Association of BKV viremia and nephropathy with adverse alloimmune outcomes in kidney transplant recipients.

BACKGROUND: Immunosuppression reduction for BK polyoma virus (BKV) must be balanced against risk of adverse alloimmune outcomes. We sought to characterize risk of alloimmune events after BKV within context of HLA-DR/DQ molecular mismatch (mMM) risk score. METHODS: This single-center study evaluated 460 kidney transplant patients on tacrolimus-mycophenolate-prednisone from 2010-2021. BKV status was classified at 6-months post-transplant as "BKV" or "no BKV" in landmark analysis. Primary outcome was T-cell mediated rejection (TCMR). Secondary outcomes included all-cause graft failure (ACGF), death-censored graft failure (DCGF), de novo donor specific antibody (dnDSA), and antibody-mediated rejection (ABMR). Predictors of outcomes were assessed in Cox proportional hazards models including BKV status and alloimmune risk defined by recipient age and molecular mismatch (RAMM) groups. RESULTS: At 6-months post-transplant, 72 patients had BKV and 388 had no BKV. TCMR occurred in 86 recipients, including 27.8% with BKV and 17% with no BKV (p = .05). TCMR risk was increased in recipients with BKV (HR 1.90, (95% CI 1.14, 3.17); p = .01) and high vs. low-risk RAMM group risk (HR 2.26 (95% CI 1.02, 4.98); p = .02) in multivariable analyses; but not HLA serological MM in sensitivity analysis. Recipients with BKV experienced increased dnDSA in univariable analysis, and there was no association with ABMR, DCGF, or ACGF. CONCLUSIONS: Recipients with BKV had increased risk of TCMR independent of induction immunosuppression and conventional alloimmune risk measures. Recipients with high-risk RAMM experienced increased TCMR risk. Future studies on optimizing immunosuppression for BKV should explore nuanced risk stratification and may consider novel measures of alloimmune risk.

BK Viremia and Viruria Does Not Depend on the Type of Double-J Stent Used During Kidney Transplantation.

OBJECTIVES: BK virus is a major cause of chronic renal allograft failure.Transplant ureteral stent use has been reported as a risk factorfor BK virus infection. Recently, the use of a new type of ureteral stent (Magnetic Black Star) was reported in kidney transplant recipients. The aim ofthis preliminary report was to compare BK virus viremia and viruria occurrence depending on the type of double-J stent (standard versus Magnetic Black Star). MATERIALS AND METHODS: We included all kidney transplants performed in our center from January to December 2022. Each case had double-J stent placement. Indwelling stents were either a 6- or 7-Fr standard double-J stent or a 6-Fr Magnetic Black Star double-J stent. The type of double-J stent was chosen according to the surgeon's preference. A standard BK virus screening protocol was followed during the study period, which consisted of routine polymerase chain reaction examination of plasma and urine samples during monthly follow-ups. RESULTS: We assessed 120 patients without missing data: 92 patients received standard double-J stents and 28 patients received Magnetic Black Star stents. Patients were mostly male in the standard group (70.7%) versus the Magnetic Black Star group (42.9%) (P = .01). ABO- and HLA-incompatible transplant rates were similar in both groups. BK viremia occurrence and BK viruria occurrence were similar between groups at 1 month, 3 months, and 6 months. CONCLUSIONS: This preliminary study showed no differences concerning BKvirus infection depending on the type of double-J stents used during kidney transplant.

Avian Polyomavirus Among Psittacine Birds in Iran: Molecular Detection Rate and Associated Risk Factors.

Avian polyomavirus (APV) infection causes various health problems in psittacine species, including death. The present study was conducted to investigate the prevalence of APV among psittacine birds in Iran. We also aimed to evaluate the impact of age, sex, species, season, and origin of the birds on the prevalence of APV. This study investigated the presence of APV among 1050 individual birds from 7 psittacine species over a 1-year period in Iran, namely, green-cheeked parakeets (Pyrrhura molinae), rosy-faced lovebirds (Agapornis roseicollis), monk parakeets (Myiopsitta monachus), sun conures (Aratinga solstitialis), Senegal parrots (Poicephalus senegalus), cockatiels (Nymphicus hollandicus), and grey parrots (Psittacus erithacus). The overall prevalence of APV in all studied species was 25% (263/1050, 95% confidence interval [CI]: 22.5-27.8). Results of the study showed that age and the season of the year were 2 important determinant factors in the prevalence of APV in psittacine birds. Young psittacine birds <6 months old were 2.94 (95% CI: 1.19-7.27) times more likely to be infected with APV than birds >1 year old, and there was a significant interaction between season and species in the multivariate analysis. In the winter season, rosy-faced lovebirds and green-cheeked parakeets were 15.6 (95% CI: 4.20-57.95) and 4.76 (95% CI: 1.4-16.21) times more likely to be infected with APV than in other seasons, respectively. This is the first report on the detection rate of APV in psittacine birds in Iran.

