Acute Rejection Clinically Defined Phenotypes Correlate With Long-term Renal Allograft Survival

Antibody-mediated rejection diagnosed in early protocol biopsies in high immunological risk kidney transplant recipients

BACKGROUND

Renal transplant recipients with donor-specific anti-HLA antibodies are at an increased risk of antibody-mediated rejection (ABMR). Early protocolized renal biopsies may serve as a strategy to improve diagnosis in this patient population.

METHODS

We evaluated 155 highly sensitized renal transplant recipients with cPRA class I + II >90% pre-transplant from 2015 to 2022. Patients with protocol biopsies within the first 2 weeks post-transplant were included.

RESULTS

A total of 122 patients were included in the study. Of these, 13 (10.6%) were diagnosed with very early antibody-mediated rejection (veABMR) within the first 2 weeks post-transplant. This corresponds to 52% (13/25 patients) of all ABMR cases reported during the follow-up of this population. The graft survival rates at 1 and 3 years were significantly lower in patients with veABMR (P < .001) compared with patients without rejection in the early protocol biopsy. In terms of severity, the veABMR cohort exhibited a hazard ratio (HR) of 10.33 (95% confidence interval 3.23-33.06, P < .001) for graft failure. The presence of donor-specific antibodies class II on the day of transplantation and a higher percentage of eplet mismatch (EpMM), particularly EpMM DQA1, correlated with the development of veABMR.

CONCLUSION

Early protocol biopsies play a pivotal role in the early detection of veABMR in high-risk immunological patients. Patients with veABMR face significant risks of graft loss, despite early treatment of rejection.

Modelling acute antibody-mediated rejection of human kidney transplants using ex-vivo warm machine perfusion

BACKGROUND

Transplant rejection is a major cause of graft loss and morbidity. Currently, no human models of antibody-mediated rejection (AMR) exist, limiting mechanistic investigation and organ-specific targeted therapy. Here, using 12 human kidneys and ex-vivo normothermic machine perfusion, we demonstrate phenotypes of AMR after addition of antibodies against either human HLA class I or blood group antigens (A, B), thus modelling clinical AMR that can follow HLA incompatible (HLAi) or blood group incompatible (ABOi) transplantation.

METHODS

Discarded human kidneys with wide ranging demographics and cold ischaemia times (11-54 h) were perfused with red blood cells and fresh frozen plasma (FFP) as a source of complement/coagulation factors. For the HLAi model, 600 μg of W6/32 anti-class 1 HLA antibody was added to the circuit (time '0'). For the ABOi model, high titre FFP of the relevant blood group antibody was added. Renal blood flow index (RBFi, mL/min/100 g), C3 desArg, prothrombin fragments 1 + 2 and histology were determined. Our endpoints included haemodynamic changes, thrombosis, and biopsy proven complement deposition.

FINDINGS

Compared to control kidneys perfused without anti-donor antibodies, both models demonstrated haemodynamic collapse after antibody perfusion with only the HLAi model showing glomerular C4d deposition.

INTERPRETATION

We show that a clinically relevant human kidney model of AMR is feasible, and anticipate that these models, with refinements, could provide a basis to test different strategies to prevent AMR.

FUNDING

The Rosetrees and Stonygate Trust, The Royal College of Surgeons of England Fellowship Grant, NIHR Biomedical Research Centre/KCL Early Career Grant, Kidney Research U.K.

Histological diagnosis from kidney transplant biopsy can contribute to prediction of graft survival

Aim

The primary aim of this study was to in depth examine if the histological findings in a transplanted kidney biopsy can predict the prognosis for the graft and the patient. The secondary aim was to extend knowledge of the impact of time elapsed on biopsy findings.

Methods

Data from 1462 patients were merged from a kidney transplantation registry and a biopsy registry during 1 January 2007 and 30 September 2017. Kaplan–Meier analysis and multivariate Cox‐regression analysis were performed and hazard ratios (HR) with 95% confidence intervals (CI) were presented.

Results

Compared to normal biopsy findings, graft survival after biopsy (gsaBiopsy) was shorter for patients with glomerular diseases (HR 8.2, CI:3.2–21.1), rejections (HR 4.2, CI:1.7–10.3), chronic changes including IFTA (HR 3.2, CI:1.3–8.0), acute tubular injuries (HR 3.0, CI:1.2–7.8), and borderline changes (HR 2.9, CI:1.1–7.6). Sub‐analysis of rejections showed shorter gsaBiopsy for chronic TCMR (HR 4.7, CI:1.9–11.3), active ABMR (HR 3.6, CI:1.7–7.7) and chronic ABMR (HR 3.5, CI:2.0–6.0). Patients with TCMR Banff grade II (HR 0.35, CI:0.20–0.63) and grade I (HR 0.52, CI:0.29–0.93) had a better gsaBiopsy compared to all other types of rejections.

