The Spectrum of Renal Allograft Failure

Defining causes of death-censored kidney allograft failure: A 5-year multicentre ANZDATA and clinical cross-sectional study

AIM

Determining specific causes of allograft failure allows a focus on understanding and treating these conditions. Previous studies highlight chronic antibody-mediated rejection as a leading cause of late allograft failure. We sought to define causes of allograft failure in a large cohort of kidney transplant recipients across multiple centres in Australia and New Zealand, including cases previously attributed to chronic allograft nephropathy (CAN).

METHODS

All death-censored allograft failures at 9 participating centres between 1 January 2014 to 31 December 2018 were included. Available clinical and biopsy data were reviewed and the "most likely" cause assigned.

RESULTS

There were 642 death-censored allograft failures in the study period. Of these, 495 (77.1%) had an informative biopsy performed a median of 13.4 months (IQR 2.5-39.1 months) prior to allograft failure. Rejection of any type was the leading cause of allograft failure (47.5%), comprised chiefly of chronic antibody-mediated rejection (37.4%) and chronic T-cell mediated rejection (6.4%). Other leading causes were undifferentiated interstitial fibrosis and tubular atrophy (10.8%), late medical and surgical complications (8.1%) and recurrent or de novo glomerulonephritis (7.0%). Polyoma viral nephropathy and calcineurin inhibitor toxicity each contributed to <2%. Causes of allograft failure previously attributed to CAN (n = 419, 65.3%) had a similar distribution to the overall cohort, with 43.9% attributed to chronic antibody-mediated rejection.

CONCLUSION

To prolong allograft survival, improved strategies are needed to curtail alloimmune responses. Greater understanding of the causes of undifferentiated interstitial fibrosis and tubular atrophy and potential treatments would also be of considerable benefit.

Anti Phospholipase A2 Receptor 1 Antibodies and Membranous Nephropathy Recurrence After Kidney Transplantation

Introduction

Membranous nephropathy can lead to end-stage kidney disease, for which kidney transplantation is the preferred therapy. However, the disease often relapses, which can impact allograft survival.

Methods

We conducted a prospective multicenter study in France involving 72 patients with membranous nephropathy who were awaiting and then underwent kidney transplantation. In addition, we established a retrospective validation cohort of 65 patients. The primary objective was to evaluate the prognostic significance of pretransplant anti phospholipase A2 receptor 1 (PLA2R1) antibodies on the recurrence of membranous nephropathy. The study also assessed the incidence rate, time to onset, and risk factors for recurrence, as well as allograft outcome.

Results

The prospective cohort showed a 26% cumulative incidence of membranous nephropathy recurrence after a median follow-up of 23.5 months. This was confirmed by a 28% cumulative incidence after a median follow-up of 67 months in the retrospective cohort. A strong association was found between the presence of anti-PLA2R1 antibodies prior to transplantation and the risk of disease recurrence (risk ratio = 5.9; 95% confidence interval [CI]: 2.3-15.7; P < 0.0001). These results were confirmed in the retrospective cohort. Monitoring of anti-PLA2R1 antibodies in the immediate posttransplant period is of limited value, because recurrence occurred early in the first 6 months (median delay of 5 [3-14] months) after transplantation despite decreasing antibody levels.

Conclusion

The presence of anti-PLA2R1 antibodies prior to transplantation was a strong predictor of recurrence of allograft membranous nephropathy. An individualized immunomonitoring and management strategy for kidney transplant candidates with anti-PLA2R1-associated membranous nephropathy should be considered.

Clinical and Histopathological Findings in HIV-positive to HIV-positive Kidney Transplant Recipients

BACKGROUND

The spectrum of histological findings in transplanted kidneys from HIV-positive donors to HIV-positive recipients is relatively unexplored. This study describes the type and timing of histological diagnoses observed in this unique cohort.

METHODS

Adequate biopsies were analyzed at implantation and posttransplant between September 2008 and May 2022. Histological disease spectrum, distributions over time, and relevant clinical characteristics and management were reported for both for-cause and protocol biopsies.

RESULTS

Twenty-four implantation biopsies from 31 deceased donors and 179 allograft biopsies (100 for-cause, 79 protocol) from 50 recipients were analyzed. Most rejection episodes occurred in the first year posttransplant. Eighteen recipients (36%) had at least 1 episode of biopsy-confirmed acute/chronic T cell-mediated rejection (TCMR) or active antibody-mediated rejection (AMR). Protocol biopsies showed no active AMR or acute/chronic TCMR. However, 9 of 79 biopsies identified borderline/suspicious TCMR. Common nonrejection diagnoses were interstitial fibrosis and tubular atrophy, ascending pyelonephritis, and calcineurin inhibitor toxicity. Classic and suspected HIV-associated nephropathy (HIVAN) were identified in 3 and 6 patients, respectively. Protocol biopsies diagnosed 1 case of classic HIVAN and 6 cases of suspected HIVAN. AMR most adversely affected kidney function and significantly contributed to graft failure.

CONCLUSIONS

The histological findings in this cohort of HIV-positive kidney transplant recipients who received grafts from unmatched HIV-positive donors revealed a spectrum of abnormalities. Protocol biopsies added to surveillance on borderline rejection and assisted in the recognition of HIVAN. Confirmed rejection occurred in 18 recipients (36%). Understanding the factors contributing to this may assist in the optimization of immunosuppressive protocols in the future.

A review of landmark studies on maintenance immunosuppressive regimens in kidney transplantation

Immunosuppressive medications play a pivotal role in kidney transplantation, and the calcineurin inhibitors (CNIs), including cyclosporine A (CsA) and tacrolimus (TAC), are considered as the backbone of maintenance immunosuppressive regimens. Since the introduction of CNIs in kidney transplantation, the incidence of acute rejection has decreased, and allograft survival has improved significantly. However, CNI nephrotoxicity has been a major concern, believed to heavily impact long-term allograft survival and function. To address this concern, several CNI-sparing regimens were developed and studied in randomized, controlled, clinical trials, aiming to reduce CNI exposure and preserve long-term allograft function. However, more recent information has revealed that CNI nephrotoxicity is not the primary cause of late allograft failure, and its histopathology is neither specific nor pathognomonic. In this review, we discuss the historical development of maintenance immunosuppressive regimens in kidney transplantation, covering the early era of transplantation, the CNI-sparing era, and the current era where the alloimmune response, rather than CNI nephrotoxicity, appears to be the major contributor to late allograft failure. Our goal is to provide a chronological overview of the development of maintenance immunosuppressive regimens and summarize the most recent information for clinicians caring for kidney transplant recipients (KTRs).

The impact of diabetes and hypertension on renal allograft survival- A single center study

Background

To determine the impact of pre-transplant diabetes mellitus (DM) and post-transplant hypertension (HT) at 1 year on renal allograft survival in all adult first kidney-only (FKO) transplant recipients at a single transplant center in Johannesburg, South Africa.

