Detection of BK polyomavirus genotypes to predict the development of BK polyomavirus-associated complications in kidney transplant recipients: A retrospective analysis

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).

Serum and urine nucleic acid screening tests for BK polyomavirus-associated nephropathy in kidney and kidney-pancreas transplant recipients

BACKGROUND

BK polyomavirus-associated nephropathy (BKPyVAN) occurs when BK polyomavirus (BKPyV) affects a transplanted kidney, leading to an initial injury characterised by cytopathic damage, inflammation, and fibrosis. BKPyVAN may cause permanent loss of graft function and premature graft loss. Early detection gives clinicians an opportunity to intervene by timely reduction in immunosuppression to reduce adverse graft outcomes. Quantitative nucleic acid testing (QNAT) for detection of BKPyV DNA in blood and urine is increasingly used as a screening test as diagnosis of BKPyVAN by kidney biopsy is invasive and associated with procedural risks. In this review, we assessed the sensitivity and specificity of QNAT tests in patients with BKPyVAN.

OBJECTIVES

We assessed the diagnostic test accuracy of blood/plasma/serum BKPyV QNAT and urine BKPyV QNAT for the diagnosis of BKPyVAN after transplantation. We also investigated the following sources of heterogeneity: types and quality of studies, era of publication, various thresholds of BKPyV-DNAemia/BKPyV viruria and variability between assays as secondary objectives.

SEARCH METHODS

We searched MEDLINE (OvidSP), EMBASE (OvidSP), and BIOSIS, and requested a search of the Cochrane Register of diagnostic test accuracy studies from inception to 13 June 2023. We also searched ClinicalTrials.com and the WHO International Clinical Trials Registry Platform for ongoing trials.

SELECTION CRITERIA

We included cross-sectional or cohort studies assessing the diagnostic accuracy of two index tests (blood/plasma/serum BKPyV QNAT or urine BKPyV QNAT) for the diagnosis of BKPyVAN, as verified by the reference standard (histopathology). Both retrospective and prospective cohort studies were included. We did not include case reports and case control studies.

DATA COLLECTION AND ANALYSIS

Two authors independently carried out data extraction from each study. We assessed the methodological quality of the included studies by using Quality Assessment of Diagnostic-Accuracy Studies (QUADAS-2) assessment criteria. We used the bivariate random-effects model to obtain summary estimates of sensitivity and specificity for the QNAT test with one positivity threshold. In cases where meta-analyses were not possible due to the small number of studies available, we detailed the descriptive evidence and used a summative approach. We explored possible sources of heterogeneity by adding covariates to meta-regression models.

MAIN RESULTS

We included 31 relevant studies with a total of 6559 participants in this review. Twenty-six studies included kidney transplant recipients, four studies included kidney and kidney-pancreas transplant recipients, and one study included kidney, kidney-pancreas and kidney-liver transplant recipients. Studies were carried out in South Asia and the Asia-Pacific region (12 studies), North America (9 studies), Europe (8 studies), and South America (2 studies).

INDEX TEST

blood/serum/plasma BKPyV QNAT The diagnostic performance of blood BKPyV QNAT using a common viral load threshold of 10,000 copies/mL was reported in 18 studies (3434 participants). Summary estimates at 10,000 copies/mL as a cut-off indicated that the pooled sensitivity was 0.86 (95% confidence interval (CI) 0.78 to 0.93) while the pooled specificity was 0.95 (95% CI 0.91 to 0.97). A limited number of studies were available to analyse the summary estimates for individual viral load thresholds other than 10,000 copies/mL. Indirect comparison of thresholds of the three different cut-off values of 1000 copies/mL (9 studies), 5000 copies/mL (6 studies), and 10,000 copies/mL (18 studies), the higher cut-off value at 10,000 copies/mL corresponded to higher specificity with lower sensitivity. The summary estimates of indirect comparison of thresholds above 10,000 copies/mL were uncertain, primarily due to a limited number of studies with wide CIs contributed to the analysis. Nonetheless, these indirect comparisons should be interpreted cautiously since differences in study design, patient populations, and methodological variations among the included studies can introduce biases. Analysis of all blood BKPyV QNAT studies, including various blood viral load thresholds (30 studies, 5658 participants, 7 thresholds), indicated that test performance remains robust, pooled sensitivity 0.90 (95% CI 0.85 to 0.94) and specificity 0.93 (95% CI 0.91 to 0.95). In the multiple cut-off model, including the various thresholds generating a single curve, the optimal cut-off was around 2000 copies/mL, sensitivity of 0.89 (95% CI 0.66 to 0.97) and specificity of 0.88 (95% CI 0.80 to 0.93). However, as most of the included studies were retrospective, and not all participants underwent the reference standard tests, this may result in a high risk of selection and verification bias.