Conclusion

Shorter gsaBiopsy was noted in kidneys with glomerular diseases, rejections, acute tubular injuries and borderline changes. TCMR Banff rejections grade I and II were associated with a better prognosis.

This Swedish single centre study showed that the impact on allograft survival is dependent on the nature of the biopsy findings, with histological findings of glomerular disease, severe rejections and chronic changes being associated with more rapid allograft loss.

Plasma cell biology: Foundations for targeted therapeutic development in transplantation

Solid organ transplantation is a life-saving procedure for patients with end-stage organ disease. Over the past 70 years, tremendous progress has been made in solid organ transplantation, particularly in T-cell-targeted immunosuppression and organ allocation systems. However, humoral alloimmune responses remain a major challenge to progress. Patients with preexisting antibodies to human leukocyte antigen (HLA) are at significant disadvantages in regard to receiving a well-matched organ, moreover, those who develop anti-HLA antibodies after transplantation face a significant foreshortening of renal allograft survival. Historical therapies to desensitize patients prior to transplantation or to treat posttransplant AMR have had limited effectiveness, likely because they do not significantly reduce antibody levels, as plasma cells, the source of antibody production, remain largely unaffected. Herein, we will discuss the significance of plasma cells in transplantation, aspects of their biology as potential therapeutic targets, clinical challenges in developing strategies to target plasma cells in transplantation, and lastly, novel approaches that have potential to advance the field.

Belatacept for Simultaneous Calcineurin Inhibitor and Chronic Corticosteroid Immunosuppression Avoidance

Immunosuppressive therapy in kidney transplantation is associated with numerous toxicities. CD28-mediated T cell costimulation blockade using belatacept may reduce long-term nephrotoxicity, compared with calcineurin inhibitor-based immunosuppression. The efficacy and safety of simultaneous calcineurin inhibitor avoidance and rapid steroid withdrawal were tested in a randomized, prospective, multi-center study. Methods All kidney transplants were performed using rapid steroid withdrawal immunosuppression. Recipients were randomized to 1:1:1 to receive belatacept with alemtuzumab induction, belatacept with rabbit antithymocyte globulin (rATG) induction, or tacrolimus with rATG induction. The composite endpoint consisted of death, kidney allograft loss, or an MDRD calculated eGFR of <45 ml/min/1.73m² at 2 years. Results The composite endpoint was observed for 11/107 (10%) participants assigned to belatacept/alemtuzumab, 13/104 (13%) assigned to belatacept /rATG, and 21/105 (21%) assigned to tacrolimus/rATG (belatacept/alemtuzumab vs tacrolimus/rATG p = 0.99: belatacept/rATG vs tacrolimus/rATG p = 0.66). Patient and graft survival rates were similar between all groups. eGFR <45 ml/min/1.73m² was observed for 9/107 (8%) participants assigned to belatacept/alemtuzuab, 8/104 (8%) participants assigned to belatacept/rATG, and 20/105 (19%) participants assigned to tacrolimus/rATG (p<0.05 for each belatacept group vs tacrolimus/rATG). Biopsy-proven acute rejection was observed for 20/107 (19%) participants assigned to belatacept/alemtuzuab, 26/104 (25%) participants assigned to belatacept/rATG, and 7/105 (7%) participants assigned to tacrolimus/rATG (belatacept/alemtuzumab vs tacrolimus/rATG p = 0.006: belatacept/rATG vs tacrolimus/rATG p < 0.001). Gastrointestinal and neurologic adverse events were less frequent with belatacept versus calcineurin based immunosuppression. Conclusions Overall two-year outcomes were similar comparing maintenance immunosuppression based on belatacept versus tacrolimus, each protocol with rapid steroid withdrawal. The incidence of eGFR <45 ml/min/1.73m² was significantly lower but the incidence of biopsy proven acute rejection significantly higher with belatacept compared with tacrolimus.

