Histopathological characteristics and causes of kidney graft failure in the current era of immunosuppression

Nanoparticle-assisted Targeting Delivery Technologies for Preventing Organ Rejection

Although organ transplantation is a life-saving medical procedure, the challenge of posttransplant rejection necessitates safe and effective immune modulation strategies. Nanodelivery approaches may have the potential to overcome the limitations of small-molecule immunosuppressive drugs, achieving efficacious treatment options for transplant tolerance without compromising overall host immunity. This review highlights recent advances in biomaterial-assisted formulations and technologies for targeted nanodrug delivery with transplant organ- or immune cell-level precision for treating graft rejection after transplantation. We provide an overview of the mechanism of transplantation rejection, current clinically approved immunosuppressive drugs, and their relevant limitations. Finally, we discuss the targeting principles and advantages of organ- and immune cell-specific delivery technologies. The development of biomaterial-assisted novel therapeutic strategies holds considerable promise for treating organ rejection and clinical translation.

Update on current and potential application of extracellular vesicles in kidney transplantation

Kidney transplantation (KT) is the best treatment for end-stage kidney disease. However, early diagnosis of graft injury remains challenging, mainly because of the lack of accurate and noninvasive diagnostic techniques. Improving graft outcomes is equally demanding, as is the development of innovative therapies. Many research efforts are focusing on extracellular vesicles, cellular particles free in each body fluid that have shown promising results as precise markers of damage and potential therapeutic targets in many diseases, including the renal field. In fact, through their receptors and cargo, they act in damage response and immune modulation. In transplantation, they may be used to determine organ quality and aging, the presence of delayed graft function, rejection, and many other transplant-related pathologies. Moreover, their low immunogenicity and safe profile make them ideal for drug delivery and the development of therapies to improve KT outcomes. In this review, we summarize current evidence about extracellular vesicles in KT, starting with their characteristics and major laboratory techniques for isolation and characterization. Then, we discuss their use as potential markers of damage and as therapeutic targets, discussing their promising use in clinical practice as a form of liquid biopsy.

Donor-Derived Cell-Free DNA at 1 Month after Kidney Transplantation Relates to HLA Class II Eplet Mismatch Load

Kidney transplantation is the preferred therapeutic option for end-stage renal disease; however, the alloimmune response is still the leading cause of renal allograft failure. To better identify immunologic disparities in order to evaluate HLA compatibility between the donor and the recipient, the concept of eplet load has arisen. Regular kidney function monitoring is essential for the accurate and timely diagnosis of allograft rejection and the appropriate treatment. Donor-derived cell-free DNA (dd-cfDNA) has been proposed as a potential biomarker of acute rejection and graft failure in kidney transplantation. The proportion of plasma dd-cfDNA was determined in forty-two kidney patients at 1 month after transplantation. A total of eleven (26.2%) patients had a dd-cfDNA proportion of ≥1.0%. The only pretransplant variable related to dd-cfDNA > 1.0% was the HLA class II eplet mismatch load, mainly the HLA-DQB1 eplet mismatch load. Furthermore, dd-cfDNA was able to discriminate the patients with antibody-mediated rejection (AbMR) (AUC 87.3%), acute rejection (AUC 78.2%), and troubled graft (AUC 81.4%). Increased dd-cfDNA levels were associated with kidney allograft deterioration, particularly rejection, as well as a greater HLA class II eplet mismatch load. Consequently, combining dd-cfDNA determination and HLA eplet mismatch load calculation should improve the assessment of the risk of short- and long-term allograft damage.

Potential utility of urinary chemokine CCL2 to creatinine ratio in prognosis of 5-year graft failure and mortality post 1-year protocol biopsy in kidney transplant recipients

BACKGROUND

Chemokines (chemotactic cytokines) are small proteins which are engaged in many pathophysiological processes, including inflammation and homeostasis. In recent years, application of chemokines in transplant medicine was intensively studied. The aim of this study was to determine the utility of urinary chemokines CCL2 (C-C motif ligand 2) and CXCL10 (C-X-C motif chemokine ligand 10) in prognosis of 5-year graft failure and mortality post 1-year protocol biopsy in renal transplant recipients.

METHODS

Forty patients who had a protocol biopsy 1 year after renal transplantation were included. Concentrations of CCL2 and CXCL10 in urine with reference to urine creatinine were measured. All patients were under the supervision of one transplant center. Long-term outcomes within 5 years after 1-year posttransplant biopsy were analyzed.