Materials and methods

A retrospective review was conducted of all adult FKO transplant procedures at the Charlotte Maxeke Johannesburg Academic Hospital transplant unit between 1966 and 2013.

Results

During the stipulated timeframe, 1685 adult FKO transplant procedures were performed. Of these, 84.1% were from deceased donors (n = 1413/1685). The prevalence of pre-transplant DM transplant recipients with no missing or incomplete records was 6.5% (n = 107/1625). Of the total cohort of 1685 adult FKO transplant recipients, 63.6% of those with no missing data survived to 1 year (n = 1072/1685). The prevalence of HT at 1-year post-transplant was 53.6% (n = 503/1072). HT at 1-year post-transplant, even after adjusted survival analysis, proved a significant risk factor for renal allograft loss (hazard ratio, 1.63; 95% confidence interval, 1.37-1.94) (p < 0.0001). Similarly, after adjusted survival analysis, the risk of renal allograft loss within the pre-transplant DM group was significantly higher (p = 0.043; hazard ratio, 1.26; 95% confidence interval, 1.01-1.58).

Conclusions

This study identified pre-transplantation diabetes mellitus and post-transplantation HT as significant risk factors for graft loss within the population assessed in this region of the world. These factors could potentially be used as independent predictors of renal graft survival.

An observational cohort study of histological screening for BK polyomavirus nephropathy following viral replication in plasma

Systematic screening for BKPyV-DNAemia has been advocated to aid prevention and treatment of polyomavirus associated nephropathy (PyVAN), an important cause of kidney graft failure. The added value of performing a biopsy at time of BKPyV-DNAemia, to distinguish presumptive PyVAN (negative SV40 immunohistochemistry) and proven PyVAN (positive SV40) has not been established. Therefore, we studied an unselected cohort of 950 transplantations, performed between 2008-2017. BKPyV-DNAemia was detected in 250 (26.3%) transplant recipients, and positive SV40 in 91 cases (9.6%). Among 209 patients with a concurrent biopsy at time of first BKPyV-DNAemia, 60 (28.7%) biopsies were SV40 positive. Plasma viral load showed high diagnostic value for concurrent SV40 positivity (ROC-AUC 0.950, 95% confidence interval 0.916-0.978) and the semiquantitatively scored percentage of tubules with evidence of polyomavirus replication (pvl score) (0.979, 0.968-0.988). SV40 positivity was highly unlikely when plasma viral load is below 4 log10 copies/ml (negative predictive value 0.989, 0.979-0.994). In SV40 positive patients, higher plasma BKPyV-DNA load and higher pvl scores were associated with slower viral clearance from the blood (hazard ratio 0.712, 95% confidence interval 0.604-0.839, and 0.327, 0.161-0.668, respectively), whereas the dichotomy positivity/negativity of SV40 immunohistochemistry did not predict viral clearance. Although the pvl score offers some prognostic value for viral clearance on top of plasma viral load, the latter provided good guidance for when a biopsy was unnecessary to exclude PyVAN. Thus, the distinction between presumptive and proven PyVAN, based on SV40 immunohistochemistry, has limited clinical value. Hence, management of BKPyV-DNAemia and immunosuppression reduction should be weighed against the risk of occurrence of rejection, or exacerbation of rejection observed concomitantly.

Evolution of kidney allograft loss causes over 40 years (1979-2019)

INTRODUCTION

The improvement of kidney allograft recipient and graft survival showed a decrease over the last 40 years. Long-term graft loss rate remained stable during a 25-year time span. Knowing the changing causes and the risk factors associated with graft loss requires special attention. The present study aimed to assess the causes of graft loss and kidney allograft recipient death. Also, we aimed to compare two different periods (1979-1999 and 2000-2019) to identify changes in the characteristics of the failed allografts and recipient and donors profile.

METHODS AND PATIENTS

We performed a single-center cohort study. We included all the kidney transplant recipients at the Hospital del Mar (Barcelona) between May 1979 and December 2019. Graft loss was defined as recipient death with functioning graft and as loss of graft function (return to dialysis or retransplantation). We assessed the causes of graft loss using clinical and histological information. We also analyzed the results of the two different transplant periods (1979-1999 and 2000-2019).

RESULTS

Between 1979 and 2019, 1522 transplants were performed. The median follow-up time was 56 (IQR 8-123) months. During follow-up, 722 (47.5%) grafts were lost: 483 (66.9%) due to graft failure and 239 (33.1%) due to death with functioning graft. The main causes of death were cardiovascular (25.1%), neoplasms (25.1%), and infectious diseases (21.8%). These causes were stable between the two periods of time. Only the unknown cause of death has decreased in the last period. The main cause of graft failure (loss of graft function) was the allograft chronic dysfunction (75%). When histologic information was available, antibody-mediated rejection (ABMR) and interstitial fibrosis/tubular atrophy (IF/TA) were the most frequent specific causes (15.9% and 12.6%). Of the graft failures, 213 (29.5%) were early (<1 year of transplantation). Vascular thrombosis was the main cause of early graft failure in the second period (2000-2019) (46.7%) and T-cell-mediated rejection (TCMR) was the main cause (31.3%) in the first period (1979-1999). The causes of late graft loss were similar between the two periods.

CONCLUSIONS

The causes of kidney allograft recipient death are still due to cardiovascular and malignant diseases. Vascular thrombosis has emerged as a frequent cause of early graft loss in the most recent years. The evaluation of the causes of graft loss is necessary to improve kidney transplantation outcomes.

Seeking Standardized Definitions for HLA-incompatible Kidney Transplants: A Systematic Review

BACKGROUND

There is no standard definition for "HLA incompatible" transplants. For the first time, we systematically assessed how HLA incompatibility was defined in contemporary peer-reviewed publications and its prognostic implication to transplant outcomes.

METHODS

We combined 2 independent searches of MEDLINE, EMBASE, and the Cochrane Library from 2015 to 2019. Content-expert reviewers screened for original research on outcomes of HLA-incompatible transplants (defined as allele or molecular mismatch and solid-phase or cell-based assays). We ascertained the completeness of reporting on a predefined set of variables assessing HLA incompatibility, therapies, and outcomes. Given significant heterogeneity, we conducted narrative synthesis and assessed risk of bias in studies examining the association between death-censored graft failure and HLA incompatibility.

RESULTS

Of 6656 screened articles, 163 evaluated transplant outcomes by HLA incompatibility. Most articles reported on cytotoxic/flow T-cell crossmatches (n = 98). Molecular genotypes were reported for selected loci at the allele-group level. Sixteen articles reported on epitope compatibility. Pretransplant donor-specific HLA antibodies were often considered (n = 143); yet there was heterogeneity in sample handling, assay procedure, and incomplete reporting on donor-specific HLA antibodies assignment. Induction (n = 129) and maintenance immunosuppression (n = 140) were frequently mentioned but less so rejection treatment (n = 72) and desensitization (n = 70). Studies assessing death-censored graft failure risk by HLA incompatibility were vulnerable to bias in the participant, predictor, and analysis domains.

