Pretransplantation seroreactivity in kidney donors and recipients as a predictive factor for posttransplant BKPyV-DNAemia.

BK polyomavirus (BKPyV) often reactivates after kidney transplantation, causing BKPyV-associated nephropathy (BKPyVAN) in 1%-10% of cases with a potential detrimental effect on allograft survival. Kidney transplant recipients are regularly screened for BKPyV DNA in plasma. As this strategy may not always reduce the risk of BKPyVAN, other predictive markers are needed. To evaluate the role of pretransplant BKPyV-specific antibody, 210 kidney transplant recipients and 130 donors were screened for BKPyV DNA and BKPyV-specific antibodies. We found that the donor BKPyV immunoglobulin G (IgG) seroprevalence and antibody level were strongly associated with BKPyV-DNAemia and BKPyVAN, although multivariant analysis found the presence of anti-BKPyV-specific antibodies as a predictive factor only for BKPyV-DNAemia. The pretransplant recipient status had no effect on posttransplant BKPyV-DNAemia and BKVAN. BKPyV IgG levels remained stable in BKPyV-negative recipients during 1-year follow-up, while a considerable increase was observed in BKPyV-positive patients. The presence of anti-BKPyV-specific antibodies in kidney allograft donors is a good and reliable predictive marker for posttransplant BKPyV replication with relevance to risk stratification in transplant recipients.

Molecular Patterns Discriminate Accommodation and Subclinical Antibody-mediated Rejection in Kidney Transplantation.

BACKGROUND: Accommodation in ABO-incompatible (ABOi) transplantation and subclinical antibody-mediated rejection in HLA-incompatible (HLAi) transplantation share several morphological similarities. Because the clinical long-term outcomes differ, we hypothesized different molecular processes involved in ABOi transplantation and subclinical antibody-mediated rejection. METHODS: Using Illumina Human HT-12 v4 Expression BeadChips, the whole transcriptome was evaluated based on 3-month protocol C4d+ biopsies in otherwise stable ABOi and HLAi kidney grafts, as well as in C4d-negative HLA-compatible grafts exhibiting normal histological findings. Top differently regulated genes were further validated using real-time quantitative polymerase chain reaction in another patient cohort and complement regulatory proteins by immunohistochemistry. RESULTS: In the case of genes involved in immune response-related biological processes, ABOi and HLAi cohorts had similar transcriptomic profiles to C4d-negative controls. The majority of deregulated genes in the ABOi and HLAi groups consisted of metallothioneins and epithelial transporter genes. Increased expression of epithelial transporters (SLC4A1, SLC4A9, SLC17A3, SLC12A3, and SLC30A2) and class 1 metallothioneins (MT1F, MT1G, and MT1X) in HLAi transplantation was validated by real-time quantitative polymerase chain reaction. In comparison to controls, both incompatible cohorts were characterized by the upregulation of intrarenal complement regulatory genes. CD46 and CD59 transcripts were increased in the ABOi cohort, whereas CD46 solely in HLAi group, and CD59 protein expression was similar in both incompatible groups. CONCLUSIONS: Several epithelial transporters and metallothioneins discriminate subclinical antibody-mediated rejection in HLAi transplantation from accommodation in ABOi transplantation, which suggest different involved downstream mechanisms and increased risk of injury in HLAi settings. Metallothioneins with their antioxidative properties may help to attenuate the inflammation response induced by donor-specific anti-HLA antibody binding.

Early isolated V-lesion may not truly represent rejection of the kidney allograft.

Intimal arteritis is known to be a negative prognostic factor for kidney allograft survival. Isolated v-lesion (IV) is defined as intimal arteritis with minimal tubulointerstitial inflammation (TI). Although the Banff classification assesses IV as T cell-mediated rejection (TCMR), clinical, and prognostic significance of early IV (early IV, eIV) with negative C4d and donor-specific antibodies (DSA) remains unclear. To help resolve if such eIV truly represents acute rejection, a molecular study was performed. The transcriptome of eIV (n=6), T cell-mediated vascular rejection with rich TI (T cell-mediated vascular rejection, TCMRV, n=4) and non-rejection histologic findings (n=8) was compared using microarrays. A total of 310 genes were identified to be deregulated in TCMRV compared with eIV. Gene enrichment analysis categorized deregulated genes to be associated primarily with T-cells associated biological processes involved in an innate and adaptive immune and inflammatory response. Comparison of deregulated gene lists between the study groups and controls showed only a 1.7% gene overlap. Unsupervised hierarchical cluster analysis revealed clear distinction of eIV from TCMRV and showed similarity with a control group. Up-regulation of immune response genes in TCMRV was validated using RT-qPCR in a different set of eIV (n=12) and TCMRV (n=8) samples. The transcriptome of early IV (< 1 month) with negative C4d and DSA is associated with a weak immune signature compared with TCMRV and shows similarity with normal findings. Such eIV may feature non-rejection origin and reflect an injury distinct from an alloimmune response. The present study supports use of molecular methods when interpreting kidney allograft biopsy findings.

