Long-term renal allograft survival in the United States: a critical reappraisal

Identification of RNA-binding protein genes associated with renal rejection and graft survival

Rejection is one of the major factors affecting the long-term prognosis of kidney transplantation, and timely recognition and aggressive treatment of rejection is essential to prevent disease progression. RBPs are proteins that bind to RNA to form ribonucleoprotein complexes, thereby affecting RNA stability, processing, splicing, localization, transport, and translation, which play a key role in post-transcriptional gene regulation. However, their role in renal transplant rejection and long-term graft survival is unclear. The aim of this study was to comprehensively analyze the expression of RPBs in renal rejection and use it to construct a robust prediction strategy for long-term graft survival. The microarray expression profiles used in this study were obtained from GEO database. In this study, a total of eight hub RBPs were identified, all of which were upregulated in renal rejection samples. Based on these RBPs, the renal rejection samples could be categorized into two different clusters (cluster A and cluster B). Inflammatory activation in cluster B and functional enrichment analysis showed a strong association with rejection-related pathways. The diagnostic prediction model had a high diagnostic accuracy for T cell mediated rejection (TCMR) in renal grafts (area under the curve = 0.86). The prognostic prediction model effectively predicts the prognosis and survival of renal grafts (p < .001) and applies to both rejection and non-rejection situations. Finally, we validated the expression of hub genes, and patient prognosis in clinical samples, respectively, and the results were consistent with the above analysis.

Improvement in Central Serous Chorioretinopathy in Renal Transplant Recipients Following Hemodialysis: Case Report

INTRODUCTION

This case report describes an elderly man experienced recurrent central serous chorioretinopathy (CSCR) for several years following a kidney transplant. Despite various treatments, his subretinal fluid was unexpectedly absorbed following hemodialysis after the loss of graft kidney function. Optical coherence tomography (OCT) imaging and best-corrected visual acuity (BCVA) measures were taken. The patient has been followed for approximately 10 years.

CONCLUSION

Hemodialysis should be considered early if there is persistent and refractory serous retinal detachment despite reducing or discontinuing glucocorticoid therapy and in the presence of decreased glomerular filtration rate.

NK Cells: Not Just Followers But Also Initiators of Chronic Vascular Rejection

Chronic graft rejection represents a significant threat to long-term graft survival. Early diagnosis, understanding of the immunological mechanisms and appropriate therapeutic management are essential to improve graft survival and quality of life for transplant patients. Knowing which immune cells are responsible for chronic vascular rejection would allow us to provide effective and appropriate treatment for these patients. It is now widely accepted that natural killer (NK) cells play an important role in chronic vascular rejection. They can either initiate chronic vascular rejection by recognizing missing self on the graft or be recruited by donor-specific antibodies to destroy the graft during antibody-mediated rejection. Whatever the mechanisms of activation of NK cells, they need to be primed to become fully activated and damaging to the graft. A better understanding of the signaling pathways involved in NK cell priming and activation would pave the way for the development of new therapeutic strategies to cure chronic vascular rejection. This review examines the critical role of NK cells in the complex context of chronic vascular rejection.

ESOT Roadmap for Advanced Therapy Medicinal Products in Transplantation: Navigating Regulatory Challenges to Enhance Access and Care

The field of organ transplantation is experiencing a transformative shift with the rise of Advanced Therapy Medicinal Products (ATMPs), which include gene therapies, somatic cell therapies, and tissue-engineered products. These therapies offer new, potentially curative treatments for longstanding medical challenges, impacting numerous patients. However, their adoption is hindered by complex regulatory frameworks, high production costs, and inconsistent access across Europe. The ESOT ATMP Task Force's position paper analyzes these challenges from research to clinical application, advocating for a coordinated strategy to position Europe as a leader in ATMP development. It proposes specific actions such as streamlining regulatory pathways to accelerate approvals, boosting funding for ATMP research, and creating specialized facilities for development and implementation. The paper also highlights the critical roles of patient engagement and real-world evidence in optimizing clinical and regulatory practices.

Allogenic MSC infusion in kidney transplantation recipients promotes within 4 hours distinct B cell and T cell phenotypes

Background

Infusion of mesenchymal stromal cells (MSCs) has been proposed as immune-modulatory therapy in solid organ transplantation. The use of allogenic MSCs could improve standardization and allow for direct availability of the product.

Method

The nonrandomized phase Ib Neptune clinical trial provided safety and feasibility data on the use of allogenic bone-marrow-derived MSCs, infused in 10 patients at week 25 and 26 post kidney transplantation. Here, we performed detailed analysis on the peripheral blood immune cell composition of these patients up to 52 weeks post transplantation. We used a 40 marker antibody panel with mass cytometry to assess potential effects of MSC therapy on the immune system.

Results

We showed minor changes in major immune lineages at week 27, 34 and 52 post kidney transplantation after MSC infusion at week 25 and week 26, confirming previous data with regular flow cytometry. However, in a direct comparison between pre- and post MSC infusion, as soon as 4 hours after MSC infusion, we observed a significant increase in cell numbers of B cell and T cell subsets that shared a unique expression of CD11b, CD11c, CD38, CD39, and Ki-67.

Conclusion

Exploring these CD11b+CD11c+CD38+CD39+Ki-67+ B cells and T cells in the context of MSC infusion after kidney transplantation may be a promising avenue to better understand the immunological effects of MSC therapy.

Early Immunomodulatory Program Triggered by Protolerogenic Bifidobacterium pseudolongum Drives Cardiac Transplant Outcomes

BACKGROUND

Despite ongoing improvements to regimens preventing allograft rejection, most cardiac and other organ grafts eventually succumb to chronic vasculopathy, interstitial fibrosis, or endothelial changes, and eventually graft failure. The events leading to chronic rejection are still poorly understood and the gut microbiota is a known driving force in immune dysfunction. We previously showed that gut microbiota dysbiosis profoundly influences the outcome of vascularized cardiac allografts and subsequently identified biomarker species associated with these differential graft outcomes.

METHODS

In this study, we further detailed the multifaceted immunomodulatory properties of protolerogenic and proinflammatory bacterial species over time, using our clinically relevant model of allogenic heart transplantation.

RESULTS

In addition to tracing longitudinal changes in the recipient gut microbiome over time, we observed that Bifidobacterium pseudolongum induced an early anti-inflammatory phenotype within 7 d, whereas Desulfovibrio desulfuricans resulted in a proinflammatory phenotype, defined by alterations in leukocyte distribution and lymph node (LN) structure. Indeed, in vitro results showed that B pseudolongum and D desulfuricans acted directly on primary innate immune cells. However, by 40 d after treatment, these 2 bacterial strains were associated with mixed effects in their impact on LN architecture and immune cell composition and loss of colonization within gut microbiota, despite protection of allografts from inflammation with B pseudolongum treatment.

CONCLUSIONS

These dynamic effects suggest a critical role for early microbiota-triggered immunologic events such as innate immune cell engagement, T-cell differentiation, and LN architectural changes in the subsequent modulation of protolerant versus proinflammatory immune responses in organ transplant recipients.

Serum IL-6 predicts risk of kidney transplant failure independently of immunological risk

Interleukin-6 (IL-6) is an important immune mediator and a target for novel antibody therapies. In this study, we aimed to determine whether serum IL-6 levels are associated with immunological risk, allograft rejection and outcomes in kidney transplant (Ktx) patients. We retrospectively analyzed the data of 104 patients who underwent Ktx at our center between 2011 and 2015. The patients were divided into high- and low-risk groups (n = 52 per group) based on panel reactive antibody (PRA) percentage ≥ 35%, the existence of pre-Ktx donor-specific antibodies (DSA), or a previous transplant. IL-6 concentrations were measured before and at 3 months, 12 months, and 3 years after Ktx. Serum IL-6 levels tended to be higher in high-risk patients than in low-risk patients prior to Ktx and at 12 months after Ktx; however, the difference did not reach statistical significance (pre-Ktx, high-risk: 1.995 ± 2.79 pg/ml vs. low-risk: 1.43 ± 1.76 pg/ml, p = 0.051; 12 mo. high-risk: 1.16 ± 1.87 pg/ml vs. low-risk: 0.78 ± 1.13 pg/ml, p = 0.067). IL-6 levels were correlated with the types (no rejection, T cell mediated rejection (TCMR), antibody-mediated rejection (ABMR), or both) and time (<1 year vs. >1 year after Ktx) of rejection, as well as patient and graft survival. Patients with both TCMR and ABMR had significantly higher IL-6 levels at 3 months (14.1 ± 25.2 pg/ml) than patients with ABMR (3.4 ± 4.8 pg/ml, p = 0.017), with TCMR (1.7 ± 1.3 pg/ml, p < 0.001), and without rejection (1.7 ± 1.4 pg/ml, p < 0.001). Three years after Ktx, patients with AMBR had significantly higher IL-6 levels (5.30 ± 7.66 pg/ml) than patients with TCMR (1.81 ± 1.61 pg/ml, p = 0.009) and patients without rejection (1.19 ± 0.95 pg/ml; p = 0.001). Moreover, three years after Ktx IL-6 levels were significantly higher in patients with late rejections (3.5 ± 5.4 pg/ml) than those without rejections (1.2 ± 1.0 pg/ml) (p = 0.006). The risk of death-censored graft failure was significantly increased in patients with elevated IL-6 levels at 12 months (IL-6 level > 1.396 pg/ml, HR 4.61, p = 0.007) and 3 years (IL-6 level > 1.976 pg/ml, HR 6.75, p = 0.003), but elevated IL-6 levels were not associated with a higher risk of death. Overall, our study highlights IL-6 as a risk factor for allograft failure and confirms that IL-6 levels are higher in patients developing ABMR compared to TCMR alone or no rejection.