CONCLUSIONS

Optimization of transplant outcomes and personalized care depends on accurate HLA compatibility assessment. Reporting on a standard set of variables will help assess generalizability of research, allow knowledge synthesis, and facilitate international collaboration in clinical trials.

Data-Driven Chronic Allograft Phenotypes: A Novel and Validated Complement for Histologic Assessment of Kidney Transplant Biopsies

BACKGROUND

No validated system currently exists to realistically characterize the chronic pathology of kidney transplants that represents the dynamic disease process and spectrum of disease severity. We sought to develop and validate a tool to describe chronicity and severity of renal allograft disease and integrate it with the evaluation of disease activity.

METHODS

The training cohort included 3549 kidney transplant biopsies from an observational cohort of 937 recipients. We reweighted the chronic histologic lesions according to their time-dependent association with graft failure, and performed consensus k-means clustering analysis. Total chronicity was calculated as the sum of the weighted chronic lesion scores, scaled to the unit interval.

RESULTS

We identified four chronic clusters associated with graft outcome, based on the proportion of ambiguous clustering. The two clusters with the worst survival outcome were determined by interstitial fibrosis and tubular atrophy (IFTA) and by transplant glomerulopathy. The chronic clusters partially overlapped with the existing Banff IFTA classification (adjusted Rand index, 0.35) and were distributed independently of the acute lesions. Total chronicity strongly associated with graft failure (hazard ratio [HR], 8.33; 95% confidence interval [CI], 5.94 to 10.88; P<0.001), independent of the total activity scores (HR, 5.01; 95% CI, 2.83 to 7.00; P<0.001). These results were validated on an external cohort of 4031 biopsies from 2054 kidney transplant recipients.

CONCLUSIONS

The evaluation of total chronicity provides information on kidney transplant pathology that complements the estimation of disease activity from acute lesion scores. Use of the data-driven algorithm used in this study, called RejectClass, may provide a holistic and quantitative assessment of kidney transplant injury phenotypes and severity.

Integrated Immunologic Monitoring in Solid Organ Transplantation: The Road Toward Torque Teno Virus-guided Immunosuppression

Potent immunosuppressive drugs have been introduced into clinical care for solid organ transplant recipients. It is now time to guide these drugs on an individual level to optimize their efficacy. An ideal tool simultaneously detects overimmunosuppression and underimmunosuppression, is highly standardized, and is straightforward to implement into routine. Randomized controlled interventional trials are crucial to demonstrate clinical value. To date, proposed assays have mainly focused on the prediction of rejection and were based on the assessment of few immune compartments. Recently, novel tools have been introduced based on a more integrated approach to characterize the immune function and cover a broader spectrum of the immune system. In this respect, the quantification of the plasma load of a highly prevalent and apathogenic virus that might reflect the immune function of its host has been proposed: the torque teno virus (TTV). Although TTV control is driven by T cells, other major immune compartments might contribute to the hosts' response. A standardized in-house polymerase chain reaction and a conformité européenne-certified commercially available polymerase chain reaction are available for TTV quantification. TTV load is associated with rejection and infection in solid organ transplant recipients, and cutoff values for risk stratification of such events have been proposed for lung and kidney transplantation. Test performance of TTV load does not allow for the diagnosis of rejection and infection but is able to define at-risk patients. Hitherto TTV load has not been used in interventional settings, but two interventional randomized controlled trials are currently testing the safety and efficacy of TTV-guided immunosuppression.

The natural history of de novo donor-specific HLA antibodies after kidney transplantation

Background

De novo donor-specific HLA antibodies (dnDSA) are key factors in the diagnosis of antibody-mediated rejection (ABMR) and related to graft loss.

Methods

This retrospective study was designed to evaluate the natural course of dnDSA in graft function and kidney allograft survival and to assess the impact of mean fluorescence intensity (MFI) evolution as detected by annual Luminex^® screening. All 400 kidney transplant recipients with 731 dnDSA against the last graft (01/03/2000-31/05/2021) were included.

Results

During 8.3 years of follow-up, ABMR occurred in 24.8% and graft loss in 33.3% of the cases, especially in patients with class I and II dnDSA, and those with multiple dnDSA. We observed frequent changes in MFI with 5-year allograft survivals post-dnDSA of 74.0% in patients with MFI reduction ≥ 50%, 62.4% with fluctuating MFI (MFI reduction ≥ 50% and doubling), and 52.7% with doubling MFI (log-rank p < 0.001). Interestingly, dnDSA in 168 (24.3%) cases became negative at some point during follow-up, and 38/400 (9.5%) patients became stable negative, which was associated with better graft survival. Multivariable analysis revealed the importance of MFI evolution and rejection, while class and number of dnDSA were not contributors in this model.

Conclusion

In summary, we provide an in-depth analysis of the natural course of dnDSA after kidney transplantation, first evidence for the impact of MFI evolution on graft outcomes, and describe a relevant number of patients with a stable disappearance of dnDSA, related to better allograft survival.

Proposed Definitions of Antibody-Mediated Rejection for Use as a Clinical Trial Endpoint in Kidney Transplantation

Antibody-mediated rejection (AMR) is caused by antibodies that recognize donor human leukocyte antigen (HLA) or other targets. As knowledge of AMR pathophysiology has increased, a combination of factors is necessary to confirm the diagnosis and phenotype. However, frequent modifications to the AMR definition have made it difficult to compare data and evaluate associations between AMR and graft outcome. The present paper was developed following a Broad Scientific Advice request from the European Society for Organ Transplantation (ESOT) to the European Medicines Agency (EMA), which explored whether updating guidelines on clinical trial endpoints would encourage innovations in kidney transplantation research. ESOT considers that an AMR diagnosis must be based on a combination of histopathological factors and presence of donor-specific HLA antibodies in the recipient. Evidence for associations between individual features of AMR and impaired graft outcome is noted for microvascular inflammation scores ≥2 and glomerular basement membrane splitting of >10% of the entire tuft in the most severely affected glomerulus. Together, these should form the basis for AMR-related endpoints in clinical trials of kidney transplantation, although modifications and restrictions to the Banff diagnostic definition of AMR are proposed for this purpose. The EMA provided recommendations based on this Broad Scientific Advice request in December 2020; further discussion, and consensus on the restricted definition of the AMR endpoint, is required.