RESULTS

Urinary CCL2:Cr at the time of biopsy was significantly increased in patients who died or had graft failure. CCL2:Cr was proven to be a significant predictor of 5-year graft failure and mortality (odds ratio [OR]: 1.09, 95% confidence interval [CI]: 1.02-1.19, p = .02; OR: 1.08, 95% CI: 1.02-1.16, p = .04; respectively).

CONCLUSION

Chemokines are easily detected by current methods. In the era of personalized medicine, urinary CCL2:Cr can be considered as a factor providing complementary information regarding risk of graft failure or increased mortality.

Three-year Outcomes After Conversion From Monthly to Every 2-month Belatacept Maintenance Therapy in Kidney Transplant Recipients: Results From a Randomized Controlled Trial

Maintenance immunosuppression with belatacept following kidney transplantation results in improved long-term graft function as compared with calcineurin inhibitors. However, broad application of belatacept has been limited, in part related to logistical barriers surrounding a monthly (q1m) infusion requirement.

Methods

To determine whether every 2-mo (q2m) belatacept is noninferior to standard q1m maintenance, we conducted a prospective, single-center randomized trial in low-immunologic-risk, stable renal transplant recipients. Here, post hoc analysis of 3-y outcomes, including renal function and adverse events, are reported.

Results

One hundred sixty-three patients received treatment in the q1m control group (n = 82) or q2m study group (n = 81). Renal allograft function as measured by baseline-adjusted estimated glomerular filtration rate was not significantly different between groups (time-averaged mean difference of 0.2 mL/min/1.73 m²; 95% confidence interval: -2.5, 2.9). There were no statistically significant differences in time to death or graft loss, freedom from rejection, or freedom from donor-specific antibodies (DSAs). During the extended 12- to 36-mo follow-up, 3 deaths, 1 graft loss occurred in the q1m group, compared with 2 deaths, and 2 graft losses in the q2m group. In the q1m group, 1 patient developed DSAs and acute rejection. In the q2m group, 3 patients developed DSAs and 2 associated with acute rejection.

Conclusions

Based on the similar renal function and survival at 36 mo compared with q1m, q2m belatacept is a potentially viable maintenance immunosuppressive strategy in low immunologic risk kidney transplant recipients that may facilitate increased clinical utilization of costimulation blockade-based immunosuppression.

Pre-transplant hypoalbuminemia is not associated with worse short-term outcomes among kidney transplant recipients

INTRODUCTION

Serum albumin is an indicator of overall health status, but it remains unclear how pre-transplant hypoalbuminemia is associated with early post-transplant outcomes.

METHODS

This study included all adult kidney transplant recipients (KTRs) at our center from 01/01/2001-12/31/2017 with serum albumin measured within 30 days before transplantation. KTRs were grouped based on pretransplant albumin level normal (≥4.0 g/dL), mild (≥3.5 - < 4.0g/dL), moderate (≥3.0 - < 3.5g/dL), or severe hypoalbuminemia (<3.0g/dL). Outcomes of interest included: length of hospital stay (LOS), readmission within 30 days, delayed graft function(DGF), and re-operation related to post-transplant surgical complications. We also analyzed rejection, graft failure, and death within 6 months post-transplant.

RESULTS

A total of 2807 KTRs were included 43.6% had normal serum albumin, 35.3% mild, 16.6% moderate, and 4.5% severe hypoalbuminemia. Mild and moderate hypoalbuminemia were associated with a shorter LOS by 1.22 (p < 0.001) and 0.80 days (p = 0.01), respectively, compared to normal albumin. Moderate (HR: 0.58; 95% CI: 0.37-0.91; p = 0.02) and severe hypoalbuminemia (HR: 0.21; 95% CI: 0.07-0.68; p = 0.01) were associated with significantly lower rates of acute rejection within 6 months post-transplant.

CONCLUSION

Patients with pre-transplant hypoalbuminemia have post-transplant outcomes similar to those with normal serum albumin, but with a lower risk of acute rejection based on the degree of hypoalbuminemia.

