The impact of repeated subclinical acute rejection on the progression of chronic allograft nephropathy

Bortezomib for antibody-mediated rejection of kidney transplant in youth: Associations with donor-specific antibody

BACKGROUND

Antibody-mediated rejection is one of the most significant risk factors for allograft dysfunction and failure in children and adolescents with kidney transplants, yet optimal treatment remains unidentified. To date, there are mixed findings regarding the use of Bortezomib, a plasma cell apoptosis inducer, as an adjunct therapy in the treatment of antibody-mediated rejection.

METHODS

In a retrospective single center study, we reviewed the efficacy and tolerability of bortezomib as adjunct therapy for treatment-refractory antibody-mediated rejection.

RESULTS

Six patients with a median age of 14.6 years (range 6.9-20.1 years) received bortezomib at a mean of 71 months (range 15-83 months) post-kidney transplant. Four patients experienced decline in estimated glomerular filtration rate (eGFR) from 4% to 42%. One patient started bortezomib while on hemodialysis and did not recover graft function, and another patient progressed to hemodialysis 6 months after receiving bortezomib. Although DSA did not completely resolve, there was a statistically significant decline in DSA MFI pre and 12-months post-BZ (p = .012, paired t-test) for the subjects who were not on dialysis at the time of bortezomib. Chronic Allograft Damage Index (CADI) score of ≥3 was seen in all six subjects at their biopsy prior to therapy. No adverse effects were reported.

CONCLUSIONS

Bortezomib was well tolerated and resulted in improvements in MFI of DSA among four pediatric subjects without allograft failure, although no effects were observed on eGFR trajectory. Further studies are needed to clarify whether earlier intervention with bortezomib could prevent renal failure progression.

Optimizing the approach to monitoring allograft inflammation using serial urinary CXCL10/creatinine testing in pediatric kidney transplant recipients

BACKGROUND

Urinary CXCL10/creatinine (uCXCL10/Cr) is proposed as an effective biomarker of subclinical rejection in pediatric kidney transplant recipients. This study objective was to model implementation in the clinical setting.

METHODS

Banked urine samples at a single center were tested for uCXCL10/Cr to validate published thresholds for rejection diagnosis (>80% specificity). The positive predictive value (PPV) for rejection diagnosis for uCXCL10/Cr-indicated biopsy was modeled with first-positive versus two-test-positive approaches, with accounting for changes associated with urinary tract infection (UTI), BK and CMV viremia, and subsequent recovery.

RESULTS

Seventy patients aged 10.5 ± 5.6 years at transplant (60% male) had n = 726 urine samples with n = 236 associated biopsies (no rejection = 167, borderline = 51, and Banff 1A = 18). A threshold of 12 ng/mmol was validated for Banff 1A versus no-rejection diagnosis (AUC = 0.74, 95% CI = 0.57-0.92). The first-positive test approach (n = 69) did not resolve a clinical diagnosis in 38 cases (55%), whereas the two-test approach resolved a clinical diagnosis in the majority as BK (n = 17/60, 28%), CMV (n = 4/60, 7%), UTI (n = 8/60, 13%), clinical rejection (n = 5/60, 8%), and transient elevation (n = 18, 30%). In those without a resolved clinical diagnosis, PPV from biopsy for subclinical rejection is 24% and 71% (p = .017), for first-test versus two-test models, respectively. After rejection treatment, uCXCL10/Cr level changes were all concordant with change in it-score. Sustained uCXCL10/Cr after CMV and BK viremia resolution was associated with later acute rejection.

CONCLUSIONS

Urinary CXCL10/Cr reliably identifies kidney allograft inflammation. These data support a two-test approach to reliably exclude other clinically identifiable sources of inflammation, for kidney biopsy indication to rule out subclinical rejection.

Early progression of chronic histologic lesions in kidney transplant biopsies is not associated with HLA histocompatibility

BACKGROUND

Early progression of chronic histologic lesions in kidney allografts represents the main finding in graft attrition. The objective of this retrospective cohort study was to elucidate whether HLA histocompatibility is associated with progression of chronic histologic lesions in the first year post-transplant. Established associations of de novo donor-specific antibody (dnDSA) formation with HLA mismatch and microvascular inflammation (MVI) were calculated to allow for comparability with other study cohorts.

METHODS

We included 117 adult kidney transplant recipients, transplanted between 2016 and 2020 from predominantly deceased donors, who had surveillance biopsies at 3 and 12 months. Histologic lesion scores were assessed according to the Banff classification. HLA mismatch scores [i.e. eplet, predicted indirectly recognizable HLA-epitopes algorithm (PIRCHE-II), HLA epitope mismatch algorithm (HLA-EMMA), HLA whole antigen A/B/DR] were calculated for all transplant pairs. Formation of dnDSAs was quantified by single antigen beads.

RESULTS

More than one-third of patients exhibited a progression of chronic lesion scores by at least one Banff grade in tubular atrophy (ct), interstitial fibrosis (ci), arteriolar hyalinosis (ah) and inflammation in the area of interstitial fibrosis and tubular atrophy (i-IFTA) from the 3- to the 12-month biopsy. Multivariable proportional odds logistic regression models revealed no association of HLA mismatch scores with progression of histologic lesions, except for ah and especially HLA-EMMA DRB1 [odds ratio (OR) = 1.10, 95% confidence interval (CI) 1.03-1.18]. Furthermore, the established associations of dnDSA formation with HLA mismatch and MVI (OR = 5.31, 95% CI 1.19-22.57) could be confirmed in our cohort.

CONCLUSIONS

These data support the association of HLA mismatch and alloimmune response, while suggesting that other factors contribute to early progression of chronic histologic lesions.

Effects of Treating Subclinical Rejection 2 Weeks After Kidney Transplantation, as Determined by Analyzing 1-Year Histologic Outcomes

Subclinical rejection (SCR) is associated with chronic allograft nephropathy. Therefore, early detection and treatment of SCR through a protocol biopsy (PB) can reduce the incidence of pathologic changes. This study evaluates the impact of early detection and treatment of SCR using a routine PB 2 weeks after kidney transplantation (KT) by examining histologic outcomes 1 year later. We reviewed 624 KT recipients at the Samsung Medical Center between August 2012 and December 2018. Protocol biopsy was planned 2 weeks and 1 year after transplantation. We compared the histologic changes between the 2 biopsies. After a propensity score matching analysis, we divided the patients into 2 groups: the proven normal group (n = 256) and the rejection group (n = 96) at the PB taken 2 weeks post-transplant. The rejection group showed no significant difference from the normal group in the flow of graft function or the Kaplan-Meier curve for graft survival. In the histologic outcomes, the pathologic differences between the groups significantly improved between the 2 time points. Treating SCR through a PB 2 weeks after KT can contribute to the maintenance of graft function and improve histologic changes 1 year after KT.

Transitional B cell cytokines risk stratify early borderline rejection after renal transplantation

Borderline rejection (BL) in renal transplantation is associated with decreased allograft survival, yet many patients with BL maintain stable graft function. Identifying patients with early BL at risk for shortened allograft survival would allow for timely targeted therapeutic intervention aimed at improving outcomes. 851/1187 patients transplanted between 2013-18 underwent early biopsy (0-4 mos). 217/851 (25%) had BL and were compared to 387/851 without significant inflammation (NI). Serial surveillance and for-cause biopsies and seven-year follow-up were used to evaluate histological and clinical progression. To identify high-risk patients, we examined clinical/histological parameters using regression and non-linear dimensionality reduction (tSNE) and a biomarker based on peripheral blood transitional-1 B cell (T1B) IL-10/TNFα ratio. Compared to NI, early BL was associated with increased progression to late acute rejection (AR; 5-12 mos), premature interstitial fibrosis and tubular atrophy (IFTA) and decreased seven-year graft survival. However, decreased graft survival was limited to BL patients who progressed to late AR or IFTA, and was not influenced by treatment. Although tSNE clustered patients into groups based on clinical factors, the ability of these factors to risk stratify BL patients was modest. In contrast, a low T1B IL-10/TNFα ratio at 3 months identified BL patients at high risk for progression to AR (ROC AUC 0.87) and poor 7-yr graft survival (52% vs. 92%, p=0.003), while BL patients with a high ratio had similar graft survival to patients with NI (91%, p=NS). Thus, progressive early allograft inflammation manifested as BL that progresses to late AR in the first post-transplant year represents a high-risk clinical state for poor allograft outcomes. Such high-risk status can be predicted by the T1B IL-10/TNFα ratio before irreversible scarring sets in, thus allowing timely risk stratification.