Rationale for Surrogate Endpoints and Conditional Marketing Authorization of New Therapies for Kidney Transplantation

Conditional marketing authorization (CMA) facilitates timely access to new drugs for illnesses with unmet clinical needs, such as late graft failure after kidney transplantation. Late graft failure remains a serious, burdensome, and life-threatening condition for recipients. This article has been developed from content prepared by members of a working group within the European Society for Organ Transplantation (ESOT) for a Broad Scientific Advice request, submitted by ESOT to the European Medicines Agency (EMA), and reviewed by the EMA in 2020. The article presents the rationale for using surrogate endpoints in clinical trials aiming at improving late graft failure rates, to enable novel kidney transplantation therapies to be considered for CMA and improve access to medicines. The paper also provides background data to illustrate the relationship between primary and surrogate endpoints. Developing surrogate endpoints and a CMA strategy could be particularly beneficial for studies where the use of primary endpoints would yield insufficient statistical power or insufficient indication of long-term benefit following transplantation.

Poor Outcomes in Patients With Transplant Glomerulopathy Independent of Banff Categorization or Therapeutic Interventions

Background

Transplant glomerulopathy (TG) may indicate different disease entities including chronic AMR (antibody-mediated rejection). However, AMR criteria have been frequently changed, and long-term outcomes of allografts with AMR and TG according to Banff 2017 have rarely been investigated.

Methods

282 kidney allograft recipients with biopsy-proven TG were retrospectively investigated and diagnosed according to Banff'17 criteria: chronic AMR (cAMR, n = 72), chronic active AMR (cAAMR, n = 76) and isolated TG (iTG, n = 134). Of which 25/72 (34.7%) patients of cAMR group and 46/76 (60.5%) of cAAMR group were treated with antihumoral therapy (AHT).

Results

Up to 5 years after indication biopsy, no statistically significant differences were detected among iTG, cAMR and cAAMR groups in annual eGFR decline (−3.0 vs. −2.0 vs. −2.8 ml/min/1.73 m2 per year), 5-year median eGFR (21.5 vs. 16.0 vs. 20.0 ml/min/1.73 m2), 5-year graft survival rates (34.1 vs. 40.6 vs. 31.8%) as well as urinary protein excretion during follow-up. In addition, cAMR and cAAMR patients treated with AHT had similar graft and patient survival rates in comparison with those free of AHT, and similar comparing with iTG group. The TG scores were not associated with 5-year postbiopsy graft failure; whereas the patients with higher scores of chronic allograft scarring (by mm-, ci- and ct-lesions) had significantly lower graft survival rates than those with mild scores. The logistic-regression analysis demonstrated that Banff mm-, ah-, t-, ci-, ct-lesions and the eGFR level at biopsy were associated with 5-year graft failure.

Conclusions

The occurrence of TG is closely associated with graft failure independent of disease categories and TG score, and the long-term clinical outcomes were not influenced by AHT. The Banff lesions indicating progressive scarring might be better suited to predict an unfavorable outcome.

Death With Function and Graft Failure After Kidney Transplantation: Risk Factors at Baseline Suggest New Approaches to Management

Background

Improving both patient and graft survival after kidney transplantation are major unmet needs. The goal of this study was to assess risk factors for specific causes of graft loss to determine to what extent patients who develop either death with a functioning graft (DWFG) or graft failure (GF) have similar baseline risk factors for graft loss.

Methods

We retrospectively studied all solitary renal transplants performed between January 1, 2006, and December 31, 2018, at 3 centers and determined the specific causes of DWFG and GF. We examined outcomes in different subgroups using competing risk estimates and cause-specific Cox models.

Results

Of the 5752 kidney transplants, graft loss occurred in 21.6% (1244) patients, including 12.0% (691) DWFG and 9.6% (553) GF. DWFG was most commonly due to malignancy (20.0%), infection (19.7%), cardiac disease (12.6%) with risk factors of older age and pretransplant dialysis, and diabetes as the cause of renal failure. For GF, alloimmunity (38.7%), glomerular diseases (18.6%), and tubular injury (13.9%) were the major causes. Competing risk incidence models identified diabetes and older recipients with higher rates of both DWFG and nonalloimmune GF.

Conclusions

These data suggest that at baseline, 2 distinct populations can be identified who are at high risk for renal allograft loss: a younger, nondiabetic patient group who develops GF due to alloimmunity and an older, more commonly diabetic population who develops DWFG and GF due to a mixture of causes-many nonalloimmune. Individualized management is needed to improve long-term renal allograft survival in the latter group.

Torque Teno Virus Load Is Associated With Subclinical Alloreactivity in Kidney Transplant Recipients: A Prospective Observational Trial

BACKGROUND

Nonpathogenic torque teno viruses (TTVs) are highly prevalent in transplant recipients and associated with immunosuppression. Studies in kidney transplant patients have proposed assessment of TTV load for risk stratification of clinically overt graft rejection. The value of TTV quantification in the context of subclinical rejection has not been evaluated.

METHODS

In this prospective trial, 307 consecutive kidney transplant recipients were subjected to per-protocol monitoring of plasma TTV. TTV was analyzed in the context of protocol biopsies (n = 82), scheduled 1 year posttransplantation.

RESULTS

TTV load at the time of biopsy was lower in recipients with rejection (n = 19; according to Banff, including borderline changes suspicious for acute T cell-mediated rejection) than those without rejection (n = 63) whereby each log increase in TTV copies/mL decreased the risk for rejection by 9% (risk ratio 0.91, 95% confidence interval, 0.85-0.97; P = 0.004). Development of chronic lesions (cg, cv, ci, ct, ah, ptcml) was associated with the number of days with a TTV load <1 × 106 copies/mL between months 3 and 12 posttransplant (β 0.07, 95% confidence interval, 0.01-0.14; P = 0.02).

CONCLUSIONS

This trial demonstrates an association between TTV and subclinical graft rejection in kidney transplant recipients. A TTV load <1 × 106 copies/mL suggests suboptimal immunosuppression.

Exploring the Complexity of Death-Censored Kidney Allograft Failure

BACKGROUND

Few studies have thoroughly investigated the causes of kidney graft loss (GL), despite its importance.

METHODS

A novel approach assigns each persistent and relevant decline in renal function over the lifetime of a renal allograft to a standardized category, hypothesizing that singular or multiple events finally lead to GL. An adjudication committee of three physicians retrospectively evaluated indication biopsies, laboratory testing, and medical history of all 303 GLs among all 1642 recipients of transplants between January 1, 1997 and December 31, 2017 at a large university hospital to assign primary and/or secondary causes of GL.

RESULTS

In 51.2% of the patients, more than one cause contributed to GL. The most frequent primary or secondary causes leading to graft failure were intercurrent medical events in 36.3% of graft failures followed by T cell-mediated rejection (TCMR) in 34% and antibody-mediated rejection (ABMR) in 30.7%. In 77.9%, a primary cause could be attributed to GL, of which ABMR was most frequent (21.5%). Many causes for GL were identified, and predominant causes for GL varied over time.

CONCLUSIONS

GL is often multifactorial and more complex than previously thought.

