Rejection-free Allograft Survival Research Articles

Treatment of borderline infiltrates with minimal inflammation in kidney transplant recipients has no effect on allograft or patient outcomes

In 2005, the Banff committee expanded the "borderline changes" category to include lesions with minimal (<10%) inflammation: "i0" borderline infiltrates. Clinical significance and optimal treatment of i0 borderline infiltrates are not known. Data suggest that i0 borderline infiltrates may have a more favorable prognosis than borderline infiltrates with higher grades of interstitial inflammation. In this single-center, retrospective, observational study, we assessed 90 renal transplant recipients with i0 borderline infiltrates on biopsies indicated for graft dysfunction. We studied the impact of treatment with corticosteroids on allograft function, allograft survival, and patient survival. We found no differences between treated and untreated groups with respect to eGFR at 4weeks and 6months after biopsy. Follow-up biopsies, available in 67% of patients, were negative for rejection in almost half of all cases, regardless of treatment status. The frequencies of persistent borderline infiltrates (38%) and higher-grade T cell-mediated rejection (1A or greater, 14%) on follow-up biopsies were similar between the two groups. There were no differences in rejection-free allograft survival, death-censored graft failure, or patient mortality among treated vs non-treated i0 borderline patients. Our findings suggest that the natural history of i0 borderline infiltrates, in relatively low immunologic risk patients, is not affected by corticosteroid treatment.

Ex Vivo Major Histocompatibility Complex I Knockdown Prolongs Rejection-free Allograft Survival.

Widespread application of vascularized composite allotransplantation (VCA) is currently limited by the required lifelong systemic immunosuppression and its associated morbidity and mortality. This study evaluated the efficacy of ex vivo (after procurement but before transplantation) engineering of allografts using small interfering RNA to knockdown major histocompatibility complex I (MHC-I) and prolong rejection-free survival. Endothelial cells (ECs) were transfected with small interfering RNA targeted against MHC-I (siMHC-I) for all in vitro experiments. MHC-I surface expression and knockdown duration were evaluated using quantitative polymerase chain reaction (qPCR) and flow cytometry. After stimulating Lewis recipient cytotoxic lymphocytes (CTL) with allogeneic controls or siMHC-I-silenced ECs, lymphocyte proliferation, CTL-mediated and natural killer-mediated EC lysis were measured. Using an established VCA rat model, allografts were perfused ex vivo with siMHC-I before transplantation. Allografts were analyzed for MHC-I expression and clinical/histologic evidence of rejection. Treatment with siMHC-I resulted in 80% knockdown of mRNA and 87% reduction in cell surface expression for up to 7 days in vitro (P < 0.05). Treatment of ECs with siMHC-I reduced lymphocyte proliferation and CTL-mediated cytotoxicity (77% and 50%, respectively, P < 0.01), without increasing natural killer-mediated cytotoxicity (P = 0.66). In a rat VCA model, ex vivo perfusion with siMHC-I reduced expression in all tissue compartments by at least 50% (P < 0.05). Knockdown prolonged rejection-free survival by 60% compared with nonsense-treated controls (P < 0.05). Ex vivo siMHC-I engineering can effectively modify allografts and significantly prolong rejection-free allograft survival. This novel approach may help reduce future systemic immunosuppression requirements in VCA recipients.

Analysis of dendritic cells and ischemia-reperfusion changes in postimplantation renal allograft biopsies may serve as predictors of subsequent rejection episodes

Ischemia-reperfusion injury increases allograft immunogenicity and enhances myeloid dendritic cell maturation and trafficking to recipient's secondary lymphoid tissue. Here, we used postreperfusion biopsies from patients who received kidney allografts from deceased donors between 2006 and 2009 to assess the impact of ischemia-reperfusion damage and myeloid dendritic cell density on subsequent allograft rejection episodes. Histologic changes of severe ischemia-reperfusion damage in postreperfusion biopsies were found to be associated with subsequent rejection episodes and suboptimal allograft survival. Using BDCA-1 as a marker of myeloid dendritic cells, postreperfusion biopsies from deceased donors had lower dendritic cell density compared to postreperfusion biopsies from living donors or normal controls. This suggests a rapid emigration of donor dendritic cells out of the allograft. In our cohort, low dendritic cell density was associated with a subsequent increase in rejection episodes. However, it appears that the donor's cause of death also influenced dendritic cell density. Therefore, we assessed the additive impact of severe ischemia-reperfusion changes and low dendritic cell density on subsequent rejection. The aforementioned combination was a powerful and independent predictor of allograft rejection. Thus, our data highlight the prognostic value of histopathologic changes associated with ischemia-reperfusion in postreperfusion biopsies and suggest a rapid posttransplant emigration of myeloid dendritic cells out of the allograft to enhance alloimmunity. These findings may provide a rationale for minimizing ischemia-reperfusion injury and therapeutic targeting of donor-derived dendritic cells to promote rejection-free allograft survival.