Analysis of individual components of frailty: Pre-transplant grip strength is the strongest predictor of post kidney transplant outcomes

Frailty is commonly assessed during kidney transplant recipient (KTR) evaluation. However, individual frailty components may have varying impact on post-transplant outcomes. In this single-center study of 825 KTRs, we determined the association between the individual components of a modified Fried frailty score and delayed graft function (DGF), early hospital readmission (EHR), cardiovascular (CV) events, acute rejection (AR), death censored graft failure (DCGF), and death. Sum frailty ≥3 was significantly associated with EHR (aOR = 3.62; 95% CI: 1.21-10.80). Among individual components, only grip strength was significantly associated with EHR (aOR = 1.54; 95% CI: 1.03-2.31). The addition of grip strength to a model with the other four components resulted in Net Reclassification Improvement (NRI) of 20.51% (p = .01). Similarly, only grip strength was significantly associated with CV events (aOR = 1.79; 95% CI: 1.12-2.86). The addition of grip strength to a model with the other four components resulted in NRI of 27.37% (p = .006). No other frailty components were associated with the outcomes of interest. Based on our findings, handgrip strength may be an important tool while assessing frailty, mainly predicting early readmission and cardiovascular events post-transplant.

Chronic Active Antibody-mediated Rejection in Kidney Transplant Recipients: Treatment Response Rates and Value of Early Surveillance Biopsies

There is limited information on the value of short-term invasive and noninvasive monitoring in kidney transplant recipients (KTR) undergoing therapy for chronic active antibody-mediated rejection (cAMR).

Methods

We describe response rates in patients with cAMR receiving pulse steroids/IVIG ± rituximab 3-mo after index biopsy.

Results

The study included 82 consecutive KTR. Mean time from transplant to cAMR was 10 y. Mean peritubular capillaritis (ptc), glomerulitis (g), microvascular inflammation (MVI), C4d, and cg Banff scores were 1.1, 2.1, 3.2, 0.2, and 2, respectively. Mean estimated glomerular filtration rate (eGFR) and urine protein creatinine (UPC) ratio were 38 mL/min and 1.6 g/g, respectively. Thirty (37%) patients lost their allograft during the mean follow-up of 2.4 y. In patients treated with pulse steroids/IVIG (n = 41), response rates for eGFR, UPC, donor-specific antibodies (DSAs), and MVI were 27%, 49%, 7%, and 19%, respectively. In the pulse steroids/IVIG/rituximab group, response rates were 66%, 61%, 20%, and 69%, respectively. Univariate analysis identified response in eGFR (HR = 0.03; P = 0.001; 95% CI, 0.004-0.26), UPC (HR = 0.38; P = 0.01; 95% CI, 0.18-0.82), and DSA (HR = 0.11; P = 0.004; 95% CI, 0.02-0.49) as predictors of graft survival. Multivariate analysis only retained eGFR response (HR = 0.12; P = 0.01; 95% CI, 0.02-0.64).

Conclusions

In cAMR, short-term response to treatment for kidney function and DSA was associated with graft survival, but the role of early surveillance biopsies needs further evaluation.

In kidney recipients from the same deceased donor, discordance in delayed graft function is associated with the worst outcomes

Delayed graft function(DGF) is a common complication among deceased donor kidney transplant recipients(DDKTs) and is associated with worse outcomes. The effect on outcomes of concordance versus discordance in DGF between two different recipients of kidneys from the same donor is largely unknown. We reviewed all adult DDKTs for which both kidneys were transplanted to two different recipients at our center between 2014-2019. DDKTs were divided into four groups based on the DGF status: concordance no DGF(cc-no-DGF); discordance no DGF(dd-no-DGF); discordance DGF(dd-DGF) and concordance in DGF(cc-DGF). Acute rejection (AR) and death censored graft failure (DCGF) were outcomes of interest. A total of 578 DDKTs fulfilled our selection criteria, 280 were in cc-no-DGF, 83 in dd-no-DGF, 83 in dd-DGF, and 132 in cc-DGF. Compared to cc-no-DGF, in univariate analysis, dd-DGF was associated with an increased risk of AR(HR:1.60; 95% CI:1.0-2.56) but cc-DGF was not(HR:1.01; 95% CI:0.63-1.62). dd-DGF was not associated with an increased risk of AR in multivariate analysis. In multivariate analysis, dd-DGF was associated with an increased risk of DCGF (HR: 2.70; 95% CI: 1.05-6.93) but cc-DGF was not (HR:2.36; 95% CI:0.97-5.70). Discordance in DGF is associated with worse outcomes and may need close follow-up and monitoring to improve the outcomes. This article is protected by copyright. All rights reserved.