Prevalence of BK and JC Polyomaviruses among Patients with Breast Cancer.

INTRODUCTION: Breast cancer, a pervasive invasive carcinoma among women globally, afflicts approximately 12% of women worldwide. Previous studies have indicated that certain viruses, including oncogenic viruses such as polyomaviruses BK and JC, may play a role in the development of breast cancer. In light of this, the present study endeavors to assess the incidence of BKV and JCV virus in breast cancer patients. MATERIALS AND METHODS: One hundred formalin-fixed paraffin-embedded tissue samples were procured and subjected to deparaffinize by xylene, followed by DNA extraction through the phenol-chloroform methodology. Detection and genotyping of BKV and JCV were carried out utilizing specific primers via PCR analysis. RESULTS: Merely 2 out of 100 (2%) ductal carcinoma in situ with grade 2 specimens exhibited positivity for BK virus genotype IV, whereas JC virus DNA was not discerned across all the samples. DISCUSSION: The findings of the current investigation demonstrate that there was an absence of JC virus detection in the breast biopsy. Additionally, a small fraction of patients diagnosed with ductal carcinoma exhibited a low prevalence of genotype IV polyomavirus BK at a rate of 2%. However, in order to gain a more comprehensive understanding of the incidence of BKV and JCV in breast cancer, a substantial number of breast samples must undergo investigation.

Analyses of tertiary lymphoid structures observed in cases of Merkel cell carcinoma showing spontaneous regression.

Merkel cell carcinoma (MCC) is a high-grade skin cancer, but spontaneous regression is observed at a markedly higher frequency than in other carcinomas. Although spontaneous regression is a phenomenon that greatly impacts treatment planning, we still cannot predict it. We previously reported on the prognostic impact of the presence or absence of tertiary lymphoid structures (TLS) and of Merkel cell polyomavirus (MCPyV) infection. To learn more about the spontaneous regression of MCC, detailed analyses were performed focusing on spontaneous regression cases. We collected 71 Japanese patients with MCC including 6 cases of spontaneous regression. Samples were analysed by immunostaining, spatial single-cell analysis using PhenoCycler, and RNA sequencing using the next-generation sequencer (NGS). All 6 cases of spontaneous regression were positive for MCPyV. TLS was positive in all 5 cases analysed. Spatial single-cell analyses revealed that PD-L1-positive tumour cells were in close proximity to CD20-positive B cell and CD3-, 4-positive T cells. Gene set enrichment analysis between MCPyV-positive and TLS-positive samples and other samples showed significantly high enrichment of "B-cell-mediated immunity" gene sets in the MCPyV-positive and TLS-positive groups. In conclusion, TLS may play an important role in the spontaneous regression of MCC.

Cell-Free Mitochondrial DNA: An Upcoming Non-Invasive Tool for Diagnosis of BK Polyomavirus-Associated Nephropathy.

Mitochondria are essential organelles that possess their own DNA. Mitochondrial dysfunction has been revealed in many kidney diseases, including BK polyomavirus-associated nephropathy (BKPyVAN). In this study, we introduce an innovative approach for non-invasive monitoring of mitochondrial impairment through urinary donor-derived cell-free mitochondrial DNA (ddcfmtDNA), addressing the crucial challenge of BKPyVAN diagnosis. Urinary samples were collected at the time of biopsy from a total of 60 kidney transplant recipients, comprising 12 with stable function, 22 with T cell-mediated rejection, and 21 with biopsy-proven BKPyVAN. Our findings reveal that the ddcfmtDNA-to-ddcfDNA ratio exhibits superior capability in distinguishing BKPyVAN from other conditions, with a cutoff value of 4.96% (area under curve = 0.933; sensitivity: 71.4%; and specificity: 97.1%). Notably, an elevation of ddcfmtDNA levels is associated with mitochondrial damage, as visualized through electron microscopy. These results underscore the promise of non-invasive monitoring for detecting subtle mitochondrial damage and its potential utility in BKPyVAN diagnosis. Further investigations are required to advance this field of research.

Performance evaluation of the high-throughput quantitative Alinity m BK virus assay.

