Lorenzo Gallon

Chimerism and Tolerance Without GVHD or Engraftment Syndrome in HLA-Mismatched Combined Kidney and Hematopoietic Stem Cell Transplantation

Durable chimerism and donor-specific tolerance can be safely achieved without GVHD in HLA-mismatched donor/recipient pairs. Teaching Tolerance According to Greek mythology, the Chimera was a fire-breathing creature made of parts from different animals: the body of a lioness, a snake’s head at the end of the tail, and the head of the goat. Sightings of this fearsome beast portended any of a number of terrible disasters. In the context of organ transplantation, a “chimera” can indicate both desirable and disastrous outcomes. For example, hematopoietic chimerism, in which the immune cells in the graft recipient come from both the host and the donor, may promote graft tolerance, but may also cause graft-versus-host disease (GVHD), in which the donor immune cells attack the healthy tissue of the host. Leventhal et al. now report mixed chimerism and tolerance without the negative side effects of GVHD or engraftment syndrome in a phase 2 clinical trial of combined kidney and hematopoietic transplantation. Leventhal et al. used a combination of mobilized cells enriched for hematopoietic stem cells and graft-facilitating cells—which are composed largely of plasmacytoid precursor dendritic cells—with nonmyeloablative conditioning in conjunction with kidney transplant from major histocompatibility complex–mismatched, nonrelated donors and recipients. Five of eight kidney transplant recipients exhibited durable chimerism and were weaned off immunosuppressive therapies by 1 year after transplantation, with no signs of GVHD or engraftment syndrome. If confirmed in larger patient cohorts, this approach to transplantation could free some patients from the difficulties associated with lifelong immunosuppression and add transplantation as a viable option for patients for whom no matched donors exist. As with the Chimera of legend, mixed chimerism may be a harbinger of things to come—albeit hopefully a brighter future for transplant patients. 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. Subjects ranged in age from 29 to 56 years. HLA match ranged from five of six loci with related donors to one of six loci with unrelated donors. The absolute neutrophil counts reached a nadir about 1 week after transplant, with recovery by 2 weeks. Multilineage chimerism at 1 month ranged from 6 to 100%. The conditioning was well tolerated, with outpatient management after postoperative day 2. Two subjects exhibited transient chimerism and were maintained on low-dose tacrolimus monotherapy. One subject developed viral sepsis 2 months after transplant and experienced renal artery thrombosis. Five subjects experienced durable chimerism, demonstrated immunocompetence and donor-specific tolerance by in vitro proliferative assays, and were successfully weaned off all immunosuppression 1 year after transplant. None of the recipients produced anti-donor antibody or exhibited engraftment syndrome or graft-versus-host disease. These results suggest that manipulation of a mobilized stem cell graft and nonmyeloablative conditioning represents a safe, practical, and reproducible means of inducing durable chimerism and donor-specific tolerance in solid organ transplant recipients.

Alemtuzumab Induction and Prednisone‐Free Maintenance Immunotherapy in Kidney Transplantation: Comparison with Basiliximab Induction—Long‐Term Results

This study examined alemtuzumab (anti‐CD 52, Campath‐1H) and basiliximab (anti‐CD 25, Simulect) as induction immunosuppression in kidney transplantation.

A prospective study of rapid corticosteroid elimination in simultaneous pancreas-kidney transplantation: comparison of two maintenance immunosuppression protocols: tacrolimus/mycophenolate mofetil versus tacrolimus/sirolimus.

