Association of BKV viremia and nephropathy with adverse alloimmune outcomes in kidney transplant recipients.

BACKGROUND: Immunosuppression reduction for BK polyoma virus (BKV) must be balanced against risk of adverse alloimmune outcomes. We sought to characterize risk of alloimmune events after BKV within context of HLA-DR/DQ molecular mismatch (mMM) risk score. METHODS: This single-center study evaluated 460 kidney transplant patients on tacrolimus-mycophenolate-prednisone from 2010-2021. BKV status was classified at 6-months post-transplant as "BKV" or "no BKV" in landmark analysis. Primary outcome was T-cell mediated rejection (TCMR). Secondary outcomes included all-cause graft failure (ACGF), death-censored graft failure (DCGF), de novo donor specific antibody (dnDSA), and antibody-mediated rejection (ABMR). Predictors of outcomes were assessed in Cox proportional hazards models including BKV status and alloimmune risk defined by recipient age and molecular mismatch (RAMM) groups. RESULTS: At 6-months post-transplant, 72 patients had BKV and 388 had no BKV. TCMR occurred in 86 recipients, including 27.8% with BKV and 17% with no BKV (p = .05). TCMR risk was increased in recipients with BKV (HR 1.90, (95% CI 1.14, 3.17); p = .01) and high vs. low-risk RAMM group risk (HR 2.26 (95% CI 1.02, 4.98); p = .02) in multivariable analyses; but not HLA serological MM in sensitivity analysis. Recipients with BKV experienced increased dnDSA in univariable analysis, and there was no association with ABMR, DCGF, or ACGF. CONCLUSIONS: Recipients with BKV had increased risk of TCMR independent of induction immunosuppression and conventional alloimmune risk measures. Recipients with high-risk RAMM experienced increased TCMR risk. Future studies on optimizing immunosuppression for BKV should explore nuanced risk stratification and may consider novel measures of alloimmune risk.

A rational approach to guide cost-effective de novo donor-specific antibody surveillance with tacrolimus immunosuppression.

De novo donor-specific antibody (dnDSA) after renal transplantation has been shown to correlate with antibody-mediated rejection and allograft loss. However, the lack of proven interventions and the time and cost associated with annual screening for dnDSA are difficult to justify for all recipients. We studied a well-characterized consecutive cohort (n = 949) with over 15 years of prospective dnDSA surveillance to identify risk factors that would help institute a resource-responsible surveillance strategy. Younger recipient age and HLA-DR/DQ molecular mismatch were independent predictors of dnDSA development. Combining both risk factors into recipient age molecular mismatch categories, we found that 52% of recipients could be categorized as low-risk for dnDSA development (median subclinical dnDSA-free survival at 5 and 10 years, 98% and 97%, respectively). After adjustment, multivariate correlates of dnDSA development included tacrolimus versus cyclosporin maintenance immunosuppression (hazard ratio [HR], 0.37; 95% CI, 0.2-0.6; P < .0001) and recipient age molecular mismatch category: intermediate versus low (HR, 2.48; 95% CI, 1.5-4.2; P = .0007), high versus intermediate (HR, 2.56; 95% CI, 1.6-4.2; P = .0002), and high versus low (HR, 6.36; 95% CI, 3.7-10.8; P < .00001). When combined, recipient age and HLA-DR/DQ molecular mismatch provide a novel data-driven approach to reduce testing by >50% while selecting those most likely to benefit from dnDSA surveillance.

The negative impact of T cell-mediated rejection on renal allograft survival in the modern era.

The prevalence and long-term impact of T cell-mediated rejection (TCMR) is poorly defined in the modern era of tacrolimus/mycophenolate-based maintenance therapy. This observational study evaluated 775 kidney transplant recipients with serial histology and correlated TCMR events with the risk of graft loss. After a ~30% incidence of a first Banff Borderline or greater TCMR detected on for-cause (17%) or surveillance (13%) biopsies, persistent (37.4%) or subsequent (26.3%) TCMR occurred in 64% of recipients on follow-up biopsies. Alloimmune risk categories based on the HLA-DR/DQ single molecule eplet molecular mismatch correlated with the number of TCMR events (p = .002) and Banff TCMR grade (p = .007). Both a first and second TCMR event correlated with death-censored and all-cause graft loss when adjusted for baseline covariates and other significant time-dependent covariates such as DGF and ABMR. Therefore, a substantial portion of kidney transplant recipients, especially those with intermediate and high HLA-DR/DQ molecular mismatch scores, remain under-immunosuppressed, which in turn identifies the need for novel agents that can more effectively prevent or treat TCMR.