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).

Correlations between serum kidney injury molecule-1, cystatin C and immunosuppressants: A cross-sectional study of renal transplant patients in Bahrain

Renal transplant patients receive several immunosuppressive drug regimens that are potentially nephrotoxic for treatment. Serum creatinine is the standard for monitoring kidney function; however, cystatin C (Cys C) and kidney injury molecule-1 (KIM-1) have been found to indicate kidney injury earlier than serum creatinine and provide a better reflection of kidney function. Here, we assessed Cys C and KIM-1 serum levels in renal transplant patients receiving mycophenolate mofetil, tacrolimus, sirolimus, everolimus, or cyclosporine to evaluate kidney function. We used both the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) 2021 equation, which is based on creatinine and combined creatinine with Cys C, and the CKD-EPI 2012 equation, which is based on Cys C alone, to estimate glomerular filtration rate (GFR). Then, we assessed the association between serum KIM-1 and GFR < 90 mL per minute per 1.73 m 2. We observed significantly higher serum Cys C levels in patients with the elevated serum creatinine, compared with those with normal serum creatinine. The estimated GFRs based on creatinine were significantly higher than those based on the other equations, while a significant positive correlation was observed among all equations. Serum KIM-1 levels were negatively correlated with the estimated GFRs by the CKD-EPI Cys C and the combined creatinine with Cys C equations. A serum KIM-1 level above 0.71 ng/mL is likely to indicate GFR < 90 mL per minute per 1.73 m 2. We observed a significant correlation between serum creatinine and Cys C in our renal transplant patients. Therefore, serum KIM-1 may be used to monitor renal function when using potentially nephrotoxic drugs in renal transplants.

The role of anticomplement therapy in the management of the kidney allograft

As the number of patients living with kidney failure grows, the need also grows for kidney transplantation, the gold standard kidney replacement therapy that provides a survival advantage. This may result in an increased rate of transplantation from HLA-mismatched donors that increases the rate of antibody-mediated rejection (AMR), which already is the leading cause of allograft failure. Plasmapheresis, intravenous immunoglobulin therapy, anti-CD20 therapies (i.e., rituximab), bortezomib and splenectomy have been used over the years to treat AMR as well as to prevent AMR in high-risk sensitized kidney transplant recipients. Eculizumab and ravulizumab are monoclonal antibodies targeting the C5 protein of the complement pathway and part of the expanding field of anticomplement therapies, which is not limited to kidney transplant recipients, and also includes complement-mediated microangiopathic hemolytic anemia, paroxysmal nocturnal hemoglobinuria, and ANCA-vasculitis. In this narrative review, we summarize the current knowledge concerning the pathophysiological background and use of anti-C5 strategies (eculizumab and ravulizumab) and C1-esterase inhibitor in AMR, either to prevent AMR in high-risk desensitized patients or to treat AMR as first-line or rescue therapy and also to treat de novo thrombotic microangiopathy in kidney transplant recipients.

A humanized IL-2 mutein expands Tregs and prolongs transplant survival in preclinical models

Long-term organ transplant survival remains suboptimal, and life-long immunosuppression predisposes transplant recipients to an increased risk of infection, malignancy, and kidney toxicity. Promoting the regulatory arm of the immune system by expanding Tregs may allow immunosuppression minimization and improve long-term graft outcomes. While low-dose IL-2 treatment can expand Tregs, it has a short half-life and off-target expansion of NK and effector T cells, limiting its clinical applicability. Here, we designed a humanized mutein IL-2 with high Treg selectivity and a prolonged half-life due to the fusion of an Fc domain, which we termed mIL-2. We showed selective and sustainable Treg expansion by mIL-2 in 2 murine models of skin transplantation. This expansion led to donor-specific tolerance through robust increases in polyclonal and antigen-specific Tregs, along with enhanced Treg-suppressive function. We also showed that Treg expansion by mIL-2 could overcome the failure of calcineurin inhibitors or costimulation blockade to prolong the survival of major-mismatched skin grafts. Validating its translational potential, mIL-2 induced a selective and sustainable in vivo Treg expansion in cynomolgus monkeys and showed selectivity for human Tregs in vitro and in a humanized mouse model. This work demonstrated that mIL-2 can enhance immune regulation and promote long-term allograft survival, potentially minimizing immunosuppression.

Predicting Kidney Transplantation Outcomes from Donor and Recipient Characteristics at Time Zero: Development of a Mobile Application for Nephrologists

(1) Background: We report on the development of a predictive tool that can estimate kidney transplant survival at time zero. (2) Methods: This was an observational, retrospective study including 5078 transplants. Death-censored graft and patient survivals were calculated. (3) Results: Graft loss was associated with donor age (hazard ratio [HR], 1.021, 95% confidence interval [CI] 1.018-1.024, p < 0.001), uncontrolled donation after circulatory death (DCD) (HR 1.576, 95% CI 1.241-2.047, p < 0.001) and controlled DCD (HR 1.567, 95% CI 1.372-1.812, p < 0.001), panel reactive antibody percentage (HR 1.009, 95% CI 1.007-1.011, p < 0.001), and previous transplants (HR 1.494, 95% CI 1.367-1.634, p < 0.001). Patient survival was associated with recipient age (> 60 years, HR 5.507, 95% CI 4.524-6.704, p < 0.001 vs. < 40 years), donor age (HR 1.019, 95% CI 1.016-1.023, p < 0.001), dialysis vintage (HR 1.0000263, 95% CI 1.000225-1.000301, p < 0.01), and male sex (HR 1.229, 95% CI 1.135-1.332, p < 0.001). The C-statistics for graft and patient survival were 0.666 (95% CI: 0.646, 0.686) and 0.726 (95% CI: 0.710-0.742), respectively. (4) Conclusions: We developed a mobile app to estimate survival at time zero, which can guide decisions for organ allocation.

Stratification of Kidney Transplant Recipients Into Five Subgroups Based on Temporal Disease Trajectories

Background

Kidney transplantation is the treatment of choice for patients with end-stage renal disease. Considerable clinical research has focused on improving graft survival and an increasing number of kidney recipients die with a functioning graft. There is a need to improve patient survival and to better understand the individualized risk of comorbidities and complications. Here, we developed a method to stratify recipients into similar subgroups based on previous comorbidities and subsequently identify complications and for a subpopulation, laboratory test values associated with survival.

Methods

First, we identified significant disease patterns based on all hospital diagnoses from the Danish National Patient Registry for 5752 kidney transplant recipients from 1977 to 2018. Using hierarchical clustering, these longitudinal patterns of diseases segregate into 3 main clusters of glomerulonephritis, hypertension, and diabetes. As some recipients are diagnosed with diseases from >1 cluster, recipients are further stratified into 5 more fine-grained trajectory subgroups for which survival, stratified complication patterns as well as laboratory test values are analyzed.

Results

The study replicated known associations indicating that diabetes and low levels of albumin are associated with worse survival when investigating all recipients. However, stratification of recipients by trajectory subgroup showed additional associations. For recipients with glomerulonephritis, higher levels of basophils are significantly associated with poor survival, and these patients are more often diagnosed with bacterial infections. Additional associations were also found.

Conclusions

This study demonstrates that disease trajectories can confirm known comorbidities and furthermore stratify kidney transplant recipients into clinical subgroups in which we can characterize stratified risk factors. We hope to motivate future studies to stratify recipients into more fine-grained, homogenous subgroups to better discover associations relevant for the individual patient and thereby enable more personalized disease-management and improve long-term outcomes and survival.