Background. We examined the feasibility of rapid corticosteroid elimination in simultaneous pancreas kidney transplantation. Methods. Forty consecutive simultaneous pancreas-kidney (SPK) transplant recipients were enrolled in a prospective study in which antithymocyte globulin induction and 6 days of corticosteroids were administered along with tacrolimus and MMF (n=20) or tacrolimus and sirolimus (n=20). Mean±SD follow-up for recipients receiving tacrolimus/MMF and tacrolimus/sirolimus were 12.7±3.9 and 13.4±2.9 months, respectively. Patient and graft survival, and rejection rates were compared to an historical control group (n=86; mean follow-up 41.5±15.4 months) of SPK recipients that received induction and tacrolimus, MMF, and corticosteroids. Results. Demographic characteristics of recipient and donor variables were similar among all groups. The 1-year actuarial patient, kidney, and pancreas survival rates in the 40 SPK transplant recipients with rapid corticosteroid elimination were 100, 100, and 100%, respectively. In the historical control group the 1-year actual patient, kidney, and pancreas survival rates were 96.5, 93.0, and 91.9%, respectively. The 1-year rejection-free survival rate recipients in the rapid steroid elimination group collectively was 97.5 vs 80.2% in the historical control group (P =0.034). At 6 and 12 months posttransplant the serum creatinine values remained stable in all groups. Conclusions. We conclude that chronic corticosteroid exposure is not required in SPK transplant recipients receiving antithymocyte globulin induction and maintenance immuno-suppression consisting of either tacrolimus and mycophenolate mofetil or tacrolimus and sirolimus.

Alemtuzumab Induction and Prednisone-Free Maintenance Immunotherapy in Simultaneous Pancreas-Kidney Transplantation Comparison With Rabbit Antithymocyte Globulin Induction – Long-Term Results

This study compared the effects of using two T‐cell depleting antibodies, alemtuzumab (anti‐CD 52, Campath‐1H®) and rabbit antithymocyte globulin (Thymoglobulin®), as induction immunosuppression for recipients of simultaneous pancreas‐kidney transplantation given a prednisone‐free maintenance regimen. We used a single‐center, nonrandomised, retrospective, sequential study design to evaluate the efficacy and safety of alemtuzumab (n = 50) or antithymocyte globulin (n = 38) induction in combination with a prednisone‐free, tacrolimus/sirolimus‐based immunosuppression protocol. Kaplan‐Meier analyses of long‐term patient and graft survivals and rejection rates were determined according to induction agent. Secondary endpoints included the quality of renal allograft function, incidence of infectious and malignant complications, and cost considerations. Overall long‐term patient and graft survival rates did not significantly differ between patients treated with alemtuzumab and antithymocyte globulin. Rejection rates were also nearly equivalent at 1 and 2 years. Viral infectious complications were statistically significantly lower in the alemtuzumab group. The cost of alemtuzumab induction was lower than antithymocyte globulin. Alemtuzumab induction followed by steroid‐free maintenance therapy with a tacrolimus/sirolimus‐based immunosuppression regimen provided an effective, safe and cost‐conscious approach to SPK transplantation.

