Incidence, Risk Factors, and Outcomes of Kidney Transplant Recipients With BK Polyomavirus-Associated Nephropathy

A novel histologic index for polyomavirus nephropathy in comparison with the Banff scoring system: Clinical validation, prognostic implication, and correlation with plasma viral load

BK Polyomavirus nephropathy (PVN) with definitive diagnosis on biopsy, presents incidentally or with varying degrees of graft dysfunction. Banff working group on PVN has proposed a novel scoring system in renal biopsies, to identify patients with higher risk of graft failure. In this study, we attempted to validate the Banff scoring system at index biopsies and correlate with a novel index score, plasma BK-virus load and graft outcome. 48 patients with index biopsies of PVN diagnosed from 2019 to 2022, with simultaneous plasma BKV-virus loads and SV-40 stains were chosen. Biopsies were scored for Banff PVN Class and by novel PVN index. Inter-observer reproducibility was tested between 3 renal pathologists for all parameters and findings were correlated with graft outcome, in a median follow-up of 42 months. Banff PVN classes 2 and 3 and novel index 3 were associated with higher percentage of graft failure and persistent viremia. The novel index score showed a stronger and consistent temporal association with plasma BK-virus levels. Kappa scores revealed a 68 % agreement for Banff PVN class scoring. Our study highlights the prognostic utility of Banff PVN scheme and novel PVN index in correlation with plasma BKV viremia and graft outcome.

Composition of the neutralising antibody response predicts risk of BK virus DNAaemia in recipients of kidney transplants

BACKGROUND

BK polyomavirus (BKV) DNAaemia occurs in 10% of recipients of kidney transplants, contributing to premature allograft failure. Evidence suggests disease is donor derived. Hypothetically, recipient infection with a different BKV serotype increases risk due to poorer immunological control. Thus, understanding the composition and activity of the humoral anti-BKV responses in donor/recipient (D/R) pairs is critical.

METHODS

Using 224 paired pre-transplant D/R samples, BKV VP1 genotype-specific pseudoviruses were employed to define the breadth of the antibody response against different serotypes (ELISA) and, to characterise specific neutralising activity (nAb) using the 50% inhibitory concentration (LogIC50). Mismatch (MM) ratios were calculated using the ratio of recipient ELISA or nAb reactive BKV serotypes relative to the number of donor reactive serotypes.

FINDINGS

BKV DNAaemia was observed in 28/224 recipients of kidney transplants. These recipients had lower nAb titres against all the serotypes, with median logIC50 values of 1.19-2.91, compared to non-viraemic recipients' median logIC50 values of 2.13-3.30. nAb D/R MM ratios >0.67 associated with significantly higher risk of BKV viraemia, with an adjusted odds ratio of 5.12 (95% CI 2.07 to 13.04; p < 0.001). Notably, a mismatch against donor serotype Ic and II associated with adjusted odds ratios of 8.12 (95% CI 2.10 to 35.61; p = 0.002) and 4.52 (95% CI 1.19 to 19.23; p = 0.03) respectively. 21 recipients demonstrated broadly neutralising responses against all the serotypes, none of whom developed BKV DNAaemia post-transplant. In contrast, there was poor concordance with PsV-specific ELISA data that quantified the total antibody response against different serotypes.

INTERPRETATION

BKV nAb mismatch predicts post-transplant BKV DNAaemia. Specific mismatches in nAb, rather than total seroreactivity, are key indicators of BKV risk post-transplant. This has the potential to risk-stratify individuals and improve clinical outcomes by influencing the frequency of monitoring and individualised tailoring of immunosuppression. Furthermore, detailed examination of individuals with broadly neutralising responses may provide future therapeutic strategies.

FUNDING

The research was funded by St. Peters Trust, Royal Free Hospital Charity and Wellcome Trust (grant numbers RFCG1718/05, SPT97 and 204870/Z/WT_/Wellcome Trust/United Kingdom).