High Rate of Kidney Graft Failure after Simultaneous Heart-Kidney Transplantation

Key Points

Simultaneous heart–kidney transplant is associated with high rates of kidney graft failure which are worse when compared with kidney transplant alone. The major causes of kidney graft failure in simultaneous heart–kidney transplant recipients were patient death and primary nonfunction of kidney graft.

Background

The indications and outcomes of simultaneous heart–kidney transplantation (SHKT) remain suboptimally defined. Risk factors for renal graft failure after SHKT also remain poorly defined.

Methods

We analyzed the renal graft outcomes among SHKT recipients using United Network for Organ Sharing database from 2015 to 2020. To evaluate for factors associated with poor renal outcomes, we compared SHKT and kidney transplantation alone recipients using propensity score matching.

Results

Among SHKT recipients, the rate of primary nonfunction (PNF) of kidney graft was 3%, the 30-day kidney graft failure rate was 7.0%, and the 30-day post-transplant mortality rate was 4.1%. The incidence of kidney delayed graft function was 27.5%. Kidney graft failure was seen early post-SHKT with most common causes of patient death (43.9%) and PNF of kidney graft (41.5%). One- and 2-year patient survival was 89.2% and 86.5%, and 1- and 2-year freedom from kidney graft failure was 85.4% and 82.7%, respectively. In subgroup analysis of SHKT recipients, use of pretransplant mechanical cardiac support (adjusted odds ratio [aOR], 2.57; P = 0.017), higher calculated panel reactive antibody (aOR, 1.76; P = 0.016), and older donor age per 10 years (aOR, 1.94; P = 0.001) were associated with PNF. Pretransplant extracorporeal membrane oxygenation support was associated with the increased risk of 30-day recipient mortality (aOR, 5.55; P = 0.002). Increased 30-day graft failure was seen in SHKT recipients with pretransplant mechanical cardiac support (aOR, 1.77; P = 0.038) and dialysis at the time of transplant (aOR, 1.72; P = 0.044). Multivariable Cox hazard analysis demonstrated that SHKT, when compared with kidney transplantation alone, is associated with increased kidney graft failure (hazard ratio, 2.56; P < 0.001) and recipient mortality (hazard ratio, 2.65; P < 0.001).

Conclusions

SHKT is associated with high rates of kidney graft failure. Identification of risk factors of renal graft failure can help optimize recipient selection for SHKT versus kidney after heart transplantation, especially after introduction of the new safety-net policy.

Association of Serum Activin Levels with Allograft Outcomes in Patients with Kidney Transplant: Results from the KNOW-KT

INTRODUCTION

Serum activin A has been reported to contribute to vascular calcification and kidney fibrosis in chronic kidney disease. We aimed to investigate whether higher serum activin levels were associated with poor allograft outcomes in patients with kidney transplantation (KT).

METHODS

A total of 860 KT patients from KNOW-KT (Korean Cohort Study for Outcome in Patients with Kidney Transplantation) were analyzed. We measured serum activin levels pre-KT and 1 year after KT. The primary outcome was the composite of a ≥50% decline in estimated glomerular filtration rate and graft failure. Multivariable cause-specific hazard model was used to analyze association of 1-year activin levels with the primary outcome. The secondary outcome was coronary artery calcification score (CACS) at 5 years after KT.

RESULTS

During the median follow-up of 6.7 years, the primary outcome occurred in 109 (12.7%) patients. The serum activin levels at 1 year were significantly lower than those at pre-KT (488.2 ± 247.3 vs. 704.0 ± 349.6). When patients were grouped based on the median activin level at 1 year, the high-activin group had a 1.91-fold higher risk (95% CI, 1.25-2.91) for the primary outcome compared to the low-activin group. A one-standard deviation increase in activin levels as a continuous variable was associated with a 1.36-fold higher risk (95% CI, 1.16-1.60) for the primary outcome. Moreover, high activin levels were significantly associated with 1.56-fold higher CACS (95% CI, 1.12-2.18).

CONCLUSION

Post-transplant activin levels were independently associated with allograft functions as well as coronary artery calcification in KT patients.

Efficacy of mTOR Inhibitors and Intravenous Immunoglobulin for Treatment of Polyoma BK Nephropathy in Kidney Transplant Recipients: A Biopsy-Proven Study

OBJECTIVES

We investigated the efficacy of a predetermined protocol that consisted of immunosuppressive drug reduction/withdrawal and intravenous immunoglobulin administration for the treatment of polyoma BK virus nephropathy.

MATERIALS AND METHODS

Patients with biopsy-proven polyoma BK virus nephropathy received a treatment regimen based on discontinuation of both calcineurin inhibitors and antiproliferative agents and switching to mTOR inhibitors accompanied by intravenous immunoglobulin administration.

RESULTS

Our study included 508 patients, with polyoma BK viremia detected in 80 patients. The mean age was 45.3 ± 9.5 years (range, 18-71 y), 64% were male, and mean follow-up was 37 ± 21 months (6-94 mo). All 16 patients who developed polyoma BK virus nephropathy and 9 patients who had highgrade polyoma BK viremia without nephropathy received intravenous immunoglobulin treatment. Compared with patients with viremia, patients with polyoma BK virus nephropathy had significantly higher rates of graft loss due to rejection (18.8% vs 1.6%; P = .024) and all-cause graft loss (31.2% vs 6.3%; P = .014). Histopathologically, viral inclusion bodies disappeared and SV40 became negative after treatment in all 13 patients who underwent protocol biopsies. Unfortunately, histopathologically complete recovery without chronic tubular and interstitial tissue damage was achieved in only 4 patients after treatment. In addition, 3 patients lost their grafts due to acute antibody-mediated or mixed-type rejection (18.8%).

CONCLUSIONS

In patients with polyoma BK virus nephropathy, clearance of viremia and SV40 should not be the sole outcomes to obtain. Aggressive reductions in maintenance immunosuppression and switching to double-drug therapy combined with high-dose intravenous immunoglobulin leads to high rates of graft loss/rejection and sequalae of chronic histological changes.

Costimulatory Blockade and Solid Organ Transplantation: The Past, Present, and Future

Belatacept is the first costimulatory blockade agent clinically approved for transplant immunosuppression. Although more than 10 years of study have demonstrated that belatacept offers superior long-term renal allograft and patient survival compared to conventional calcineurin inhibitor (CNI)-based immunosuppression regimens, the clinical adoption of belatacept has continued to lag because of concerns of an early risk of acute cellular rejection (ACR) and various logistical barriers to its administration. In this review, the history of the clinical development of belatacept is examined, along with the findings of the seminal BENEFIT and BENEFIT-EXT trials culminating in the clinical approval of belatacept. Recent efforts to incorporate belatacept into novel CNI-free immunosuppression regimens are reviewed, as well as the experience of the Emory Transplant Center in using a tapered course of low-dose tacrolimus in belatacept-treated renal allograft patients to garner the long-term outcome benefits of belatacept without the short-term increased risks of ACR. Potential avenues to increase the clinical adoption of belatacept in the future are explored, including surmounting the logistical barriers of belatacept administration through subcutaneous administration or more infrequent belatacept dosing. In addition, belatacept conversion strategies and potential expanded clinical indications of belatacept are discussed for pediatric transplant recipients, extrarenal transplant recipients, treatment of antibody-mediated rejection (AMR), and in patients with failed renal allografts. Finally, we discuss the novel immunosuppressive drugs currently in the development pipeline that may aid in the expansion of costimulation blockade utilization.

Donor-Derived Cell-Free DNA (dd-cfDNA) in Kidney Transplant Recipients With Indication Biopsy-Results of a Prospective Single-Center Trial

Donor-derived cell-free DNA (dd-cfDNA) identifies allograft injury and discriminates active rejection from no rejection. In this prospective study, 106 kidney transplant recipients with 108 clinically indicated biopsies were enrolled at Heidelberg University Hospital between November 2020 and December 2022 to validate the clinical value of dd-cfDNA in a cohort of German patients. dd-cfDNA was quantified at biopsy and correlated to histopathology. Additionally, dd-cfDNA was determined on days 7, 30, and 90 post-biopsy and analyzed for potential use to monitor response to anti-rejection treatment. dd-cfDNA levels were with a median (IQR) % of 2.00 (0.48-3.20) highest in patients with ABMR, followed by 0.92 (0.19-11.25) in patients with TCMR, 0.44 (0.20-1.10) in patients with borderline changes and 0.20 (0.11-0.53) in patients with no signs of rejection. The AUC for dd-cfDNA to discriminate any type of rejection including borderline changes from no rejection was at 0.72 (95% CI 0.62-0.83). In patients receiving anti-rejection treatment, dd-cfDNA levels significantly decreased during the 7, 30, and 90 days follow-up compared to levels at the time of biopsy (p = 0.006, p = 0.002, and p < 0.001, respectively). In conclusion, dd-cfDNA significantly discriminates active rejection from no rejection. Decreasing dd-cfDNA following anti-rejection treatment may indicate response to therapy. Clinical Trial Registration: https://drks.de/search/de/trial/DRKS00023604, identifier DRKS00023604.