Non-HLA Antibodies in Kidney Transplantation: Immunity and Genetic Insights

The polymorphic human leukocyte antigen (HLA) system has been considered the main target for alloimmunity, but the non-HLA antibodies and autoimmunity have gained importance in kidney transplantation (KT). Apart from the endothelial injury, secondary self-antigen exposure and the presence of polymorphic alloantigens, respectively, auto- and allo- non-HLA antibodies shared common steps in their development, such as: antigen recognition via indirect pathway by recipient antigen presenting cells, autoreactive T cell activation, autoreactive B cell activation, T helper 17 cell differentiation, loss of self-tolerance and epitope spreading phenomena. Both alloimmunity and autoimmunity play a synergic role in the formation of non-HLA antibodies, and the emergence of transcriptomics and genome-wide evaluation techniques has led to important progress in understanding the mechanistic features. Among them, non-HLA mismatches between donors and recipients provide valuable information regarding the role of genetics in non-HLA antibody immunity and development.

How Should Acute T-cell Mediated Rejection of Kidney Transplants Be Treated: Importance of Follow-up Biopsy

Background.

Limited published data exist to guide patient monitoring after the treatment of T-cell mediated rejection (TCMR) of kidney allografts.

Methods.

We reviewed the kidney function and histological outcomes after treatment of 163 first episodes of biopsy-proven TCMR between January 1‚ 2015‚ and July 31‚ 2020.

Results.

Of the 146 patients treated with steroid pulse alone, complete histological response was seen in 83% of patients with borderline rejection, 82.5% with grade 1A, 67% with grade 1B, and 50% with grade IIA. Of the 17 patients treated with steroids plus antithymocyte globulin, the complete histological response rate was 100% with grade 1A, 75% with grade 1B, 100% with grade IIA, and 57% with grade IIB. Among the patients with complete response as assessed by kidney function, 14% only had a partial or no response histologically. Among patients with no kidney function response, 68% had a complete response histologically.

Conclusion.

We thus find that responses based on kidney function alone do not correlate well with histological responses. If further treatment had been based solely on changes in estimated glomerular filtration rate, a significant number of patients would have been subsequently undertreated or overtreated. These results support the use of protocol follow-up biopsies after the treatment of TCMR.

Adipose tissue macrophages and atherogenesis – a synergy with cholesterolaemia

Antibody-mediated rejection (ABMR) is a major obstacle to the long-term success in kidney transplantation. Diagnosis of ABMR is determined according to the internationally recognized Banff criteria. However, a significant proportion of patients does not meet all the defined criteria, and the outcome of such cases remains poorly understood. The histology of ABMR frequently lacks sensitivity and specificity. More importantly, mixed forms of ABMR and T cell-mediated rejection as well as findings of nonspecific injury are common in clinical settings. Donor-specific anti-HLA antibodies (DSA) are detectable only in half of the ABMR cases by histology. Prognostic role of non-HLA antibodies against various endothelial proteins has been discussed. Antibody independent NK cell activation reflecting killer-cells’ inhibitory receptor incompatibility is suggested in microvascular inflammation in DSA negative patients. Molecular assessment of ABMR has been prioritized to overcome high interobserver variability and improve diagnostics in mixed forms of rejections and in DSA negative cases. Finally, donor-derived cell-free DNA detected in a recipient’s peripheral blood sample has been proposed as a noninvasive marker for diagnosis of graft rejection, and thus might serve as a liquid biopsy in the near future. Despite all achievements, diagnosing ABMR in kidney allografts remains to be a challenge in a significant number of cases.

Factors affecting sensitization following kidney allograft failure

Management of immunosuppression in a kidney transplant recipient with a failed allograft is complex; continuation carries infectious and metabolic risks, and discontinuation can lead to sensitization. We evaluated risk factors for sensitization in 89 kidney or simultaneous kidney-pancreas recipients, whose kidney transplant failed after 1/2013 and who were subsequently re-evaluated for kidney transplantation. Among recipients with pre graft failure cPRA <50%, calcineurin inhibitor (CNI) continuation (OR 0.11, p = 0.003) and steroid continuation (OR 0.17, p = 0.04) were associated with significantly lower odds of developing an absolute increase in cPRA of ≥50%. Each additional HLA mismatch was associated with OR of 2.16 (p = 0.02). CNI use was associated with OR of 0.09 (p = 0.001) for increase in cPRA to ≥80% if pre graft failure cPRA was <50%, and OR of 0.08 (p = 0.02) for increase in cPRA to ≥98% if pre graft cPRA was <80%. Anti-metabolites were continued more often among recipients who had a <50% increase (p = 0.006), however the association was lost on multivariate analyses. Weaning off immunosuppression and higher number of HLA mismatches are associated with greater likelihood of sensitization. While both CNI and steroid continuation conferred some protection against increase in cPRA, CNI continuation was the only factor protecting against becoming highly sensitized. This article is protected by copyright. All rights reserved.