Isolated v-lesion represents a benign phenotype of vascular rejection of the kidney allograft - a retrospective study.

While the detrimental impact of the humoral acute vascular rejection (AVR) phenotype is recognized, the prognostic significance of isolated v-lesion (IV) remains unclear. In this retrospective single-centre study, AVR was found in 98 of 1015 patients (9.7%) who had undergone kidney transplantation in 2010-2014, with donor-specific antibodies (DSA) evaluated in all of them. The outcome of four AVR phenotypes was evaluated during median follow-up of 59 months; in 25 patients with IV, 18 with T-cell-mediated vascular rejection (TCMVR), 19 with antibody-mediated vascular rejection (AMVR) and 36 with suspected antibody-mediated rejection (sAMVR). AVR was diagnosed mainly by for-cause biopsy (81%) early after transplantation (median 19 POD) and appeared as mild-grade intimal arteritis. IV occurred in low-sensitized patients after the first transplantation (96%) in the absence of DSA. IV responded satisfactorily to treatment (88%), showed no persistence of rejection in surveillance biopsy, and had stable graft function, minimal proteinuria and excellent DCGS (96%). Contrary to that, Kaplan-Meier estimate of 3-year DCGS of AMVR was 66% (log-rank = 0.0004). Early IV represents a benign phenotype of AVR with a favourable outcome. This study prompts further research to evaluate the nature of IV before considering any change in the classification and management.

Molecular patterns of subclinical and clinical rejection of kidney allograft: quantity matters.

BACKGROUND/AIMS: Subclinical rejection diagnosed from protocol biopsies is thought to be a risk factor of long- term allograft dysfunction. The reason why in some patients subclinical rejection does not represent risk for progression is not fully understood. METHODS: The intragraft expression of 376 target genes involved in chemokine defense, apoptosis, inflammation, tolerance and TGF-ß signalling pathways was measured using quantitative real-time RT-PCR (2(-)∆∆(Ct)) method in subclinical inflammation (SCI, n=10), clinical inflammation in acute T-cell mediated rejection (CI, n=10) and no rejection samples (n=9). RESULTS: Clinical inflammation group showed a increased expression of genes for chemotaxis mediating cytokines (CCL1, CCL17, CCL24, CCL25, CCL26), cytokine receptors (CCR1, CCRL2, IL1RAPL2, CXCR5), proinflammatory cytokines (IL12A, LTA), inflammatory mediator (PTAFR), complement protein C3, executioner protein of apoptosis (CASP7), growth factor (TGFA), colony stimulating factor (CSF-2), proteins involved in dendritic cells differentiation and interaction (CD209, LAMP3), regulation of immune response (LILRB2, LILBRB4). The quantitative difference in transcripts signature between SCI and CI is consistent with stronger proinflammatory setting of CI. Prostaglandin E2 receptor gene expression was independently associated with lower risk of further graft function deterioration (OR 0.11, CI 0.01-0.78, p<0.0001). CONCLUSION: Subclinical acute kidney inflammation has transcriptional profile of immune injury of lower extend compared to clinical acute inflammation.

New strategies for evaluating the quality of kidney grafts from elderly donors.

The increased demand for kidney transplantation and organ shortage resulted in the increased use of kidneys from suboptimal donors. Therefore, identification of kidneys that can be accepted without significantly compromising the outcome of allograft or recipient has become critical. A robust assessment of organ quality is of particular importance especially in kidneys from elderly donors in whom morphological and functional changes associated with aging and diseases are obvious. A number of predictive tools have been developed to help with evaluating the suitability of a deceased-donor kidney for transplantation. Among those, Kidney Donor Profile Index and zero hour graft biopsy in elderly donors have been already implemented in several transplant programs. This review captures the recent literature on this subject and discusses approaches for evaluating the quality of kidney grafts from elderly donors.

