Impact of Pretransplant Donor BK Viruria in Kidney Transplant Recipients

The value and complexity of studying cellular immunity against BK Polyomavirus in kidney transplant recipients

BK Polyomavirus is of particular concern for kidney transplant recipients, due to their immunosuppression. This problem is exacerbated by the high effectiveness of antirejection therapies, which also compromise the organism's ability to fight viral infections. The long-term risk is loss of graft function through BKPyV-associated nephropathy (BKPyVAN). The assessment of host immunity and its link to the control of viral infections is a major challenge. In terms of humoral immunity, researchers have highlighted the prognostic value of the pre-transplantation anti-BKPyV immunoglobulin G titer. However, humoral immunity alone does not guarantee viral clearance, and the correlation between the humoral response and the time course of the infection remains weak. In contrast, cellular immunity variables appear to be more closely associated with viral clearance, given that the cellular immune response to the kidney transplant is the main target of immunosuppressive treatments in recipients. However, the assessment of the cellular immune response to BK Polyomavirus is complex, and many details still need to be characterized. Here, we review the current state of knowledge about BKPyV cellular immunity, as well as the difficulties that may be encountered in studying it in kidney transplant recipient. This is an essential area of research for optimizing the management of transplant recipients and minimizing the risks associated with insidious BKPyV disease.

Increased CMV disease and "severe" BK viremia with belatacept vs. sirolimus three-drug maintenance immunosuppression

OBJECTIVES

Belatacept may provide benefit in delayed graft function, but its association with infectious complications is understudied. We aim to assess the incidence of CMV and BK viremia in patients treated with sirolimus or belatacept as part of a three-drug immunosuppression regimen after kidney transplantation.

MATERIALS AND METHODS

Kidney transplant recipients from 01/01/2015 to 10/01/2021 were retrospectively reviewed. Maintenance immunosuppression was either tacrolimus, mycophenolate and sirolimus (B0) or tacrolimus, mycophenolate, and belatacept (5.0 mg/kg monthly) (B1). Primary outcomes of interest were BK and CMV viremia which were followed until the end of the study period. Secondary outcomes included graft function (serum creatinine, eGFR) and acute rejection through 12 months.

RESULTS

Belatacept was initiated in patients with a higher mean kidney donor profile index (B0:0.36 vs. B1:0.44, p = .02) with more delayed graft function (B0:6.1% vs. B1:26.1%, p < .001). Belatacept therapy was associated with more "severe" CMV viremia >25,000 copies/mL (B0:1.2% vs. B1:5.9%, p = .016) and CMV disease (B0:0.41% vs. B1:4.2%, p = .015). However, there was no difference in the overall incidence of CMV viremia >200 IU/mL (B0:9.4% vs. B1:13.5%, p = .28). There was no difference in the incidence of BK viremia >200 IU/mL (B0:29.7% vs. B1:31.1%, p = .78) or BK-associated nephropathy (B0:2.4% vs. B1:1.7%, p = .58), but belatacept was associated with "severe" BK viremia, defined as >10,000 IU/mL (B0:13.0% vs. B1:21.8%, p = .03). The mean serum Cr was significantly higher with belatacept therapy at 1-year follow up (B0:1.24 mg/dL vs. B1:1.43 mg/dL, p = .003). Biopsy-proven acute rejection (B0:1.2% vs. B1:2.6%, p = .35) and graft loss (B0:1.2% vs. B1:0.84%, p = .81) were comparable at 12 months.

CONCLUSIONS

Belatacept therapy was associated with an increased risk of CMV disease and "severe" CMV and BK viremia. However, this regimen did not increase the overall incidence of infection and facilitated comparable acute rejection and graft loss at 12-month follow up.

A multivalent polyomavirus vaccine elicits durable neutralizing antibody responses in macaques

In 2019, there were about 100,000 kidney transplants globally, with more than a quarter of them performed in the United States. Unfortunately, some engrafted organs are lost to polyomavirus-associated nephropathy (PyVAN) caused by BK and JC viruses (BKPyV and JCPyV). Both viruses cause brain disease and possibly bladder cancer in immunosuppressed individuals. Transplant patients are routinely monitored for BKPyV viremia, which is an accepted hallmark of nascent nephropathy. If viremia is detected, a reduction in immunosuppressive therapy is standard care, but the intervention comes with increased risk of immune rejection of the engrafted organ. Recent reports have suggested that transplant recipients with high levels of polyomavirus-neutralizing antibodies are protected against PyVAN. Virus-like particle (VLP) vaccines, similar to approved human papillomavirus vaccines, have an excellent safety record and are known to induce high levels of neutralizing antibodies and long-lasting protection from infection. In this study, we demonstrate that VLPs representing BKPyV genotypes I, II, and IV, as well as JCPyV genotype 2 produced in insect cells elicit robust antibody titers. In rhesus macaques, all monkeys developed neutralizing antibody titers above a previously proposed protective threshold of 10,000. A second inoculation, administered 19 weeks after priming, boosted titers to a plateau of ≥ 25,000 that was maintained for almost two years. No vaccine-related adverse events were observed in any macaques. A multivalent BK/JC VLP immunogen did not show inferiority compared to the single-genotype VLP immunogens. Considering these encouraging results, we believe a clinical trial administering the multivalent VLP vaccine in patients waiting to receive a kidney transplant is warranted to evaluate its ability to reduce or eliminate PyVAN.

BK Virus Nephropathy in Kidney Transplantation: A State-of-the-Art Review

BK virus maintains a latent infection that is ubiquitous in humans. It has a propensity for reactivation in the setting of a dysfunctional cellular immune response and is frequently encountered in kidney transplant recipients. Screening for the virus has been effective in preventing progression to nephropathy and graft loss. However, it can be a diagnostic and therapeutic challenge. In this in-depth state-of-the-art review, we will discuss the history of the virus, virology, epidemiology, cellular response, pathogenesis, methods of screening and diagnosis, evidence-based treatment strategies, and upcoming therapeutics, along with the issue of re-transplantation in patients.