Single antigen testing to reduce early antibody-mediated rejection risk in female recipients of a spousal donor kidney

Female recipients of a spousal donor kidney transplant are at greater risk of donor-specific pre-immunization, which may increase the risk of acute antibody-mediated rejection (ABMR). We assessed the incidence of early ABMR (within two weeks after transplantation), risk factors for ABMR and graft function in 352 complement-dependent cytotoxicity test-negative LURD transplant recipients, transplanted between 1997 and 2014 at the Leiden University Medical Center in The Netherlands. Risk factors for immunization were retrieved from the health records. As methods to screen for preformed donor-specific antibodies (pDSA) have developed through time, we retrospectively screened those with ABMR for pDSA using pooled-antigen bead (PAB) and single-antigen bead (SAB) assays. The cumulative incidence of rejection in the first six months after transplantation was 18% (TCMR 15%; early ABMR 3%). Early ABMR resulted in inferior graft survival and was more common in women who received a kidney from their spouse (10%) than in other women (2%) and men (<1%). The SAB assay retrospectively identified pDSA in seven of nine cases of early ABMR (78%), while the PAB detected pDSA in only three cases (33%). Seeing that early ABMR occurred in 10% of women who received a kidney from their spouse, a SAB assay should be included in the pre-transplant assessment of this group of women, regardless of the result of the PAB assay.

Treatment of antibody-mediated rejection with double-filtration plasmapheresis, low dose IVIg plus rituximab after kidney transplantation

Antibody-mediated rejection (ABMR) at early or late post-transplantation remains challenging. We performed a single-center single-arm study where four cases of acute ABMR and nine cases of chronic active ABMR (defined by Banff classification) were treated with double-filtration plasmapheresis (two cycles of three consecutive daily sessions with a 4-day gap between). At the end of the third and sixth DFPP sessions, the patients received rituximab 375 mg/m² . After a median follow-up of 1078 (61-1676) days, kidney-allograft survival was 50%. Before DFPP/rituximab therapy, the median donor-specific alloantibody (DSA) mean fluorescence intensity (MFI) was 9160 (4000-15 400); 45 days (D45) later it had significantly decreased to 7375 (215-18 100) (P = .018). In addition, at one-year (Y1) post-therapy, MFI had decreased further, that is, 4060 (400-7850) (P = .001). In two patients, DSA MFIs decreased and remained below 2000. The slope of estimated glomerular-filtration rate within the 6 months preceding intervention was -1.18 mL/min/month and remained unchanged at -1.29 mL/min/month within the year after intervention. Proteinuria remained unchanged. Baseline Banff scores on repeat allograft biopsies (post-therapy D45, Y1) did not show any improvement. Side-effects were mild to moderate. We conclude that the combined DFPP/rituximab significantly decreased DSAs in ABMR kidney-transplant recipients but did not improve renal function or renal histology at 1-year follow-up.

Re-evaluating Blood Markers as Predictors of Outcome in Multivisceral and Intestinal Transplantation

BACKGROUND

Multivisceral transplant (MVTx) and isolated intestinal transplant (ITx) are complex surgical procedures. The subsequent proinflammatory state in the immediate postoperative period makes interpretation of blood markers difficult.

METHOD

We aimed to establish the course of various blood markers after MVTx/ITx, and to evaluate their use as diagnostic markers of complications. This was a single center prospective cohort. We analyzed blood markers collected preoperatively, on alternate days for the first postoperative week, and then weekly for 4 weeks. This study was in compliance with The Declaration of Helsinki.

RESULTS

Over a 16-month period (July 2017-October 2018), 20 subjects aged 2 to 67 years with a median age of 24.5 years received MVTx/ITx. Twelve recipients (60%) had an infection. Neutrophil lymphocyte count ratio (NLCR) was higher than established upper limits of normal, regardless of infection status. NLCR and white blood cell count were useful to identify infected MVTx/ITx recipients, with P values <.05 for 2 and 1 of 7 time points post transplant, respectively. Higher preoperative eosinophil% predicted future acute cellular rejection (P value .023).

CONCLUSIONS

This is the first study to extensively track the course of blood markers post MVTx/ITx and identified NLCR and white blood cell count as potential diagnostic blood markers of infection.

Complex Surgical Reconstruction of Upper Pole Artery in Living-Donor Kidney Transplantation

Background

The use of allografts with multiple renal arteries has increased in the era of laparoscopic donor nephrectomy. Although several studies recommend reconstructing lower pole arteries (LPAs) to reduce risk of urologic complications, it is common opinion to ligate upper pole arteries (UPAs) with a diameter less than 2 mm because of increased risk of thrombosis related to their reconstruction. This retrospective study evaluates the feasibility and safety of reconstructing thin UPAs during living-donor kidney transplantation, with the goal of maintaining the integrity of the graft and assuring its maximal function.

Material/Methods

Data from 922 living-donor kidney transplants performed between 2009 and 2019 were reviewed. Six cases with UPAs were identified (0.65%). The study endpoints were incidence of allograft vascular and urologic complications, slow graft function, delayed graft function, graft failure, and graft and patient survival.

Results

The UPAs had a mean diameter of 1.8±0.28 mm. Methods of reconstruction included: interposition graft (n=2), end-to-side anastomosis inside the renal hilum to a branch of the main renal artery (n=3), and side-to-side anastomosis with the main renal artery (n=1). Additional reconstruction of LPAs (n=2) and main renal arteries (n=2) was performed. During a median (range) follow-up of 14.5 (9–49) months no complications were observed.

Conclusions

Ex vivo reconstruction of UPAs with a diameter less than 2 mm is worth attempting, particularly in the setting of living-donor kidney transplantation.

Chronic Histologic Changes Are Present Regardless of HLA Mismatches: Evidence from HLA Identical Living Donor Kidney Transplants

BACKGROUND

At 5 and 10 years after kidney transplantation, chronic histologic changes such as arteriolar hyalinosis and mesangial expansion are common, however, determining etiology is difficult. We compared surveillance biopsies in living donor kidney transplants (LDKTx) from HLA matched siblings (termed HLA-identical (HLA-ID)) to HLA non-ID to investigate which histologic changes were likely due to alloimmune injury and which were due to non-alloimmune injury.

METHODS

We performed a retrospective, cohort study comparing HLA-ID sibling LDKTx (n=175) to HLA non-ID LDKTx (n=175; matched for age, sex and year of transplant +/- 2 years) performed at a single institution from 03/1999 to 11/2018.

RESULTS

Baseline characteristics and maintenance immunosuppression were similar. Mortality rates were similar, but in the HLA-ID group, 10-year death-censored graft survival was higher (93.8% vs 80.9% HLA non-ID LDKTx, p<0.001), rejection rates were lower (after 1 year 9.6% vs 27.1%; p<0.001) and Banff inflammation scores including glomerulitis and peritubular capillaritis were lower on surveillance biopsies at 1, 5 and 10 years. In contrast, chronic Banff scores (interstitial fibrosis, arteriolar hyalinosis, mesangial expansion, etc.) were similar in prevalence and severity on surveillance biopsies at 1, 5 and 10 years.