Ex vivo allotransplantation engineering: Delivery of mesenchymal stem cells prolongs rejection-free allograft survival.

Current pharmacologic regimens in transplantation prevent allograft rejection through systemic recipient immunosuppression but are associated with severe morbidity and mortality. The ultimate goal of transplantation is the prevention of allograft rejection while maintaining recipient immunocompetence. We hypothesized that allografts could be engineered ex vivo (after allotransplant procurement but before transplantation) by using mesenchymal stem cell-based therapy to generate localized immunomodulation without affecting systemic recipient immunocompetence. To this end, we evaluated the therapeutic efficacy of bone marrow-derived mesenchymal stem cells in vitro and activated them toward an immunomodulatory fate by priming in inflammatory or hypoxic microenvironments. Using an established rat hindlimb model for allotransplantation, we were able to significantly prolong rejection-free allograft survival with a single perioperative ex vivo infusion of bone marrow-derived mesenchymal stem cells through the allograft vasculature, in the absence of long-term pharmacologic immunosuppression. Critically, transplanted rats rejected a second, nonengineered skin graft from the same donor species to the contralateral limb at a later date, demonstrating that recipient systemic immunocompetence remained intact. This study represents a novel approach in transplant immunology and highlights the significant therapeutic opportunity of the ex vivo period in transplant engineering.

Beneficial Effects of Pretransplantation Microchimerism on Rejection-Free Survival in HLA-Haploidentical Family Donor Renal Transplantation

Fetal-maternal microchimerism (MC) can develop during pregnancy and may persist for decades. Pretransplantation fetal-maternal MC may be present between mother and child and between siblings; however, its effect on renal transplantation is not known. We investigated the effects of pretransplantation MC on allograft outcomes in human leukocyte antigen (HLA)-haploidentical family donor transplantation. A total of 106 cases transplanted from 1996 to 2004 were retrospectively studied, with median follow-up of 96 months. The study and control groups included 63 and 43 cases of HLA-haploidentical and HLA-identical donor transplantations, respectively. MC against mismatched donor HLA-DRB1 allele was detected in the recipient's peripheral blood using nested polymerase chain reaction-single-strand conformation polymorphism method. The allograft outcomes of HLA-haploidentical MC (+) and (-) subgroups were compared with those of HLA-identical group. Pretransplantation MC in the HLA-haploidentical recipients was detected in 22.2% (14 of 63). Compared with HLA-identical group, MC (-) subgroup showed significantly inferior allograft outcomes: higher acute rejection rate (11.6% vs. 42.9%; P=0.001), higher 5-year serum creatinine level (1.1 vs. 1.4 mg/dL; P=0.009), and lower 10-year rejection-free survival rate (83.7% vs. 54.5%; log-rank P=0.001). In contrast, MC (+) subgroup showed no significant differences from HLA-identical group in acute rejection rate (14.3%), 5-year serum creatinine level (1.1 mg/dL), and 10-year rejection-free survival rate (85.7%). Multivariate analysis revealed that pretransplantation MC is associated with a significantly lower risk of acute rejection (odds ratio=0.10; P=0.021). Pretransplantation MC present in the recipient may have beneficial effects on rejection-free allograft survival in renal transplantation.

The promise of co-stimulatory blockade in transplantation

A new study by Lo et al. presents a novel immunosuppressive combination in a clinically relevant primate model of renal allografting. Using belatacept, a fusion protein that inhibits CD28–CD80/CD86 co-stimulation, plus the mammalian target of rapamycin inhibitor sirolimus, they were able to achieve rejection-free allograft survival without the induction of memory T cells or alloantibody.