Polyoma BK Virus in Kidney Transplant Recipients: Screening, Monitoring, and Management

Polyomavirus BK virus (BKPyV) infection is an important complication of kidney transplantation and allograft failure. The prevalence of viremia is 10%-15%, compared with BK-associated nephropathy (BKPyVAN) at 3%-5%. Given that there are no effective antiviral prophylaxis or treatment strategies for BKPyVAN, active screening to detect BKPyV viremia is recommended, particularly during the early posttransplant period. Immunosuppression reduction to allow viral clearance may avoid progression to severe and irreversible allograft damage. The frequency and duration of screening are highly variable between transplant centers because the evidence is reliant largely on observational data. While the primary treatment goals center on achieving viral clearance through immunosuppression reduction, prevention of subsequent acute rejection, premature graft loss, and return to dialysis remain as major challenges. Treatment strategies for BKPyV infection should be individualized to the recipient's underlying immunological risk and severity of the allograft infection. Efficacy data for adjuvant therapies including intravenous immunoglobulin and cidofovir are sparse. Future well-powered and high-quality randomized controlled trials are needed to inform evidence-based clinical practice for the management of BKPy infection.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

DISCUSSION

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

Deceased-Donor Acute Kidney Injury and BK Polyomavirus in Kidney Transplant Recipients

BACKGROUND AND OBJECTIVES

BK polyomavirus (BKV) infection commonly complicates kidney transplantation, contributing to morbidity and allograft failure. The virus is often donor-derived and influenced by ischemia-reperfusion processes and disruption of structural allograft integrity. We hypothesized that deceased-donor AKI associates with BKV infection in recipients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We studied 1025 kidney recipients from 801 deceased donors transplanted between 2010 and 2013, at 13 academic centers. We fitted Cox proportional-hazards models for BKV DNAemia (detectable in recipient blood by clinical PCR testing) within 1 year post-transplantation, adjusting for donor AKI and other donor- and recipient-related factors. We validated findings from this prospective cohort with analyses for graft failure attributed to BKV within the Organ Procurement and Transplantation Network (OPTN) database.

RESULTS

The multicenter cohort mean kidney donor profile index was 49±27%, and 26% of donors had AKI. Mean recipient age was 54±13 years, and 25% developed BKV DNAemia. Donor AKI was associated with lower risk for BKV DNAemia (adjusted hazard ratio, 0.53; 95% confidence interval, 0.36 to 0.79). In the OPTN database, 22,537 (25%) patients received donor AKI kidneys, and 272 (0.3%) developed graft failure from BKV. The adjusted hazard ratio for the outcome with donor AKI was 0.7 (95% confidence interval, 0.52 to 0.95).

CONCLUSIONS

In a well-characterized, multicenter cohort, contrary to our hypothesis, deceased-donor AKI independently associated with lower risk for BKV DNAemia. Within the OPTN database, donor AKI was also associated with lower risk for graft failure attributed to BKV.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2021_03_10_CJN18101120_final.mp3.

BK Virus-Associated Nephropathy after Renal Transplantation

Recent advances in immunosuppressive therapy have reduced the incidence of acute rejection and improved renal transplantation outcomes. Meanwhile, nephropathy caused by BK virus has become an important cause of acute or chronic graft dysfunction. The usual progression of infection begins with BK viruria and progresses to BK viremia, leading to BK virus associated nephropathy. To detect early signs of BK virus proliferation before the development of nephropathy, several screening tests are used including urinary cytology and urinary and plasma PCR. A definitive diagnosis of BK virus associated nephropathy can be achieved only histologically, typically by detecting tubulointerstitial inflammation associated with basophilic intranuclear inclusions in tubular and/or Bowman’s epithelial cells, in addition to immunostaining with anti-Simian virus 40 large T-antigen. Several pathological classifications have been proposed to categorize the severity of the disease to allow treatment strategies to be determined and treatment success to be predicted. Since no specific drugs that directly suppress the proliferation of BKV are available, the main therapeutic approach is the reduction of immunosuppressive drugs. The diagnosis of subsequent acute rejection, the definition of remission, the protocol of resuming immunosuppression, and long-term follow-up remain controversial.

Thermally stable and uniform DNA amplification with picosecond laser ablated graphene rapid thermal cycling device

Rapid thermal cycling (RTC) in an on-chip device can perform DNA amplification in vitro through precise thermal control at each step of the polymerase chain reaction (PCR). This study reports a straightforward fabrication technique for patterning an on-chip graphene-based device with hole arrays, in which the mechanism of surface structures can achieve stable and uniform thermal control for the amplification of DNA fragments. A thin-film based PCR device was fabricated using picosecond laser (PS-laser) ablation of the multilayer graphene (MLG). Under the optimal fluence of 4.72 J/cm2 with a pulse overlap of 66%, the MLG can be patterned with arrays of 250 μm2 hole surface structures. A 354-bp DNA fragment of VP1, an effective marker for diagnosing the BK virus, was amplified on an on-chip device in less than 60 min. A thin-film electrode with the aforementioned MLG as the heater was demonstrated to significantly enhance temperature stability for each stage of the thermal cycle. The temperature control of the heater was performed by means of a developed programmable PCR apparatus. Our results demonstrated that the proposed integration of a graphene-based device and a laser-pulse ablation process to form a thin-film PCR device has cost benefits in a small-volume reagent and holds great promise for practical medical use of DNA amplification.