BK Polyomavirus Infection in Kidney Transplantation: A Comprehensive Review of Current Challenges and Future Directions

BK polyomavirus (BKPyV) infection of the kidney graft remains a major clinical issue in the field of organ transplantation. Risk factors for BKPyV-associated nephropathy (BKPyVAN) and molecular tools for determining viral DNA loads are now better defined. BKPyV DNAemia in plasma, in particular, plays a central role in diagnosing active infection and managing treatment decisions. However, significant gaps remain in the development of reliable biomarkers that can anticipate BKPyV viremia and predict disease outcomes. Biomarkers under active investigation include urine-based viral load assays, viral antigen detection, and immune responses against BKPyV, which may offer more precise methods for monitoring disease progression. In addition, treatment of BKPyVAN is currently based on immunosuppression minimization, while the role of adjunctive therapies remains an area of active research, highlighting the need for more personalized treatment regimens. Ongoing clinical trials are also exploring the efficacy of T-cell-based immunotherapies. The clinical management of BKPyV infection, based on proactive virological monitoring, immune response assessment, integrated histopathology, and timely immunosuppression reduction, is likely to reduce the burden of disease and improve outcomes in kidney transplantation.

Cellular Immunity Against BK Polyomavirus in Kidney Transplant Recipients: A Comprehensive Review

BK polyomavirus (BKPyV) is an important opportunistic viral infection that complicates kidney transplantation. Uncontrolled viral replication may result in BKPyV-associated nephropathy (BKPyVAN), a major cause of premature allograft damage and failure. In the continued absence of proven treatments, management relies on the empirical reduction of immunosuppression to facilitate an effective host immune response to clear the virus. This may be complicated by the risk of allograft rejection. There is compelling evidence that cellular immune responses are key to establishing control after viral reactivation. Measurable peripheral BKPyV-specific T cell responses temporally correlate with declining viral loads and subsequent clearance. Conversely, these responses are delayed or absent in BKPyVAN. How these peripheral findings correspond to the intragraft response, and whether BKPyV-specific T cells contribute to the immunopathology of BKPyVAN, remains poorly understood. Molecular techniques have provided some insights; however, these have been unable to fully discriminate BKPyVAN from cellular rejection to date. Furthermore, the contributions of components of innate cellular immunity, such as natural killer cells, are not known. Herein, we review the role of cellular immunity in BKPyV infection in kidney transplant recipients. We discuss advances in the understanding of how the development, phenotype, and functionality of these responses may determine the balance between viral control and immunopathology, and how this knowledge is being translated into tools to prognosticate and guide individualized immunosuppression reduction. Lastly, we consider how further elucidation of these responses may inform the design of therapies that would revolutionize how BKPyV is managed after transplantation.

Approach to Kidney Allograft Dysfunction: A Brief Review

It is important for providers caring for kidney transplant recipients to be familiar with the common causes of allograft dysfunction. Early detection of allograft dysfunction leads to timely management, with the goal of preventing or delaying progression to allograft failure. Although transplant rejection is always a concern, the differential diagnoses for allograft dysfunction are broad and include perioperative complications, infections, recurrent disease, and calcineurin nephrotoxicity. In this review, we will go over early and late causes of allograft dysfunction and discuss the basic workup and principles of management for each condition.

Report on post-transplantation cancer in southeast Asia from the Thai kidney transplantation cohort

Post-transplantation cancer is a significant cause of mortality among kidney transplant recipients (KTR). The incidence of post-transplantation cancer varies based on geographic region and ethnicity. However, data on KTR from South East Asia, where characteristics differ from other parts of Asia, is lacking. We conducted a retrospective cohort study at a transplant center in Thailand to investigate the incidence of post-transplantation cancer and mortality rates. Factors associated with post-transplantation cancer and patient outcomes were analyzed using competing-risks regression. The study included 1156 KTR with a post-transplant follow-up duration of 5.1 (2.7-9.4) years. The age- and sex-adjusted incidence rate of post-transplant cancer was highest for urothelial cancer (6.9 per 1000 person-years), which also resulted in the highest standardized incidence ratio (SIR) of 42.5 when compared to the general population. Kidney cancer had the second-highest SIR of 24.4. Increasing age was the factor associated with an increased risk of post-transplant cancer (SHR 1.03; 95% CI 1.01-1.05). Human leukocyte antigen (HLA) DR mismatch was associated with a decreased risk of post-transplant cancer (SHR 0.72; 95% CI 0.52-0.98). Post-transplantation cancer was significantly associated with patient mortality (HR 3.16; 95% CI 2.21-4.52). Cancer significantly contributes to KTR mortality, and the risk profile for cancer development in Thai KTRs differs from that of Western and most Asian counterparts. Further research is essential to explore appropriate screening protocols for countries with high rates of urothelial and kidney cancer, including Thailand.