Belatacept and Sirolimus Prolong Nonhuman Primate Renal Allograft Survival Without a Requirement for Memory T Cell Depletion

Belatacept is an inhibitor of CD28/B7 costimulation that is clinically indicated as a calcineurin inhibitor (CNI) alternative in combination with mycophenolate mofetil and steroids after renal transplantation. We sought to develop a clinically translatable, nonlymphocyte depleting, belatacept-based regimen that could obviate the need for both CNIs and steroids. Thus, based on murine data showing synergy between costimulation blockade and mTOR inhibition, we studied rhesus monkeys undergoing MHC-mismatched renal allotransplants treated with belatacept and the mTOR inhibitor, sirolimus. To extend prior work on costimulation blockade-resistant rejection, some animals also received CD2 blockade with alefacept (LFA3-Ig). Belatacept and sirolimus therapy successfully prevented rejection in all animals. Tolerance was not induced, as animals rejected after withdrawal of therapy. The regimen did not deplete T cells. Alefecept did not add a survival benefit to the optimized belatacept and sirolimus regimen, despite causing an intended depletion of memory T cells, and caused a marked reduction in regulatory T cells. Furthermore, alefacept-treated animals had a significantly increased incidence of CMV reactivation, suggesting that this combination overly compromised protective immunity. These data support belatacept and sirolimus as a clinically translatable, nondepleting, CNI-free, steroid-sparing immunomodulatory regimen that promotes sustained rejection-free allograft survival after renal transplantation.

Conversion From Mycophenolate Mofetil to Azathioprine in Renalallograft Patients Within the First Month Posttransplantation

This retrospective study evaluated the safety of conversion from mycophenolate mofetil (MMF) to azathioprine (Aza) within the first month posttransplantation in 117 renal allograft patients concomittantly treated with cyclosporine (CsA) and prednisone. In 52 Conversion from MMF to Aza was conducted at 2 to 4 weeks posttransplantation in 52 patients (conversion group). Thirty-six patients received MMF (MMF group) and 29 patients were treated with Aza (Aza group). Patients were monitored for allograft function, acute rejection episodes, and CsA levels. The demographics were comparable between groups with respect to age, as well as warm and cold ischemic times of allografts. The cumulative allograft survival rates at 1, 2, 3, and 5 years were 98% ± 2%, 96% ± 3%, 90% ± 4%, 90% ± 4% in the conversion ( n = 52) group versus 79% ± 7%, 79% ± 7%, 79% ± 7%, and 75% ± 8% in the MMF group ( n = 36) versus 93% ± 5%, 93% ± 5%, 82% ± 7%, and 78% ± 8% in the Aza group ( n = 29). The CsA trough levels at 1 year posttransplantation were 208.39 ± 93.79 ng/mL in the conversion group; 159.30 ± 52.99 ng/mL in the MMF group; and 241.82 ± 112.76 ng/mL in the Aza group. The acute rejection rates during a 5-year follow-up were 28.85% in the conversion group; 27.78% in the MMF group; and 24.14% in the Aza group. The rejection-free allograft survival between the conversion group and the MMF group was identical ( P < .921). However, allograft survival in the conversion group with acute rejection was significantly higher than the MMF group ( P < .024). In conclusion, early conversion from MMF to Aza among renal allograft patients was safe without increased acute allograft rejection during a 5-year follow-up. The overall allograft survival in the conversion group was comparable to patients treated with MMF or Aza therapies.

Effects of Combined Treatment with CD25- and CD154-Specific Monoclonal Antibodies in Non-Human Primate Allotransplantation

The CD154-specific monoclonal antibody (Mab) hu5c8 greatly prolongs allograft survival in primates. The CD25-specific Mab daclizumab has not, to date, been paired with hu5c8. We evaluated the effects of hu5c8 in vitro, alone and in combination with daclizumab on rhesus-mixed lymphocyte reactions (MLRs). We then evaluated therapy with hu5c8 and daclizumab in four monkey renal allograft recipients compared with monkeys untreated or contemporaneously treated with hu5c8 alone. Lymphocyte proliferation in MLR was reduced by both daclizumab and hu5c8, and their combined effects were additive. Rejection-free allograft survival in monkeys treated with both hu5c8 and daclizumab (74–479 days) was not significantly better than animals treated with hu5c8 alone (257–587 days), and one combined therapy animal rejected while still on hu5c8 therapy, a condition not typically seen with hu5c8 monotherapy. Although daclizumab and hu5c8 are additively effective in MLR, they do not appear to be synergistic in vivo in rhesus monkeys.