A noninferiority design for a delayed calcineurin inhibitor substitution trial in kidney transplantation.

Improving long-term kidney transplant outcomes requires novel treatment strategies, including delayed calcineurin inhibitor (CNI) substitution, tested using informative trial designs. An alternative approach to the usual superiority-based trial is a noninferiority trial design that tests whether an investigational agent is not unacceptably worse than standard of care. An informative noninferiority design, with biopsy-proven acute rejection (BPAR) as the endpoint, requires determination of a prespecified, evidence-based noninferiority margin for BPAR. No such information is available for delayed CNI substitution in kidney transplantation. Herein we analyzed data from recent kidney transplant trials of CNI withdrawal and "real world" CNI- based standard of care, containing subjects with well-documented evidence of immune quiescence at 6 months posttransplant-ideal candidates for delayed CNI substitution. Our analysis indicates an evidence-based noninferiority margin of 13.8% for the United States Food and Drug Administration's composite definition of BPAR between 6 and 24 months posttransplant. Sample size estimation determined that ~225 randomized subjects would be required to evaluate noninferiority for this primary clinical efficacy endpoint, and superiority for a renal function safety endpoint. Our findings provide the basis for future delayed CNI substitution noninferiority trials, thereby increasing the likelihood they will provide clinically implementable results and achieve regulatory approval.

Evidence for the alloimmune basis and prognostic significance of Borderline T cell-mediated rejection.

Prognostic biomarkers of T cell-mediated rejection (TCMR) have not been adequately studied in the modern era. We evaluated 803 renal transplant recipients and correlated HLA-DR/DQ molecular mismatch alloimmune risk categories (low, intermediate, high) with the severity, frequency, and persistence of TCMR. Allograft survival was reduced in recipients with Banff Borderline (hazard ratio [HR] 2.4, P = .003) and Banff ≥ IA TCMR (HR 4.3, P < .0001) including a subset who never developed de novo donor-specific antibodies (P = .002). HLA-DR/DQ molecular mismatch alloimmune risk categories were multivariate correlates of Banff Borderline and Banff ≥ IA TCMR and correlated with the severity and frequency of rejection episodes. Recipient age, HLA-DR/DQ molecular mismatch category, and cyclosporin vs tacrolimus immunosuppression were independent correlates of Banff Borderline and Banff ≥ IA TCMR. In the subset treated with tacrolimus (720/803) recipient age, HLA-DR/DQ molecular mismatch category, and tacrolimus coefficient of variation were independent correlates of TCMR. The correlation of HLA-DR/DQ molecular mismatch category with TCMR, including Borderline, provides evidence for their alloimmune basis. HLA-DR/DQ molecular mismatch may represent a precise prognostic biomarker that can be applied to tailor immunosuppression or design clinical trials based on individual patient risk.

Early Antibody-Mediated Kidney Transplant Rejection Associated With Anti-Vimentin Antibodies: A Case Report.

Improving precision in predicting alloreactivity is an important unmet need and may require individualized consideration of non-HLA antibodies. We report a 21-year-old man with kidney failure from immunoglobulin A nephropathy who met all traditional criteria for a "low-risk" transplant for immune memory. He was unsensitized and received a haplotype-matched living donor kidney transplant from his mother. There were no anti-HLA donor-specific antibodies and flow cross-match was negative. After immediate function, he developed delayed graft function on postoperative day 2. The transplant biopsy specimen was suggestive of antibody-mediated rejection and acute tubular injury with increased vimentin proximal tubular expression compared to the implantation biopsy specimen. He had a history of juvenile idiopathic arthritis, and non-HLA antibody screening demonstrated preformed anti-vimentin antibody. He was successfully treated with plasmapheresis, intravenous immunoglobulin, antithymocyte globulin, and methylprednisolone, with renal recovery. The follow-up biopsy specimen demonstrated decreased vimentin expression with decreased alloinflammation, and graft function remains stable at 1 year posttransplantation (estimated glomerular filtration rate, 62mL/min/1.73m2). We postulate that preformed anti-vimentin autoantibodies bound to vimentin expressed on apoptotic tubular epithelial cells induced by ischemia-reperfusion injury and to constitutively expressed vimentin on peritubular capillaries and podocytes. Our case is suggestive of the involvement of anti-vimentin antibody, for which the pathogenic epitopes may be exposed during ischemia-reperfusion injury.