The Protective Role of Protocol Biopsy for Allograft Kidney Maintenance in Kidney Transplantation

Many studies have reported that protocol biopsy (PB) may help preserve kidney function in kidney transplant recipients. Early detection and treatment of subclinical rejection may reduce the incidence of chronic antibody-mediated rejection and graft failure. However, no consensus has been reached regarding PB effectiveness, timing, and policy. This study aimed to evaluate the protective role of routine PB performed 2 weeks and 1 year after kidney transplantation. We reviewed 854 kidney transplant recipients at the Samsung Medical Center between July 2007 and August 2017, with PBs planned at 2 weeks and 1 year after transplantation. We compared the trends in graft function, chronic kidney disease (CKD) progression, new-onset CKD, infection, and patient and graft survival between the 504 patients who underwent PB and 350 who did not undergo PB. The PB group was again divided into 2 groups: the single PB group (n = 207) and the double PB group (n = 297). The PB group was significantly different from the no-PB group in terms of the trends in graft function (estimated glomerular filtration rate). The Kaplan-Meier curve showed that PB did not significantly improve graft or overall patient survival. However, in the multivariate Cox analysis, the double PB group had advantages in graft survival, CKD progression, and new-onset CKD. PB can play a protective role in the maintenance of kidney grafts in kidney transplant recipients.

Regulatory and transitional B cells: potential biomarkers and therapeutic targets in organ transplantation

PURPOSE OF THE REVIEW

Regulatory B cells (Bregs) play a prominent role in various disease settings. While progress has been hindered by the lack of a specific Breg marker, new findings highlight their role modulating the alloimmune response and promoting allograft survival.

RECENT FINDINGS

Herein, we focus on the recent advances in Breg biology and their role in transplantation. We review studies showing that T-cell immunoglobulin and mucin domain 1 (TIM-1) is an inclusive and functional Breg marker in mice that may have human relevance. We highlight the utility of the B cell interleukin-10/tumor necrosis factor-alpha (IL-10/TNFα) ratio in identifying underlying immunological reactivity and predicting clinical outcomes in kidney transplantation. This may identify patients requiring more immunosuppression and provide insight into potential therapeutic approaches that can modulate the Breg: B effector cell (Beff) balance.

SUMMARY

Emerging data support Bregs as potent modulators of immune responses in humans. Their ability to promote allograft survival must await development of approaches to expand Bregs in vitro/in vivo . The low IL-10/TNFα ratio reflecting decreased Breg/Beff balance, predicts acute rejection (AR) and poorer outcomes in renal transplantation. It remains to be determined whether this paradigm can be extended to other allografts and whether therapy aiming to correct the relative deficiency of Bregs will improve outcomes.

Proposed Definitions of T Cell-Mediated Rejection and Tubulointerstitial Inflammation as Clinical Trial Endpoints in Kidney Transplantation

The diagnosis of acute T cell-mediated rejection (aTCMR) after kidney transplantation has considerable relevance for research purposes. Its definition is primarily based on tubulointerstitial inflammation and has changed little over time; aTCMR is therefore a suitable parameter for longitudinal data comparisons. In addition, because aTCMR is managed with antirejection therapies that carry additional risks, anxieties, and costs, it is a clinically meaningful endpoint for studies. This paper reviews the history and classifications of TCMR and characterizes its potential role in clinical trials: a role that largely depends on the nature of the biopsy taken (indication vs protocol), the level of inflammation observed (e.g., borderline changes vs full TCMR), concomitant chronic lesions (chronic active TCMR), and the therapeutic intervention planned. There is ongoing variability—and ambiguity—in clinical monitoring and management of TCMR. More research, to investigate the clinical relevance of borderline changes (especially in protocol biopsies) and effective therapeutic strategies that improve graft survival rates with minimal patient morbidity, is urgently required. The present paper was developed from documentation produced by the European Society for Organ Transplantation (ESOT) as part of a Broad Scientific Advice request that ESOT submitted to the European Medicines Agency for discussion in 2020. This paper proposes to move toward refined definitions of aTCMR and borderline changes to be included as primary endpoints in clinical trials of kidney transplantation.

Banff classification from 1991 to 2019. A significant contribution to our understanding and reporting of allograft renal biopsies

The Banff schema of classification of renal allograft biopsies, first proposed at the meeting in Banff, Canada in 1991 has evolved through subsequent meetings held once in two years and is the internationally accepted scheme of classification which is consensual, current, validated and in clinical use. This review traces the evolution of the classification and our understanding of renal transplant pathology, with emphasis on alloimmune reactions. The proceedings of the meetings and the important studies which have shaped the classification are covered.

Advanced Tertiary Lymphoid Tissues in Protocol Biopsies are Associated with Progressive Graft Dysfunction in Kidney Transplant Recipients

BACKGROUND

Tertiary lymphoid tissues (TLTs) are ectopic lymphoid tissues found in chronically inflamed organs. Although studies have documented TLT formation in transplanted kidneys, the clinical relevance of these TLTs remains controversial. We examined the effects of TLTs on future graft function using our histologic TLT maturity stages and the association between TLTs and Banff pathologic scores. We also analyzed the risk factors for the development of TLTs.

METHODS

Serial protocol biopsy samples (0 hour, 1, 6, and 12 months) without rejection were retrospectively analyzed from 214 patients who underwent living donor kidney transplantation. TLTs were defined as lymphocyte aggregates with signs of proliferation and their stages were determined by the absence (stage I) or presence (stage II) of follicular dendritic cells.

RESULTS

Only 4% of patients exhibited TLTs at the 0-hour biopsy. Prevalence increased to almost 50% at the 1-month biopsy, and then slightly further for 12 months. The proportion of advanced stage II TLTs increased gradually, reaching 19% at the 12-month biopsy. Presence of stage II TLTs was associated with higher risk of renal function decline after transplantation compared with patients with no TLT or stage I TLTs. Stage II TLTs were associated with more severe tubulitis and interstitial fibrosis/tubular atrophy at 12 months and predicted poorer graft function independently from the degree of interstitial inflammation. Pretransplantation rituximab treatment dramatically attenuated the development of stage II TLTs.

CONCLUSIONS

TLTs are commonly found in clinically stable transplanted kidneys. Advanced stage II TLTs are associated with progressive graft dysfunction, independent of interstitial inflammation.

Evaluation of Cardiac Scan in Diagnosing Coronary-artery Disease

BACKGROUND

With the evaluation of focal epicardial coronary stenosis and non-obstructive atherosclerosis, the cardiac scans play a significant role in diagnosing coronary artery disease (CAD). Moreover, the advancements in the imaging techniques leading to improved risk assessment and timely therapies help in early diagnosis of CAD with greater accuracy.

AIMS

To evaluate the role of cardiac scan in diagnosing CAD.

METHODS

Recruited 100 individuals without any history of CAD that refers to the assessment of suspected angina, conducted the prospective study. Electrocardiogram (ECG) findings assisted in the evaluation of left bundle branch blockage, abnormalities of ST-segment, and pathological Q waves.

RESULTS

The results depicted negative N.M findings among 38 respondents; whereas, ischemia and myocardial infarctions were diagnosed in 26% and 19% of the respondents, respectively. The majority of the males (59) were positive in contrast to 37 females with positive results. Similarly, 24 respondents were presented with mild dilated left atria (LA), 37 respondents suffered from impaired relaxation pattern of left ventricular (LV) diastolic filling; while, 40 of the respondents had normal global LV systolic function.

CONCLUSION

The study results have concluded that non-invasive, low-risk, and cost-effective technique like ECG is an important beneficial advancement in the diagnosis of CAD.

Transitional B cell cytokines predict renal allograft outcomes

Early immunological biomarkers that predict rejection and chronic allograft loss are needed to inform preemptive therapy and improve long-term outcomes. Here, we prospectively examined the ratio of interleukin-10 (IL-10) to tumor necrosis factor-α (TNFα) produced by transitional-1 B cells (T1B) 3 months after transplantation as a predictive biomarker for clinical and subclinical renal allograft rejection and subsequent clinical course. In both Training (n = 162) and Internal Validation (n = 82) Sets, the T1B IL-10/TNFα ratio 3 months after transplantation predicted both clinical and subclinical rejection anytime in the first year. The biomarker also predicted subsequent late rejection with a lead time averaging 8 months. Among biomarker high-risk patients, 60% had early rejection, of which 48% recurred later in the first posttransplant year. Among high-risk patients without early rejection, 74% developed rejection later in the first year. In contrast, only 5% of low-risk patients had early and 5% late rejection. The biomarker also predicted rejection in an External Validation Set (n = 95) and in key patient subgroups, confirming generalizability. Biomarker high-risk patients exhibited progressively worse renal function and decreased 5-year graft survival compared to low-risk patients. Treatment of B cells with anti-TNFα in vitro augmented the IL-10/TNFα ratio, restored regulatory activity, and inhibited plasmablast differentiation. To conclude, the T1B IL-10/TNFα ratio was validated as a strong predictive biomarker of renal allograft outcomes and provides a rationale for preemptive therapeutic intervention with TNF blockade.