BK virus (BKV) infection or reactivation in immunocompromised individuals can lead to adverse health consequences including BKV-associated nephropathy (BKVAN) in kidney transplant patients and BKV-associated hemorrhagic cystitis (BKV-HC) in allogeneic hematopoietic stem cell transplant recipients. Monitoring BKV viral load plays an important role in post-transplant patient care. This study evaluates the performance of the Alinity m BKV Investigational Use Only (IUO) assay. The linearity of the Alinity m BKV IUO assay had a correlation coefficient of 1.000 and precision of SD ≤ 0.25 Log IU/mL for all panel members tested (2.0-7.3 Log IU/mL). Detection rate at 50 IU/mL was 100%. Clinical plasma specimens tested comparing Alinity m BKV IUO to ELITech MGB Alert BKV lab-developed test (LDT) on the Abbott m2000 platform using specimen extraction protocols for DNA or total nucleic acid (TNA) resulted in coefficient of correlation of 0.900 and 0.963, respectively, and mean bias of 0.03 and -0.54 Log IU/mL, respectively. Alinity m BKV IUO compared with Altona RealStar BKV and Roche cobas BKV assays demonstrated coefficient of correlation of 0.941 and 0.980, respectively, and mean bias of -0.47 and -0.31 Log IU/mL, respectively. Urine specimens tested on Alintiy m BKV IUO and ELITech BKV LDT using TNA specimen extraction had a coefficient of correlation of 0.917 and mean bias of 0.29 Log IU/mL. The Alinity m BKV IUO assay was performed with high precision across the dynamic range and correlated well with other available BKV assays. IMPORTANCE: BK virus (BKV) in transplant patients can lead to adverse health consequences. Viral load monitoring is important in post-transplant patient care. This study evaluates the Alinity m BKV assay with currently available assays.

Impact of BK polyomavirus viremia on the outcomes of allogeneic hematopoietic stem cell transplantation.

Although it is known that BK polyomavirus (BKPyV) causes hemorrhagic cystitis (HC) after allogeneic hematopoietic stem cell transplantation (HSCT), the clinical significance of BKPyV viremia has not been fully evaluated. We retrospectively analyzed the results of quantitative polymerase chain reaction (PCR) evaluations for detecting BKPyV in the whole blood samples of patients undergoing allogeneic HSCT during the period from January 2010 to June 2020 at a single institute, Tokyo Medical and Dental University. BKPyV was detected in the blood of 28 of the 107 evaluated patients, and the cumulative incidence of was 27.9% (95%CI: 20.2-37.9%). HC due to BKPyV developed in four of the 28 patients with BKPyV viremia (14.3%) and in two of the 79 patients without it (2.5%; P < 0.05). BKPyV viremia itself did not affect the patients' post-transplant estimated glomerular filtration rate (eGFR), but BKPyV viremia with a high viral load was significantly associated with decreased eGFR values (P < 0.05). BKPyV viremia was also associated with significantly lower progression-free survival at 3 years (35.1% [95%CI: 17.8-53.1%] vs. 60.4% [95%CI: 48.4-70.5], P < 0.05). Our findings demonstrated that BKPyV viremia was associated with onset of HC, an early decline of renal function, and poorer survival after allogeneic HSCT. Further studies are needed to test these results and elucidate the mechanisms of renal dysfunction associated with BKPyV viremia.

Effect of steroid pulses in severe BK virus allograft nephropathy with extensive interstitial inflammation.

INTRODUCTION: As there is no specific antiviral treatment currently available for BK polyomavirus associated nephropathy (BKVAN), its management relies on immunosuppression reduction in kidney transplant patients. Data on efficacy of steroid pulses in this indication are lacking. METHODS: We performed a retrospective monocenter study on 64 patients diagnosed with biopsy-proven BKVAN. Patients within the "pulse group" (n = 37) received IV methylprednisolone 10 mg/kg 3 days consecutively. In the "low dose" steroid group (n = 27), patients were continued oral prednisone 5 mg daily. RESULTS: Mean follow up was 78 months in the steroid pulse group and 56 months in the low dose group (p = 0.15). Mean eGFR values at diagnosis were comparable, as well as other demographic characteristics. Mean BK plasma viral load was higher in "pulse" than in "low dose" steroid group. Pulse group had higher inflammation and tubulitis (p < 0.05). Graft loss reached 57% in the "pulse" group versus 41% in the "low dose" group, p = 0.20. Rejection events were similar. No major adverse event was statistically associated with steroid pulse, including infections, cancer, and de novo diabetes. CONCLUSION: No significant differences were found in the evolution of both groups of patients, despite patients receiving "pulse" steroids were identified as the most severe sharing higher BK viral load and more frequent active lesions on histology.