HLA-DR/DQ molecular mismatch: A prognostic biomarker for primary alloimmunity.

Alloimmune risk stratification in renal transplantation has lacked the necessary prognostic biomarkers to personalize recipient care or optimize clinical trials. HLA molecular mismatch improves precision compared to traditional antigen mismatch but has not been studied in detail at the individual molecule level. This study evaluated 664 renal transplant recipients and correlated HLA-DR/DQ single molecule eplet mismatch with serologic, histologic, and clinical outcomes. Compared to traditional HLA-DR/DQ whole antigen mismatch, HLA-DR/DQ single molecule eplet mismatch improved the correlation with de novo donor-specific antibody development (area under the curve 0.54 vs 0.84) and allowed recipients to be stratified into low, intermediate, and high alloimmune risk categories. These risk categories were significantly correlated with primary alloimmune events including Banff ≥1A T cell-mediated rejection (P = .0006), HLA-DR/DQ de novo donor-specific antibody development (P < .0001), antibody-mediated rejection (P < .0001), as well as all-cause graft loss (P = .0012) and each of these correlations persisted in multivariate models. Thus, HLA-DR/DQ single molecule eplet mismatch may represent a precise, reproducible, and widely available prognostic biomarker that can be applied to tailor immunosuppression or design clinical trials based on individual patient risk.

Comparison of the effects of standard vs low-dose prolonged-release tacrolimus with or without ACEi/ARB on the histology and function of renal allografts.

Targeting the renin-angiotensin system and optimizing tacrolimus exposure are both postulated to improve outcomes in renal transplant recipients (RTRs) by preventing interstitial fibrosis/tubular atrophy (IF/TA). In this multicenter, prospective, open-label controlled trial, adult de novo RTRs were randomized in a 2 × 2 design to low- vs standard-dose (LOW vs STD) prolonged-release tacrolimus and to angiotensin-converting enzyme inhibitors/angiotensin II receptor 1 blockers (ACEi/ARBs) vs other antihypertensive therapy (OAHT). There were 2 coprimary endpoints: the prevalence of IF/TA at month 6 and at month 24. IF/TA prevalence was similar for LOW vs STD tacrolimus at month 6 (36.8% vs 39.5%; P = .80) and ACEi/ARBs vs OAHT at month 24 (54.8% vs 58.2%; P = .33). IF/TA progression decreased significantly with LOW vs STD tacrolimus at month 24 (mean [SD] change, +0.42 [1.477] vs +1.10 [1.577]; P = .0039). Across the 4 treatment groups, LOW + ACEi/ARB patients exhibited the lowest mean IF/TA change and, compared with LOW + OAHT patients, experienced significantly delayed time to first T cell-mediated rejection. Renal function was stable from month 1 to month 24 in all treatment groups. No unexpected safety findings were detected. Coupled with LOW tacrolimus dosing, ACEi/ARBs appear to reduce IF/TA progression and delay rejection relative to reduced tacrolimus exposure without renin-angiotensin system blockade. ClinicalTrials.gov identifier: NCT00933231.

Carpe diem-Time to transition from empiric to precision medicine in kidney transplantation.

The current immunosuppressive pipeline in kidney transplantation is limited. In part, this is due to excellent one-year allograft outcomes with the current standard of care (ie, calcineurin inhibitor in combination with anti-proliferative agents). Despite this success, a recent Federal government-sponsored systematic review has identified gaps/limits in the evidence of what constitutes optimal calcineurin inhibitor use in the short- and long-term. Moreover, recent empiric approaches to minimize/withdraw/convert from calcineurin inhibitors have come with the price of increased alloreactivity. As the time horizon to replace calcineurin inhibitors on a global scale may be distant, the transplant community should seize the opportunity to develop ways to personalize calcineurin inhibitor immunosuppression to the individual-transitioning from empiricism to precision. The authors argue in this viewpoint that the path to precision will require measures capable of detecting subclinical alloreactivity to define adequacy of immunosuppression, as well as novel genetic analytics to accurately define alloimmune risk at the individual level-both approaches will require validation in clinical trials.

Class II Eplet Mismatch Modulates Tacrolimus Trough Levels Required to Prevent Donor-Specific Antibody Development.