Yield and utility of surveillance kidney biopsies in pediatric kidney transplant recipients at various time points post-transplant

BACKGROUND

Due to a lack of consensus on SB for pediatric kidney transplant recipients, we evaluated the yield and clinical utility of SB findings at various time points post-transplant.

METHODS

Patients transplanted at a single institution between 2014 and 2020 with at least one SB at 1.5, 3, 6, 12, and 24 months post-transplant were included. Additional biopsies were done for indication (IB). TCMR was classified by Banff criteria (score ≥i1t1).

RESULTS

Forty-seven patients had 142 biopsies (SB = 113, IB = 29); 19 (40.4%) of whom experienced at least one TCMR episode in the first-year post-transplant. The greatest SB yield of any pathologic abnormality was at 6 months (57.1%; P < .001). Six months also had the highest yield for TCMR (42.9%), compared with 3.3%, 20.8%, 15.0%, and 9.1% at 1.5, 3, 12 months, and 24 months, respectively (P = .003). SB instigated intensification of immunosuppression (28.3% cases), reduction of immunosuppression (2.7% cases), and other non-immunosuppressant changes (1.8% cases). The 6-month SB led to the greatest number of changes in management (53.6%), compared with 1.5, 3, 12, and 24 months (13.3, 20.8, 25.0, and 36.4%, respectively; P = .012). There were no major biopsy-related complications.

CONCLUSIONS

SBs identify an important burden of subclinical rejection and other pathology leading to changes in clinical management. The greatest yield was at 6 months, whereas the least utility was at the 1.5 months. Selection of SB timing may be tailored such that the optimal yield is balanced against the procedural risk.

Kidney Allograft Fibrosis: Diagnostic and Therapeutic Strategies

Interstitial fibrosis with tubule atrophy (IF/TA) is the response to virtually any sustained kidney injury and correlates inversely with kidney function and allograft survival. IF/TA is driven by various pathways that include hypoxia, renin-angiotensin-aldosterone system, transforming growth factor (TGF)-β signaling, cellular rejection, inflammation and others. In this review we will focus on key pathways in the progress of renal fibrosis, diagnosis and therapy of allograft fibrosis. This review discusses the role and origin of myofibroblasts as matrix producing cells and therapeutic targets in renal fibrosis with a particular focus on renal allografts. We summarize current trends to use multi-omic approaches to identify new biomarkers for IF/TA detection and to predict allograft survival. Furthermore, we review current imaging strategies that might help to identify and follow-up IF/TA complementary or as alternative to invasive biopsies. We further discuss current clinical trials and therapeutic strategies to treat kidney fibrosis.Supplemental Visual Abstract; http://links.lww.com/TP/C141.

B Cell Activating Factor (BAFF) Is Required for the Development of Intra-Renal Tertiary Lymphoid Organs in Experimental Kidney Transplantation in Rats

Intra-renal tertiary lymphoid organs (TLOs) are associated with worsened outcome in kidney transplantation (Ktx). We used an anti-BAFF (B cell activating factor) intervention to investigate whether BAFF is required for TLO formation in a full MHC-mismatch Ktx model in rats. Rats received either therapeutic immunosuppression (no rejection, NR) or subtherapeutic immunosuppression (chronic rejection, CR) and were sacrificed on d56. One group additionally received an anti-BAFF antibody (CR + AB). Intra-renal T (CD3⁺) and B (CD20⁺) cells, their proliferation (Ki67⁺), and IgG⁺ plasma cells were analyzed by immunofluorescence microscopy. Formation of T and B cell zones and TLOs was assessed. Intra-renal expression of TLO-promoting factors, molecules of T:B crosstalk, and B cell differentiation was analyzed by qPCR. Intra-renal B and T cell zones and TLOs were detected in CR and were associated with elevated intra-renal mRNA expression of TLO-promoting factors, including CXCL13, CCL19, lymphotoxin-β, and BAFF. Intra-renal plasma cells were also elevated in CR. Anti-BAFF treatment significantly decreased intra-renal B cell zones and TLO, as well as intra-renal B cell-derived TLO-promoting factors and B cell differentiation markers. We conclude that BAFF-dependent intra-renal B cells promote TLO formation and advance local adaptive alloimmune responses in chronic rejection.

Kidney Graft Surveillance Biopsy Utilization and Trends: Results From a Survey of High-Volume Transplant Centers

An e-mail-based market research survey focused on high-volume US adult transplant centers was developed and implemented to assess surveillance based on United Network for Organ Sharing/Scientific Registry of Transplant Recipients data: 51 to 100 transplants, 101 to 200 transplants, and more than 200 transplants. Eighty-three centers responded to the survey. Respondent centers represented 13,837/21,167 (65%) of the total kidney transplants in 2018. In total, 38/83 (46%) centers reported the use of surveillance biopsies-20 centers in all patients and 18 in select patients. Surveillance biopsies were performed in 37% (7/19) of centers performing 51 to 100 transplants annually, in 44% (15/34) doing 101 to 200 transplants, and in 53% (16/30) of centers doing more than 200 transplants. Of the 20 centers doing surveillance biopsies in all patients, 17/20 (85%) perform more than 100 annual transplants, and 3/20 (15%) perform less than 100 annual transplants. Of the 45 centers not currently doing surveillance biopsies, 13 (29%) used surveillance biopsies in the past; discontinuation was primarily due to patient inconvenience, adverse events, and cost. Using survey percentages, it is estimated that surveillance biopsies are performed in approximately 34% of kidney transplant recipients and that 74% of all surveillance biopsies occur in centers performing more than 100 kidney transplants per year.

Early subclinical tubulitis and interstitial inflammation in kidney transplantation have adverse clinical implications

This prospective observational cohort study compared the impact of subclinical tubulitis with or without interstitial inflammation to interstitial inflammation alone and to no inflammation in early post kidney transplant biopsies. A study cohort of 415 patients (living and deceased donor recipients) was divided into three groups on the basis of their three-month biopsy: 149 patients with No Inflammation (NI), 83 patients with Isolated Interstitial Inflammation (IIF), and 183 patients with Tubulitis [(with or without interstitial inflammation) (TIF) but not meeting criteria for Banff IA]. TIF was further divided into 56 patients with tubulitis without interstitial inflammation (TIF0) and 127 patients with tubulitis alongside interstitial inflammation (TIF1). TIF was significantly associated with higher incidence of subsequent T-cell mediated rejection (clinical or subclinical) at one year compared to IIF (31% vs 15%) and NI (31% vs 17%). Chronicity on one-year biopsy was significantly higher in TIF compared to IIF (22% vs 11%) and NI (22% vs 7%). De novo donor-specific antibody development was significantly higher in TIF compared to NI (6% vs 0.7%). Tubulitis subgroups (TIF0 and TIF1) revealed comparable effects on de novo donor-specific antibody and interstitial fibrosis/tubular atrophy development. However, tubulitis with interstitial inflammation had a significantly higher incidence of subsequent rejection and posed an increased hazard for the composite end point (subsequent acute rejection and death censored graft loss) compared to other groups [adjusted hazard 2.1 (95% confidence interval 1.2-3.5)]. Thus, subclinical tubulitis is a marker of adverse immunological events, but tubulitis with interstitial inflammation has a worse prognosis. Hence, the Banff 1997 (TIF1) and Banff 2005 classifications (TIF) for borderline change may have different implications.

Transcriptome Analysis in Renal Transplant Biopsies Not Fulfilling Rejection Criteria

The clinical significance of renal transplant biopsies displaying borderline changes suspicious for T-cell mediated rejection (TCMR) or interstitial fibrosis and tubular atrophy (IFTA) with interstitial inflammation has not been well defined. Molecular profiling to evaluate renal transplant biopsies using microarrays has been shown to be an objective measurement that adds precision to conventional histology. We review the contribution of transcriptomic analysis in surveillance and indication biopsies with borderline changes and IFTA associated with variable degrees of inflammation. Transcriptome analysis applied to biopsies with borderline changes allows to distinguish patients with rejection from those in whom mild inflammation mainly represents a response to injury. Biopsies with IFTA and inflammation occurring in unscarred tissue display a molecular pattern similar to TCMR while biopsies with IFTA and inflammation in scarred tissue, apart from T-cell activation, also express B cell, immunoglobulin and mast cell-related genes. Additionally, patients at risk for IFTA progression can be identified by genes mainly reflecting fibroblast dysregulation and immune activation. At present, it is not well established whether the expression of rejection gene transcripts in patients with fibrosis and inflammation is the consequence of an alloimmune response, tissue damage or a combination of both.