Intimal Arteritis and Microvascular Inflammation Are Associated With Inferior Kidney Graft Outcome, Regardless of Donor-Specific Antibodies

Background: The prognostic role of intimal arteritis of kidney allografts in donor-specific antibody negative (DSA–) antibody-mediated rejection (ABMR) remains unclear.

Methods: Seventy-two out of 881 patients who had undergone kidney transplantation from 2014 to 2017 exhibited intimal arteritis in biopsies performed during the first 12 months. In 26 DSA negative cases, the intimal arteritis was accompanied by tubulointerstitial inflammation as part of T cell-mediated vascular rejection (TCMRV, N = 26); intimal arteritis along with microvascular inflammation occurred in 29 DSA negative (ABMRV/DSA–) and 19 DSA positive cases (ABMRV, DSA+, N = 17). In 60 (83%) patients with intimal arteritis, the surveillance biopsies after antirejection therapy were performed. Hundred and two patients with non-vascular ABMR with DSA (ABMR/DSA+, N = 55) and without DSA (ABMR/DSA–, N = 47) served as controls. Time to transplant glomerulopathy (TG) and graft failure were the study endpoints.

Results: Transplant glomerulopathy -free survival at 36 months was 100% in TCMRV, 85% in ABMR/DSA–, 65% in ABMRV/DSA-, 54% in ABMR/DSA+ and 31% in ABMRV/DSA+ (log rank p < 0.001). Death-censored graft survival at 36 months was 98% in ABMR/DSA-, 96% in TCMRV, 86% in ABMRV/DSA–, 79% in ABMR/DSA+, and 64% in ABMRV/DSA+ group (log rank p = 0.001). In surveillance biopsies, the resolution of rejection was found in 19 (90%) TCMRV, 14 (58%) ABMRV/DSA–, and only 4 (27%) ABMRV/DSA+ patients (p = 0.006). In the multivariable model, intimal arteritis as part of ABMR represented a significant risk for TG development (HR 2.1, 95% CI 1.2–3.8; p = 0.012) regardless of DSA status but not for graft failure at 36 months.

Conclusions: Intimal arteritis as part of ABMR represented a risk for early development of TG regardless of the presence or absence of DSA. Intimal arteritis in DSA positive ABMR represented the high-risk phenotype.

Risk factors and outcomes of BK viremia among deceased donor kidney transplant recipients based on donor characteristics

INTRODUCTION

BK polyomavirus (BKV) is a common infection among kidney transplant recipients (KTR). Risk factors and outcomes based on donor characteristics remain largely unknown.

METHODS

In this study, we aimed to analyze the impact of donor factors through a paired kidney analysis. We included 289 pairs of adult deceased donor transplants (578 KTRs total); each pair had received kidneys from the same donor. Recipient pairs were divided into three groups: "no BK group" if neither KTR developed BK viremia (n = 336), "discordant" if the only one did (n = 176), and "concordant" if both did (n = 66). Acute rejection (AR), graft failure, and BK nephropathy (BKN) were outcomes of interest.

RESULTS

Donors in the concordant group were younger, had lower kidney donor profile index (KDPI), and were less likely to be donor after circulatory death (DCD). In multivariate analyses, KTRs who had a donor with a higher body mass index (BMI) (hazard ratio (HR): 0.97; 95% confidence interval (CI): 0.95-0.99; p = .009) were less likely to develop BKV. Concordance was not associated with AR (HR: 0.83; 95% CI: 0.51-1.34; p = .45), graft failure (HR: 1.77; 95% CI: 0.42-7.50; p = .43), or BKN (HR: 1.02; 95% CI: 0.51-2.03; p = .96).

DISCUSSION

Our study suggests lower donor BMI is associated with BKV infection, and concordance or discordance between paired kidney recipients is not associated with poor outcomes.