Establishment of COS-BK cells persistently infected with archetype BK polyomavirus.

BK polyomavirus (BKPyV) was the first human polyomavirus to be isolated from an immunosuppressed kidney transplant recipient in 1971. BKPyV reactivation causes BKPyV-associated nephropathy and hemorrhagic cystitis. However, the mechanisms underlying BKPyV replication remain unclear. In the present study, we performed the long-term cultivation of COS-7 cells transfected with archetype KOM-5 DNA, which were designated as COS-BK cells. BKPyV derived from COS-BK cells was characterized by analyzing the amount of the virus based on hemagglutination, viral replication, and the production of viral protein 1 (VP1). Immunostaining showed that VP1-positive cells accounted for a small percentage of COS-BK cells. The nucleotide sequences encompassing the origin of the DNA replication of BKPyV derived from COS-BK cells were generated from KOM-5 by the deletion of an 8-bp sequence, which did not involve T antigen binding sites. BKPyV replicated most efficiently in COS-BK cells in DMEM containing 2% fetal bovine serum. These results indicate that COS-BK cells are a suitable culture system for studying the persistent infection of archetype BKPyV.

High-Dose Intravenous Immunoglobulin to Treat Anti-Thymocyte Globulin Induction-Related BK Virus and Cytomegalovirus Infection in Patients with ABO-Incompatible Kidney Transplantation.

BACKGROUND: ABO-incompatible (ABOi) transplantation is a novel method transplantation method that carries a heightened risk of infection caused by the use of high immunosuppressant doses. This elevated risk is particularly concerning for viral infections, such as cytomegalovirus (CMV) and the BK virus (BKV) increases. Herein, we present a case where high-dose intravenous immunoglobulin (IVIG) was effective in treating viral infections after transplantation. METHODS: A 41-year-old man underwent an ABOi transplantation. The initial isoagglutinin titer was 1:32. The patient received 200 mg of rituximab, and 3 rounds of plasmapheresis were performed. Subsequently, renal function remained normal; however, 7 months later, the renal function declined, and BK nephropathy and CMV infection were diagnosed through biopsy and serologic tests. The FK level was reduced, and mycophenolate mofetil was discontinued. Although ciprofloxacin and leflunomide were administered, their effects were minimal. Therefore, high-dose IVIG (1 g/kg) was administered 5 times over 5 weeks, which led to a reduction in BK viral load and CMV infectivity in the serum. CONCLUSIONS: High-dose IVIG may serve as a promising alternative treatment to mitigate early transplant rejection and BKV and CMV infections.

The diagnostic utility of Merkel cell polyoma virus immunohistochemistry in cytology specimens.

OBJECTIVE: Merkel cell carcinoma (MCC) is an aggressive cutaneous neuroendocrine neoplasm that predominantly affects elderly and immunocompromised patients. Merkel cell polyoma virus (MCPyV) is clonally integrated into the majority of MCCs and has been linked to patient outcomes, playing a central role in the pathogenesis of the disease. We aimed to assess the utility of MCPyV immunohistochemistry (IHC) in the diagnosis of MCC in cytology cell block specimens and correlating with clinicopathologic features. METHODS: Fifty-three cytology samples of MCC with sufficient cell block material were stained for MCPyV by IHC and scored semi-quantitatively in extent and intensity. Morphologic mimics of MCC including small cell lung carcinoma (n = 10), non-Hodgkin lymphoma (n = 10), basaloid squamous cell carcinoma (n = 6) and other neuroendocrine carcinomas (n = 8) were stained in parallel. Positive staining was defined as >1% of the tumour cells showing at least moderate staining intensity. RESULTS: The cytologic features of MCC were characterized by high nuclear-cytoplasmic ratios, hyperchromatic nuclei with 'salt and pepper' chromatin, and nuclear moulding. MCPyV was detected in 24 of 53 cases (45%). Staining was strong and diffuse in roughly half of the positive samples. Of the morphologic mimics, one follicular lymphoma showed strong and diffuse staining. In contrast to prior studies, we saw no association between MCPyV status and patient outcomes. CONCLUSION: Merkel cell polyoma virus IHC is highly specific (97%) for the diagnosis of MCC in our cohort, and can serve as a useful diagnostic tool for distinguishing MCC for morphologic mimics.

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.

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.

A multicenter prospective study to define the natural history of BK viral infections in kidney transplantation.