CONCLUSIONS

HLA-ID LDKTx have less inflammation and less transplant glomerulopathy, but most chronic histologic changes were similar to less-well matched LDKTx. We conclude that these types of chronic changes are not associated with HLA mismatches and may be due to non-immunologic causes (hypertension, obesity, etc.) suggesting that new management approaches to prevent these lesions may be needed.

Circulating Long Noncoding RNA LNC-EPHA6 Associates with Acute Rejection after Kidney Transplantation

Acute rejection (AR) of a kidney graft in renal transplant recipients is associated with microvascular injury in graft dysfunction and, ultimately, graft failure. Circulating long noncoding RNAs (lncRNAs) may be suitable markers for vascular injury in the context of AR. Here, we first investigated the effect of AR after kidney transplantation on local vascular integrity and demonstrated that the capillary density markedly decreased in AR kidney biopsies compared to pre-transplant biopsies. Subsequently, we assessed the circulating levels of four lncRNAs (LNC-RPS24, LNC-EPHA6, MALAT1, and LIPCAR), that were previously demonstrated to associate with vascular injury in a cohort of kidney recipients with a stable kidney transplant function (n = 32) and recipients with AR (n = 15). The latter were followed longitudinally six and 12 months after rejection. We found higher levels of circulating LNC-EPHA6 during rejection, compared with renal recipients with a stable kidney function (p = 0.017), that normalized one year after AR. In addition, LNC-RPS24, LNC-EPHA6, and LIPCAR levels correlated significantly with the vascular injury marker soluble thrombomodulin. We conclude that AR and microvascular injury are associated with higher levels of circulating LNC-EPHA6, which emphasizes the potential role of lncRNAs as biomarker in the context of AR.

Torque teno virus for risk stratification of graft rejection and infection in kidney transplant recipients-A prospective observational trial

The nonpathogenic and ubiquitous torque teno virus (TTV) is associated with immunosuppression in solid organ transplant recipients. Studies in kidney transplant patients proposed TTV quantification for risk stratification of graft rejection and infection. In this prospective trial (DRKS00012335) 386 consecutive kidney transplant recipients were subjected to longitudinal per-protocol monitoring of plasma TTV load by polymerase chain reaction for 12 months posttransplant. TTV load peaked at the end of month 3 posttransplant and reached steady state thereafter. TTV load after the end of month 3 was analyzed in the context of subsequent rejection diagnosed by indication biopsy and infection within the first year posttransplant, respectively. Each log increase in TTV load decreased the odds for rejection by 22% (odds ratio [OR] 0.78, 95% confidence interval [CI] 0.62-0.97; P = .027) and increased the odds for infection by 11% (OR 1.11, 95% CI 1.06-1.15; P < .001). TTV was quantified at a median of 14 days before rejection was diagnosed and 27 days before onset of infection, respectively. We defined a TTV load between 1 × 10⁶ and 1 × 10⁸ copies/mL as optimal range to minimize the risk for rejection and infection. These data support the initiation of an interventional trial assessing the efficacy of TTV-guided immunosuppression to reduce infection and graft rejection in kidney transplant recipients.

A Review on the Function and Regulation of ARHGDIB/RhoGDI2 Expression Including the Hypothetical Role of ARHGDIB/RhoGDI2 Autoantibodies in Kidney Transplantation

Challenging and still unsolved problems in kidney transplantation are risk stratification and the treatment of humoral rejection. Antibody-mediated rejection is an important cause of early and chronic rejection. The impact of donor-specific HLA antibodies on antibody-mediated rejection–causing graft damage is well known, but the clinical relevance of non-HLA antibodies remains unclear. Recently, in 2 independent studies, a new correlation was found between the presence of non-HLA anti-Rho guanosine diphosphate dissociation inhibitor 2 (ARHGDIB) antibodies and increased graft failure. RhoGDI2, another name for ARHGDIB, is a negative regulator of the Rho guanosine triphosphate (RhoGTP)ases RhoA, Rac1m, and Cdc42, whose main function is regulating the actin network in a variety of cells. RhoGDI2 is mainly expressed intracellularly, and some expression is observed on the cell surface. Currently, there is no mechanism known to explain this correlation. Additionally, the reason why the antibodies are produced is unknown. In this review, we will address these questions, provide an overview of other diseases in which these antibodies are prevalent, and describe the physiological role of RhoGDI2 itself. If the mechanism and impact of RhoGDI2 antibodies in kidney graft failure are known, improved risk stratification can be provided to decrease the rate of donor kidney graft failure.

Urinary MicroRNA-21-5p as Potential Biomarker of Interstitial Fibrosis and Tubular Atrophy (IFTA) in Kidney Transplant Recipients

Chronic renal allograft dysfunction (CAD) is a major limiting factor of long-term graft survival. The hallmarks of progressive CAD are interstitial fibrosis and tubular atrophy (IFTA). MicroRNAs are small, regulatory RNAs involved in many immunological processes. In particular, microRNA-21-5p (miR-21) is considered to be strongly associated with pathogenesis regarding tubulointerstitium. The aim of this study was to assess urinary miR-21 expression levels in the kidney transplant recipients and determine their application in the evaluation of IFTA and kidney allograft function. The expression levels of miR-21 were quantified in the urine of 31 kidney transplant recipients with biopsy-assessed IFTA (IFTA 0 + I: n = 17; IFTA II + III: n = 14) by real-time quantitative PCR. Urine samples were collected at the time of protocolar biopsies performed 1 or 2 years after kidney transplantation. MicroRNA-191-5p was used as reference gene. MiR-21 was significantly up-regulated in IFTA II + III group compared to IFTA 0 + I group (p = 0.003). MiR-21 correlated significantly with serum concentration of creatinine (r = 0.52, p = 0.003) and eGFR (r = -0.45; p = 0.01). ROC analysis determined the diagnostic value of miR-21 with an area under curve (AUC) of 0.80 (p = 0.0002), sensitivity of 0.86 and specificity of 0.71. miR-21 is associated with renal allograft dysfunction and IFTA. Therefore, it could be considered as a potential diagnostic, non-invasive biomarker for monitoring renal graft function.

Torquetenovirus Serum Load and Long-Term Outcomes in Renal Transplant Recipients

Following transplantation, patients must take immunosuppressive medication for life. Torquetenovirus (TTV) is thought to be marker for immunosuppression, and TTV–DNA levels after organ transplantation have been investigated, showing high TTV levels, associated with increased risk of infections, and low TTV levels associated with increased risk of rejection. However, this has been investigated in studies with relatively short follow-up periods. We hypothesized that TTV levels can be used to assess long term outcomes after renal transplantation. Serum samples of 666 renal transplant recipients were tested for TTV DNA. Samples were taken at least one year after renal transplantation, when TTV levels are thought to be relatively stable. Patient data was reviewed for graft failure, all-cause mortality and death due to infectious causes. Our data indicates that high TTV levels, sampled more than one year post-transplantation, are associated with all-cause mortality with a hazard ratio (HR) of 1.12 (95% CI, 1.02–1.23) per log₁₀ increase in TTV viral load, (p = 0.02). Additionally, high TTV levels were also associated with death due to infectious causes (HR 1.20 (95% CI 1.01–1.43), p = 0.04). TTV levels decrease in the years following renal transplantation, but remain elevated longer than previously thought. This study shows that TTV level may aid in predicting long-term outcomes, all-cause mortality and death due to an infectious cause in renal transplant patients sampled over one year post-transplantation.