BK polyomavirus DNAemia, allograft rejection, and de novo donor-specific antibodies after lowering target tacrolimus levels in pediatric kidney transplant recipients

BACKGROUND

BK polyomavirus (BKV) DNAemia is a challenging infectious complication after kidney transplant (KT). Reduction of immunosuppression is the mainstay of management, and tacrolimus is often the first immunosuppressive medication adjusted upon the diagnosis of BKV DNAemia. This study aimed to evaluate the impact of a new institutional protocol with lower target tacrolimus levels on BKV DNAemia, allograft rejection, and de novo donor-specific antibodies (dnDSA) among pediatric KT recipients.

METHODS

We conducted a retrospective chart review of all KT episodes between January 2013 and December 2018. The new protocol with lower target tacrolimus levels was implemented in March 2015. One hundred twenty-seven patients were included in primary analysis. All patients received induction with basiliximab and methylprednisolone and were maintained on a steroid-based immunosuppressive regimen.

RESULTS

In the post-intervention cohort, cumulative incidence of BKV DNAemia at 100 days (13.4% vs. 17.8%, p = .605) and 18 months post-KT (34.1% vs. 26.7%, p = .504) was not significantly different from the pre-intervention cohort. Biopsy-proven rejection rate did not change. However, we observed a trend toward earlier development of dnDSA in the post-intervention cohort using the Kaplan-Meier survival analysis (log-rank p = .06). Younger recipient age at the time of transplant was found to slightly increase the risk of BKV DNAemia (OR: 1.09, 95% CI [1.01, 1.16], p = .024). There was an association between BKV DNAemia and biopsy-proven rejection of any type (adjustedOR: 2.77, 95% CI [1.26, 6.23], p = .012), especially acute T-cell-mediated rejection grade 1A and above (adjustedOR: 2.95, 95% CI [1.06, 8.30], p = .037), after adjusted for recipient age at the time of transplant.

CONCLUSIONS

Targeting lower tacrolimus levels did not decrease the incidence of BKV DNAemia within 100 days or 18 months post-KT, nor did it increase the risk of biopsy-proven rejection among pediatric KT recipients in our center. However, there was a trend toward earlier development of dnDSA, which may portend worse long-term graft outcome post-KT. Our findings highlight the need for individualized immunosuppressive regimens based on immunologic and infectious risk factors and the importance of implementing innovative biomarkers to guide therapy and improve outcomes.

Incidence and Outcomes of BK Virus Nephropathy in Kidney Transplant Recipients With Steroid-Free Maintenance Immunosuppression

BACKGROUND

BK virus nephropathy (BKVN) is a significant complication in kidney transplant recipients, resulting in graft dysfunction and potentially leading to graft loss. This study aims to investigate the incidence and outcomes of BKVN in kidney transplant recipients receiving steroid-free maintenance immunosuppression in a Latin -American cohort.

METHODS

Case series study of BKVN among kidney transplant recipients who underwent transplantation between 2008 and 2023. The primary outcome was graft loss caused by BKVN, excluding death with function. Secondary outcomes included graft function and acute rejection episodes. The statistical analysis involved descriptive statistics and the Kaplan-Meier (K-M) method to plot the overall probabilities of not initiating dialysis.

RESULTS

During the 15-year period, 2236 kidney transplants were performed, BKVN was histologically diagnosed in 38 kidney recipients and 33 cases were analyzed. Median age was 50 years and men were 48.5% of patients. A total of 45.4% of BKVN occurred within the first 12 months of transplant. The incidence of BKVN was 1.6% but it varied by era. The rate of graft loss was 75.7% (25 cases). The K-M graft survival probability at 6 months and 12 months after diagnosis of BKVN was 38.3% (95% CI 24.7-59.4) and 22.3% (95% CI 11.7-42.8), respectively.

CONCLUSION

BKVN affected 1.6% of transplant recipients and it was associated with high-rate of graft loss. We observed that significant graft disfunction at the time of diagnosis resulted in worse outcomes with a reduced probability of graft survival.