Deep learning identified pathological abnormalities predictive of graft loss in kidney transplant biopsies

Interstitial fibrosis, tubular atrophy, and inflammation are major contributors to kidney allograft failure. Here we sought an objective, quantitative pathological assessment of these lesions to improve predictive utility and constructed a deep-learning-based pipeline recognizing normal vs. abnormal kidney tissue compartments and mononuclear leukocyte infiltrates. Periodic acid- Schiff stained slides of transplant biopsies (60 training and 33 testing) were used to quantify pathological lesions specific for interstitium, tubules and mononuclear leukocyte infiltration. The pipeline was applied to the whole slide images from 789 transplant biopsies (478 baseline [pre-implantation] and 311 post-transplant 12-month protocol biopsies) in two independent cohorts (GoCAR: 404 patients, AUSCAD: 212 patients) of transplant recipients to correlate composite lesion features with graft loss. Our model accurately recognized kidney tissue compartments and mononuclear leukocytes. The digital features significantly correlated with revised Banff 2007 scores but were more sensitive to subtle pathological changes below the thresholds in the Banff scores. The Interstitial and Tubular Abnormality Score (ITAS) in baseline samples was highly predictive of one-year graft loss, while a Composite Damage Score in 12-month post-transplant protocol biopsies predicted later graft loss. ITASs and Composite Damage Scores outperformed Banff scores or clinical predictors with superior graft loss prediction accuracy. High/intermediate risk groups stratified by ITASs or Composite Damage Scores also demonstrated significantly higher incidence of estimated glomerular filtration rate decline and subsequent graft damage. Thus, our deep-learning approach accurately detected and quantified pathological lesions from baseline or post-transplant biopsies and demonstrated superior ability for prediction of post-transplant graft loss with potential application as a prevention, risk stratification or monitoring tool.

The clinical value of donor-derived cell-free DNA measurements in kidney transplantation

Early diagnosis is critical to minimizing the damage rejection can do to the transplanted kidney. Donor-derived cell-free DNA (dd-cfDNA) represents non-encapsulated fragmented DNA that is continuously shed into the bloodstream from the allograft undergoing injury, with a half-life of about 30 min. This article reviews the available evidence regarding the diagnostic value of dd-cfDNA in kidney transplantation, as a result of which two assays, Allosure and Prospera, have garnered Medicare approval. We provide information on important scenarios and contexts including antibody-mediated rejection, T-cell mediated rejection, pre-test probability of rejection, timing of the test, repeat transplants, and background cell-free DNA levels to help our understanding of the test characteristics and utility of these assays in clinical practice. Data on multimodality assays including gene expression profiles and serial monitoring of dd-cfDNA in high risk situations are emerging.

The causes and frequency of kidney allograft failure in a low-resource setting: observational data from Iraqi Kurdistan

Background

In the developing world, transplantation is the most common long-term treatment for patients with end-stage renal disease, but rates and causes of graft failure are uncertain.

Methods

This was a retrospective outcomes study of renal transplant patients seen in Iraqi Kurdistan nephrology clinics in the year 2019. In 2019, 871 renal transplant patients were registered and outcomes followed through 12/31/2020. Indicated renal biopsies were obtained on 431 patients at 1 day to 18 years post-transplantation. Outcomes were compared with United States Renal Data System (USRDS) living donor reports.

Results

All donors were living. The recipient age was 38.5 ± 13.3 years, 98.2% were < 65 years old, 3.7% had previous transplants, and 2.8% had pretransplant donor-specific antibodies (DSA). Gehan-Breslow estimated failure rates for all-cause, return to HD, and death with functional graft were 6.0, 4.2, and 1.9% at 1 year and 18.1, 13.7, and 5.1% at 5 years post-engraftment (USRDS 2000; 1 year: 7.0, 5.0, 2.6%; 5 year: 22.3, 15.2, 10.6%. USRDS 2010; 1 year: 3.7, 2.4, 1.4%; 5 year: 15.3, 9.6, 7.3%). The median graft survival was 15 years. Acute tubular injury (ATI), infarction, and acute T cell-mediated rejection accounted for 22.2% of graft loss, with > 75% of these failures taking place in the first year. Most graft failures occurred late, at a median post-transplant time of 1125 (interquartile range, 365–2555) days, and consisted of interstitial fibrosis and tubular atrophy (IF/TA) (23.8%), transplant glomerulopathy (13.7%), and acquired active antibody-mediated rejection (12.0%). The significant predictors of graft loss were C4d + biopsies (P < 0.01) and advanced IF/TA (P < 0.001).