A urine score for noninvasive accurate diagnosis and prediction of kidney transplant rejection

Accurate and noninvasive monitoring of renal allograft posttransplant is essential for early detection of acute rejection (AR) and to affect the long-term survival of the transplant. We present the development and validation of a noninvasive, spot urine-based diagnostic assay based on measurements of six urinary DNA, protein, and metabolic biomarkers. The performance of this assay for detecting kidney injury in both native kidneys and renal allografts is presented on a cohort of 601 distinct urine samples. The urinary composite score enables diagnosis of AR, with a receiver-operator characteristic curve area under the curve of 0.99 and an accuracy of 96%. In addition, we demonstrate the clinical utility of this assay for predicting AR before a rise in the serum creatinine, enabling earlier detection of rejection than currently possible by standard of care tests. This noninvasive, sensitive, and quantitative approach is a robust and informative method for the rapid and routine monitoring of renal allografts.

Pediatric Kidney Transplantation in Perú: A Single-Center Initial Experience

BACKGROUND

Pediatric kidney transplantation (PKTx) is the preferred therapy for children with end-stage renal disease (ESRD) worldwide. Regrettably, in Perú, access to PKTx is extremely difficult due to recipient/donor socio-economic status, health care structure and especially, scarcity of organs. Our center (the only pediatric institute in the country) has recently started a PKTx program with good midterm results. The aim of this study was to present our outcomes.

METHODS

Retrospective analysis of prospectively collected data between December 2017 and August 2019. Fourteen PKTx (< 18 years old) were achieved. As per our protocol: pre-implantation/protocol biopsies, antibody assessment (T/B cell flow cytometric plus HLA testing applying polymerase chain reaction-based technology), triple immunosuppression (tacrolimus, mycophenolate mofetil, steroids) and induction therapy was performed in every case.

RESULTS

The recipient's mean age at the time of PKTx was 14.14 ± 2.62, 8/14 (57.14%) were male, 50% developed ESRD due to undetermined etiology, 11/14 (78.57%) received a deceased donor allograft, and 9/14 (64.28%) required induction with thymoglobulin. Postoperative complications included: delayed graft function (1/14, 7.14%), 1 (7.14%) developed gross hematuria associated with allograft disfunction post-protocol allograft biopsy that was managed conservatively and 1 recipient (7.14%) developed grade II oligoastrocytoma, at 10 months post PKTx.

CONCLUSIONS

PKTx is the best therapeutic option for children with ESRD. Our group demonstrated that even in countries with limited resources like Perú, good midterm results can be achieved. Emphasis should be given to improve access to transplantation especially in the setting of pediatric recipients.

A Novel, Dose-Adjusted Tacrolimus Trough-Concentration Model for Predicting and Estimating Variance After Kidney Transplantation

Background and Objective

Given that a high intrapatient variability (IPV) of tacrolimus whole blood concentration increases the risk for a poor kidney transplant outcome, some experts advocate routine IPV monitoring for detection of high-risk patients. However, attempts to estimate the variance of tacrolimus trough concentrations (TTC) are limited by the need for patients to receive a fixed dose over time and/or the use of linear statistical models. A goal of this study is to overcome the current limitations through the novel application of statistical methodology generalizing the relationship between TTC and dose through the use of nonparametric functional regression modeling.

Methods

With TTC as a response and dose as a covariate, the model employs an unknown bivariate function, allowing for the potentially complex, nonlinear relationship between the two parameters. A dose-adjusted variance of TTC is then derived based on standard functional principal component analysis (FPCA). To assess the model, it was compared against an FPCA-based model and linear mixed-effects models using prediction error, bias, and coverage probabilities for simulated data as well as phase III data from the Astellas new drug application studies for extended-release tacrolimus.

Results

Our numerical investigation indicates that the new model better predicts dose-adjusted TTCs compared with the prediction of linear mixed effects models. Estimated coverage probabilities also indicate that the new model accurately accounts for the variance of TTC during the periods of large fluctuation in dose, whereas the linear mixed effects model consistently underestimates the coverage probabilities because of the inaccurate characterization of TTC fluctuation.

Conclusion

This is the first known application of a functional regression model to assess complex relationships between TTC and dose in a real clinical setting. This new method has applicability in future clinical trials including real-world data sets due to flexibility of the nonparametric modeling approach.

Electronic supplementary material

The online version of this article (10.1007/s40268-019-0271-2) contains supplementary material, which is available to authorized users.

Discovery and cross-validation of peripheral blood and renal biopsy gene expression signatures from ethnically diverse kidney transplant populations

We determined peripheral blood (PB) and biopsy (Bx) RNA expression signatures in a Brazilian and US cohort of kidney transplant patients. Phenotypes assigned by precise histology were: acute rejection (AR), interstitial fibrosis/tubular atrophy/chronic rejection (CR), excellent functioning transplants (TX), and glomerulonephritis recurrence (GN). Samples were analyzed on microarrays and profiles from each cohort were cross-validated on the other cohort with similar phenotypes. We discovered signatures for each tissue: (1) AR vs TX, (2) CR vs TX, and (3) GN vs TX using the Random Forests algorithm. We validated biopsies signatures of AR vs TX (area under the curve [AUC] 0.97) and CR vs TX (AUC 0.87). We also validated both PB and Bx signatures of AR vs TX and CR vs TX with varying degrees of accuracy. Several biological pathways were shared between AR and CR, suggesting similar rejection mechanisms in these 2 clinical phenotypes. Thus, we identified gene expression signatures for AR and CR in transplant patients and validated them in independent cohorts of significantly different racial/ethnic backgrounds. These results reveal that there are strong unifying immune mechanisms driving transplant diseases and identified in the signatures discovered in each cohort, suggesting that molecular diagnostics across populations are feasible despite ethnic and environmental differences.

Urinary Human Epididymis Secretory Protein 4 as a Useful Biomarker for Subclinical Acute Rejection Three Months after Kidney Transplantation

Kidney transplantation is the treatment of choice for patients with advanced chronic kidney disease (CKD) and end stage renal disease (ESRD). However, acute rejection (AR) is a common complication in kidney transplantation and is associated with reduced graft survival. Current diagnosis of AR relies mainly on clinical monitoring including serum creatinine, proteinuria, and confirmation by histopathologic assessment in the biopsy specimen of graft kidney. Although an early protocol biopsy is indispensable for depicting the severity of pathologic lesions in subclinical acute rejection (subAR), it is not acceptable in some cases and cannot be performed because of its invasive nature. Therefore, we examined the detection of noninvasive biomarkers that are closely related to the pathology of subAR in protocol biopsies three months after kidney transplantation. In this study, the urinary level of microtubule-associated protein 1 light chain 3 (LC3), monocyte chemotactic protein-1 (MCP-1), liver-type fatty acid-binding protein (L-FABP), neutrophil gelatinase-associated lipocalin (NGAL), and human epididymis secretory protein 4 (HE4) were measured three months after kidney transplantation. Urine samples of 80 patients undergoing kidney transplantation between August 2014 to September 2016, were prospectively collected after three months. SubAR was observed in 11 patients (13.8%) in protocol biopsy. The urinary levels of LC3, MCP-1, NGAL, and HE4 were significantly higher in patients with subAR than in those without, while those of L-FABP did not differ between the two groups. Multivariate regression models, receiver-operating characteristics (ROC), and areas under ROC curves (AUC) were used to identify predicted values of subAR. Urinary HE4 levels were able to better identify subAR (AUC = 0.808) than the other four urinary biomarkers. In conclusion, urinary HE4 is increased in kidney transplant recipients of subAR three months after kidney transplantation, suggesting that HE4 has the potential to be used as a novel clinical biomarker for predicting subAR.

A Peripheral Blood Gene Expression Signature to Diagnose Subclinical Acute Rejection

BACKGROUND

In kidney transplant recipients, surveillance biopsies can reveal, despite stable graft function, histologic features of acute rejection and borderline changes that are associated with undesirable graft outcomes. Noninvasive biomarkers of subclinical acute rejection are needed to avoid the risks and costs associated with repeated biopsies.

METHODS

We examined subclinical histologic and functional changes in kidney transplant recipients from the prospective Genomics of Chronic Allograft Rejection (GoCAR) study who underwent surveillance biopsies over 2 years, identifying those with subclinical or borderline acute cellular rejection (ACR) at 3 months (ACR-3) post-transplant. We performed RNA sequencing on whole blood collected from 88 individuals at the time of 3-month surveillance biopsy to identify transcripts associated with ACR-3, developed a novel sequencing-based targeted expression assay, and validated this gene signature in an independent cohort.