Mechanisms of acquired thymic unresponsiveness to renal allografts

We have recently shown that a single intrathymic injection of synthetic 25mer peptides, representing full sequences of the hypervariable domain of RT1.BuB (4 peptides) and RT1.Du beta (4 peptides) WF class II MHC molecules, 48 hr before transplantation induces donor-specific unresponsiveness to WF rat renal allografts in adult LEW recipients. The induction of unresponsiveness was abrogated by the recipients thymectomy within the first week after intrathymic injection. Peripheral T cells of long-term survivors exhibited antigen-specific hyporesponsiveness in the LEW x WF MLR. Studies on the mechanisms of induction of acquired thymic unresponsiveness to alloantigen in vivo and in vitro are now reported. First, since we have previously demonstrated in LEW responders that only 4 of the 8 synthetic 25mer peptides, 2 RT1.Du beta and 2 RT1.Bu beta sequences, were immunogenic in vitro and in vivo, we compared the tolerogenicity of the immunogenic versus the nonimmunogenic peptides. While LEW rats intrathymically injected with the nonimmunogenic peptides acutely rejected their renal allografts within 6-10 days, animals injected with the immunogenic peptides did not reject their grafts and are surviving > 100 days with normal allograft function. In vitro studies established that peripheral T cells from intrathymically tolerized animals exhibited antigen-specific hyporesponsiveness in the LEW x WF MLR starting as early as 1 week posttransplant. Immunohistological evaluation of renal allografts from intrathymically tolerized animals 1 week postengraftment showed marked reduction in mononuclear cell infiltrates with no evidence of tubulitis, and marked reduction in intragraft staining for activation and inflammatory cytokines and alloantibodies, as compared with acutely rejecting controls. Systemic administration of 1000 U of rIL-2 daily for 5 days starting on the day of transplantation abrogated the tolerogenic effect of intrathymic MHC allopeptides. Injection of 100 micrograms of a single immunogenic peptide, RT1.Du beta 2 (residues 20-44), into the thymus of responder LEW rats 48 hrs before immunization with RT1.Du beta 2 effected significant reduction of in vitro proliferation of primed lymphocytes to RT1.Du beta 2, an effect that was abrogated by addition of rIL-2 in vitro. In contrast, thymectomy beyond 2 weeks and administration of rIL-2 at 4-6 weeks after transplantation failed to cause rejection. These observations indicate that thymic recognition of immunodominant class II MHC allopeptides leads to peripheral T cell anergy that mediates the induction phase of systemic unresponsiveness to renal allografts. The maintenance phase appears to be mediated by dense anergy or clonal deletion.(ABSTRACT TRUNCATED AT 400 WORDS)

Mammalian Target of Rapamycin Inhibitor Dyslipidemia in Kidney Transplant Recipients

The incidence, pathogenesis, consequences and treatment of mammalian target of rapamycin (mTOR) inhibitor dyslipidemia are not well described. We conducted a systematic review of randomized controlled trials reporting cholesterol and triglycerides in mTOR versus non‐mTOR inhibitor immunosuppressive treatment regimens in kidney transplant recipients. All but one of 17 trials reported higher levels of cholesterol and triglycerides, or an increased prevalence of treatment with lipid‐lowering agents. Approximately 60% of mTOR inhibitor‐treated patients received lipid‐lowering agents (2‐fold higher than controls). There appeared to be little difference between dyslipidemias caused by sirolimus (14 trials) versus everolimus (3 trials). It was difficult to determine the extent to which declines in lipids over time posttransplant were due to lipid‐lowering therapy, changes in doses and/or discontinuations of mTOR inhibitors. From the four trials that measured lipoproteins, it appeared that at least some of the increase in total cholesterol with mTOR inhibitors was due to increased low‐density lipoprotein cholesterol. What direct or indirect effects mTOR inhibitors have on atherosclerotic cardiovascular disease in kidney transplant patients are unknown. However, in the absence of the necessary clinical trials, dyslipidemia should be managed, as it would be in nontransplant patients at high risk for cardiovascular disease.

Effect of sirolimus on malignancy and survival after kidney transplantation: systematic review and meta-analysis of individual patient data.

Objective To examine risk of malignancy and death in patients with kidney transplant who receive the immunosuppressive drug sirolimus. Design Systematic review and meta-analysis of individual patient data. Data sources Medline, Embase, and the Cochrane Central Register of Controlled Trials from inception to March 2013. Eligibility Randomized controlled trials comparing immunosuppressive regimens with and without sirolimus in recipients of kidney or combined pancreatic and renal transplant for which the author was willing to provide individual patient level data. Two reviewers independently screened titles/abstracts and full text reports of potentially eligible trials to identify studies for inclusion. All eligible trials reported data on malignancy or survival. Results The search yielded 2365 unique citations. Patient level data were available from 5876 patients from 21 randomized trials. Sirolimus was associated with a 40% reduction in the risk of malignancy (adjusted hazard ratio 0.60, 95% confidence interval 0.39 to 0.93) and a 56% reduction in the risk of non-melanoma skin cancer (0.44, 0.30 to 0.63) compared with controls. The most pronounced effect was seen in patients who converted to sirolimus from an established immunosuppressive regimen, resulting in a reduction in risk of malignancy (0.34, 0.28 to 0.41), non-melanoma skin cancer (0.32, 0.24 to 0.42), and other cancers (0.52, 0.38 to 0.69). Sirolimus was associated with an increased risk of death (1.43, 1.21 to 1.71) compared with controls. Conclusions Sirolimus was associated with a reduction in the risk of malignancy and non-melanoma skin cancer in transplant recipients. The benefit was most pronounced in patients who converted from an established immunosuppressive regimen to sirolimus. Given the risk of mortality, however, the use of this drug does not seem warranted for most patients with kidney transplant. Further research is needed to determine if different populations, such as those at high risk of cancer, might benefit from sirolimus.