Kidney transplant tolerance associated with remote autologous mesenchymal stromal cell administration

Here we report the case of successful immune tolerance induction in a living‐donor kidney transplant recipient remotely treated with autologous bone marrow‐derived mesenchymal stromal cells (MSC). This case report, which to the best of our knowledge is the first in the world in this setting, provides evidence that the modulation of the host immune system with MSC can enable the safe withdrawal of maintenance immunosuppressive drugs while preserving optimal long‐term kidney allograft function.

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

BACKGROUND

The histopathological findings on the failing kidney allograft in the modern era is not well studied. In this study, we present our experience working with kidney transplant recipients with graft failure within one year of the biopsy.

AIM

To report the histopathological characteristics of failed kidney allografts in the current era of immunosuppression based on the time after transplant, cause of the end-stage renal disease and induction immunosuppressive medications.

METHODS

In a single-center observational study, we characterized the histopathological findings of allograft biopsies in kidney transplant recipients with graft failure within one year after the biopsy.

RESULTS

We identified 329 patients with graft failure that met the selection criteria between January 1, 2006 and December 31, 2016. The three most common biopsy findings were interstitial fibrosis and tubular atrophy (IFTA, 53%), acute rejection (AR, 43%) and transplant glomerulopathy (TG, 33%). Similarly, the three most common causes of graft failure based on the primary diagnosis were AR (40%), TG (17%), and IFTA (13%). Most grafts failed within two years of post-transplant (36%). Subsequently, approximately 10%-15% of grafts failed every two years: > 2-4 years (16%), > 4-6 years (13%), > 6-8 years (11%), > 8-10 years (9%) and > 10 years (16%). AR was the most common cause of graft failure in the first six years (48%), whereas TG was the most prevalent cause of graft failure after 6 years (32%) of transplant.

CONCLUSION

In the current era of immunosuppression, AR is still the most common cause of early graft failure, while TG is the most prevalent cause of late graft failure.

Management of Chronic Active Antibody-Mediated Rejection in Renal Transplant Recipients: Single-Center Experience

OBJECTIVES

Data on the management of chronic antibody-mediated rejection after kidney transplantation are limited. We aimed to assess the impact of treatment of biopsy-proven chronic active antibodymediated rejection with combined plasma exchange, intravenous immunoglobulin, and rituximab treatment versus intravenous immunoglobulin alone or conservative management on the evolution of renal function in renal transplant recipients.

MATERIALS AND METHODS

In this retrospective study, we compared patients diagnosed with chronic active antibody-mediated rejection who were treated with standard of care steroids, intravenous immunoglobulin, plasma exchange, and rituximab (n = 40) at our center versus those who received intravenous immunoglobulin only or just intensified maintenance immunosuppression (n = 28). All patients were followed for 12 months clinically and by laboratory tests for graft and patient outcomes.

RESULTS

The two groups were matched regarding mean recipient age (41.9 ± 15.4 vs 37.8 ± 15.5 y in patients with conservative versus combined treatment), recipient sex, mean body weight, and the cause of end-stage kidney disease. Most patients and their donors were males. Glomerulonephritis represented the most common cause of end-stage kidney disease in both groups followed by diabetic nephropathy. The type of induction and pretransplant comorbidities were not different between groups (P > .05) except for the significantly higher number of chronic hepatitis C infections in patients who received conservative treatment (P = .007). Mean serum creatinine values before and after treatment of chronic active antibodymediated rejection were comparable between groups (P > .05). Active treatment with heavier immunosuppression (rituximab and plasma exchange) was associated with posttreatment viral (cytomegalovirus and BK virus) and bacterial infections that necessitated more hospitalization (P > .05). However, graft and patient outcomes were significantly better in the active treatment group than in patients with conservative treatment (P = .002 and .028, respectively).

CONCLUSIONS

Combined treatment of chronic active antibody-mediated rejection with plasma exchange, intravenous immunoglobulin, and rituximab can significantly improve outcomes after renal transplant.

T Follicular Regulatory Cells and Antibody Responses in Transplantation

De novo donor-specific antibody (DSA) formation is a major problem in transplantation, and associated with long-term graft decline and loss as well as sensitization, limiting future transplant options. Forming high-affinity, long-lived antibody responses involves a process called the germinal center (GC) reaction, and requires interaction between several cell types, including GC B cells, T follicular helper (Tfh) and T follicular regulatory (Tfr) cells. T follicular regulatory cells are an essential component of the GC reaction, limiting its size and reducing nonspecific or self-reactive responses.An imbalance between helper function and regulatory function can lead to excessive antibody production. High proportions of Tfh cells have been associated with DSA formation in transplantation; therefore, Tfr cells are likely to play an important role in limiting DSA production. Understanding the signals that govern Tfr cell development and the balance between helper and regulatory function within the GC is key to understanding how these cells might be manipulated to reduce the risk of DSA development.This review discusses the development and function of Tfr cells and their relevance to transplantation. In particular how current and future immunosuppressive strategies might allow us to skew the ratio between Tfr and Tfh cells to increase or decrease the risk of de novo DSA formation.

Source and Relevance of the BK Polyomavirus Genotype for Infection After Kidney Transplantation

Background

BK polyomavirus (BKPyV)–associated nephropathy (BKPyVAN) is a major threat for kidney transplant recipients (KTRs). The role of specific BKPyV genotypes/serotypes in development of BKPyVAN is poorly understood. Pretransplantation serotyping of kidney donors and recipients and posttransplantation genotyping of viremic recipients, could reveal the clinical relevance of specific BKPyV variants.

Methods

A retrospective cohort of 386 living kidney donor-recipient pairs was serotyped before transplantation against BKPyV genotype I–IV viral capsid protein 1 antigen, using a novel BKPyV serotyping assay. Replicating BKPyV isolates in viremic KTRs after transplantation were genotyped using real-time polymerase chain reaction and confirmed by means of sequencing. BKPyV serotype and genotype data were used to determine the source of infection and analyze the risk of viremia and BKPyVAN.

Results

Donor and recipient BKPyV genotype and serotype distribution was dominated by genotype I (>80%), especially Ib, over II, III and IV. Donor serotype was significantly correlated with the replicating genotype in viremic KTRs (P < .001). Individual donor and recipient serotype, serotype (mis)matching and the recipient replicating BKPyV genotype were not associated with development of viremia or BKPyVAN after transplantation.