RESULTS

Study participants with ACR-3 had significantly higher risk than those without ACR-3 of subsequent clinical acute rejection at 12 and 24 months, faster decline in graft function, and decreased graft survival in adjusted Cox analysis. We identified a 17-gene signature in peripheral blood that accurately diagnosed ACR-3, and validated it using microarray expression profiles of blood samples from 65 transplant recipients in the GoCAR cohort and three public microarray datasets. In an independent cohort of 110 transplant recipients, tests of the targeted expression assay on the basis of the 17-gene set showed that it identified individuals at higher risk of ongoing acute rejection and future graft loss.

CONCLUSIONS

Our targeted expression assay enabled noninvasive diagnosis of subclinical acute rejection and inflammation in the graft and may represent a useful tool to risk-stratify kidney transplant recipients.

Multicentre randomised controlled trial protocol of urine CXCL10 monitoring strategy in kidney transplant recipients

INTRODUCTION

Subclinical inflammation is an important predictor of death-censored graft loss, and its treatment has been shown to improve graft outcomes. Urine CXCL10 outperforms standard post-transplant surveillance in observational studies, by detecting subclinical rejection and early clinical rejection before graft functional decline in kidney transplant recipients.

METHODS AND ANALYSIS

This is a phase ii/iii multicentre, international randomised controlled parallel group trial to determine if the early treatment of rejection, as detected by urine CXCL10, will improve kidney allograft outcomes. Incident adult kidney transplant patients (n~420) will be enrolled to undergo routine urine CXCL10 monitoring postkidney transplant. Patients at high risk of rejection, defined as confirmed elevated urine CXCL10 level, will be randomised 1:1 stratified by centre (n=250). The intervention arm (n=125) will undergo a study biopsy to check for subclinical rejection and biopsy-proven rejection will be treated per protocol. The control arm (n=125) will undergo routine post-transplant monitoring. The primary outcome at 12 months is a composite of death-censored graft loss, clinical biopsy-proven acute rejection, de novo donor-specific antibody, inflammation in areas of interstitial fibrosis and tubular atrophy (Banff i-IFTA, chronic active T-cell mediated rejection) and subclinical tubulitis on 12-month surveillance biopsy. The secondary outcomes include decline of graft function, microvascular inflammation at 12 months, development of IFTA at 12 months, days from transplantation to clinical biopsy-proven rejection, albuminuria, EuroQol five-dimension five-level instrument, cost-effectiveness analysis of the urine CXCL10 monitoring strategy and the urine CXCL10 kinetics in response to rejection therapy.

ETHICS AND DISSEMINATION

The study has been approved by the University of Manitoba Health Research Ethics Board (HS20861, B2017:076) and the local research ethics boards of participating centres. Recruitment commenced in March 2018 and results are expected to be published in 2023. De-identified data may be shared with other researchers according to international guidelines (International Committee of Medical Journal Editors [ICJME]).

TRIAL REGISTRATION NUMBER

NCT03206801; Pre-results.

Benefits and risks of protocol biopsies in pediatric renal transplantation

Protocol biopsies are defined as sampling of allograft tissue at predetermined times regardless of function. This procedure can be justified due to the lack of non-invasive methods to reliably diagnose rejection (acute or subclinical). Changes in creatinine are not seen with subclinical rejection or early acute rejection and do not always correlate with efficacy of treatment. Parents and providers are still hesitant to pursue protocol biopsy due to the potential complications and lack of definitive evidence of a benefit from doing this procedure. Importantly, the rate of transplant renal biopsy complications requiring additional intervention is low. It is unclear if detection and treatment of subclinical rejection detected on protocol biopsy will lead to improved graft survival. Our goal is to review the literature on this topic and share some of the experience in our center. Definition, indications, and complications of diagnostic transplant renal biopsies are not included in this review.

Urine Angiotensin II Signature Proteins as Markers of Fibrosis in Kidney Transplant Recipients

BACKGROUND

Interstitial fibrosis/tubular atrophy (IFTA) is an important cause of kidney allograft loss; however, noninvasive markers to identify IFTA or guide antifibrotic therapy are lacking. Using angiotensin II (AngII) as the prototypical inducer of IFTA, we previously identified 83 AngII-regulated proteins in vitro. We developed mass spectrometry-based assays for quantification of 6 AngII signature proteins (bone marrow stromal cell antigen 1, glutamine synthetase [GLNA], laminin subunit beta-2, lysophospholipase I, ras homolog family member B, and thrombospondin-I [TSP1]) and hypothesized that their urine excretion will correlate with IFTA in kidney transplant patients.

METHODS

Urine excretion of 6 AngII-regulated proteins was quantified using selected reaction monitoring and normalized by urine creatinine. Immunohistochemistry was used to assess protein expression of TSP1 and GLNA in kidney biopsies.

RESULTS

The urine excretion rates of AngII-regulated proteins were found to be increased in 15 kidney transplant recipients with IFTA compared with 20 matched controls with no IFTA (mean log2[fmol/µmol of creatinine], bone marrow stromal cell antigen 1: 3.8 versus 3.0, P = 0.03; GLNA: 1.2 versus -0.4, P = 0.03; laminin subunit beta-2: 6.1 versus 5.4, P = 0.06; lysophospholipase I: 2.1 versus 0.6, P = 0.002; ras homolog family member B: 1.2 versus -0.1, P = 0.006; TSP1_GGV: 2.5 versus 1.9; P = 0.15; and TSP1_TIV: 2.0 versus 0.6, P = 0.0006). Receiver operating characteristic curve analysis demonstrated an area under the curve = 0.86 for the ability of urine AngII signature proteins to discriminate IFTA from controls. Urine excretion of AngII signature proteins correlated strongly with chronic IFTA and total inflammation. In a separate cohort of 19 kidney transplant recipients, the urine excretion of these 6 proteins was significantly lower following therapy with AngII inhibitors (P < 0.05).

CONCLUSIONS

AngII-regulated proteins may represent markers of IFTA and guide antifibrotic therapies.

Protocol biopsies in pediatric renal transplantation: a precious tool for clinical management

BACKGROUND

Kidney transplantation is the best treatment for children with end-stage kidney disease. Early results have improved, but late graft loss is still a major problem. Non-invasive, fully reliable early biomarkers of acute rejection are currently missing.

METHODS

Our aim was to evaluate the efficacy of protocol biopsies (PBXs) in a pediatric population. During 11 years, 209 renal transplantations were performed in 204 pediatric patients. Biopsies were performed 3-6 months, 1 year, and 5 years after transplantation. Procedure-related complications were systematically looked for by means of ultrasound scans.

RESULTS

Unexpected findings (mainly subclinical rejections) requiring therapeutic intervention were found in 19.3% biopsies performed at 3-6 months, in 18.4% in 12-month biopsies and in none of those performed after 5 years. The 13.6% patients at 12-month biopsies and 23.6% at 5-year biopsies showed calcineurin inhibitor (CNI) toxicity. Interstitial fibrosis and tubular atrophy (IF/TA) was found in 17.6 and 83.6% of patients at 12-month and 5-year biopsies, respectively. Complications of the PBX were infrequent. Five-year estimated glomerular filtration rate (GFR) was not significantly different in patients who received treatment for any cause and patients with normal histology.

CONCLUSIONS

Although we do not have a control group, we may speculate that patients who received treatment returned to a "standard" condition possibly improving final outcome. Protocol biopsies are a powerful diagnostic tool for the management of pediatric renal transplant recipients. In view of the lack of evidence that biopsies taken 5 years after transplantation lead to any therapeutic change, their use should be reconsidered.

Evolution of renal function and urinary biomarker indicators of inflammation on serial kidney biopsies in pediatric kidney transplant recipients with and without rejection

Urinary CXCL10 and metabolites are biomarkers independently associated with TCMR. We sought to test whether these biomarkers fluctuate in association with histological severity of TCMR over short time frames. Forty-nine pairs of renal biopsies obtained 1-3 months apart from 40 pediatric renal transplant recipients were each scored for TCMR acuity score (i + t; Banff criteria). Urinary CXCL10:Cr and TCMR MDS were obtained at each biopsy and were tested for association with changes between biopsies in acuity, estimated GFR (ΔeGFR), and 12-month ΔeGFR. Sequential biopsies were obtained 1.8 ± 0.8 months apart. Biopsy 1 was usually obtained under protocol (75%), and 62% percent had evidence of TCMR. Using each biopsy pair for comparison, ΔeGFR did not predict change in acuity. By contrast, change in acuity was significantly correlated with change in urinary CXCL10:Cr (ρ 0.45, P = .003) and MDS (ρ 0.29, P = .04) between biopsies. The 12-month ΔeGFR was not predicted by TCMR acuity or CXCL10:Cr at Biopsy 2; however, an inverse correlation was seen with urinary MDS (ρ -0.35; P = .02). Changes in eGFR correlate poorly with evolving TCMR acuity on histology. Urinary biomarkers may be superior for non-invasive monitoring of rejection, including histological response to therapy, and may be prognostic for medium-term function.