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. Maintenance immunosuppression, consisting of tacrolimus and mycophenolate, was weaned over 1 year. Results All but one patient demonstrated peripheral blood macrochimerism after transplantation. Engraftment failure occurred in a highly sensitized (panel reactive antibody [PRA] of 52%) recipient. Chimerism was lost in three patients at 2, 3, and 6 months after transplantation. Two of these subjects had received either a reduced cell dose or incomplete conditioning; the other two had PRA greater than 20%. All demonstrated donor-specific hyporesponsiveness and were weaned from full-dose immunosuppression. Complete immunosuppression withdrawal at 1 year after transplantation was successful in all patients with durable chimerism. There has been no graft-versus-host disease or engraftment syndrome. Renal transplantation loss occurred in one patient who developed sepsis following an atypical viral infection. Two subjects with only transient chimerism demonstrated subclinical rejection on protocol biopsy despite donor-specific hyporesponsiveness. Conclusions Low-intensity conditioning plus FCRx safely achieved durable chimerism in mismatched allograft recipients. Sensitization represents an obstacle to successful induction of chimerism. Sustained T-cell chimerism is a more robust biomarker of tolerance than donor-specific hyporeactivity.

Mechanisms of allo-recognition. Recognition by in vivo-primed T cells of specific major histocompatibility complex polymorphisms presented as peptides by responder antigen-presenting cells.

There is evidence of two pathways of allorecognition, the direct pathway where T cells recognize intact allo-MHC molecules on the surface of target cells, and the indirect pathway where T cells recognize processed allo-MHC presented by self antigen-presenting cells. We used synthetic class II MHC allopeptides to study the cellular mechanisms of the indirect allorecognition pathway and its potential role in vascularized allograft rejection. LEW (RT1l) rat T cells--which are primed by immunization with a mixture of four 25 mer class II MHC allopeptides, representing the full length sequence of the beta chain of the hypervariable domain of the RT1.Du (WF), or by primary WF (RT1u) vascularized cardiac allografts--were capable of recognizing and proliferating to specific polymorphic class II MHC sequences when presented as peptides by responder APCs. T cells from naive LEW animals, WF animals immunized with syngeneic RT1.Du beta peptides, or LEW recipients of third-party BN (RT1n) vascularized cardiac allografts did not proliferate to the RT1.Du beta peptides, indicating the specificity of allopeptide recognition. In the strain combination used, immunogenicity of class II MHC allopeptides is determined by factors other than polymorphisms alone, since epitopic differences in 2 of the 4 RT1.Du beta allopeptides were not immunogenic. Responder T cells were CD4+, and were inhibited by monomorphic anticlass II monoclonal antibodies, and by specific anticlass II alloantibodies. These observations confirm the occurrence of self MHC-restricted recognition of processed allo-MHC in primary vascularized allograft rejection, and provide the rationale to develop novel and specific immunotherapies in organ transplantation.

Resolution of Recurrent Focal Segmental Glomerulosclerosis after Retransplantation

The authors of this letter describe the successful retransplantation of an allograft that was failing in its first recipient owing to recurrent primary focal segmental glomerulosclerosis. In the second recipient, all evidence of the nephrotic syndrome resolved.