Oral efficacy of the new immunomodulator FTY720 in cynomolgus monkey kidney allotransplantation, given alone or in combination with cyclosporine or RAD.

FTY720 is a novel immunomodulator with a unique mechanism of action, i.e. chemokine-dependent lymphocyte homing into secondary lymphoid organs associated with profound lymphocyte depletion in blood. We investigated its efficacy, either FTY720 alone or together with cyclosporine or the rapamycin derivative rapamycin derivative (RAD), in cynomolgus monkey kidney allotransplantation. Life-supporting allotransplantation was performed in bilaterally nephrectomized hosts. Compounds were given once daily by oral gavage. Monitoring was done by serum creatinine and urea, and rejection was concluded when values exceeded 500 micromol/L and 50 mmol/L, respectively (5-6 times the upper limit of reference values). Rejection was confirmed by graft histology. The termination point was set to 100 days after transplantation. In addition, animals were monitored for 24 hr drug concentrations and thorough inspection of potential adverse side effects. FTY720 given alone at 3.0 mg/kg per day prolonged rejection-free survival (33-85 days, mean 24 hr concentration between 54 and 66 ng/mL [n=3]), but it was not efficacious at a 0.3 mg/kg per day dose. For cyclosporine alone, 30 mg/kg per day during maintenance was efficacious (average concentration above 100 ng/mL, historical data from our group), and for RAD alone 0.75 mg/kg per day (concentration above 10 ng/mL). Efficacious FTY720-cyclosporine-A (CsA) or FTY720-RAD combinations were established using 0.1-0.3 mg/kg per day FTY720, 10-30 mg/kg per day cyclosporine, and/or 0.25-0.50 mg/kg per day RAD. Compared with single-compound treatment, FTY720 effective doses and 24 hr trough concentrations were at least tenfold lower in combination treatment and those of cyclosporine and RAD about twofold lower, indicative of effective synergy between the compounds. Already at the lowest FTY720 dose tested (0.03 mg/kg per day), there was a profound lymphocyte depletion down to about 30% of pretransplant values, which further increased at the highest dose (3.0 mg/kg per day, to about 14% of pretransplant values). Lymphocyte depletion was reflected by a decrease in T and B subpopulations. FTY720 is an effective immunosuppressant in prevention of acute kidney allograft rejection in cynomolgus monkeys and synergizes with cyclosporine and/or RAD in yielding rejection-free allograft survival.

Rejection-free allograft survival a possibility?

Rejection-free allograft survival a possibility?

CTLA4-Ig and anti-CD40 ligand prevent renal allograft rejection in primates.

Selective inhibition of T cell costimulation using the B7-specific fusion protein CTLA4-Ig has been shown to induce long-term allograft survival in rodents. Antibodies preventing the interaction between CD40 and its T cell-based ligand CD154 (CD40L) have been shown in rodents to act synergistically with CTLA4-Ig. It has thus been hypothesized that these agents might be capable of inducing long-term acceptance of allografted tissues in primates. To test this hypothesis in a relevant preclinical model, CTLA4-Ig and the CD40L-specific monoclonal antibody 5C8 were tested in rhesus monkeys. Both agents effectively inhibited rhesus mixed lymphocyte reactions, but the combination was 100 times more effective than either drug alone. Renal allografts were transplanted into nephectomized rhesus monkeys shown to be disparate at major histocompatibility complex class I and class II loci. Control animals rejected in 5-8 days. Brief induction doses of CTLA4-Ig or 5C8 alone significantly prolonged rejection-free survival (20-98 days). Two of four animals treated with both agents experienced extended (>150 days) rejection-free allograft survival. Two animals treated with 5C8 alone and one animal treated with both 5C8 and CTLA4-Ig experienced late, biopsy-proven rejection, but a repeat course of their induction regimen successfully restored normal graft function. Neither drug affected peripheral T cell or B cell counts. There were no clinically evident side effects or rejections during treatment. We conclude that CTLA4-Ig and 5C8 can both prevent and reverse acute allograft rejection, significantly prolonging the survival of major histocompatibility complex-mismatched renal allografts in primates without the need for chronic immunosuppression.