BACKGROUND: BK polyomavirus (BKV) can cause permanent loss of allograft function due to BKV-associated nephropathy (BKVN) in kidney transplant recipients. Besides immunosuppression reduction, there are no consistently effective interventions for BKV infection. Study purpose was to define natural history of BKV infection, identify risk factors for BKV reactivation and BKVN in kidney transplant recipients, and inform the design/conduct of future clinical trials of BKV-targeted therapeutics. METHODS: We conducted a multicenter prospective observational study of incident kidney transplant recipients at six U.S. transplant centers. Participants were monitored every 4 weeks for BKV reactivation and followed for up to 24 months post-transplant. We used regression models (logistic, survival, mixed models) to study relationships between BK viremia/BKVN, clinical characteristics, and allograft function. RESULTS: We enrolled 335 participants. Fifty-eight (17%) developed BK viremia, 6 (2%) developed biopsy-proven BKVN, and 29 (9%) developed suspected/presumed BKVN (defined as BKV viral load > 10,000 copies/mL without biopsy). Male donor sex was associated with lower odds for BK viremia, whereas recipient Black race was associated with two-fold increased odds for BK viremia. Recipient female sex was associated with more rapid clearance of BK viremia. Persistent BK viremia/BKVN was associated with poorer allograft function by 24 months post-transplant. CONCLUSIONS: We identified multiple donor and recipient demographic factors associated with risk for BKV infection and poorer allograft function by 24 months post-transplant. This may help design future clinical trials of therapies to prevent or mitigate the deleterious impact of BKV reactivation on kidney transplant outcomes.

The risk factors associated with post-transplantation BKPyV nephropathy and BKPyV DNAemia: a prospective study in kidney transplant recipients.

BACKGROUND: BK polyomavirus (BKPyV) infection after kidney transplantation can lead to serious complications such as BKPyV-associated nephropathy (BKPyVAN) and graft loss. The aim of this study was to investigate the incidence of BKPyVAN after implementing a BKPyV screening program, to map the distribution of BKPyV genotypes and subtypes in the Uppsala-Örebro region and to identify host and viral risk factors for clinically significant events. METHODS: This single-center prospective cohort study included kidney transplant patients aged ≥ 18 years at the Uppsala University Hospital in Sweden between 2016 and 2018. BKPyV DNA was analyzed in plasma and urine every 3 months until 18 months after transplantation. Also genotype and subtype were determined. A logistic regression model was used to analyze selected risk factors including recipient sex and age, AB0 incompatibility and rejection treatment prior to BKPyVAN or high-level BKPyV DNAemia. RESULTS: In total, 205 patients were included. Of these, 151 (73.7%) followed the screening protocol with 6 plasma samples, while184 (89.8%) were sampled at least 5 times. Ten (4.9%) patients developed biopsy confirmed BKPyVAN and 33 (16.1%) patients met criteria for high-level BKPyV DNAemia. Male sex (OR 2.85, p = 0.025) and age (OR 1.03 per year, p = 0.020) were identified as significant risk factors for developing BKPyVAN or high-level BKPyV DNAemia. BKPyVAN was associated with increased viral load at 3 months post transplantation (82,000 vs. < 400 copies/mL; p = 0.0029) and with transient, high-level DNAemia (n = 7 (27%); p < 0.0001). The most common genotypes were subtype Ib2 (n = 50 (65.8%)) and IVc2 (n = 20 (26.3%)). CONCLUSIONS: Male sex and increasing age are related to an increased risk of BKPyVAN or high-level BKPyV DNAemia. BKPyVAN is associated with transient, high-level DNAemia but no differences related to viral genotype were detected.

Visual, rapid, and cost-effective BK virus detection system for renal transplanted patients using gold nanoparticle coupled loop-mediated isothermal amplification (nanoLAMP).

A substantial percentage of kidney transplant recipients show transplant failure due to BK virus-induced nephropathy. This can be clinically controlled by the rapid and timely detection of BK virus infection in immune-compromised patients. We report a rapid (two hours from sample collection, processing, and detection), cost-effective (< 2$), highly sensitive and BKV-specific nanoLAMP (loop-mediated isothermal amplification) diagnostic methodology using novel primers and gold nanoparticles complex-based visual detection. The standardized nanoLAMP showed an analytical sensitivity of 25 copies/µl and did not cross-react with closely related JC and SV40 viruses. This nanoLAMP showed diagnostic sensitivity and specificity as 91% and 96%, respectively, taking 50 BK virus-negative (confirmed by qPCR from the plasma of healthy donors) and 57 positive BKV patient samples (confirmed by clinical parameters and qPCR assay). This simple two-step, low-cost, and quick (1-2 h/test) detection would be advantageous over the currently used diagnostic methodology. It may change the paradigm for polyomavirus infection-based failure of renal transplant.