Recent trials in immunosuppression and their consequences for current therapy.

PURPOSE OF REVIEW: Although the scarcity of clinical trials with de-novo immunosuppression has been typical over the last 2 years, several attempts have been made in drug conversion, dosing optimization, and bioequivalence. On the basis of recent clinical and animal studies, future directions of management and treatment are outlined. RECENT FINDINGS: Studies with new tacrolimus formulations showed better bioavailability and lower doses, which might translate into less toxicity. The long-term results of studies with costimulation blockade confirmed their safety and efficacy. Calcineurin inhibitor (CNI)-free regimens based on mTOR inhibitors were shown to be associated with increased risk of the humoral response. Therefore, ongoing trials are predominantly designed to minimize calcineurin inhibitor dose only. Biologics, such as B-cell-specific agents (bortezomib and rituximab) and complement inhibitors (eculizumab) used to treat antibody-mediated rejection, recurrence of glomerulonephritis, are shifted to more preventive applications. The pretransplant quantification of alloreactive memory/effector T cell response may help to better stratify a patient's immunologic risk and allow for drug minimization. SUMMARY: Despite clinical trials with innovative protocols with already established agents, tacrolimus-based and induction-based protocols have been shown to be the mainstay of immunosuppressive regimens. In the future, research aims to focus on biomarker-driven immunosuppression and cell therapy approaches.

Enhanced posttransplant management of patients with diabetes improves patient outcomes.

The survival of patients with diabetes mellitus in the general population has improved in recent years. Here we assessed whether similar trends have occurred in 1688 kidney recipients, including 413 with diabetes prior to transplant between 1996 and 2007. Compared to patients without diabetes, the 5-year mortality was significantly increased (hazard ratio (HR) 2.68 (1.95-3.69)) due to higher cardiovascular-, infection-, and malignancy-related deaths in those with diabetes. However, 5-year mortality in patients with diabetes significantly declined over time (HR 0.883 (0.817-0.954)), narrowing the mortality difference between patients with and those without diabetes and in more recent years largely eliminating it. Post transplant, patients with diabetes experienced a significant decline in major fatal/nonfatal cardiac events (HR 0.853 (0.782-0.930)) and infectious deaths over time. In contrast, neither cardiac events nor overall mortality declined in recipients without diabetes. The decline in mortality due to diabetes did not relate to a reduced pretransplant risk profile and was independent of posttransplant variables. The use of cardioprotective medications and glycemic control improved over time post transplant. Furthermore, graft function and serum albumin significantly improved over time and these parameters related to better survival (albumin, HR 0.365 (0.223-0.599); eGFR, HR 0.803 (0.756-0.852)). Thus, survival of kidney recipients with diabetes mellitus has improved markedly since 1996 likely reflecting, at least in part, enhanced posttransplant management and outcomes.

Tubular atrophy and low netrin-1 gene expression are associated with delayed kidney allograft function.

BACKGROUND: Delayed graft function (DGF) caused by ischemia/reperfusion injury (I/RI) negatively influences the outcome of kidney transplantation. This prospective single-center study characterized the intrarenal transcriptome during I/RI as a means of identifying genes associated with DGF development. METHODS: Characterization of the intrarenal transcription profile associated with I/RI was carried out on three sequential graft biopsies from respective allografts before and during transplantation. The intragraft expression of 92 candidate genes was measured using quantitative real-time reverse transcriptase polymerase chain reaction (2) in delayed (n=9) and primary function allografts (n=26). RESULTS: Cold storage was not associated with significant changes to the expression profile of the target gene transcripts; however, up-regulation of 16 genes associated with enhanced activation of innate and adaptive immune responses and apoptosis was observed after reperfusion. Multivariate logistic regression analysis revealed that higher tubular atrophy scores (ct) together with a lower expression of Netrin-1 might predict DGF development (training area under the receiver operating curve=0.89, cross-validated area under the receiver operating curve=0.81). CONCLUSIONS: Poor baseline tubular cell quality (defined by a higher rate of tubular atrophy) combined with the reduced potential of apoptotic survival factors represented by decreased Netrin-1 gene expression were associated with delayed kidney graft function.

Dual kidney transplant: a single-center experience and review of the literature.