Despite more than two decades of use, the optimal maintenance dose of tacrolimus for kidney transplant recipients is unknown. We hypothesized that HLA class II de novo donor-specific antibody (dnDSA) development correlates with tacrolimus trough levels and the recipient's individualized alloimmune risk determined by HLA-DR/DQ epitope mismatch. A cohort of 596 renal transplant recipients with 50,011 serial tacrolimus trough levels had HLA-DR/DQ eplet mismatch determined using HLAMatchmaker software. We analyzed the frequency of tacrolimus trough levels below a series of thresholds <6 ng/ml and the mean tacrolimus levels before dnDSA development in the context of HLA-DR/DQ eplet mismatch. HLA-DR/DQ eplet mismatch was a significant multivariate predictor of dnDSA development. Recipients treated with a cyclosporin regimen had a 2.7-fold higher incidence of dnDSA development than recipients on a tacrolimus regimen. Recipients treated with tacrolimus who developed HLA-DR/DQ dnDSA had a higher proportion of tacrolimus trough levels <5 ng/ml, which continued to be significant after adjustment for HLA-DR/DQ eplet mismatch. Mean tacrolimus trough levels in the 6 months before dnDSA development were significantly lower than the levels >6 months before dnDSA development in the same patients. Recipients with a high-risk HLA eplet mismatch score were less likely to tolerate low tacrolimus levels without developing dnDSA. We conclude that HLA-DR/DQ eplet mismatch and tacrolimus trough levels are independent predictors of dnDSA development. Recipients with high HLA alloimmune risk should not target tacrolimus levels <5 ng/ml unless essential, and monitoring for dnDSA may be advisable in this setting.

The perils of immunosuppression minimization: lessons from protocol biopsies of renal allografts.

PURPOSE OF REVIEW: To emphasize the pathogenicity of subclinical cellular inflammation in renal transplant recipients, and its relation to poor graft outcomes and the development of de-novo donor-specific antibody (DSA). RECENT FINDINGS: Protocol biopsies have identified the gene signatures of innate and adaptive immunity in patients with minimal inflammation that correlate with the subsequent development of graft interstitial fibrosis, transplant glomerulopathy and antibody-mediated rejection. The risks of immunosuppression minimization, especially in HLA mismatched donor-recipient pairs, are highlighted. SUMMARY: The major cause of renal allograft loss is immunological and a contributor to this is the minimization of immunosuppression. The prevention of premature graft loss requires better matching of class II HLA antigens, the targets of de-novo DSA, and monitoring for subclinical inflammation rejection with protocol biopsies or urine chemokines.

Urinary biomarkers of renal transplant outcome.

PURPOSE OF REVIEW: Renal allograft loss remains an important cause of morbidity and mortality. The objective of this review was to provide a rationale for noninvasive monitoring to identify patients at high risk for graft loss; discuss key steps in prognostic biomarker development from bench-to-bedside; and review promising biomarkers for late renal allograft outcomes. RECENT FINDINGS: In a multicentre prospective cohort, early 6-month urinary CCL2 was demonstrated to be associated with the development of 24-month interstitial fibrosis/tubular atrophy and inflammation (IFTA+i). These findings were extended to a single centre cohort, which showed that 6-month urinary CCL2 was a predictor of death-censored graft loss independent of donor-specific antibody and delayed graft function. In a large, multicentre prospective observational study (CTOT-01), 6-month urinary CXCL9 was significantly associated with more than 30% decline of graft function at 24 months. SUMMARY: Urinary chemokines may identify recipients who are at high risk of graft loss. The early detection of high-risk recipients may allow for more intensive posttransplant surveillance; avoidance of drug minimization/withdrawal protocols; and the identification of patients who may benefit from enrolment in novel interventional trials. Prospective trials are needed to demonstrate that urinary chemokine-guided posttransplant surveillance strategies improve long-term graft outcomes.

Proteomic characterization of serine hydrolase activity and composition in normal urine.

