Development and clinical validity of a novel blood-based molecular biomarker for subclinical acute rejection following kidney transplant.

Noninvasive biomarkers are needed to monitor stable patients after kidney transplant (KT), because subclinical acute rejection (subAR), currently detectable only with surveillance biopsies, can lead to chronic rejection and graft loss. We conducted a multicenter study to develop a blood-based molecular biomarker for subAR using peripheral blood paired with surveillance biopsies and strict clinical phenotyping algorithms for discovery and validation. At a predefined threshold, 72% to 75% of KT recipients achieved a negative biomarker test correlating with the absence of subAR (negative predictive value: 78%-88%), while a positive test was obtained in 25% to 28% correlating with the presence of subAR (positive predictive value: 47%-61%). The clinical phenotype and biomarker independently and statistically correlated with a composite clinical endpoint (renal function, biopsy-proved acute rejection, ≥grade 2 interstitial fibrosis, and tubular atrophy), as well as with de novo donor-specific antibodies. We also found that <50% showed histologic improvement of subAR on follow-up biopsies despite treatment and that the biomarker could predict this outcome. Our data suggest that a blood-based biomarker that reduces the need for the indiscriminate use of invasive surveillance biopsies and that correlates with transplant outcomes could be used to monitor KT recipients with stable renal function, including after treatment for subAR, potentially improving KT outcomes.

Incidence and impact of rejection following simultaneous liver-kidney transplantation.

BACKGROUND & AIMS: Due to hepatic immunoregulation, simultaneous liver-kidney recipients are presumed to be reasonably protected from kidney rejection and typically receive less immunosuppression compared to kidney transplants alone. However, data to support these conclusions and practices are sparse. METHODS: We characterized the incidence and types of rejection, graft function, and graft and patient survival in a large population of simultaneous liver-kidney recipients (n=140) with long-term follow-up at our centre (1998-2010). RESULTS: Acute cellular, antibody-mediated, and chronic kidney rejection was diagnosed in 9 (6.4%), 2 (1.4%), and 1 (0.7%) patient, respectively. Borderline acute kidney rejection was diagnosed in another 16 patients (11.4%). Acute cellular liver rejection occurred in 16 (11.4%) and chronic liver rejection in 4 (2.9%). One-, three-, and five-year patient survival was 86.4%, 78.0%, and 74.0%, respectively, and did not significantly differ by presence or absence of kidney or liver rejection. However, kidney rejection was associated with decreased renal function by lower serum GFR over time (p=0.003). CONCLUSIONS: Various forms of kidney rejection occurred in ∼20% of our simultaneous liver-kidney recipients and were associated with deterioration in graft function, indicating that the liver may not confer complete protective allo-immunity. More stringent graft monitoring and management strategies, perhaps more akin to kidney transplant alone, should be prospectively studied in simultaneous liver-kidney recipients.

Cellular and molecular immune profiles in renal transplant recipients after conversion from tacrolimus to sirolimus.

Tacrolimus and sirolimus are commonly used maintenance immunosuppressants in kidney transplantation. As their effects on immune cells and allograft molecular profiles have not been elucidated, we characterized the effects of tacrolimus to sirolimus conversion on the frequency and function of T cells, and on graft molecular profiles. Samples from renal transplant patients in a randomized trial of 18 patients with late sirolimus conversion and 12 on tacrolimus maintenance were utilized. Peripheral blood was collected at 0, 6, 12, and 24 months post randomization, with T-cell subpopulations analyzed by flow cytometry and T-cell alloreactivity tested by IFN-γ ELISPOT. Graft biopsy samples obtained 24 months post randomization were used for gene expression analysis. Sirolimus conversion led to an increase in CD4(+)25(+++)Foxp3(+) regulatory T cells. While tacrolimus-maintained patients showed a decrease in indirect alloreactivity over time post transplant, sirolimus conversion increased indirect alloreactive T-cell frequencies compared with tacrolimus-maintained patients. No histological differences were found in graft biopsies, but molecular profiles showed activation of the antigen presentation, IL-12 signaling, oxidative stress, macrophage-derived production pathways, and increased inflammatory and immune response in sirolimus-converted patients. Thus, chronic immune alterations are induced after sirolimus conversion. Despite the molecular profile being favorable to calcineurin inhibitor-based regimen, there was no impact in renal function over 30 months of follow-up.

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.

Comparison of four different immunosuppression protocols without long-term steroid therapy in kidney recipients monitored by surveillance biopsy: five-year outcomes.