Conclusions

Kurdistan transplant patients had graft failure rates similar to living donors reported by the USRDS for the year 2000 but higher than reported for 2010. Compared to USRDS 2010, Kurdistan patients had a moderate excess of HD failures at one and 5 years post-engraftment. Nevertheless, prolonged survival is the norm, with chronic disorders and acquired DSA being the leading causes of graft loss.

Evaluation of Early Renal Allograft Dysfunction from Living Donors among Egyptian Patients (Histopathological and Immunohistochemical Study)

BACKGROUND: Early renal graft dysfunction is a major problem in the early post-transplantation period and is considered a major cause of graft loss. Clinical diagnosis based on the clinical criteria alone is unreliable; therefore, biopsy remains the gold standard to differentiate between rejection and non-rejection causes. AIM: This study was designed to identify and differentiate between causes of early graft dysfunction during the first post-transplantation month and to correlate between histological lesions and immunohistochemistry (IHC) for accurate diagnosis and a better outcome. MATERIALS AND METHODS: A total of 163 renal allograft biopsies, performed in the first post-transplantation month over 6 years, were included in the study. New sections were prepared from the paraffin blocks and stained with conventional stains. Additional sections were prepared and treated by complement fragment 4d (C4d) and cluster differentiation 3 (CD3) antibodies for IHC evaluation. RESULTS: All the studied cases were from living donors. The mean patient age was 39 years with predominant males. The clinical indication for most biopsies (94.5%) was impaired graft function. Acute rejection (AR) was the main diagnostic category observed in (98/163, 60.1%); out of which, T cell-mediated rejection (TCMR) was observed in (62/98, 63.2%). Drug toxicity was suspected in (53/163, 32.5%), acute tubular injury (ATI) not otherwise specified (nos) in (21/163, 12.9%), and other lesions including thrombotic microangiopathy were observed in the remaining biopsies. The most common cause of graft dysfunction in the 1st and 2nd weeks was AR representing. A significant correlation was seen between mild glomerulitis (g1) and mild peritubular capillaritis (PTC) 1, on the one side, and negative C4d staining, on the other side. No significant correlation was seen between moderate glomerulitis (g2) and moderate ptc2 at one side and positive C4d staining at the other side reflecting the poor association between the microvascular inflammation (“g” and “ptc” scores) and C4d positivity (r = 0.2). Missed mild tubulitis (t1) was found in a single case and missed moderate tubulitis (t2) was found in a single case detected by CD3 IHC. CONCLUSION: AR and drug toxicity account for the majority of early graft dysfunction, however, other pathological lesions, per se or coincide with them may be the cause. The significance of g2 per se as a marker for diagnosis of antibody-mediated rejection requires further study. Considering C4d score 1 (by IHC) positive; also requires further study with follow-up.

Risk factors for progression from low level BK dnaemia to unfavorable outcomes after BK management via immunosuppressive reduction

BACKGROUNDS

Effective management of BK viremia (BKPyV-DNAemia) in kidney transplant recipients (KTRs) involves regular monitoring and adjustment of immunosuppression. With this strategy, the majority of patients will clear BK or have ongoing, but non-significant, low-level BKPyV-DNAemia. However, despite adjustments, some will develop more severe sequelae of BK including BKPyV-DNAemia >5 log₁₀ copies/mL and BK nephropathy, and others may develop de novo DSA (dnDSA) or acute rejection (AR).

METHODS

This was a single-center study of KTRs transplanted at the University of Wisconsin-Madison between 01/01/2015 and 12/31/2017. In this study, we sought to elucidate characteristics associated with the progression of BKPyV-DNAemia to unfavorable outcomes after decreasing immunosuppressive medications for the management of BK viremia as described in consensus guidelines.

