this protein is protective or detrimental. We hypothesized that iNOS is protective in myocytes but detrimental in inflammatory cells. To test this hypothesis, we created chimeric mice with iNOS-deficient peripheral blood cells by transplanting iNOS knockout (KO) bone marrow in wild-type (WT) mice after lethal irradiation.