Reducing Donor-specific Antibody During Acute Rejection Diminishes Long-term Renal Allograft Loss: Comparison of Early and Late Rejection

BACKGROUND

Reduction in donor-specific antibody (DSA) has been associated with improved renal allograft survival after antibody-mediated rejection (AMR). These observations have not been separately analyzed for early and late AMR and mixed acute rejection (MAR). The purpose of this study was to evaluate long-term responses to proteasome inhibitor-based therapy for 4 rejection phenotypes and to determine factors that predict allograft survival.

METHODS

Retrospective cohort study evaluating renal transplant recipients with first AMR episodes treated with proteasome inhibitor-based therapy from January 2005 to July 2015.

RESULTS

A total of 108 patients were included in the analysis. Immunodominant DSA reduction at 14 days differed significantly (early AMR 79.6%, early MAR 54.7%, late AMR 23.4%, late MAR 21.1%, P < 0.001). Death-censored graft survival (DCGS) differed at 3 years postrejection (early AMR 88.3% versus early MAR 77.8% versus late AMR 56.7% versus late MAR 54.9%, P = 0.02). Multivariate analysis revealed that immunodominant DSA reduction > 50% at 14 days was associated with improved DCGS (odds ratio, 0.12, 95% CI, 0.02-0.52, P = 0.01).

CONCLUSIONS

In summary, significant differences exist across rejection phenotypes with respect to histological and DSA responses. The data suggest that DSA reduction may be associated with improved DCGS in both early and late AMR.

Recommended Treatment for Antibody-mediated Rejection After Kidney Transplantation: The 2019 Expert Consensus From the Transplantion Society Working Group

With the development of modern solid-phase assays to detect anti-HLA antibodies and a more precise histological classification, the diagnosis of antibody-mediated rejection (AMR) has become more common and is a major cause of kidney graft loss. Currently, there are no approved therapies and treatment guidelines are based on low-level evidence. The number of prospective randomized trials for the treatment of AMR is small, and the lack of an accepted common standard for care has been an impediment to the development of new therapies. To help alleviate this, The Transplantation Society convened a meeting of international experts to develop a consensus as to what is appropriate treatment for active and chronic active AMR. The aim was to reach a consensus for standard of care treatment against which new therapies could be evaluated. At the meeting, the underlying biology of AMR, the criteria for diagnosis, the clinical phenotypes, and outcomes were discussed. The evidence for different treatments was reviewed, and a consensus for what is acceptable standard of care for the treatment of active and chronic active AMR was presented. While it was agreed that the aims of treatment are to preserve renal function, reduce histological injury, and reduce the titer of donor-specific antibody, there was no conclusive evidence to support any specific therapy. As a result, the treatment recommendations are largely based on expert opinion. It is acknowledged that properly conducted and powered clinical trials of biologically plausible agents are urgently needed to improve patient outcomes.

Belatacept-based immunosuppression with simultaneous calcineurin inhibitor avoidance and early corticosteroid withdrawal: A prospective, randomized multicenter trial

Simultaneous calcineurin inhibitor avoidance (CNIA) and early corticosteroid withdrawal (ESW) have not been achieved primarily due to excessive acute rejection. This trial compared 2 belatacept-based CNIA/ESW regimens with a tacrolimus-based ESW regimen. Kidney transplant recipients were randomized to receive alemtuzumab/belatacept, rabbit anti-thymocyte globulin (rATG)/belatacept, or rATG/tacrolimus. The combinatorial primary endpoint consisted of patient death, renal allograft loss, or a Modification of Diet in Renal Disease-calculated eGFR of <45 mL/min/1.73 m² at 12 months. Results are reported by treatment group (alemtuzumab/belatacept, rATG/belatacept, and rATG/tacrolimus). Superiority was not observed at 1 year for the primary endpoint (9/107 [8.4%], 15/104 [14.4%], and 14/105 [13.3%], respectively; P = NS) for either belatacept-based regimen. Differences were not observed for secondary endpoints (death, death-censored graft loss, or estimated glomerular filtration rates < 45 mL/min/1.73 m² ). Differences were observed in biopsy-proved acute cellular rejection (10.3%, 18.3%, and 1.9%, respectively) (P < .001), but not in antibody-mediated rejection, mixed acute rejection, or de novo donor-specific anti-HLA antibodies. Neurologic and electrolyte abnormality adverse events were less frequent under belatacept. Belatacept-based CNIA/ESW regimens did not prove to be superior for the primary or secondary endpoints. Belatacept-treated patients demonstrated an increase in biopsy-proved acute cellular rejection and reduced neurologic and metabolic adverse events. These results demonstrate that simultaneous CNIA/ESW is feasible without excessive acute rejection.