Novel non-invasive biomarkers diagnostic of acute rejection in renal transplant recipients: A systematic review

BACKGROUND AND OBJECTIVES

Acute rejection is a significant complication detrimental to kidney transplant function. Current accepted means of diagnosis is percutaneous renal biopsy, a costly and invasive procedure. There is an urgent need to detect and validate non-invasive biomarkers capable of replacing the biopsy.

DESIGN, SETTING, PARTICIPANTS AND MEASUREMENTS

Comprehensive literature searches of Medline, EMBASE and Cochrane Central Register of Controlled Trials databases were performed. Eligible studies were included as per inclusion criteria and assessed for quality using the GRADE quality of evidence tool. Outcomes evaluated included biomarker diagnostic performance, number of patients/samples, mean age and gender ratio, immunosuppression regime, in addition to clinical applications of the biomarker(s) tested. PRISMA guidelines were followed. Where possible, statistical analysis of comparative performance data was performed.

RESULTS

23 studies were included in this review, including 19 adult, 3 paediatric and 1 mixed studies. A total of 2858 participants and 50 candidate non-invasive tests were identified. Sensitivity, specificity and area under the curve performance values ranged 36%-100%, 30%-100% and 0.55-0.98, respectively.

CONCLUSIONS

Although larger, more robust multi-centre validation studies are needed before non-invasive biomarkers can replace the biopsy, numerous candidate tests have demonstrated significant promise for various facets of postoperative management. Suggested uses include: ruling out patients with a low risk of acute rejection to avoid the need for biopsy, non-invasive testing where the biopsy is contraindicated and a prompt diagnosis is needed, and integration into a serial blood monitoring protocol in conjunction with serum creatinine.

Intraoperative blood transfusion in pediatric patients undergoing renal transplant-Effect of renal graft size

In pediatric RT, donor allograft size often exceeds the expected recipient norms, especially in younger recipients. An "oversize" graft might not only present a technical- and space-related challenge, but may possibly lead to increased demands in perioperative volume requirements due to the disparity between donor and recipient in renal blood flow. We evaluated transfusion practices at a single tertiary institution with special consideration of kidney graft size, hypothesizing that oversize graft kidneys might lead to a quantifiable increased need of blood transfusion in smaller recipients. Retrospective analysis of all patients who underwent pediatric RT from January 2004 to June 2014 at a tertiary pediatric centre was performed. Variables analyzed included patient age, weight, pre- and postoperative Hb concentration, graft size, EBL, amount of intraoperative blood transfusion, and preoperative use of erythropoietin. Based on graft size in relation to patient's age, a SMR and an OvR were identified. A subcohort of age-matched pairs was used to allow for comparison between groups. We calculated the expected procedure- and transfusion-induced changes in Hb and compared these changes to the observed difference in pre- vs postoperative Hb to assess the influence of graft size on transfusion requirements. RT was performed in 188 pediatric recipients during the study period. In the matched cohort, percentage of transfused patients during transplantation in the OvR group was more than double compared with SMR (89% vs 39%, P < .001); similarly, the median number of transfused PRBC units in OvR was 1, while the median of SMR did not receive transfusion (P < .001). The difference between expected (calculated) and observed change in Hb was significantly higher in OvR with a median of 1.9 g/dL compared with SMR with a median of 1.0 g/dL (P = .026). Correspondingly, the calculated median volume taken up by a regular size kidney was significantly higher with 213 mL compared with 313 mL (P = .031) taken up by an oversize graft kidney. Median estimated intraoperative blood loss was significantly higher in OvR than in SMR (6.9 mL/kg, vs 5.3 mL/kg, respectively; P = .04). Median postoperative Hb was similar among groups (10.4 g/dL vs 10.6 g/dL for SMR vs OvR, respectively). Transplantation of an oversized kidney in pediatric RT recipients is associated with a quantifiable higher need for blood transfusion. This may be caused by a higher intraoperative EBL and/or greater blood volume sequestered by the larger renal allograft and requires further evaluation.

The utility of surveillance biopsies in pediatric kidney transplantation

BACKGROUND

Surveillance biopsies (SBs) are performed in some pediatric kidney transplant programs, based on data obtained in earlier immunosuppressive eras that the treatment of subclinical acute rejection results in better graft survival. The benefit of SBs for patients on modern immunosuppression regimens is unclear. We have therefore evaluated the clinical utility of SBs in a population of children receiving a kidney transplant.

METHODS

We have performed SBs at 3, 6 and 12 months post-transplantation as standard of care at our institution since 2013 in patients on a regimen of rabbit anti-thymocyte globulin, tacrolimus, mycophenolate and rapid steroid taper (RST; steroids maintained in some exceptions). We reviewed pathology reports of 82 SBs from 34 transplants in 34 children for all abnormal findings and adequacy of specimens. Clinical records were reviewed for changes in management resulting from SB findings and for significant procedure complications.

RESULTS

Of the 82 biopsies, 41 (50%) had abnormal findings separate from fibrosis, including five Banff Grade I rejections, ten borderline rejections, six calcineurin-inhibitor nephrotoxicity, four BK-virus nephropathy, five recurrent disease and three acute pyelonephritis. Moderate or more fibrosis was present in nine of the 82 (11%) biopsies. Management changes due to SB findings occurred in nine cases (11.0%). The proportion of abnormal findings or management changes did not differ between the RST or steroid-based groups. Patients performing clean intermittent catheterization showed inflammatory changes often read as rejection, but were managed differently. Three biopsies were deemed inadequate. No significant complications occurred.

CONCLUSIONS

A high percentage of the SBs performed under modern immunosuppression showed abnormal findings even when fibrosis was excluded. However, management changes due to the SB findings were less frequent, although they occurred in a clinically meaningful percentage of cases. Complications or inadequate specimens were rare.

The causes, significance and consequences of inflammatory fibrosis in kidney transplantation: The Banff i-IFTA lesion

Inflammation within areas of interstitial fibrosis and tubular atrophy (i-IFTA) is associated with adverse outcomes in kidney transplantation. We evaluated i-IFTA in 429 indication- and 2052 protocol-driven biopsy samples from a longitudinal cohort of 362 kidney-pancreas recipients to determine its prevalence, time course, and relationships with T cell-mediated rejection (TCMR), immunosuppression, and outcome. Sequential histology demonstrated that i-IFTA was preceded by cellular interstitial inflammation and followed by IF/TA. The prevalence and intensity of i-IFTA increased with developing chronic fibrosis and correlated with inflammation, tubulitis, and immunosuppression era (P < .001). Tacrolimus era-based immunosuppression was associated with reduced histologic inflammation in unscarred and scarred i-IFTA compartments, ameliorated progression of IF, and increased conversion to inactive IF/TA (compared with cyclosporine era, P < .001). Prior acute (including borderline) TCMR and subclinical TCMR were followed by greater 1-year i-IFTA, remaining predictive by multivariate analysis and independent of humoral markers. One-year i-IFTA was associated with accelerated IF/TA, arterial fibrointimal hyperplasia, and chronic glomerulopathy and with reduced renal function (P < .001 versus no i-IFTA). In summary, i-IFTA is the histologic consequence of active T cell-mediated alloimmunity, representing the interface between inflammation and tubular injury with fibrotic healing. Uncontrolled i-IFTA is associated with adverse structural and functional outcomes.

Renal allograft rejection, lymphocyte infiltration, and de novo donor-specific antibodies in a novel model of non-adherence to immunosuppressive therapy

Background

Non-adherence has been associated with reduced graft survival. The aim of this study was to investigate the immunological mechanisms underlying chronic renal allograft rejection using a model of non-adherence to immunosuppressive therapy. We used a MHC (major histocompatibility complex) -mismatched rat model of renal transplantation (Brown Norway to Lewis), in which rats received daily oral cyclosporine A. In analogy to non-adherence to therapy, one group received cyclosporine A on alternating days only. Rejection was histologically graded according to the Banff classification. We quantified fibrosis by trichrome staining and intra-graft infiltration of T cells, B cells, and monocytes/macrophages by immunohistochemistry. The distribution of B lymphocytes was assessed using immunofluorescence microscopy. Intra-graft chemokine, chemokine receptor, BAFF (B cell activating factor belonging to the TNF family), and immunoglobulin G transcription levels were analysed by RT-PCR. Finally, we evaluated donor-specific antibodies (DSA) and complement-dependent cytotoxicity using flow cytometry.