BK Polyomavirus in Pediatric Renal Transplantation-What We Know and What We Do Not

BK polyomavirus (BKPyV) is still a real threat in the management of kidney transplantation. Immunosuppressive treatment disrupts the equilibrium between virus replication and immune response, and uncontrolled BKPyV replication leads to nephropathy (BKPyV nephropathy). The first evidence of BKPyV reactivation in transplant recipients is the detection of viral shedding in urine, which appears in 20% to 60% of patients, followed by BKPyV viremia in 10-20% of kidney transplant recipients. BKPyV nephropathy eventually occurs in 1-10% of this population, mainly within the first 2 years post-transplantation, causing graft loss in about half of those patients. Few data exist regarding the pediatric population and we focus on them. In this paper, we review the existing diagnostic methods and summarize the evidence on the role of BKPyV humoral and cellular immunity in modulating the clinical course of BKPyV infection and as potential predictors of the outcome. We look at the known risk factors for BKPyV nephropathy in the immunosuppressed patient. Finally, we propose a sensible clinical attitude in order to screen and manage BKPyV infection in kidney transplant children.

Posoleucel in Kidney Transplant Recipients with BK Viremia: Multicenter, Randomized, Double-Blind, Placebo-Controlled Phase 2 Trial

Key Points

Posoleucel was generally safe, well tolerated, and associated with a greater reduction of BK viremia compared with placebo. BK viremia reduction occurred coincident with an increase in the circulating frequency of BK virus–specific T cells in posoleucel recipients. The presence and persistence of posoleucel was confirmed by T-cell receptor variable β sequencing.

Background

Kidney transplant recipients with BK virus infection are at risk of developing BK virus–associated nephropathy, allograft rejection, and subsequent graft loss. There are no approved treatments for BK virus infection. Posoleucel is an off-the-shelf, allogeneic, multivirus-specific T-cell investigational therapy targeting BK virus, as well as five other opportunistic viruses: adenovirus, cytomegalovirus, Epstein–Barr virus, human herpesvirus 6, and John Cunningham virus.

Methods

In this phase 2, double-blind study, kidney transplant recipients with BK viremia were randomized 1:1:1 to receive posoleucel weekly for 3 weeks and then every 14 days (bi-weekly dosing) or every 28 days (monthly dosing) or placebo for 12 weeks. Participants were followed for 12 weeks after completing treatment. The primary objective was safety; the secondary objective was plasma BK viral load reduction.

Results

Sixty-one participants were randomized and dosed. Baseline characteristics were similar across groups. No deaths, graft-versus-host disease, or cytokine release syndrome occurred. The proportion of patients who had adverse events (AEs) judged by the investigators to be treatment-related was slightly lower in recipients of posoleucel: 20% (4 of 20 patients) and 18% (4 of 22) in those infused on a bi-weekly and monthly schedule, respectively, and 26% (5 of 19) in placebo recipients. None of the grade 3–4 AEs or serious AEs in any group were deemed treatment-related. No deaths, graft-versus-host disease, or cytokine release syndrome occurred. Three participants had allograft rejection, but none were deemed treatment-related by investigators. In posoleucel recipients, BK viremia reduction was associated with an increase in the circulating frequency of BK virus–specific T cells, and the presence and persistence of posoleucel was confirmed by T-cell receptor sequencing.

Conclusions

Posoleucel was generally safe, well tolerated, and associated with a larger reduction of BK viremia compared with placebo. Limitations of this study include the relatively short duration of follow-up and lack of power to detect significant differences in clinical outcomes.

Clinical Trial registry name and registration number:

Study of Posoleucel (Formerly Known as ALVR105; Viralym-M) in Kidney Transplant Patients With BK Viremia, NCT04605484 .

BK polyomavirus infection: more than 50 years and still a threat to kidney transplant recipients

BK polyomavirus (BKPyV) is a ubiquitous human polyomavirus and a major infection after kidney transplantation, primarily due to immunosuppression. BKPyV reactivation can manifest as viruria in 30%-40%, viremia in 10%-20%, and BK polyomavirus-associated nephropathy (BKPyVAN) in 1%-10% of recipients. BKPyVAN is an important cause of kidney graft failure. Although the first case of BKPyV was identified in 1971, progress in its management has been limited. Specifically, there is no safe and effective antiviral agent or vaccine to treat or prevent the infection. Even in the current era, the mainstay approach to BKPyV is a reduction in immunosuppression, which is also limited by safety (risk of de novo donor specific antibody and rejection) and efficacy (graft failure). However, recently BKPyV has been getting more attention in the field, and some new treatment strategies including the utilization of viral-specific T-cell therapy are emerging. Given all these challenges, the primary focus of this article is complications associated with BKPyV, as well as strategies to mitigate negative outcomes.