Risk factors for death in kidney transplant patients: analysis from a large protocol biopsy registry

BACKGROUND

Identification and quantification of the relevant factors for death can improve patients' individual risk assessment and decision-making. We used a well-documented patient cohort (n = 892) in a renal transplant programme with protocol biopsies to establish multivariable Cox models for risk assessment at 3 and 12 months post-transplantation.

METHODS

Patients transplanted between 2000 and 2007 were observed up to 11 years (total observation 5227 patient-years; median 5.9 years). Loss to follow-up was negligible (n = 15). A total of 2251 protocol biopsies and 1214 biopsies for cause were performed. All rejections and clinical borderline rejections in protocol biopsies were treated.

RESULTS

Overall 10-year patient survival was 78%, with inferior survival of patients with graft loss and superior survival of patients with living-donor transplantation. Eight factors were common in the models at 3 and 12 months, including age, pre-transplant heart failure and a score of cardiovascular disease and type 2 diabetes, post-transplant urinary tract infection, treatment of rejection, new-onset heart failure, coronary events and malignancies. Additional variables of the model at 3 months included deceased donor transplantation, transplant lymphocele, BK virus nephropathy and severe infections. Graft function and graft loss were significant factors of the model at 12 months. Internal validation and validation with a separate cohort of patients (n = 349) demonstrated good discrimination of the models.

CONCLUSIONS

The identified factors indicate the important areas that need special attention in the pre- and post-transplant care of renal transplant patients. On the basis of these models, we provide nomograms as a tool to weigh individual risks that may contribute to decreased survival.

CD45RC Expression of Circulating CD8+ T Cells Predicts Acute Allograft Rejection: A Cohort Study of 128 Kidney Transplant Patients

Predictive biomarkers of acute rejection (AR) are lacking. Pre-transplant expression of CD45RC on blood CD8⁺ T cells has been shown to predict AR in kidney transplant (KT) patients. The objective of the present study was to study CD45RC expression in a large cohort of KT recipients exposed to modern immunosuppressive regimens. CD45RC expression on T cells was analyzed in 128 KT patients, where 31 patients developed AR, of which 24 were found to be T-cell mediated (TCMR). Pre-transplant CD4⁺ and CD8⁺ CR45RC^high T cell proportions were significantly higher in patients with AR. The frequency of CD45RC^high T cells was significantly associated with age at transplantation but was not significantly different according to gender, history of transplantation, pre-transplant immunization, and de novo donor specific anti-Human Leucocyte Antigen (HLA) antibody. Survival-free AR was significantly better in patients with CD8⁺ CD45RC^high T cells below 58.4% (p = 0.0005), but not different according to CD4⁺ T cells (p = 0.073). According to multivariate analysis, CD8⁺ CD45RC^high T cells above 58.4% increased the risk of AR 4-fold (HR 3.96, p = 0.003). Thus, pre-transplant CD45RC expression on CD8⁺ T cells predicted AR, mainly TCMR, in KT patients under modern immunosuppressive therapies. We suggest that CD45RC expression should be evaluated in a prospective study to validate its usefulness to quantify the pre-transplant risk of AR.

Preformed Donor-specific Antibodies Against HLA Class II and Graft Outcomes in Deceased-donor Kidney Transplantation

Background

Many kidney transplant centers in the United States report both HLA class I and II antibodies detected by sensitive solid-phase assays (SPAs) to United Network for Organ Sharing as unacceptable antigens, significantly reducing the compatible donor organ pool and prolonging waiting time for highly sensitized patients. However, the clinical relevance of all detected donor-specific antibodies (DSAs) by SPA is not unequivocal, because fluorescence intensity does not always accurately reflect antibody pathogenicity. Our center does not exclude patients from transplantation based on DSA class II.

Methods

We performed a retrospective analysis in 179 deceased-donor kidney transplant recipients with solely DSA class II before transplant and patients without DSA and compared graft survival, rejection, and clinical outcomes. Patient survival was also compared with matched controls on the waiting list.