Optimizing medication adherence with home-monitoring - A feasibility study using capillary microsampling and mHealth in solid organ-transplanted adolescents

BACKGROUND

Reliable methods to detect and reduce medication nonadherence in solid organ-transplanted (SOT) adolescents are warranted. We aimed to evaluate the feasibility of combining a medication-manager application (TusenTac®-app) with home-sampling of tacrolimus (Tac) in young SOT recipients.

METHODS

Kidney and combined SOT recipients between 14 and 25 years were included. During an 8-week intervention period, the participants were instructed to use the transplant-specific, age-adapted TusenTac®-app daily and to perform weekly at-home Tac trough finger-prick microsampling. Microsample Tac concentrations were controlled against timed venous samples twice. Medication implementation and persistence adherence were measured with BAASIS© questionnaires, TusenTac®-registrations, Tac trough concentration coefficient of variation (CV%) and self-reporting by interview. For comparison, venous Tac trough CV% were obtained from the year before and after the short-term intervention.

RESULTS

Twenty-two recipients were included, two withdrawals, leaving 20; median age 17.9 (14.5-24.8) years, 12 females (60%). The participants registered their dosage intake 88% (1502/1703) of the expected times, and 90% (106/118) of the microsamples were obtained correctly. At inclusion, 11 recipients (55%) were nonadherent assessed with BAASIS© questionnaire, four of these (36%) turned adherent during the intervention period. At the end, 70% reported improved timing-adherence at the interview. There was no significant change in TacCV% from the year before to the year after the short-term intervention. Home-sampling was reliable and measured Tac concentrations accurately.

CONCLUSIONS

Home-monitoring, combining Tac finger-prick microsampling and a medication-manager app, is feasible in adolescent SOT recipients with 70% perceived improvement in medication timing-adherence. There were no significant long-term changes in TacCV% confirming the need for continuous use and individualized interventions.

The Diagnostic Significance of C3d Antigen in Kidney and Skin Histopathology - The Current State-Of-The-Art and Practical Examples

The aim of this narrative review is to summarize recent knowledge about the diagnostic significance of immunobiological detection of C3d with a focus on renal and skin tissue biopsies. We completed the present narrative review with our own experiences with preparation and practical use of monoclonal C3d antibodies at a small national level.

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

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

Amiloride evokes significant natriuresis and weight loss in kidney transplant recipients with and without albuminuria

Albuminuria in kidney transplant recipients (KTRs) is associated with hypertension and aberrant glomerular filtration of serine proteases that may proteolytically activate the epithelial Na+ channel (ENaC). The present nonrandomized, pharmacodynamic intervention study aimed to investigate if inhibition of ENaC increases Na+ excretion and reduces extracellular volume in KTRs dependent on the presence of albuminuria. KTRs with and without albuminuria (albumin-to-creatinine ratio > 300 mg/g, n = 7, and <30 mg/g, n = 7, respectively) were included and ingested a diet with fixed Na+ content (150 mmol/day) for 5 days. On the last day, amiloride at 10 mg was administered twice. Body weight, 24-h urine electrolyte excretion, body water content, and ambulatory blood pressure as well as plasma renin, angiotensin II, and aldosterone concentrations were determined before and after amiloride. Amiloride led to a significant decrease in body weight, increase in 24-h urinary Na+ excretion, and decrease in 24-h urinary K+ excretion in both groups. Urine output increased in the nonalbuminuric group only. There was no change in plasma renin, aldosterone, and angiotensin II concentrations after amiloride, whereas a significant decrease in nocturnal systolic blood pressure and increase in 24-h urine aldosterone excretion was observed in albuminuric KTRs only. There was a significant correlation between 24-h urinary albumin excretion and amiloride-induced 24-h urinary Na+ excretion. In conclusion, ENaC activity contributes to Na+ and water retention in KTRs with and without albuminuria. ENaC is a relevant pharmacological target in KTRs; however, larger and long-term studies are needed to evaluate whether the magnitude of this effect depends on the presence of albuminuria.NEW & NOTEWORTHY Amiloride has a significant natriuretic effect in kidney transplant recipients (KTRs) that relates to urinary albumin excretion. The epithelial Na+ channel may be a relevant direct pharmacological target to counter Na+ retention and hypertension in KTRs. Epithelial Na+ channel blockers should be further investigated as a mean to mitigate Na+ and water retention and to potentially obtain optimal blood pressure control in KTRs.

Klotho and Fibroblast Growth Factor 23 Are Independent of Vitamin D, and Unlike Vitamin D, Are Not Associated With Graft- and Patient Survival After Kidney Transplantation

Short-term survival after kidney transplantation is excellent but long-term survival remains suboptimal. The aim of the study was to explore the relationship between soluble α-Klotho (sKlotho) and intact fibroblast growth factor 23 (iFGF23) measured 8 wk and 1 y posttransplant with long-term graft- and patient survival in a cohort of kidney transplant recipients with deficient and nondeficient vitamin D (25[OH]D) levels.

Methods

Vitamin D, sKlotho, and iFGF23 were measured 8 wk and 1 y posttransplant in 132 recipients transplanted between November 2012 and October 2013.

Results

Of the 132 kidney transplant recipients, 49 had deficient vitamin D levels (<30 nmol/L) and 83 had nondeficient vitamin D levels (≥30 nmol/L) at 8 wk posttransplant. The mean age was 51 y and the median follow-up was 7.4 y. At 1 y posttransplant, vitamin D increased significantly. There were no significant differences in sKlotho or iFGF23 levels between the 2 vitamin D groups neither at 8 wk nor 1 y. sKlotho increased significantly and iFGF23 decreased significantly in the whole cohort. During the follow-up, there were 36 graft losses (27%) and 27 deaths (20%). Ninety-four percent of the transplant recipients with nondeficient vitamin D levels were alive with a well-functioning graft after 5 y using Kaplan-Meier survival estimates, compared with 84% of the patients with deficient vitamin D levels (P = 0.014). Klotho and FGF23 levels did not influence graft- and patient survival.

Conclusions

In this nationwide cohort of kidney transplant recipients, long-term graft- and patient survival were significantly better in patients with vitamin D ≥30 nmol/L 8 wk posttransplant compared with those with vitamin D <30 nmol/L. sKlotho levels increased and iFGF23 levels decreased from 8 wk to 1 y posttransplant. Klotho and FGF23 levels were not associated with graft- and patient survival.

Intragraft B cell differentiation during the development of tolerance to kidney allografts is associated with a regulatory B cell signature revealed by single cell transcriptomics

Mouse kidney allografts are spontaneously accepted in select, fully mismatched donor-recipient strain combinations, like DBA/2J to C57BL/6 (B6), by natural tolerance. We previously showed accepted renal grafts form aggregates containing various immune cells within 2 weeks posttransplant, referred to as regulatory T cell-rich organized lymphoid structures, which are a novel regulatory tertiary lymphoid organ. To characterize the cells within T cell-rich organized lymphoid structures, we performed single-cell RNA sequencing on CD45+ sorted cells from accepted and rejected renal grafts from 1-week to 6-months posttransplant. Analysis of single-cell RNA sequencing data revealed a shifting from a T cell-dominant to a B cell-rich population by 6 months with an increased regulatory B cell signature. Furthermore, B cells were a greater proportion of the early infiltrating cells in accepted vs rejecting grafts. Flow cytometry of B cells at 20 weeks posttransplant revealed T cell, immunoglobulin domain and mucin domain-1+ B cells, potentially implicating a regulatory role in the maintenance of allograft tolerance. Lastly, B cell trajectory analysis revealed intragraft differentiation from precursor B cells to memory B cells in accepted allografts. In summary, we show a shifting T cell- to B cell-rich environment and a differential cellular pattern among accepted vs rejecting kidney allografts, possibly implicating B cells in the maintenance of kidney allograft acceptance.