BACKGROUND: Serine hydrolases constitute a large enzyme family involved in a diversity of proteolytic and metabolic processes which are essential for many aspects of normal physiology. The roles of serine hydrolases in renal function are largely unknown and monitoring their activity may provide important insights into renal physiology. The goal of this study was to profile urinary serine hydrolases with activity-based protein profiling (ABPP) and to perform an in-depth compositional analysis. METHODS: Eighteen healthy individuals provided random, mid-stream urine samples. ABPP was performed by reacting urines (n = 18) with a rhodamine-tagged fluorophosphonate probe and visualizing on SDS-PAGE. Active serine hydrolases were isolated with affinity purification and identified on MS-MS. Enzyme activity was confirmed with substrate specific assays. A complementary 2D LC/MS-MS analysis was performed to evaluate the composition of serine hydrolases in urine. RESULTS: Enzyme activity was closely, but not exclusively, correlated with protein quantity. Affinity purification and MS/MS identified 13 active serine hydrolases. The epithelial sodium channel (ENaC) and calcium channel (TRPV5) regulators, tissue kallikrein and plasmin were identified in active forms, suggesting a potential role in regulating sodium and calcium reabsorption in a healthy human model. Complement C1r subcomponent-like protein, mannan binding lectin serine protease 2 and myeloblastin (proteinase 3) were also identified in active forms. The in-depth compositional analysis identified 62 serine hydrolases in urine independent of activity state. CONCLUSIONS: This study identified luminal regulators of electrolyte homeostasis in an active state in the urine, which suggests tissue kallikrein and plasmin may be functionally relevant in healthy individuals. Additional serine hydrolases were identified in an active form that may contribute to regulating innate immunity of the urinary tract. Finally, the optimized ABPP technique in urine demonstrates its feasibility, reproducibility and potential applicability to profiling urinary enzyme activity in different renal physiological and pathophysiological conditions.

Immune monitoring of kidney allografts.

Current strategies for posttransplant monitoring of kidney transplants consist of measuring serial serum creatinine levels, clinical follow-up, and in some programs, protocol biopsies. These strategies may be insufficient to predict acute rejection in kidney transplants, which remains the major factor affecting long-term transplant outcomes. Immune monitoring may conceptually be divided into strategies for detecting humoral rejection (eg, donor-specific antibody) or cellular rejection. Cellular rejection markers may be separated further into those related to cytotoxic T lymphocytes (granzyme A/B, perforin, Fas ligand, and serpin B9), regulatory T cells (FOXP3), and CD4 T cells (the chemokines CXCL9, CXCL10, CXCL11, CCL2, and fractalkine, as well as TIM-3). Finally, transcriptomic changes and renal tubular injury markers also may be useful for detecting early inflammatory changes post-kidney transplant. Ultimately, novel strategies for monitoring the immune status of the kidney transplant may lead to early therapeutic intervention and improved kidney transplant outcomes.

Serum creatinine measurement immediately after cardiac surgery and prediction of acute kidney injury.

BACKGROUND: After heart surgery, acute kidney injury (AKI) confers substantial long-term risk of death and chronic kidney disease. We hypothesized that small changes in serum creatinine (SCr) levels measured within a few hours of exit from the operating room could help discriminate those at low versus high risk of AKI. STUDY DESIGN: Prospective cohort of 350 elective cardiac surgery patients (valve or coronary artery bypass grafting) recruited in Winnipeg, Canada. Baseline SCr level was obtained at the preoperative visit 2 weeks before surgery. The postoperative SCr level was drawn within 6 hours of completion of surgery and then daily while the patient was in the hospital. PREDICTOR: Immediate (ie, <6 hours) postoperative SCr level change (ΔSCr), categorized as within 10% (reference), decrease >10%, or increase >10% relative to baseline. OUTCOME: AKI, defined according to the new KDIGO (Kidney Disease: Improving Global Outcomes) consensus definition as an increase in SCr level >0.3 mg/dL within 48 hours or >1.5 times baseline within 1 week. MEASUREMENTS: We compared the C statistic of logistic models with and without inclusion of immediate postoperative ΔSCr. RESULTS: After surgery, 176 patients (52%) experienced a decrease >10% in SCr level, 26 (7.4%) experienced an increase >10%, and 143 had ΔSCr within ±10% of baseline. During hospitalization, 53 (14%) developed AKI. Bypass pump time, baseline estimated glomerular filtration rate, and European System for Cardiac Operative Risk Evaluation (euroSCORE) were associated with AKI in a parsimonious base logistic model. Added to the base model, immediate postoperative ΔSCr was associated strongly with subsequent AKI and significantly improved model discrimination over the base model (C statistic, 0.78 [95% CI, 0.71-0.85] vs 0.69 [95% CI, 0.62-0.77]; P < 0.001). A ≥10% SCr level decrease predicted significantly lower AKI risk (OR, 0.37; 95% CI, 0.18-0.76), whereas a ≥10% SCr level increase predicted significantly higher (OR, 6.38; 95% CI, 2.37-17.2) AKI risk compared with the reference category. LIMITATIONS: We used a surrogate marker of AKI. External validation of our results is warranted. CONCLUSION: In elective cardiac surgery patients, measurement of immediate postoperative ΔSCr improves prediction of AKI.