Results

Patients transplanted with DSA class II showed a clear survival benefit compared with matched patients who remained on dialysis or were waitlisted on dialysis/transplanted at 5 years (100%, 34%, and 73%, respectively). After a mean follow-up of 5.5 years, there was no significant difference in death-censored graft survival between transplanted patients without DSA and those with preformed DSA class II (adjusted HR 1.10; 95% confidence interval, 0.41-2.97), although the incidence of rejection was higher in recipients with DSA class II (adjusted HR 5.84; 95% confidence interval, 2.58-13.23; P < 0.001). Serum creatinine levels at 1, 3, and 5 years posttransplant did not differ between groups. No predictors of rejection were found, although patients who received basiliximab induction therapy had higher incidence of rejection (100%) compared with those who received antithymocyte globulin (52%).

Conclusions

We conclude that for highly sensitized patients, deceased-donor kidney transplantation with DSA class II yields a survival benefit over prolonged waiting time on dialysis. Instead of listing DSA class II as unacceptable antigens, an individual approach with further immunologic risk assessment is recommended.

Clinical and Pathological Features of Plasma Cell-Rich Acute Rejection After Kidney Transplantation

BACKGROUND

Plasma cell-rich acute rejection (PCAR) is a rare type of allograft rejection characterized by the presence of mature plasma cells. In general, the prognosis of PCAR is poor, and its clinical and pathological features remain unclear.

METHODS

We performed a retrospective observational study and compared allograft survival between kidney transplant recipients who developed PCAR and those who did not develop PCAR. We further analyzed clinical and pathological risk factors for allograft failure in PCAR patients.

RESULTS

Of 1956 recipients, 40 developed PCAR. There was a higher prevalence of deceased donor transplants (27.5% vs 11.7%, P = 0.0059), longer median total ischemia time (99 minutes; interquartile range, 71-144 vs 77 minutes; interquartile range, 59-111; P = 0.0309), and lower prevalence of ABO-incompatible transplantation (7.5% vs 22.5%; P = 0.0206) in patients with PCAR than in those without PCAR.Multivariate Cox regression analysis showed that development of PCAR was associated with allograft loss (hazard ratio, 8.03; 95% confidence interval, 3.89-14.80; P < 0.0001).We classified PCAR according to the Banff 2015 criteria into a borderline change group, a T cell-mediated rejection (TCMR) group, an antibody-mediated rejection (AMR) or suspected of having AMR (AMR/sAMR) group, and a mixed rejection (TCMR/AMR) group. The AMR/sAMR group was associated with a lower rate of allograft survival without significant difference (log-rank test, P = 0.1692).

CONCLUSIONS

The results indicated that PCAR was an independent risk factor for allograft loss. PCAR presented with all types of rejection in the Banff 2015 criteria, and AMR/sAMR was associated with poor allograft survival.

Impact of Induction Therapy on Circulating T Follicular Helper Cells and Subsequent Donor-Specific Antibody Formation After Kidney Transplant

Introduction

The cellular events that contribute to generation of donor-specific anti-HLA antibodies (DSA) post-kidney transplantation (KTx) are not well understood. Characterization of such mechanisms could allow tailoring of immunosuppression to benefit sensitized patients.

Methods

We prospectively monitored circulating T follicular helper (cT_FH) cells in KTx recipients who received T-cell depleting (thymoglobulin, n = 54) or T-cell nondepleting (basiliximab, n = 20) induction therapy from pre-KTx to 1 year post-KTx and assessed their phenotypic changes due to induction and DSA occurrence, in addition to healthy controls (n = 13), for a total of 307 blood samples.

Results

Before KTx, patients displayed comparable levels of resting, central memory cT_FH cells with similar polarization to those of healthy controls. Unlike basiliximab induction, thymoglobulin induction significantly depleted cT_FH cells, triggered lymphopenia-induced proliferation that skewed cT_FH cells toward increased Th1 polarization, effector memory, and elevated programmed cell death protein 1 (PD-1)^int/hi expression, resembling activated phenotypes. Regardless of induction, patients who developed DSA post-KTx, harbored pre-KTx donor-reactive memory interleukin (IL)-21⁺ cT_FH cells and showed higher % cT_FH and lower % of T regulatory (T_REG) cells post-KTx resulting in elevated cT_FH:T_REG ratio at DSA occurrence.