Results

After 28 days, cellular rejection occurred during non-adherence in 5/6 animals, mixed with humoral rejection in 3/6 animals. After non-adherence, the number of T lymphocytes were elevated compared to daily immunosuppression. Monocyte numbers declined over time. Accordingly, lymphocyte chemokine transcription was significantly increased in the graft, as was the transcription of BAFF, BAFF receptor, and Immunoglobulin G. Donor specific antibodies were elevated in non-adherence, but did not induce complement-dependent cytotoxicity.

Conclusion

Cellular and humoral rejection, lymphocyte infiltration, and de novo DSA are induced in this model of non-adherence.

Electronic supplementary material

The online version of this article (doi: 10.1186/s12865-017-0236-6) contains supplementary material, which is available to authorized users.

Utility of Serial Protocol Biopsies Performed After 1 Year in Predicting Long-Term Kidney Allograft Function According to Histologic Phenotype

OBJECTIVES

Prognostic implications of early protocol biopsies have been studied; however, the value of late protocol biopsy in predicting graft outcome has not been well defined. Here, we compared the effects of early and late protocol biopsy histologic findings in stable kidney allografts and aimed to understand the significance of "borderline" rejection on allograft function.

MATERIALS AND METHODS

We studied 261 biopsies from 159 renal transplant recipients who were on a steroid-free, calcineurin inhibitor and mycophenolate mofetil regimen and who received transplants between 2004 and 2012 with mean follow-up of 5 years. Early (between 3 and 9 mo) and subsequent late (between 12 and 24 mo) protocol biopsies were performed. Biopsies were classified as normal, interstitial fibrosis and/or tubular atrophy, subclinical acute rejection with interstitial fibrosis and/or tubular atrophy, and borderline rejection with interstitial fibrosis and/or tubular atrophy. A linear mixed-effects model was used to determine the effects of early and late protocol biopsies on estimated glomerular filtration rate changes, with baseline time for estimated glomerular filtration rate fixed at 12 months.

RESULTS

The adjusted model showed that estimated glomerular filtration rate at 3 months, donor age, delayed graft function, and early protocol biopsies were associated with baseline estimated glomerular filtration rate at 12 months. Estimated glomerular filtration rate changes over time were associated with findings of interstitial fibrosis and/or tubular atrophy at early biopsy and subclinical acute rejection and borderline rejection at late biopsy. At last follow-up, final estimated glomerular filtration rate was significantly associated with interstitial fibrosis and/or tubular atrophy at early biopsy and with subclinical acute rejection at late biopsy.

CONCLUSIONS

Although early protocol biopsy predicted baseline estimated glomerular filtration rate, late biopsy was important for predicting changes in function over time. In addition, a diagnosis of "borderline" rejection on protocol biopsies predicted long-term graft function.

Molecular and Functional Noninvasive Immune Monitoring in the ESCAPE Study for Prediction of Subclinical Renal Allograft Rejection

BACKGROUND

Subclinical acute rejection (sc-AR) is a main cause for functional decline and kidney graft loss and may only be assessed through surveillance biopsies.

METHODS

The predictive capacity of 2 novel noninvasive blood biomarkers, the transcriptional kidney Solid Organ Response Test (kSORT), and the IFN-γ enzyme-linked immunosorbent spot assay (ELISPOT) assay were assessed in the Evaluation of Sub-Clinical Acute rejection PrEdiction (ESCAPE) Study in 75 consecutive kidney transplants who received 6-month protocol biopsies. Both assays were run individually and in combination to optimize the use of these techniques to predict sc-AR risk.

RESULTS

Subclinical acute rejection was observed in 22 (29.3%) patients (17 T cell-mediated subclinical rejection [sc-TCMR], 5 antibody-mediated subclinical rejection [sc-ABMR]), whereas 53 (70.7%) showed a noninjured, preserved (stable [STA]) parenchyma. High-risk (HR), low-risk, and indeterminate-risk kSORT scores were observed in 15 (20%), 50 (66.7%), and 10 (13.3%) patients, respectively. The ELISPOT assay was positive in 31 (41%) and negative in 44 (58.7%) patients. The kSORT assay showed high accuracy predicting sc-AR (specificity, 98%; positive predictive value 93%) (all sc-ABMR and 58% sc-TCMR showed HR-kSORT), whereas the ELISPOT showed high precision ruling out sc-TCMR (specificity = 70%, negative predictive value = 92.5%), but could not predict sc-ABMR, unlike kSORT. The predictive probabilities for sc-AR, sc-TCMR, and sc-ABMR were significantly higher when combining both biomarkers (area under the curve > 0.85, P < 0.001) and independently predicted the risk of 6-month sc-AR in a multivariate regression analysis.

CONCLUSIONS

Combining a molecular and immune cell functional assay may help to identify HR patients for sc-AR, distinguishing between different driving alloimmune effector mechanisms.

Circulating miR-150, miR-192, miR-200b, and miR-423-3p as Non-invasive Biomarkers of Chronic Allograft Dysfunction

BACKGROUND AND AIMS

Chronic allograft dysfunction (CAD) is the major cause of renal allograft loss and can only be diagnosed by invasive histological examinations. The current study aimed to determine whether or not the circulating miR-125a, miR-150, miR-192, miR-200b, miR-423-3p and miR-433 could serve as predictors of graft outcome in the renal transplant recipients with CAD.

METHODS

To evaluate the expression levels of miRNAs, we used quantitative real-time PCR (qPCR) and analyzed the plasma samples of 53 renal transplant recipients, including: 27 recipients with stable graft function (SGF), 26 recipients with biopsy-proven interstitial fibrosis and tubular atrophy (IFTA) and 15 healthy controls. Possible correlation between the clinicopathological parameters and the studied circulating miRNAs was also evaluated.

RESULTS

miR-150 (p <0.001), miR-192 (p = 0.003), miR-200b (p = 0.048) and miR-423-3p (p <0.001) were differentially expressed between IFTA and SGF plasma samples. Creatinine correlated with miR-192 (r = 0.414, p = 0.036) and miR-423-3p (r = -0.431, p = 0.028). Moreover, the estimated glomerular filtration rate (eGFR) significantly correlated with the circulating miR-192 (r = -0.390, p = 0.049) and miR-423 (r = 0.432, p = 0.028). Receiver operating characteristic (ROC) analysis indicated that four miRNAs possessed the best diagnostic value for discriminating IFTA from SGF recipients with the areas under the curve (AUC) of 0.87 and high sensitivity and specificity values of 78% and 91%, respectively.

CONCLUSIONS

The results suggest that aberrant plasma levels of these miRNAs are associated with the renal allograft dysfunction. Therefore, they are proposed to be considered as potential diagnostic biomarkers for monitoring of renal graft function.

Orthogonal Comparison of Molecular Signatures of Kidney Transplants With Subclinical and Clinical Acute Rejection: Equivalent Performance Is Agnostic to Both Technology and Platform

We performed orthogonal technology comparisons of concurrent peripheral blood and biopsy tissue samples from 69 kidney transplant recipients who underwent comprehensive algorithm-driven clinical phenotyping. The sample cohort included patients with normal protocol biopsies and stable transplant (sTx) function (n = 25), subclinical acute rejection (subAR, n = 23), and clinical acute rejection (cAR, n = 21). Comparisons between microarray and RNA sequencing (RNA-seq) signatures were performed and demonstrated a strong correlation between the blood and tissue compartments for both technology platforms. A number of shared differentially expressed genes and pathways between subAR and cAR in both platforms strongly suggest that these two clinical phenotypes form a continuum of alloimmune activation. SubAR is associated with fewer or less expressed genes than cAR in blood, whereas in biopsy tissues, this clinical phenotype demonstrates a more robust molecular signature for both platforms. The discovery work done in this study confirms a clear ability to detect gene expression profiles for sTx, subAR, and cAR in both blood and biopsy tissue, yielding equivalent predictive performance that is agnostic to both technology and platform. Our data also provide strong biological insights into the molecular mechanisms underlying these signatures, underscoring their logistical potential as molecular diagnostics to improve clinical outcomes following kidney transplantation.

Average Tacrolimus Trough Level in the First Month After Transplantation May Predict Acute Rejection

BACKGROUND

Although tacrolimus is one of the essential drugs used for the prevention of rejection in kidney recipients, target trough levels are not well established. In this study, we aimed to investigate the association between average tacrolimus trough levels (TTLs) of the first month after transplantation and biopsy-proven acute rejection (BPAR) during the first 12 months after transplant.