Induction and maintenance immunosuppression protocols with or without long-term steroid therapy in kidney transplant recipients are variable and are transplant center-specific. The aim of this prospective randomized pilot study was to compare 5-year outcomes in kidney recipients maintained on 4 different calcineurin inhibitor (CNI)-based immunosuppression protocols without long-term steroid therapy. Two hundred consenting patients who received kidney transplants between June 2000 and October 2004 were enrolled in 4 immunosuppression protocol groups, with 50 patients in each group: cyclosporine (CSA)/mycophenolate mofetil (MMF), CSA/sirolimus (SRL), tacrolimus (TAC)/MMF, and TAC/SRL. Induction therapy was done with basiliximab and methylprednisolone. Steroids were withdrawn on post-transplant day 2, and long-term steroid therapy was not used. Demographic characteristics among the four groups were comparable; approximately 50% of the recipients were African American and > or =80% of the kidneys transplanted were from deceased donors. Clinical acute rejection (CAR) was confirmed by biopsy and treated with intravenous pulse steroid therapy. Steroid-unresponsive CAR was treated with Thymoglobulin. Surveillance biopsies were performed at 1, 6, 12, 24, 36, 48, and 60 months to evaluate subclinical acute rejection (SCAR), chronic allograft injury (CAI), and other pathological changes per the Banff 2005 schema. The primary end point was CAR, and secondary end points were 5-year patient and graft survival rates, renal function, SCAR, CAI, and adverse events. In the first year post-transplant, the incidence of CAR was 18% in the CSA/MMF group, 8% in the CSA/SRL group, 14% in the TAC/MMF group, and 4% in the TAC/SRL group (CSA/MMF vs. TAC/SRL; p=0.05). The incidence of SCAR was 22% in the CSA/MMF group, 8% in the CSA/SRL group, 16% in the TAC/MMF group, and 6% in the TAC/SRL group (CSA/MMF vs. CSA/SRL and TAC/SRL; p=0.05). After the first year, the incidences of CAR and SCAR decreased and were comparable in all 4 groups. At 5 years post-transplant, cumulative CAI due to interstitial fibrosis/tubular atrophy (IF/TA), hypertension (HTN), and chronic calcineurin inhibitor (CNI) toxicity was observed in 54%, 48%, and 8% of the CSA/MMF group vs. 16%, 36%, and 12% of the CSA/SRL group vs. 38%, 24% and 6% of the TAC/MMF group vs. 14%, 25% and 12% of the TAC/SLR group (IF/TA: CSA/MMF vs. CSA/SRL and TAC/SRL; p=0.04, HTN: CSA/MMF vs. TAC/MMF and TAC/SRL; p=0.05, CNI toxicity: TAC/SRL and CSA/SRL vs. TAC/MMF; p=0.05). Five-year patient and graft survival rates were 82% and 60% in the CSA/MMF group, 82% and 60% in the CSA/SRL group, 84% and 62% in the TAC/MMF group, and 82% and 64% in the TAC/SRL group (p=0.9). Serum creatinine levels and creatinine clearances at 5 years were comparable among the groups. Our data show that the rates of CAR and SCAR in the first year post-transplant were significantly lower in the CSA/SRL and TAC/SRL groups and that cumulative CAI rates due to IF/TA and HTN at 5 years were significantly lower in the TAC/MMF, TAC/SRL, and CSA/SRL groups than in the CSA/MMF group. Despite significant differences in the incidences of CAR and SCAR and prevalence of different types of CAI at 5 years, renal function and patient and graft survival rates at 5 years were comparable among kidney recipients maintained on 4 different immunosuppression protocols without long-term steroid therapy.

Successful transplantation of kidneys from deceased donors with acute renal failure: Three-year results.

BACKGROUND: Kidneys from deceased donors with acute renal failure (ARF) are generally not accepted for transplantation because of the expected poor outcome. This prospective study examined the utilization of kidneys from donors with ARF for transplantation and the outcomes. METHODS: Fifty-five kidneys from donors with ARF were transplanted. The outcome was compared with concurrent and matched 55 recipients of standard criteria donor (SCD) kidneys and 55 expanded criteria donor (ECD) kidneys. ARF kidneys were accepted from donors aged <50 years, a negative history for kidney disease, and a negative pretransplant biopsy for chronic structural changes. The immunosuppression was similar in all three groups. The outcome measurements included three-year patient and graft survival, biopsy-proven acute rejection (BPAR), subclinical acute rejection (SCAR), and chronic allograft nephropathy (CAN), serum creatinine, and creatinine clearance. RESULTS: Three-year patient and graft survival was 90% and 90% in ARF group, 100% and 89% in SCD group and 83% and 66% in ECD group. BPAR and SCAR were comparable in the groups but CAN was significantly higher in ECD group. Mean serum creatinine levels were 1.9+/-1.1, 1.9+/-0.9, and 2.2+/-1.3 mg/dl and mean creatinine clearances were 66+/-15, 68+/-14, and 58+/-10 mls/minute in ARF, SCD, and ECD groups, respectively (SCD and ARF vs. ECD P = 0.04). CONCLUSIONS: Transplantation of kidneys from selected deceased donors with ARF provides comparable survival and function compared to kidneys from non-ARF donors and may be considered for transplantation to expand the donor pool to overcome the current acute shortage of kidneys.

Avoidance of chronic steroid therapy in african american kidney transplant recipients monitored by surveillance biopsy: 1-year results.

African American (AA) kidney recipients receive chronic steroid therapy to improve outcomes, despite their high susceptibility to side effects, particularly diabetes and hypertension. This study evaluated the safety and efficacy of avoidance of chronic steroid therapy in AA compared to non-AA kidney recipients. Two hundred and six kidney recipients were studied; 103 AA recipients versus 103 non-AA recipients. Induction was basiliximab and maintenance was a calcineurin inhibitor plus mycophenolate mofetil or sirolimus. Surveillance biopsies were preformed at 1, 6 and 12 months to assess subclinical acute rejection (SCAR) and chronic allograft nephropathy (CAN). Biopsy-proven acute rejection (AR) and SCAR were treated by methylprednisolone. The primary end point was AR. Secondary end points were graft function, 1-year patient and graft survival. AR was observed in 16% of AA and 13% of non-AA recipients. SCAR at 1 month was significantly higher in the AA group (p=0.04). One-year actual patient and graft survival in the AA group was 96% and 88% and in the non-AA group 97% and 89%, respectively. Avoidance of chronic steroid therapy directed by surveillance biopsies provides equivalent AR, CAN and 1-year patient and graft survival in AA versus non-AA recipients and a 5% incidence of new onset diabetes mellitus. All recipients remain free of chronic steroid therapy. Longer-term follow-up is ongoing.