Conclusion

Induction therapy distinctly shapes cT_FH cell phenotype post-KTx. Monitoring cT_FH cells before and after KTx may help detect those patients prone to DSA generation post-KTx.

iTRAQ-based quantitative proteomic analysis reveals potential early diagnostic markers in serum of acute cellular rejection after liver transplantation

Liver transplantation (LT) is the most effective treatment method for advanced stage liver disease but acute cellular rejection (ACR) seriously affects the prognosis of LT. To discover novel diagnostic biomarkers of ACR after LT, Isobaric Tags for Relative and Absolute Quantitation (iTRAQ)-based mass spectrometry was performed to characterize alterations of serum proteins among patients validated to be pathologically ACR or pathologically no-ACR after LT and healthy controls. As a result, 10 differentially expressed proteins were found out between the ACR group and the No-ACR group; 88 differentially expressed proteins were found out between the ACR group and the Healthy Control group; 39 differentially expressed proteins were found out between No-ACR group and Healthy Control group. After analysis and ELISA validation, the results showed that CFHR1, CFHR5 and CFH could be candidate protein biomarkers for the early diagnosis of ACR after LT.

The Efficacy of Rabbit Anti-Thymocyte Globulin for Acute Kidney Transplant Rejection in Patients Using Calcineurin Inhibitor and Mycophenolate Mofetil-Based Immunosuppressive Therapy

Background

T cell depleting antibody therapy with rabbit anti-thymocyte globulin (rATG) is the treatment of choice for glucocorticoid-resistant acute kidney allograft rejection (AR) and is used as first-line therapy in severe AR. Almost all studies investigating the effectiveness of rATG for this indication were conducted at the time when cyclosporine A and azathioprine were the standard of care. Here, the long-term outcome of rATG for AR in patients using the current standard immunosuppressive therapy (i.e., tacrolimus and mycophenolate mofetil) is described.

Material/Methods

Between 2002 to 2012, 108 patients were treated with rATG for AR. Data on kidney function in the year following rATG and long-term outcomes were collected.

Results

Overall survival after rATG was comparable to overall survival of all kidney transplantation patients (P=0.10). Serum creatinine 1 year after rATG was 179 μmol/L (interquartile range (IQR) 136–234 μmol/L) and was comparable to baseline serum creatinine (P=0.22). Early AR showed better allograft survival than late AR (P=0.0007). In addition, 1 year after AR, serum creatinine was lower in early AR (157 mol/L; IQR 131–203) compared to late AR (216 mol/L; IQR 165–269; P<0.05). The Banff grade of rejection, kidney function at the moment of rejection, and reason for rATG (severe or glucocorticoid resistant AR) did not influence the allograft survival.

Conclusions

Treatment of AR with rATG is effective in patients using current standard immunosuppressive therapy, even in patients with poor allograft function. Early identification of AR followed by T cell depleting treatment leads to better allograft outcomes.

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

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

Dynamic Prognostic Score to Predict Kidney Allograft Survival in Patients with Antibody-Mediated Rejection

No tool is available for the early assessment of response to antibody-mediated rejection (ABMR) therapies in kidney allograft recipients. This study was designed to define a dynamic composite prognostic ABMR score to predict kidney allograft survival, integrating the disease characteristics at diagnosis and the response to treatment. Among 1978 kidney recipients who underwent transplant between 2008 and 2014, we included 278 patients diagnosed with active ABMR and receiving standard treatment, including plasma exchange, intravenous Ig, and rituximab. Patients were prospectively assessed at diagnosis and after treatment for clinical data, histologic characteristics (allograft biopsy specimen), and donor-specific anti-HLA antibodies (DSA). The dynamic ABMR prediction model included GFR (P<0.001) and presence of interstitial fibrosis/tubular atrophy (P=0.003) at diagnosis and changes in GFR (P<0.001), peritubular capillaritis Banff score (P=0.002), and DSA mean fluorescence intensity (P<0.001) after treatment. Overall, this model showed good calibration and discrimination (C-statistic=0.84). The ABMR prognostic score derived from the prediction model identified three risk strata with 6-year kidney allograft survival rates of 6.0% (high-risk group, n=40), 44.9% (intermediate-risk group, n=36), and 84.4% (low-risk group, n=202), and it provided greater net clinical benefit to patients than did considering them all to have the same level of risk of allograft loss. The performance of the ABMR prognostic score was validated in an independent cohort of 202 kidney recipients with ABMR (C-statistic=0.79). The ABMR prognostic score could be used to inform therapeutic decisions in clinical practice and for the design of clinical trials.