Subclinical Inflammation in Renal Transplantation.

The standardization of renal allograft pathology began in 1991 at the first Banff Conference held in Banff, Alberta, Canada. The first task of transplant pathologists, clinicians, and surgeons was to establish diagnostic criteria for T-cell-mediated rejection (TCMR). The histological threshold for this diagnosis was arbitrarily set at "i2t2": a mononuclear interstitial cell infiltrate present in at least 25% of normal parenchyma and >4 mononuclear cells within the tubular basement membrane of nonatrophic tubules. TCMR was usually found in dysfunctional grafts with an elevation in the serum creatinine; however, our group and others found this extent of inflammation in "routine" or "protocol" biopsies of normally functioning grafts: "subclinical" TCMR. The prevalence of TCMR is higher in the early months posttransplant and has decreased with the increased potency of current immunosuppressive agents. However, the pathogenicity of lesser degrees of inflammation under modern immunosuppression and the relation between ongoing inflammation and development of donor-specific antibody has renewed our interest in subclinical alloreactivity. Finally, the advances in our understanding of pretransplant risk assessment, and our increasing ability to monitor patients less invasively posttransplant, promises to usher in the era of precision medicine.

Activity-based Protein Profiling Approaches for Transplantation.

Enzyme activity may be more pathophysiologically relevant than enzyme quantity and is regulated by changes in conformational status that are undetectable by traditional proteomic approaches. Further, enzyme activity may provide insights into rapid physiological responses to inflammation/injury that are not dependent on de novo protein transcription. Activity-based protein profiling (ABPP) is a chemical proteomic approach designed to characterize and identify active enzymes within complex biological samples. Activity probes have been developed to interrogate multiple enzyme families with broad applicability, including but not limited to serine hydrolases, cysteine proteases, matrix metalloproteases, nitrilases, caspases, and histone deacetylases. The goal of this overview is to describe the overall rationale, approach, methods, challenges, and potential applications of ABPP to transplantation research. To do so, we present a case example of urine serine hydrolase ABPP in kidney transplant rejection to illustrate the utility and workflow of this analytical approach. Ultimately, developing novel transplant therapeutics is critically dependent on understanding the pathophysiological processes that result in loss of transplant function. ABPP offers a new dimension for characterizing dynamic changes in clinical samples. The capacity to identify and measure relevant enzyme activities provides fresh opportunities for understanding these processes and may help identify markers of disease activity for the development of novel diagnostics and real-time monitoring of patients. Finally, these insights into enzyme activity may also help to identify new transplant therapeutics, such as enzyme-specific inhibitors.

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.

Pre-transplant AT1R antibodies correlate with early allograft rejection.

Studies investigating the potential pathogenic effects of non-HLA antibodies (Ab) have identified Ab against the angiotensin II type 1 receptor (AT1R-Ab) as a risk factor for rejection and kidney graft loss. This study sought to validate the risk of AT1R-Ab for acute rejection and to explore the role of other non-HLA Abs in this capacity. Pre- and post-transplant sera from a cohort of 101 patients (n=453 samples total) were tested for AT1R-Ab and other non-HLA Ab using a commercially available ELISA kit and the Luminex platform, respectively. Patients positive for pre-transplant AT1R-Ab were more likely to develop de novo donor-specific Ab (dnDSA) compared to patients that were negative for AT1R-Ab (28% vs 10%, p=0.027). Pre-transplant positivity for AT1R-Ab was associated with TCMR in the first year post-transplant (p=0.034), but did not predict graft loss independent of dnDSA (p=0.063). AT1R-Ab positivity was significantly associated with positivity for Ab against the endothelin A type 1 receptor (ETAR-Ab) inclusive of all study time points (p=0.0021). Given the high prevalence of AT1R-Ab pre-transplant (20%) and its association with dnDSA and early TCMR, a prospective study to determine if more intense immunosuppression and/or AT1R blockade has an impact on outcomes in these patients is warranted.