Molecular immune monitoring in kidney transplant rejection: a state-of-the-art review

Although current regimens of immunosuppressive drugs are effective in renal transplant recipients, long-term renal allograft outcomes remain suboptimal. For many years, the diagnosis of renal allograft rejection and of several causes of renal allograft dysfunction, such as chronic subclinical inflammation and infection, was mostly based on renal allograft biopsy, which is not only invasive but also possibly performed too late for proper management. In addition, certain allograft dysfunctions are difficult to differentiate from renal histology due to their similar pathogenesis and immune responses. As such, non-invasive assays and biomarkers may be more beneficial than conventional renal biopsy for enhancing graft survival and optimizing immunosuppressive drug regimens during long-term care. This paper discusses recent biomarker candidates, including donor-derived cell-free DNA, transcriptomics, microRNAs, exosomes (or other extracellular vesicles), urine chemokines, and nucleosomes, that show high potential for clinical use in determining the prognosis of long-term outcomes of kidney transplantation, along with their limitations.

A single centre in-depth analysis of death with a functioning kidney graft and reasons for overall graft failure

BACKGROUND

High numbers of unknown classifications and inconsistent methodologies in previous studies make the interpretation of causes leading to graft loss difficult. In addition, data on a holistic view looking at both death with a functioning graft (DWFG) and death-censored graft failure (DCGF) are sparse.

METHODS

In this single-centre study we included 1477 adult kidney transplants performed between 1997 and 2017, of which all 286 DWFGs until the end of observation were analysed and causes for death assigned. Additionally, the results were compared with the causes of 303 DCGFs of the same cohort to evaluate the impact of causes for overall graft loss.

RESULTS

The most frequent causes for DWFG were cardiovascular disease (CVD) in 30.8%, malignancy in 28.3% and infections in 21%. Only 9.4% of reasons for DWFG were unknown. Sudden death occurred in 40% (35/88) of patients classified as DWFG due to CVD. Overall graft loss was related to the effect of immunosuppression in 36.2% [infection 20.9% (123/589), malignancy 15.3% (90/589)] and CVD in 22.4% (132/589). In 27.4% (161/589), graft failure was associated with underimmunosuppression (rejection). For infections (60 DWFG, 63 DCGF) and CVD (88 DWFG, 44 DCGF), a considerable overlap was observed between DWFG and DCGF. For patients >70 years of age at transplantation, medical events accounted for 78% of overall graft losses and only 6.5% were associated with rejection.

CONCLUSIONS

DWFG and DCGF share more causes for graft loss than previously reported and sudden death plays an underestimated role in death with a functioning graft.

Emerging Therapies for Antibody-Mediated Rejection in Kidney Transplantation

Despite the advances in immunosuppressive medications, antibody-mediated rejection (AMR) continues to be a major cause of kidney allograft failure and remains a barrier to improving long-term allograft survival. Recently, there have been significant advances in the understanding of the pathophysiological process of AMR, along with the development of new therapeutic options. Additionally, surveillance protocols with donor-derived cell-free DNA and gene profile testing have been established, leading to the early detection of AMR. A multitude of clinical trials are ongoing, opening numerous opportunities for improving outcome in kidney transplant recipients. In this brief review, we discuss the emerging therapies for managing both active and chronic active AMR and highlight the ongoing clinical trials.

Congenic hematopoietic stem cell transplantation promotes survival of heart allografts in murine models of acute and chronic rejection

The ability to induce tolerance would be a major advance in the field of solid organ transplantation. Here, we investigated whether autologous (congenic) hematopoietic stem cell transplantation (HSCT) could promote tolerance to heart allografts in mice. In an acute rejection model, fully MHC-mismatched BALB/c hearts were heterotopically transplanted into C57BL/6 (CD45.2) mice. One week later, recipient mice were lethally irradiated and reconstituted with congenic B6 CD45.1 Lin-Sca1+ckit+ cells. Recipient mice received a 14-day course of rapamycin both to prevent rejection and to expand regulatory T cells (Tregs). Heart allografts in both untreated and rapamycin-treated recipients that did not undergo HSCT were rejected within 33 days (median survival time = 8 days for untreated recipients, median survival time = 32 days for rapamycin-treated recipients), whereas allografts in HSCT-treated recipients had a median survival time of 55 days (P < 0.001 vs. both untreated and rapamycin-treated recipients). Enhanced allograft survival following HSCT was associated with increased intragraft Foxp3+ Tregs, reduced intragraft B cells, and reduced serum donor-specific antibodies. In a chronic rejection model, Bm12 hearts were transplanted into C57BL/6 (CD45.2) mice, and congenic HSCT was performed two weeks following heart transplantation. HSCT led to enhanced survival of allografts (median survival time = 70 days vs. median survival time = 28 days in untreated recipients, P < 0.01). Increased allograft survival post-HSCT was associated with prevention of autoantibody development and absence of vasculopathy. These data support the concept that autologous HSCT can promote immune tolerance in the setting of allotransplantation. Further studies to optimize HSCT protocols should be performed before this procedure is adopted clinically.

The Perspectives of General Nephrologists Toward Transitions of Care and Management of Failing Kidney Transplants

The management of failing kidney allograft and transition of care to general nephrologists (GN) remain a complex process. The Kidney Pancreas Community of Practice (KPCOP) Failing Allograft Workgroup designed and distributed a survey to GN between May and September 2021. Participants were invited via mail and email invitations. There were 103 respondents with primarily adult nephrology practices, of whom 41% had an academic affiliation. More than 60% reported listing for a second kidney as the most important concern in caring for patients with a failing allograft, followed by immunosuppression management (46%) and risk of mortality (38%), while resistant anemia was considered less of a concern. For the initial approach to immunosuppression reduction, 60% stop antimetabolites first, and 26% defer to the transplant nephrologist. Communicating with transplant centers about immunosuppression cessation was reported to occur always by 60%, and sometimes by 29%, while 12% reported making the decision independently. Nephrologists with academic appointments communicate with transplant providers more than private nephrologists (74% vs. 49%, p = 0.015). There are heterogeneous approaches to the care of patients with a failing allograft. Efforts to strengthen transitions of care and to develop practical practice guidelines are needed to improve the outcomes of this vulnerable population.

Peripheral Blood Immune Cell Composition After Autologous MSC Infusion in Kidney Transplantation Recipients

Tacrolimus is the backbone of immunosuppressive agents to prevent transplant rejection. Paradoxically, tacrolimus is nephrotoxic, causing irreversible tubulointerstitial damage. Therefore, infusion of mesenchymal stromal cells (MSC) 6 and 7 weeks post-transplantation was assessed to facilitate withdrawal of tacrolimus in the randomized phase II TRITON trial. Here, we performed detailed analysis of the peripheral blood immune composition using mass cytometry to assess potential effects of MSC therapy on the immune system. We developed two metal-conjugated antibody panels containing 40 antibodies each. PBMC samples from 21 MSC-treated patients and 13 controls, obtained pre-transplant and at 24 and 52 weeks post-transplantation, were analyzed. In the MSC group at 24 weeks, 17 CD4⁺ T cell clusters were increased of which 14 Th2-like clusters and three Th1/Th2-like clusters, as well as CD4+FoxP3+ Tregs. Additionally, five B cell clusters were increased, representing either class switched memory B cells or proliferating B cells. At 52 weeks, CCR7⁺CD38⁺ mature B cells were decreased. Finally, eight Tc1 (effector) memory cytotoxic T cell clusters were increased. Our work provides a comprehensive account of the peripheral blood immune cell composition in kidney transplant recipients after MSC therapy and tacrolimus withdrawal. These results may help improving therapeutic strategies using MSCs with the aim to reduce the use of calcineurin inhibitors. Clinical Trial Registration: ClinicalTrials.gov, identifier NCT02057965.

Prospective cohort study of Torque Teno Virus (TTV) viral load kinetics and the association with graft rejection in renal transplant patients

INTRODUCTION

Graft survival is mainly determined by rejections and infectious complications in transplant recipients. Torque Teno Virus (TTV), a nonpathogenic and ubiquitous single-stranded DNA virus, has been proposed as a biomarker of the immune status in transplant patients. This study aimed to determine the correlation between a Home-Brew TTV PCR and R-GENE®PCR; the TTV viral load kinetics in renal transplant recipients and the association with graft rejection.

MATERIALS AND METHODS

Prospective cohort study on 107 adult renal transplant recipients. TTV viral load was determined in 746 plasma samples collected before and after renal transplantation by a Home-Brew PCR and a commercial PCR (R-GENE®PCR). Associations of TTV viral load with graft rejections were analyzed.

RESULTS

Agreement of both PCR assays was 93.2% and Pearson correlation coefficient was r: 0.902 (95%CI: 0.8881-0.9149, p < 0.0001). TTV viral load kinetics showed an initial gradual increase reaching a peak at 3 months. This highest value was followed by a slight decrease, reaching a plateau significantly higher than the initial baseline at 6 months (p < 0.0001). Between (181-270) days post-transplantation, TTV median viral load in patients with graft rejection was significantly lower, 3.59 Log₁₀ copies/mL (by Home-Brew PCR) and 3.10 Log₁₀ copies/mL (by R-GENE®PCR) compared to patients without graft rejection (6.14 and 5.96 Log₁₀ copies/mL, respectively).