OBJECTIVES: Adult dual kidney transplant is a strategy to overcome the imbalance between limited nephron mass supplied from an older donor and a recipient with a metabolic request. MATERIALS AND METHODS: In our report, we review the literature and present our single-center experience. From June 2007 until July 2012, nine hundred twenty-eight single and seventeen dual kidney transplants from deceased donors were performed. RESULTS: The average donor was 71.5 ± 3.6 years of age with an average serum creatinine, creatinine clearance, and an average number of sclerotic glomeruli, 106.1 ± 44.2 µmol/L, 0.97 ± 0.37 mL/s, and 22.4 ± 14.2. Immediate graft function and acute rejection episodes were observed in 75% and 6% of patients. The overall patient survival rates at 1 and 2 years after transplant were 93%. The overall graft survival rates at 1 and 2 years were 88%. CONCLUSIONS: Previous studies and our single-center experience suggest that the dual transplant procedure may help improve results of kidney transplants from expanded criteria donors and extend the donor pool by using kidneys that would be discarded otherwise.

Identification of expanded-criteria donor kidney grafts at lower risk of delayed graft function.

BACKGROUND: Organ shortage leads to the increased use of expanded-criteria donor (ECD) kidneys, which contribute to a higher risk of delayed graft function (DGF) after transplantation. The aim of this study was to determine factors that may better predict the risk of DGF. METHODS: Histologic assessments of donor renal biopsy were used with other clinical variables to predict the risk of DGF after kidney transplantation. The total Banff score equaled the sum of interstitial fibrosis (CI), tubular atrophy, arteriolar hyaline thickening, fibrous intimal thickening (CV), and fraction of sclerotized glomeruli. RESULTS: In total, 126 of 344 patients developed DGF after kidney transplantation. The histologic score for CI, tubular atrophy, and CV and the total Banff score were increased in patients with DGF. Only CI and CV were independent predictors of DGF (P<0.01). A CIV score (CI+CV; odds ratio, 2.68; 95% confidence interval, 1.55-4.66; P<0.001) was superior to the combination of the total Banff score (odds ratio, 1.48; 95% confidence interval, 0.85-2.55; P=NS). A CIV score≥1, donor age more than 51 years, and anoxia donor brain injury were associated with the highest risk of DGF. A CIV<1 identified a subgroup of ECDs at a lower risk of DGF comparable with standard-criteria donors (29.3% vs. 28.4%). CONCLUSIONS: Composite CIV score better identifies ECD kidneys with a lower risk of developing DGF. Morphologic evaluation of ECD kidneys and donor characteristics may improve kidney allocation.

B-cell-related biomarkers of tolerance are up-regulated in rejection-free kidney transplant recipients.

BACKGROUND: Molecular signatures have recently been identified in operationally tolerant long-term kidney transplant patients; however, their expression in patients on immunosuppression remains unclear. METHODS: In this prospective study, the gene expression profiles of eight selected tolerance-associated genes (MS4A1, CD79B, TCL1A, TMEM176B, FOXP3, TOAG-1, MAN1A1, and TLR5) in the peripheral blood of 67 kidney transplant recipients at days 0, 7, 14, 21, 28, 60, 90, and at 6 and 12 months, and in graft biopsies were measured. Similarly, using flow cytometry, CD45CD19CD3 B-cell counts were evaluated in the follow-up. Expression patterns were compared among patients with biopsy-proven acute rejection, borderline changes, and in rejection-free patients. A generalized linear mixed model with gamma distribution for repeated measures adjusted for induction therapy was used for statistical analysis of longitudinal data and Kruskal-Wallis test for case biopsy data. RESULTS: Compared to patients with rejection, a significantly higher number of peripheral B cells were observed during follow-up in rejection-free patients and in patients with borderline changes. Gene expression patterns of MS4A1 (CD20), TCL1A, CD79B, TOAG-1, and FOXP3 genes were significantly higher in rejection-free patients as compared to rejection group with the highest differences during the first 3 months. In contrast, TMEM176B (TORID) was up-regulated in the rejection group. Similar trends were also observed between patients with borderline changes and acute rejection. Higher intragraft expression of TOAG-1 was observed in rejection-free patients. CONCLUSIONS: These observations suggest an association of B-cell signatures, seen also in drug-free tolerant patients, with controlled alloimmune response.