Conclusions

BKPyV donor and recipient serotyping and genotyping indicates the donor origin of replicating BKPyV in viremic KTRs but provides no evidence for BKPyV genotype–specific virulence.

Intrarenal Complement System Transcripts in Chronic Antibody-Mediated Rejection and Recurrent IgA Nephropathy in Kidney Transplantation

Background: The complement system activation and regulation have been linked to post-transplant pathologies including chronic antibody mediated rejection (cAMR) and the recurrence of IgA nephropathy (ReIgAN) but distinct mechanisms remain to be elucidated.

Methods: In this retrospective single center study, the outcome of kidney transplantation was studied in 150 patients with late histological diagnosis to be either cAMR or ReIgAN, 14 stable kidney grafts at 3 months and finally 11 patients with native kidney IgAN nephropathy. To study a role of complement cascade and regulation in cAMR and ReIgAN, the RNA was extracted from available frozen kidney biopsy samples and using RT-qPCR transcripts of 11 target genes along with clinical data were determined and compared with stable grafts at 3 months protocol biopsies or IgAN native kidney nephropathy. Immunohistologically, CD46 (MCP), and C5 proteins were stained in biopsies.

Results: Interestingly, there were no differences in kidney graft survival between cAMR and ReIgAN since transplantation. cAMR was associated with significantly higher intragraft transcripts of C3, CD59, and C1-INH as compared to ReIgAN (p < 0.05). When compared to normal stable grafts, cAMR grafts exhibited higher C3, CD55, CD59, CFH, CFI, and C1-INH (p < 0.01). Moreover, ReIgAN was associated with the increase of CD46, CD55, CD59 (p < 0.01), and CFI (p < 0.05) transcripts compared with native kidney IgAN. Rapid progression of cAMR (failure at 2 years after biopsy) was observed in patients with lower intrarenal CD55 expression (AUC 0.77, 78.6% sensitivity, and 72.7 specificity). There was highly significant association of several complement intrarenal transcripts and the degree of CKD regardless the diagnosis; C3, CD55, CFH, CFI, and C1-INH expressions positively correlated with eGFR (for all p < 0.001). Neither the low mRNA transcripts nor the high mRNA transcripts biopsies were associated with distinct trend in MCP or C5 proteins staining.

Conclusions: The intrarenal complement system transcripts are upregulated in progressively deteriorated kidney allografts.

Treatment of chronic antibody mediated rejection with intravenous immunoglobulins and rituximab: A multicenter, prospective, randomized, double-blind clinical trial

There are no approved treatments for chronic antibody mediated rejection (ABMR). We conducted a multicenter, prospective, randomized, placebo-controlled, double-blind clinical trial to evaluate efficacy and safety of intravenous immunoglobulins (IVIG) combined with rituximab (RTX) (EudraCT 2010-023746-67). Patients with transplant glomerulopathy and anti-HLA donor-specific antibodies (DSA) were eligible. Patients with estimated glomerular filtration rate (eGFR) <20 mL/min per 1.73m² and/or severe interstitial fibrosis/tubular atrophy were excluded. Patients were randomized to receive IVIG (4 doses of 0.5 g/kg) and RTX (375 mg/m² ) or a wrapped isovolumetric saline infusion. Primary efficacy variable was the decline of eGFR at one year. Secondary efficacy variables included evolution of proteinuria, renal lesions, and DSA at 1 year. The planned sample size was 25 patients per group. During 2012-2015, 25 patients were randomized (13 to the treatment and 12 to the placebo group). The planned patient enrollment was not achieved because of budgetary constraints and slow patient recruitment. There were no differences between the treatment and placebo groups in eGFR decline (-4.2 ± 14.4 vs. -6.6 ± 12.0 mL/min per 1.73 m² , P-value = .475), increase of proteinuria (+0.9 ± 2.1 vs. +0.9 ± 2.1 g/day, P-value = .378), Banff scores at one year and MFI of the immunodominant DSA. Safety was similar between groups. These data suggest that the combination of IVIG and RTX is not useful in patients displaying transplant glomerulopathy and DSA.

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

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

Polyoma virus nephropathy in kidney transplantation

BK virus (BKV) is a polyomavirus that is able to cause renal dysfunction in transplanted grafts via BK virus-associated nephritis (BKVAN). This condition was mis-diagnosed in the past due to clinical and histopthological similarities with acute rejection. Due to the prevalence of the virus in the population, it is an important pathogen in this context, and so it is important to understand how this virus functions and its' relationship with the pathogenesis of BKVN. Screening for BKV often reveals viruria and/or viremia, which then manifests as BKVN, which can be asymptomatic or result in clinical features namely renal dysfunction. The pathogenesis of BKV infection is still unclear and needs to be further investigated; nevertheless there are a variety of hypotheses that indicate that there are a host of factors that play important roles. Treatments for BKVAN include a reduction in immunosuppression, the use of antiviral therapy or the combination of both treatment options.

IL-21 Receptor Antagonist Inhibits Differentiation of B Cells toward Plasmablasts upon Alloantigen Stimulation

Interaction between T follicular helper (Tfh) cells and B cells is complex and involves various pathways, including the production of IL-21 by the Tfh cells. Secretion of IL-21 results in B cell differentiation toward immunoglobulin-producing plasmablasts. In patients after kidney transplantation, the formation of alloantibodies produced by donor antigen-activated B cells are a major cause of organ failure. In this allogeneic response, the role of IL-21-producing Tfh cells that regulate B cell differentiation is unknown. Here, we tested, in an alloantigen-driven setting, whether Tfh cell help signals control B cell differentiation with its dependency on IL-21. Pre-transplantation patient PBMCs were sorted into pure CD4^posCXCR5^pos Tfh cells and CD19^posCD27^pos memory B cells and stimulated with donor antigen in the presence or absence of an IL-21 receptor (IL-21R) antagonist (αIL-21R). Donor antigen stimulation initiated expression of the activation markers inducible co-stimulator (ICOS) and programmed death 1 (PD-1) on Tfh cells and a shift toward a mixed Tfh2 and Tfh17 phenotype. The memory B cells underwent class switch recombination and differentiated toward IgM- and IgG-producing plasmablasts. In the presence of αIL-21R, a dose-dependent inhibition of STAT3 phosphorylation was measured in both T and B cells. Blockade of the IL-21R did not have an effect on PD-1 and ICOS expression on Tfh cells but significantly inhibited B cell differentiation. The proportion of plasmablasts decreased by 78% in the presence of αIL-21R. Moreover, secreted IgM and IgG2 levels were significantly lower in the presence of αIL-21R. In conclusion, our results demonstrate that IL-21 produced by alloantigen-activated Tfh cells controls B cell differentiation toward antibody producing plasmablasts. The IL-21R might, therefore, be a useful target in organ transplantation to prevent antigen-driven immune responses leading to graft failure.