CONCLUSIONS

Significantly lower TTV viral load was observed in patients with renal rejection occurring at a median of 243 days post-transplantation. Given the dynamic behavior of TTV viral load post-transplantation, cut-off values for risk stratification to predict rejection might be determined in relation to the post-transplant period.

Complement activation and kidney transplantation; a complex relationship

Although kidney transplantation is the best treatment for end stage kidney disease, the benefits are limited by factors such as the short fall in donor numbers, the burden of immunosuppression and graft failure. Although there have been improvements in one-year outcomes, the annual rate of graft loss beyond the first year has not significantly improved, despite better therapies to control the alloimmune response. There is therefore a need to develop alternative strategies to limit kidney injury at all stages along the transplant pathway and so improve graft survival. Complement is primarily part of the innate immune system, but is also known to enhance the adaptive immune response. There is increasing evidence that complement activation occurs at many stages during transplantation and can have deleterious effects on graft outcome. Complement activation begins in the donor and occurs again on reperfusion following a period of ischemia. Complement can contribute to the development of the alloimmune response and may directly contribute to graft injury during acute and chronic allograft rejection. The complexity of the relationship between complement activation and allograft outcome is further increased by the capacity of the allograft to synthesise complement proteins, the contribution complement makes to interstitial fibrosis and complement's role in the development of recurrent disease. The better we understand the role played by complement in kidney transplant pathology the better placed we will be to intervene. This is particularly relevant with the rapid development of complement therapeutics which can now target different the different pathways of the complement system. Combining our basic understanding of complement biology with preclinical and observational data will allow the development and delivery of clinical trials which have best chance to identify any benefit of complement inhibition.

Proton Pump Inhibitors, Kidney Damage, and Mortality: An Updated Narrative Review

Since their approval by the Food and Drug Administration (FDA) in 1989, proton pump inhibitors (PPIs) have become one of the most highly utilized drugs in the United States, assuming a position as one of the top 10 most prescribed medications in the country. The purpose of PPIs is to limit the amount of gastric acid secreted by the parietal cells via irreversible inhibition of the H+/K+-ATPase pump, therefore maintaining an elevated gastric acid pH of greater than 4 for 15-21 h. Even though PPIs have many clinical uses, they are not without their adverse effects, mimicking achlorhydria. Besides electrolyte abnormalities and vitamin deficiencies, long-term use of PPIs has been linked to acute interstitial nephritis, bone fractures, poor COVID-19 infection outcomes, pneumonia, and possibly an increase in all-cause mortality. The causality between PPI use and increased mortality and disease risk can be questioned since most studies are observational. Confounding variables can greatly affect an observational study and explain the wide-ranging associations with the use of PPIs. Patients on PPIs are generally older, obese, sicker with a higher number of baseline morbidities, and on more medications than the compared PPI non-users. These findings suggest that PPI users are at a higher risk of mortality and complications based on pre-existing conditions. This narrative review aims to update readers on the concerning effects that proton pump inhibitor use can have on patients and give providers a resource to create informed decisions on appropriate PPI use.

CD28-Selective Inhibition Prolongs Non-Human Primate Kidney Transplant Survival

Costimulation blockade using belatacept results in improved renal function after kidney transplant as well as decreased likelihood of death/graft loss and reduced cardiovascular risk; however, higher rates and grades of acute rejection have prevented its widespread clinical adoption. Treatment with belatacept blocks both positive (CD28) and negative (CTLA-4) T cell signaling. CD28-selective therapies may offer improved potency by blocking CD28-mediated costimulation while leaving CTLA-4 mediated coinhibitory signals intact. Here we test a novel domain antibody directed at CD28 (anti-CD28 dAb (BMS-931699)) in a non-human primate kidney transplant model. Sixteen macaques underwent native nephrectomy and received life-sustaining renal allotransplantation from an MHC-mismatched donor. Animals were treated with belatacept alone, anti-CD28 dAb alone, or anti-CD28 dAb plus clinically relevant maintenance (MMF, Steroids) and induction therapy with either anti-IL-2R or T cell depletion. Treatment with anti-CD28 dAb extended survival compared to belatacept monotherapy (MST 187 vs. 29 days, p=0.07). The combination of anti-CD28 dAb and conventional immunosuppression further prolonged survival to MST ∼270 days. Animals maintained protective immunity with no significant infectious issues. These data demonstrate CD28-directed therapy is a safe and effective next-generation costimulatory blockade strategy with a demonstrated survival benefit and presumed advantage over belatacept by maintaining intact CTLA-4 coinhibitory signaling.

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.

mTOR Inhibition Impairs the Activation and Function of Belatacept-Resistant CD4+CD57+ T Cells In Vivo and In Vitro

Calcineurin inhibitors have improved graft survival in solid-organ transplantation but their use is limited by toxicity, requiring a switch to another immunosuppressor in some cases. Belatacept is one option that has been shown to improve graft and patient survival despite being associated with a higher risk of acute cellular rejection. This risk of acute cellular rejection is correlated with the presence of belatacept-resistant T cells. We performed a transcriptomic analysis of in vitro-activated cells to identify pathways affected by belatacept in belatacept-sensitive cells (CD4⁺CD57^-) but not in belatacept-resistant CD4⁺CD57⁺ T cells. mTOR was significantly downregulated in belatacept-sensitive but not belatacept-resistant T cells. The inhibition of mTOR strongly decreases the activation and cytotoxicity of CD4⁺CD57⁺ cells. In humans, the use of a combination of mTOR inhibitor and belatacept prevents graft rejection and decreases the expression of activation markers on CD4 and CD8 T cells. mTOR inhibition decreases the functioning of belatacept-resistant CD4⁺CD57⁺ T cells in vitro and in vivo. It could potentially be used in association with belatacept to prevent acute cellular rejection in cases of calcineurin intolerance.

Impact of early blood transfusion after kidney transplantation on the clinical outcomes and allograft survival

INTRODUCTION

Anemia in chronic kidney disease is of great concern regarding blood transfusions and the possibility of allosensitization for future kidney transplants and the occurrence of rejection and allograft loss in the post-transplant period. The aim of this study was to evaluate the effect of early blood transfusion on the occurrence of rejections, allograft function and survival in the first year after transplantation.

MATERIAL AND METHODS

This retrospective study was carried out with 445 patients submitted to kidney transplant allocated to two groups. The first group received early blood transfusions after transplant (n = 125, 28.09%), and the second group did not receive blood transfusions (n = 320, 71.91%). The patient outcomes were evaluated during a 1-year follow-up.

RESULTS

14 patients given blood transfusion (11.2%) lost their allograft in the first year in comparison with 8 (2.5%) without transfusion (p < 0.001). There were 9 deaths in each group, which corresponded to 7.2% of the patients who received blood transfusions and 2.81% of those who did not (p < 0.035). Patient hospitalization lasted 15 days in transfusion group and 8.5 days in non-transfusion group (p < 0.001). Creatinine levels were higher in the patients who received blood transfusion than in those without transfusion in the first and third months after transplantation (p = 0.012 and 0.038, respectively). During the first year, the patients who received blood products experienced more antibody-mediated rejection (ABMR) (13.60%) than patients who did not (4.38%) (p < 0.001). Those who received blood transfusions also developed de novo DSA in higher proportion than those without transfusion against both class I and class II HLA (p < 0.001).

CONCLUSION

This study showed that blood transfusions in the first month after transplantation had a negative impact on kidney function, graft survival, and contributed to the development of de novo DSA, an increased risk of ABMR and infections.

Chemoprophylaxis for the prevention of tuberculosis in kidney transplant recipients: A systematic review and meta-analysis

Background: A systematic review and meta-analysis was performed to investigate the efficacy and safety of isoniazid (INH) prophylaxis to prevent tuberculosis (TB) infection in kidney transplant recipients (KTRs).

Methods: Web of Science, SCOPUS, and PubMed were searched to identify relevant studies that compared the effects among patients who received INH prophylaxis after transplantation.

Results: A total of 13 studies (involving 6,547 KTRs) were included in our analysis. We found that the risk of active TB infection (RR: 0.35, 95%CI 0.27–0.45, p &lt; 0.01) for KTRs was lower in the INH treatment group than in those without prophylaxis. However, there was no significant difference between the two groups in mortality (RR: 0.93, 95%CI 0.67–1.28, p = 0.64), acute rejection (RR: 0.82, 95%CI 0.44–1.51, p = 0.52), and hepatotoxicity (RR: 1.25, 95%CI 0.94–1.65, p = 0.12).