METHODS

A total of 274 patients who underwent kidney-alone transplantation between 2002 and 2014 were enrolled in the study. Average TTLs of the first month were assessed by means of receiver operating characteristic (ROC) curve analysis to discriminate patients with and those without BPAR. Univariate and multivariate Cox proportional hazards models were used to determine the effect of average TTLs of the first month on BPAR.

RESULTS

According to ROC curve analysis, the highest area under the curve (AUC) was obtained from 8 ng/mL (AUC = 0.73 ± 0.11; 95% confidence interval [CI], 0.62-0.84). Forty-two (31.8%) of the 132 patients with average TTLs <8 ng/mL and 13 (9.1%) of 142 patients with ≥8 ng/mL had BPAR during the first 12 months after transplant (P < .001). In univariable analysis, average TTLs of the first month <8 ng/mL were associated with higher risk of BPAR (P < .001), and the significance remained in Cox multivariable analysis (hazard ratio, 2.79; 95% CI, 1.76-3.82; P = .001). No significant differences were observed in the glomerular filtration rate, cytomegalovirus, BK viremia, or BK nephropathy between groups at post-transplant month 12.

CONCLUSIONS

Keeping the average TTLs of the first month after transplantation at ≥8 ng/mL not only prevents BPAR occurrence but also minimizes the toxic effects of the use of a single-trough level.

Subclinical Rejection in Renal Transplantation: Reappraised

Short-term outcomes in renal transplantation have improved significantly in the past few years. However, the improvement in long-term outcomes has been modest. The reasons for graft failure beyond the first year of transplantation have been attributed to several different factors. We believe that subclinical rejection (SCR) may be 1 of the factors that contribute to graft loss in the long run. We also believe that there are data to suggest that SCR leads to progressive fibrosis and loss of graft function. This has been demonstrated even in patients who have mild degrees of subclinical inflammation. This review outlines the major studies that have been published on this important topic. It also outlines potential risk factors for the development of SCR. The current approach and diagnostic methods are discussed as well as their pros and cons. Newer noninvasive methods of diagnosis as well as molecular diagnostics and their merits and shortcomings are also discussed in some depth. Thus, the proposed state of the art review on SCR will create a renewed interest at all levels including transplant clinicians, transplant researchers, pharmaceutical industries as well as regulatory organizations.

Kidney Fibrosis: Origins and Interventions

All causes of renal allograft injury, when severe and/or sustained, can result in chronic histological damage of which interstitial fibrosis and tubular atrophy are dominant features. Unless a specific disease process can be identified, what drives interstitial fibrosis and tubular atrophy progression in individual patients is often unclear. In general, clinicopathological factors known to predict and drive allograft fibrosis include graft quality, inflammation (whether "nonspecific" or related to a specific diagnosis), infections, such as polyomavirus-associated nephropathy, calcineurin inhibitors (CNI), and genetic factors. The incidence and severity of chronic histological damage have decreased substantially over the last 3 decades, but it is difficult to disentangle what effects individual innovations (eg, better matching and preservation techniques, lower CNI dosing, BK viremia screening) may have had. There is little evidence that CNI-sparing/minimization strategies, steroid minimization or renin-angiotensin-aldosterone system blockade result in better preservation of intermediate-term histology. Treatment of subclinical rejections has only proven beneficial to histological and functional outcome in studies in which the rate of subclinical rejection in the first 3 months was greater than 10% to 15%. Potential novel antifibrotic strategies include antagonists of transforming growth factor-β, connective tissue growth factor, several tyrosine kinase ligands (epidermal growth factor, platelet-derived growth factor, vascular endothelial growth factor), endothelin and inhibitors of chemotaxis. Although many of these drugs are mainly being developed and marketed for oncological indications and diseases, such as idiopathic pulmonary fibrosis, a number may hold promise in the treatment of diabetic nephropathy, which could eventually lead to applications in renal transplantation.

Reduction of Extended-Release Tacrolimus Dose in Low-Immunological-Risk Kidney Transplant Recipients Increases Risk of Rejection and Appearance of Donor-Specific Antibodies: A Randomized Study

The aim of this study (ClinicalTrials.gov, NCT01744470) was to determine the efficacy and safety of two different doses of extended-release tacrolimus (TacER) in kidney transplant recipients (KTRs) between 4 and 12 mo after transplantation. Stable steroid-free KTRs were randomized (1:1) after 4 mo: Group A had a 50% reduction in TacER dose with a targeted TacER trough level (C₀ ) >3 μg/L; group B had no change in TacER dose (TacER C₀ 7-12 μg/L). The primary outcome was estimated GFR at 1 year. Of 300 patients, the intent-to-treat analysis included 186 patients (group A, n = 87; group B, n = 99). TacER C₀ was lower in group A than in group B at 6 mo (4.1 ± 2.7 vs. 6.7 ± 3.9 μg/L, p < 0.0001) and 12 mo (5.6 ± 2.0 vs. 7.4 ± 2.1 μg/L, p < 0.0001). Estimated GFR was similar in both groups at 12 mo (group A, 56.0 ± 17.5 mL/min per 1.73 m²; group B, 56.0 ± 22.1 mL/min per 1.73 m²). More rejection episodes occurred in group A than group B (11 vs. 3; p = 0.016). At 1 year, subclinical inflammation occurred more frequently in group A than group B (inflammation score [i] >0: 21.4% vs. 8.8%, p = 0.047; tubulitis score [t] >0: 19.6% vs. 8.7%, p = 0.076; i + t: 1.14 ± 1.21 vs. 0.72 ± 1.01, p = 0.038). Anti-HLA donor-specific antibodies appeared only in group A (6 vs. 0 patients, p = 0.008). TacER C₀ should be maintained >7 μg/L during the first year after transplantation in low-immunological-risk, steroid-free KTRs receiving a moderate dose of mycophenolic acid.

Macrophage density in early surveillance biopsies predicts future renal transplant function

Inflammation impairs renal allograft survival but is difficult to quantify by eye at low densities. Here we measured leukocyte abundance in early surveillance biopsies by digital image analysis to test for a role of chemokine receptor genotypes and analyze the predictive value of leukocyte subsets to allograft function. In six-week surveillance biopsies, T-cell (CD3), B-cell (CD20), macrophage (CD68), and dendritic cell (CD209) densities were assessed in whole slide scans. Renal cortical CD3, CD20, and CD68 were significantly higher in histologic rejection. The CCR2 V64I genotype was associated with lower CD3 and CD209 densities. Above-median CD68 density was significantly associated with lower combined patient and graft survival with a hazard ratio of 3.5 (95% confidence interval 1.1-11.0). Both CD20 and CD68 densities inversely correlated with estimated glomerular filtration rate (eGFR) four years after transplantation. Additionally, CD68 correlated with eGFR loss. Among histological measurements including a complete Banff classification, only CD68 density was a significant predictor of an eGFR under 30ml/min after four years (odds ratio 7.4, 1.8-31.0) and part of the best eGFR prediction set in a multivariable linear regression analysis of multiple clinical and pathologic parameters. In a second independent cohort, the original CD68 median maintained its discriminative power for survival and eGFR. Thus, digital high-resolution assessment of CD68⁺ leukocyte infiltration significantly improves prognostic value of early renal transplant biopsies.

Kidney allograft surveillance biopsy practices across US transplant centers: A UNOS survey

BACKGROUND

The approach to the diagnosis and management of subclinical rejection (SCR) in kidney transplant recipients remains controversial.

METHODS

We conducted a survey through UNOS across US transplant centers regarding their approach to surveillance biopsies and reasons for the nonperformance of surveillance biopsies.

RESULTS

Responses were obtained from 106/238 centers (45%), and only 18 (17%) of the centers performed surveillance biopsies on all patients and 22 (21%) performed biopsy for select cases. The most common time points for surveillance biopsies were 3 and 12  months post-transplant. The common reasons for not performing biopsies were low yield (n = 44, 65%) and the belief that it will not change outcome (n = 24, 36%). The incidence of SC-TCMR was ≥ 10% among 39% of centers. The mean serum creatinine was slightly worse by 0.06 mg/dL at 1 year and 0.07 mg/dL at 3 years among centers performing biopsy, P < .0001. The. 1-and 3-year Observed-Expected (O-E) graft survival was similar among centers performing biopsies vs. those not performing biopsy (P = .07, .88).

CONCLUSION

Only 17% of US centers perform surveillance biopsies, with another 21% performing surveillance biopsies in select cases (among centers that responded to the survey). Greater uniformity in the approach and management of this condition is of paramount importance.