RESULTS

A total of 224 KTRs fulfilled our selection criteria; 118 (53%) resolved or had persistent low DNAemia, 64 (28%) had severe BK/nephropathy, and 42 (19%) developed dnDSA or AR. In multivariable analysis, female gender (HR: 2.05; 95% CI: 1.08-3.90; P = .02); previous rejection (HR: 2.90; 95% CI: 1.04-8.12; P = .04), and early infection (HR: 0.81; 95% CI: 0.72-0.90; P < .001) were associated with the development of severe BK/nephropathy. Conversely, non-depleting induction at transplant (HR: 2.06; 95% CI: 1.03-4.11; P = .03), HLA mismatches >3 (HR: 2.27; HR: 1.01-5.06; P = .04), and delayed graft function (HR: 4.14; 95% CI: 1.12-15.28; P = .03) were associated with development of dnDSA and/or rejection.

CONCLUSION

Our study suggests that almost half of KTRs with BKPyV-DNAemia managed by our immunosuppressant adjustment protocol progress unfavorably. Identification of these risk factors could assist the frontline clinician in creating an individualized immunosuppressive modification plan potentially mitigating negative outcomes.

Urinary nitrate concentration as a marker for kidney transplant rejection

BACKGROUND

Early identification and treatment of kidney transplant rejection episodes is vital to limit loss of function and prolong the life of the transplanted kidney and recipient. Current practice depends on detecting a creatinine rise. A biomarker to diagnose transplant rejection at an earlier time point than current practice, or to inform earlier decision making to biopsy, could be transformative. It has previously been shown that urinary nitrate concentration is elevated in renal transplant rejection. Nitrate is a nitric oxide (NO) oxidation product. Transplant rejection upregulates NO synthesis via inducible nitric oxide synthase leading to elevations in urinary nitrate concentration. We have recently validated a urinary nitrate concentration assay which could provide results in a clinically relevant timeframe. Our aim was to determine whether urinary nitrate concentration is a useful tool to predict renal transplant rejection in the context of contemporary clinical practice.

METHODS

We conducted a prospective observational study, recruiting renal transplant participants over an 18-month period. We made no alterations to the patients' clinical care including medications, immunosuppression, diet and frequency of visits. We collected urine samples from every clinical attendance. We assessed the urinary nitrate to creatinine ratio (uNCR) between patient groups: routine attendances, biopsy proven rejection, biopsy proven no rejection and other call backs. uNCR was examined over time for those with biopsy proven transplant rejection. These four groups were compared using an ANOVA test.

RESULTS

A total of 2656 samples were collected. uNCR during biopsy proven rejection, n = 15 (median 49 μmol/mmol, IQR 23-61) was not significantly different from that of routine samples, n = 164 (median 55 μmol/mmol, IQR 37-82) (p = 0.55), or biopsy proven no rejection, n = 12 (median 39 μmol/mmol, IQR 21-89) (P = 0.77). Overall uNCR was highly variable with no diagnostic threshold for kidney transplant rejection. Furthermore, within-patient uNCR was highly variable over time, and thus it was not possible to produce individualised patient thresholds to identify rejection. The total taking Tacrolimus was 204 patients, with no statistical difference between the uNCR of all those on Tacrolimus, against those not, p = 0.18.

CONCLUSION

The urinary nitrate to creatinine ratio is not a useful biomarker for renal transplant rejection.

Donor-specific antibodies in kidney transplantation: the University of Wisconsin experience

PURPOSE OF REVIEW

Antibody-mediated rejection (ABMR) is the leading cause of allograft failure in kidney transplant recipients. This article provides a summary of the clinical research relating to donor-specific antibodies (DSA) and ABMR in kidney transplant recipients at the University of Wisconsin-Madison Transplant Center.

RECENT FINDINGS

Over 40% of the kidney transplant candidates on the UNOS waitlist are sensitized, and both preformed and de novo DSA are associated with increased risk of rejection and graft loss. We have developed graded induction-desensitization treatment and monitoring protocols based on the degree of immunologic risk. We have also implemented standard treatment and surveillance strategies for patients with ABMR. Additional important observations from our studies include high rates of ABMR in patients with positive C4d staining in postreperfusion biopsies and rise in DSA at 1 week after transplant, and increased risk of kidney allograft failure in patients with de novo DSA and ABMR, as well as in patients with HLA-DSA undetectable ABMR. We also found worse outcomes with de novo DSA following simultaneous pancreas--kidney and liver--kidney transplantation. Notably, favorable long-term graft outcomes were observed in patients with DSA who do not present the classic histopathological findings of ABMR.

SUMMARY

In order to improve long-term outcomes for kidney transplant recipients, further research focusing on the pathogenic mechanisms elicited by HLA and non-HLA DSA, and novel therapies targeting these pathways is needed.