A Model of Acute Antibody-Mediated Renal Allograft Rejection in the Sensitized Rata

OBJECTIVES

Antibody-mediated rejection in transplant recipients with preexisting donor-specific antibodies is a challenging clinical situation. However, we lack suitable animal models to study this scenario. The aim of this study was to develop an animal model of acute antibody-mediated rejection of renal allografts in sensitized recipients.

MATERIALS AND METHODS

We used major histocompatibility complex class I and II incompatible rat strains (Dark Agouti RT1av1 and Lewis RT1l), which develop aggressive rejection. Recipient Lewis rats were immunized with donor strain spleen cells 5 days before surgery to induce donor-specific antibodies. Rats underwent bilateral nephrectomy and orthotopic transplant of the donor kidney. To minimize T-cell-mediated rejection while allowing the development of donor-specific antibodies, recipient animals were given tacrolimus starting the day before surgery.

RESULTS

Hyperacute rejection was not seen, but acute graft dysfunction was evident on day 1 with a rapid deterioration of graft function by day 3. Histologic damage featured glomerulopathy, capillaritis, capillary thrombosis, and acute tubular injury. Recipients exhibited high serum levels of donor-specific antibodies and deposition of immunoglobulin G and C4d on graft endothelium. Immunostaining showed substantial endothelial damage, fibrin deposition in glomerular and peritubular capillaries, and infiltrates of macrophages, neutrophils, and natural killer cells. T-cell activation was efficiently suppressed by tacrolimus.

CONCLUSIONS

We have developed a clinically relevant model of acute antibody-mediated rejection in recipients with preexisting donor-specific antibodies, which is suitable for testing novel therapies.

Six-Month Urinary CCL2 and CXCL10 Levels Predict Long-term Renal Allograft Outcome

BACKGROUND

Early prognostic markers that identify high-risk patients could lead to increased surveillance, personalized immunosuppression, and improved long-term outcomes. The goal of this study was to validate 6-month urinary chemokine ligand 2 (CCL2) as a noninvasive predictor of long-term outcomes and compare it with 6-month urinary CXCL10.

METHODS

A prospective, observational renal transplant cohort (n = 185; minimum, 5-year follow-up) was evaluated. The primary composite outcome included 1 or more: allograft loss, renal function decline (>20% decrease estimated glomerular filtration rate between 6 months and last follow-up), and biopsy-proven rejection after 6 months. CCL2/CXCL10 are reported in relation to urine creatinine (ng/mmol).

RESULTS

Fifty-two patients (52/185, 28%) reached the primary outcome at a median 6.0 years, and their urinary CCL2:Cr was significantly higher compared with patients with stable allograft function (median [interquartile range], 38.6 ng/mmol [19.7-72.5] vs 25.9 ng/mmol [16.1-45.8], P = 0.009). Low urinary CCL2:Cr (≤70.0 ng/mmol) was associated with 88% 5-year event-free survival compared with 50% with high urinary CCL2:Cr (P < 0.0001). In a multivariate Cox-regression model, the only independent predictors of the primary outcome were high CCL2:Cr (hazard ratio [HR], 2.86; 95% confidence interval [95% CI], 1.33-5.73) and CXCL10:Cr (HR, 2.35; 95% CI, 1.23-4.88; both P = 0.009). Urinary CCL2:Cr/CXCL10:Cr area under the curves were 0.62 (P = 0.001)/0.63 (P = 0.03), respectively. Time-to-endpoint analysis according to combined high or low urinary chemokines demonstrates that endpoint-free survival depends on the overall early chemokine burden.

CONCLUSIONS

This study confirms that urinary CCL2:Cr is an independent predictor of long-term allograft outcomes. Urinary CCL2:Cr/CXCL10:Cr alone have similar prognostic performance, but when both are elevated, this suggests a worse prognosis. Therefore, urinary chemokines may be a useful tool for timely identification of high-risk patients.

Human Pooled Immunoglobulin as Treatment of Active Antibody-Mediated Rejection of Transplanted Kidney

BACKGROUND

Antibody-mediated rejection (ABMR) has emerged as the leading cause of renal graft loss. The optimal treatment protocol in ABMR remains unknown. This study aimed to assess the efficacy of intravenous immunoglobulin (IVIG) for treatment of ABMR in renal recipients.