Conclusion: Isoniazid prophylaxis is a safe and effective for KTRs on reactivation of latent TB infection.

Comparative transcriptome profile of mouse macrophages treated with the RhoA/Rock pathway inhibitors Y27632, Fingolimod (Gilenya), and Rezurock (Belumosudil, SLx-2119)

Macrophages play a crucial role in, the currently uncurable, chronic rejection of transplants. In rodent transplantation models, inhibition of the RhoA/Rock pathway disrupts actin-related functions of macrophages, preventing them from entering the graft, and reducing vessel occlusion, fibrosis, and chronic rejection. Among RhoA/Rock inhibitors that inhibit chronic rejection in mouse transplantation are Y27632, Fingolimod, and Rezurock. In a mouse model, Rezurok is more effective in preventing fibrosis and less effective in preventing vessel occlusion than Y27632 or Fingolimod. Fingolimod is FDA-approved for treating multiple sclerosis (MS) and Rezurock for chronic graft versus host disease (GVHD). Still, none had been tested for chronic rejection in humans. To explain the differences in the anti-chronic rejection properties of Y27632, Fingolimod, and Rezurock, we compared the transcriptome profile of mouse macrophages treated with these compounds separately. Treatment with Y27632 or Fingolimod downregulated GTPase and actin pathways involved in cell migration. Rezurock downregulated genes related to fibrosis, such as PTX3, CCR2, CCL2, cell cycle, DNA replication, adaptive immune response, and organelle assembly, while Fingolimod also specifically downregulated NOTCH1 at mRNA . The result of this study not only uncovers which pathways are shared or specific for these drugs but will help in the development of macrophage pathway-targeted therapies in human transplantation, MS, and GVHD. Because macrophages are the major players in immune response, tissue regeneration, renewal, and homeostasis, and development of many diseases, including cancer, the data compiled here will help in designing novel or improved therapies in many clinical applications.

Remarkable 107-year-old kidney with a 49-year of long-term allograph survival through continuous azathioprine monotherapy

BACKGROUND

The main goal of kidney allograft transplantation is to improve survival in patients with end-stage kidney failure. Herein, we report a 49-year long-term allograft survival with non-identical human leukocyte antigens (HLA). The purpose of this study was to report the successful clinical outcome of 49 years of transplant survival in a 79-year-old patient with a 107-year-old kidney undergoing continued immunosuppressive monotherapy.

MATERIAL AND METHODS

The patient was evaluated clinically and immunologically with HLA typing and anti-HLA antibodies before transplantation. Post-transplant, the patient's clinical and immunological survival were monitored for 49 years. The state of the chimerism was assessed using the polymerase chain reaction to amplify 24 short tandem repeats using a DNA thermocycler and DNA analyzer.

RESULTS

The patient and donor were haploidentical and the patient was treated with azathioprine monotherapy. Donor-specific antibodies were detected only for the HLA-DPB1* 03:01 mismatch. This patient developed multiple skin tumors 26 years after transplant, which were successfully treated with topical therapy or surgical removal. The patient developed an intestinal adenocarcinoma 43 years after kidney transplantation, which was surgically removal; six years later, adenocarcinoma was diagnosed in a finger, followed by axillar and hepatic metastases. After 49 years of graft survival of a kidney of 107 years old in a patient with 79 years of age, the patient's health worsened with severe dehydration, anemia, and bacterial infection. The patient was hospitalized with a serum creatinine level of 3.45 mg/dL, urea level of 188 mg/dL, and estimated glomerular filtration rate of 22 mL/1.72 m²; septicemia developed and was treated with antibiotics. The patient had poor clinical progress, was intubated, and later died due to septic shock.

CONCLUSIONS

To the best of our knowledge, this is the first case of a 107-year-old kidney, transplanted into a recipient who was treated with azathioprine monotherapy for 49 years.

Microbial and metabolic features in renal transplant recipients with post-transplantation diabetes mellitus

OBJECTIVE

Post-transplantation diabetes mellitus (PTDM) is a common complication in renal transplant recipients (RTRs). Gut microbiome plays important roles in a variety of chronic metabolic diseases, but its association with the occurrence and development of PTDM is still unknown. The present study integrates the analysis of gut microbiome and metabolites to further identify the characteristics of PTDM.

METHODS

A total of 100 RTRs fecal samples were collected in our study. Among them, 55 samples were submitted to Hiseq sequencing, and 100 samples were used for non-targeted metabolomics analysis. The gut microbiome and metabolomics of RTRs were comprehensively characterized.

RESULTS

The species Dialister invisus was significantly associated with fasting plasma glucose (FPG). The functions of tryptophan and phenylalanine biosynthesis were enhanced in RTRs with PTDM, while the functions of fructose and butyric acid metabolism were reduced. Fecal metabolome analysis indicated that RTRs with PTDM had unique metabolite distribution characteristics, and two differentially expressed specific metabolites were significantly correlated with FPG. The correlation analysis of gut microbiome and metabolites showed that gut microbiome had an obvious effect on the metabolic characteristics of RTRs with PTDM. Moreover, the relative abundance of microbial function is associated with the expression of several specific gut microbiome and metabolites.

CONCLUSIONS

Our study identified the characteristics of gut microbiome and fecal metabolites in RTRs with PTDM, and we also found two important metabolites and a bacterium were significantly associated with PTDM, which might be used as novel targets in the research field of PTDM.

Reliability and Validity of the Japanese Version of the Basel Assessment of Adherence to Immunosuppressive Medications Scale in Kidney Transplant Recipients

A valid and reliable instrument that can measure adherence is needed to identify nonadherent patients and to improve adherence. However, there is no validated Japanese self-report instrument to evaluate adherence to immunosuppressive medications for transplant patients. The purpose of this study was to determine the reliability and validity of the Japanese version of the Basel Assessment of Adherence to Immunosuppressive Medications Scale (BAASIS).

Methods

We translated the BAASIS into Japanese and developed the Japanese version of the BAASIS (J-BAASIS) according to the International Society of Pharmacoeconomics and Outcomes Research task force guidelines. We analyzed the reliability (test-retest reliability and measurement error) and validity of the J-BAASIS (concurrent validity with the medication event monitoring system and the 12-item Medication Adherence Scale) referring to the COSMIN Risk of Bias checklist.

Results

A total of 106 kidney transplant recipients were included in this study. In the analysis of test-retest reliability, Cohen's kappa coefficient was found to be 0.62. In the analysis of measurement error, the positive and negative agreement were 0.78 and 0.84, respectively. In the analysis of concurrent validity with the medication event monitoring system, sensitivity and specificity were 0.84 and 0.90, respectively. In the analysis of concurrent validity with the 12-item Medication Adherence Scale, the point-biserial correlation coefficient for the "medication compliance" subscale was 0.38 (P < 0.001).

Conclusions

The J-BAASIS was determined to have good reliability and validity. Using the J-BAASIS to evaluate adherence can help clinicians to identify medication nonadherence and institute appropriate corrective measures to improve transplant outcomes.

Risk of Severe Alphaherpesvirus Infection after Solid Organ Transplantation: A Nationwide Population-Based Cohort Study

Patients after solid organ transplantation (SOT) are more susceptible to various viral infections, including alphaherpesviruses. Therefore, the aim of our study was to investigate the risk of alphaherpesvirus infections, including herpes simplex and herpes zoster, after solid organ transplantation. Inpatient records from the Taiwan National Health Insurance Research Database (NHIRD) defined solid organ recipients, including heart, liver, lung, and kidney, hospitalized for alphaherpesvirus infections as a severe case group of transplants and matched them with a nontransplant cohort. We enrolled 18,064 individuals, of whom 9032 were in each group. A higher risk of severe alphaherpesvirus infection was noted in solid organ recipients (aHR = 9.19; p < 0.001) than in the general population. In addition, solid organ transplant recipients had the highest risk of alphaherpesvirus infection within 1 year after transplantation (aHR = 25.18). The comparison found a higher risk of herpes zoster and herpes simplex infections in recipients of kidney (aHR = 9.13; aHR = 12.13), heart (aHR = 14.34; aHR = 18.54), and liver (aHR = 5.90; aHR = 8.28) transplants. Patients who underwent solid organ transplantation had a significantly higher risk of alphaherpesvirus infection than the general population.