Association of UGT1A Gene Polymorphisms with BKV Infection in Renal Transplantation Recipients

BACKGROUND

BK virus (BKV) infection is an opportunistic infectious complication and constitutes a risk factor for premature graft failure in kidney transplantation. Our research aimed to identify associations and assess the impact of single-nucleotide polymorphisms (SNPs) on metabolism-related genes in patients who have undergone kidney transplantation with BKV infection.

MATERIAL/METHODS

The DNA samples of 200 eligible kidney transplant recipients from our center, meeting the inclusion criteria, have been collected and extracted. Next-generation sequencing was used to genotype SNPs on metabolism-associated genes (CYP3A4/5/7, UGT1A4/7/8/9, UGT2B7). A general linear model (GLM) was used to identify and eliminate confounding factors that may influence the outcome events. Multiple inheritance models and haplotype analyses were utilized to identify variation loci associated with infection caused by BKV and ascertain haplotypes, respectively.

RESULTS

A total of 141 SNPs located on metabolism-related genes were identified. After Hardy-Weinberg equilibrium (HWE) and minor allele frequency (MAF) analysis, 21 tagger SNPs were selected for further association analysis. Based on GLM results, no confounding factor was significant in predicting the incidence of BK polyomavirus-associated infection. Then, multiple inheritance model analyses revealed that the risk of BKV infection was significantly associated with rs3732218 and rs4556969. Finally, we detect significant associations between haplotype T-A-C of block 2 (rs4556969, rs3732218, rs12468274) and infection caused by BKV (P = 0.0004).

CONCLUSION

We found that genetic variants in the UGT1A gene confer BKV infection susceptibility after kidney transplantation.

Clinicopathological Correlation of Polyomavirus Nephropathy in Renal Allograft Recipients According to the Banff 2018 Classification

BACKGROUND

Polyomavirus nephropathy (PVN) is a rare kidney disease caused by the BK virus, a strain of polyomavirus. The disease primarily affects transplant recipients, which is related to intensive immunosuppression protocol and can lead to kidney allograft failure.

OBJECTIVES

The objective of this study is to analyze histopathological features of PVN using the Banff 2018 PVN classification and to determine clinical features and outcomes of patients with PVN in each histologic class.

MATERIALS AND METHODS

The study included 44 patients who had been diagnosed with PVN by renal allograft biopsy in a large tertiary care hospital in Thailand from January 2011 to January 2020. The kidney biopsy slides were reviewed for Banff 2018 PVN classification and other histologic features. Patient demographic information, clinical data, and laboratory results were retrospectively collected.

RESULTS

Nine (20.45%), 27 (61.36%), and eight (18.18%) cases of PVN were Class I, Class II, and Class III, respectively. The time from transplant to PVN diagnosis for Classes I, II, and III was four, 19, and 33.5 months, respectively. Class III had the worst clinical outcomes in terms of deterioration of allograft function, the lowest rate of resolution, and the highest rate of graft failure.

CONCLUSIONS

PVN classification provides prognostic information in renal allograft biopsy. Our study confirmed the validity of the three-tier histologic PVN classification put forward by the Banff Working Group in 2018.

Impact of Infection-Related Immunosuppressant Reduction on Kidney Transplant Outcomes: A Retrospective Study Considering the Temporal Dynamics of Immunosuppressive Requirements

Immunosuppressant reduction (ISR) is a common treatment for kidney transplant recipients experiencing infections, but its impacts on kidney transplant outcomes remains unclear. This retrospective single-center study included 300 patients who underwent kidney transplantation between January 2017 and April 2020. The post-transplant timeline was divided into four distinct phases: ≤1 month, 2-6 months, 7-12 months, and >12 months. Patients were categorized based on the presence of clinically relevant infections and whether they received ISR. Significant differences were observed in the spectrum of clinically relevant infections across the post-transplant phases. During the ≤1 month phase, primary infections were associated surgical operation, such as urinary tract infections involving Enterococcus spp. and Candida spp. Cytomegalovirus and BK polyomavirus (BKPyV) infections increased during the 2-6 months and 7-12 months periods. Approximately one-third of patients experienced ISR due to infection, with BKPyV infections being the primary causes. Recipients who experienced their first ISR due to infection between 2-6 months and 7-12 months had worse graft survival comparing with patients without any infections. ISR due to infections between 2 and 6 months was associated with a higher risk of rejection. Tailored ISR strategies should be developed according to temporal dynamics of immunosuppressive intensity to prevent rejection.