METHODS

Thirty-nine ABO-compatible cross-match-negative renal recipients with biopsy-proven ABMR composed the study group. Pulses of methylprednisolone (MP) and appropriate enhancement of net state of immunosuppression were applied in all individuals; 17/39 recipients were administered IVIG (IVIG group); the remaining 22/39 patients, identified to be nonadherent or unsatisfactorily immunosuppressed, were kept on the initial treatment (MP group). Serum creatinine concentration was obtained at each of 10 intended visits, and glomerular filtration rate (GFR) was estimated with the use of the standard Modification of Diet in Renal Disease (MDRD) formula. Generalized linear mixed model was used for statistical analysis.

RESULTS

Renal function (modeled as linear slope of MDRD-based GFR change over time, separately for the pre- and post-intervention periods) improved significantly in IVIG-treated recipients. Pre-intervention slopes were -0.72 and -0.46 mL/min/mo for IVIG and MP groups, respectively (P = NS), whereas post-intervention the slopes changed to -0.03 and -0.47 mL/min/mo (IVIG and MP, respectively; P < .005). Within-group changes of slopes at the time of intervention were 0.69 and -0.01 mL/min/mo in IVIG (P < .01) and MP (P = NS) groups, respectively. The relative slope change (pre- to post-intervention) was 0.7 mL/min/mo in favor of the IVIG group (P < .033). None of the classic immunologic or nonimmunologic graft function predictors influenced GFR during 12 months of follow-up.

CONCLUSIONS

IVIG improved graft function in renal recipients diagnosed with ABMR.

Infectious complications as the leading cause of death after kidney transplantation: analysis of more than 10,000 transplants from a single center

AIM

To identify specific causes of graft failure in a large sample of kidney transplant patients from a middle-income, developing country.

METHODS

Retrospective cohort study analyzing all consecutive single kidney transplants (KTs) performed at a single center in Brazil between January 1st 1998 and December 31st 2013. The database closing date was December 31st 2014.

RESULTS

Out of 10,400 KTs, there were 1191 (11.45%) deaths with a functioning graft, 40 cases (0.38%) of primary non-function (PNF) and 1417 cases (13.62%) of graft loss excluding death and PNF as the cause. Infectious complications (404 cases, 34% of all deaths) were the major cause of death. Most deaths due to infection occurred within the first year after transplantation (157 deaths, 38.86%). Immunologic mechanisms, comprising acute rejection and immune-mediated interstitial fibrosis/tubular atrophy (IF/TA), were responsible for 52% of all cases of graft failure not involving recipient death. Half of the losses by acute rejection occurred late after transplantation.

CONCLUSION

Contrary to what is observed in developed countries, infectious complications are the main challenge with kidney transplantation in Brazil. Non-adherence to treatment also appears to contribute significantly to long-term kidney graft loss. Strategies for improvement should focus on better compliance and a greater safety profile of immunosuppressive treatment.

Precision Subtypes of T Cell-Mediated Rejection Identified by Molecular Profiles

Among kidney transplant recipients, the treatment of choice for acute T cell-mediated rejection (TCMR) with pulse steroids or antibody protocols has variable outcomes. Some rejection episodes are resistant to an initial steroid pulse, but respond to subsequent antibody protocols. The biological mechanisms causing the different therapeutic responses are not currently understood. Histological examination of the renal allograft is considered the gold standard in the diagnosis of acute rejection. The Banff Classification System was established to standardize the histopathological diagnosis and to direct therapy. Although widely used, it shows variability among pathologists and lacks criteria to guide precision individualized therapy. The analysis of the transcriptome in allograft biopsies, which we analyzed in this study, provides a strategy to develop molecular diagnoses that would have increased diagnostic precision and assist the development of individualized treatment. Our hypothesis is that the histological classification of TCMR contains multiple subtypes of rejection. Using R language algorithms to determine statistical significance, multidimensional scaling, and hierarchical, we analyzed differential gene expression based on microarray data from biopsies classified as TCMR. Next, we identified KEGG functions, protein–protein interaction networks, gene regulatory networks, and predicted therapeutic targets using the integrated database ConsesnsusPathDB (CPDB). Based on our analysis, two distinct clusters of biopsies termed TCMR01 and TCMR02 were identified. Despite having the same Banff classification, we identified 1933 differentially expressed genes between the two clusters. These genes were further divided into three major groups: a core group contained within both the TCMR01 and TCMR02 subtypes, as well as genes unique to TCMR01 or TCMR02. The subtypes of TCMR utilized different biological pathways, different regulatory networks and were predicted to respond to different therapeutic agents. Our results suggest approaches to identify more precise molecular diagnoses of TCMR, which could form the basis for personalized treatments.