Diabetic Kidney Disease in Post-Transplant Diabetes Mellitus: Causes, Treatment and Outcomes

Kidney transplant recipients are a unique subgroup of chronic kidney disease patients due to their single functioning kidney, immunosuppressive agent usage, and long-term complications related to transplantation. Post-transplant diabetes mellitus (PTDM) has a significant adverse effect on renal outcomes in particular. As transplantations enable people to live longer, cardiovascular morbidity and mortality become more prevalent, and PTDM is a key risk factor for these complications. Although PTDM results from similar risk factors to those of type 2 diabetes, the conditions differ in their pathophysiology and clinical features. Transplantation itself is a risk factor for diabetes due to chronic exposure to immunosuppressive agents. Considering current evidence, this article describes the risk factors, pathogenesis, diagnostic criteria, prevention strategies, and management of PTDM. The therapeutic options are discussed regarding their safety and potential drug-drug interactions with immunosuppressive agents.

Optimized immunosuppression to prevent graft failure in renal transplant recipients with HLA antibodies (OuTSMART): a randomised controlled trial

BACKGROUND

3% of kidney transplant recipients return to dialysis annually upon allograft failure. Development of antibodies (Ab) against human leukocyte antigens (HLA) is a validated prognostic biomarker of allograft failure. We tested whether screening for HLA Ab, combined with an intervention to improve adherence and optimization of immunosuppression could prevent allograft failure.

METHODS

Prospective, open-labelled randomised biomarker-based strategy (hybrid) trial in 13 UK transplant centres [EudraCT (2012-004308-36) and ISRCTN (46157828)]. Patients were randomly allocated (1:1) to unblinded or double-blinded arms and screened every 8 months. Unblinded HLA Ab+ patients were interviewed to encourage medication adherence and had tailored optimisation of Tacrolimus, Mycophenolate mofetil and Prednisolone. The primary outcome was time to graft failure in an intention to treat analysis. The trial had 80% power to detect a hazard ratio of 0.49 in donor specific antibody (DSA)+ patients.

FINDINGS

From 11/9/13 to 27/10/16, 5519 were screened for eligibility and 2037 randomised (1028 to unblinded care and 1009 to double blinded care). We identified 198 with DSA and 818 with non-DSA. Development of DSA, but not non-DSA was predictive of graft failure. HRs for graft failure in unblinded DSA+ and non-DSA+ groups were 1.54 (95% CI: 0.72 to 3.30) and 0.97 (0.54-1.74) respectively, providing no evidence of an intervention effect. Non-inferiority for the overall unblinded versus blinded comparison was not demonstrated as the upper confidence limit of the HR for graft failure exceeded 1.4 (1.02, 95% CI: 0.72 to 1.44). The only secondary endpoint reduced in the unblinded arm was biopsy-proven rejection.

INTERPRETATION

Intervention to improve adherence and optimize immunosuppression does not delay failure of renal transplants after development of DSA. Whilst DSA predicts increased risk of allograft failure, novel interventions are needed before screening can be used to direct therapy.

FUNDING

The National Institute for Health Research Efficacy and Mechanism Evaluation programme grant (ref 11/100/34).

Transcriptionally Distinct B Cells Infiltrate Allografts After Kidney Transplantation

BACKGROUND

Following allogeneic kidney transplantation, a substantial proportion of graft loss is attributed to the formation of donor-specific antibodies and antibody-mediated rejection. B cells infiltrate kidney grafts during antibody-mediated rejection; however, the origins, repertoires, and functions of these intrarenal B cells remain elusive.

METHODS

Here, we use murine allogeneic kidney transplant models to study the origins, transcriptional programming and B cell receptor repertoire of intragraft B cells, and in vitro stimulation assays to evaluate the ability of intragraft B cells to promote CD4+ T cell expansion.

RESULTS

B cells infiltrate kidney grafts in settings of allogeneic, but not syngeneic, transplantation. Intragraft B cells have characteristics of activation but are transcriptionally distinct from germinal center B cells and resemble innate-like B cells. B cell receptor sequencing demonstrates that the majority of intragraft B cells do not originate from lymph node germinal center B cells and are largely germline. Class-switched intragraft B cells are rare but can be donor-specific and produce IgG capable of binding to the kidney allograft. Lastly, intrarenal B cells are capable of stimulating naive T cells but have an altered ability to promote T follicular helper cell expansion.

CONCLUSIONS

Together, these data demonstrate that intrarenal B cells during transplant rejection are transcriptionally distinct from lymph node B cells.

Identification of PDCD1 as a potential biomarker in acute rejection after kidney transplantation via comprehensive bioinformatic analysis

Background

Acute rejection is a determinant of prognosis following kidney transplantation. It is essential to search for novel noninvasive biomarkers for early diagnosis and prompt treatment.

Methods

Gene microarray data was downloaded from the Gene Expression Omnibus (GEO) expression profile database and the intersected differentially expressed genes (DEGs) was calculated. We conducted the DEGs with Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. Distribution of immune cell infiltration was calculated by CIBERSORT. A hub gene marker was identified by intersecting the rejection-related genes from WGCNA and a selected KEGG pathway-T cell receptor signaling pathway (hsa04660), and building a protein-protein interaction network using the STRING database and Cytoscape software. We performed flow-cytometry analysis to validate the hub gene.

Results

A total of 1450 integrated DEGs were obtained from five datasets (GSE1563, GSE174020, GSE98320, GSE36059, GSE25902). The GO, KEGG and immune infiltration analysis results showed that AR was mainly associated with T cell activation and various T-cell related pathways. Other immune cells, such as B cells, Macrophage and Dendritic cells were also associated with the progress. After utilizing the WGCNA and PPI network, PDCD1 was identified as the hub gene. The flow-cytometry analysis demonstrated that both in CD4⁺ and CD8⁺ T cells, PD1⁺CD57^-, an exhausted T cell phenotype, were downregulated in the acute rejection whole blood samples.

Conclusions

Our study illustrated that PDCD1 may be a candidate diagnostic biomarker for acute kidney transplant rejection via integrative bioinformatic analysis.

Impact of iron status on kidney outcomes in kidney transplant recipients

Iron plays an important role in hemodynamics and the immunity, independent of anemia. Since dynamic changes occur in iron storage after kidney transplantation (KT), we investigated the association between iron status and kidney outcomes in KT patients. We analyzed data from the KoreaN cohort study for Outcome in patients With KT (KNOW-KT). The iron status was classified into three groups based on ferritin or transferrin saturation (TSAT) levels one year after KT, with reference ranges of 20‒35% and 100‒300 ng/mL for TSAT and ferritin, respectively. The primary outcome was the composite outcome, which consisted of death, graft failure, and an estimated glomerular filtration rate decline ≥ 50%. In total, 895 patients were included in the final analysis. During a median follow-up of 5.8 years, the primary outcome occurred in 94 patients (19.8/1000 person-years). TSAT levels decreased one year after KT and thereafter gradually increased, whereas ferritin levels were maintained at decreased levels. The adjusted hazard ratios (95% confidence intervals) for the composite outcome were 1.67 (1.00-2.77) and 1.20 (0.60-2.40) in the TSAT > 35% and ferritin > 300 ng/mL groups, respectively. High iron status with high TSAT levels increases the risk of graft failure or kidney functional deterioration after KT.

Changes over time in the causes of death with a functioning graft in kidney transplantation recipients

INTRODUCTION

Death with a functioning graft (DWFG) is the most frequent cause of loss of kidney transplantation (KT).

OBJECTIVE

To analyze the evolution of the causes of DWFG and the frequency of the types of cancer causing DWFG.

METHODS

Retrospective study of KT in Andalusia from 1984 to 2018. We analyzed the evolution according to eras (1984-1995; 1996-2007; 2008-2018) and according to post-transplant period (early death: first year post-KT; late death: after first year post-KT).

RESULTS

A total of 9905 KT were performed, registering 1861 DWFG. The most frequent causes were cardiovascular disease (25.1%), infections (21.5%) and cancer (19.9%). In early death we did not observe changes, and infections were always the main cause. In late death, cardiovascular death decreased (1984-1995: 35.2%, 1996-2007: 22.6%, 2008-2018: 23.9%), but infections (1984-1995: 12.5%, 1996-2007: 18.3%, 2008-2018: 19.9%) and, above all, cancer-related deaths increased (1984-1995: 21.8%, 1996-2007: 29%, 2008-2018: 26.8%) (P < .001). In the multivariable analysis for late death due to cardiovascular disease, recipient age, retransplantation, diabetes, and the first period were risk factors, while the risk of late death due to cancer and infections was associated with recent eras. In the first year after transplantation, the most frequent neoplasia causing DWFG was post-transplant lymphoproliferative disease, and after the first year, it was lung cancer, without differences when it was analyzed by eras.

CONCLUSIONS

Despite the greater comorbidity of the recipients, cardiovascular deaths have decreased. Cancer has been the main cause of late death in recent years. Lung cancer is the most frequent malignancy that causes DWFG in our transplant patients.