INDEX TEST

urine BKPyV QNAT There was insufficient data to thoroughly investigate both accuracy and thresholds of urine BKPyV QNAT resulting in an imprecise estimation of its accuracy based on the available evidence.

AUTHORS' CONCLUSIONS

There is insufficient evidence to suggest the use of urine BKPyV QNAT as the primary screening tool for BKPyVAN. The summary estimates of the test sensitivity and specificity of blood/serum/plasma BKPyV QNAT test at a threshold of 10,000 copies/mL for BKPyVAN were 0.86 (95% CI 0.78 to 0.93) and 0.95 (95% CI 0.91 to 0.97), respectively. The multiple cut-off model showed that the optimal cut-off was around 2000 copies/mL, with test sensitivity of 0.89 (95% CI 0.66 to 0.97) and specificity of 0.88 (95% CI 0.80 to 0.93). While 10,000 copies/mL is the most commonly used cut-off, with good test performance characteristics and supports the current recommendations, it is important to interpret the results with caution because of low-certainty evidence.

Accurate Multiplex qPCR Detection of Epstein-Barr Virus/Cytomegalovirus/BK Virus in Kidney Transplant Patients: Pilot Study

Chronic kidney disease is a really important heath issue, and transplantation is an intervention that can greatly increase patient quality of life and survival. The aim of this study was to perform a comprehensive evaluation of the BK virus, CMV, and EBV in kidney transplant recipients (KTRs); to assess the prevalence of infections; and to test if our detection method would be feasible for use in follow-ups with KTRs. A total of 157 KTRs registered at the Clinical Hospital "Dr. C. I. Parhon", Iași, Romania, were selected using specific inclusion/exclusion criteria. We tested the blood samples from each patient for BK, EBV, and CMV using a multiplex real-time PCR (qPCR) assay and the TaqMan PCR principle. The highest prevalence was detected for BKV (11/157, 7%), followed by CMV (9/157, 5.7%) and EBV (5/157, 3.2%). By simultaneously detecting three possible nephropathic viruses and oncogenes in KTRs using multiplex real-time PCR, we aimed to optimize their monitoring and follow-up. The prevalence of the tested nephropathogenic viruses-BKV, CMV, and EBV-was comparable to that analyzed in other studies. We demonstrate that the use of qPCR for viral detection in KTRs is a robust, cost-effective method for case monitoring.

The Second International Consensus Guidelines on the Management of BK Polyomavirus in Kidney Transplantation

BK polyomavirus (BKPyV) remains a significant challenge after kidney transplantation. International experts reviewed current evidence and updated recommendations according to Grading of Recommendations, Assessment, Development, and Evaluations (GRADE). Risk factors for BKPyV-DNAemia and biopsy-proven BKPyV-nephropathy include recipient older age, male sex, donor BKPyV-viruria, BKPyV-seropositive donor/-seronegative recipient, tacrolimus, acute rejection, and higher steroid exposure. To facilitate early intervention with limited allograft damage, all kidney transplant recipients should be screened monthly for plasma BKPyV-DNAemia loads until month 9, then every 3 mo until 2 y posttransplant (3 y for children). In resource-limited settings, urine cytology screening at similar time points can exclude BKPyV-nephropathy, and testing for plasma BKPyV-DNAemia when decoy cells are detectable. For patients with BKPyV-DNAemia loads persisting >1000 copies/mL, or exceeding 10 000 copies/mL (or equivalent), or with biopsy-proven BKPyV-nephropathy, immunosuppression should be reduced according to predefined steps targeting antiproliferative drugs, calcineurin inhibitors, or both. In adults without graft dysfunction, kidney allograft biopsy is not required unless the immunological risk is high. For children with persisting BKPyV-DNAemia, allograft biopsy may be considered even without graft dysfunction. Allograft biopsies should be interpreted in the context of all clinical and laboratory findings, including plasma BKPyV-DNAemia. Immunohistochemistry is preferred for diagnosing biopsy-proven BKPyV-nephropathy. Routine screening using the proposed strategies is cost-effective, improves clinical outcomes and quality of life. Kidney retransplantation subsequent to BKPyV-nephropathy is feasible in otherwise eligible recipients if BKPyV-DNAemia is undetectable; routine graft nephrectomy is not recommended. Current studies do not support the usage of leflunomide, cidofovir, quinolones, or IVIGs. Patients considered for experimental treatments (antivirals, vaccines, neutralizing antibodies, and adoptive T cells) should be enrolled in clinical trials.

BK virus genotypes and humoral response in kidney transplant recipients with BKV associated nephropathy

BACKGROUND

Among kidney transplant recipients (KTR) with BK virus associated nephropathy (BKVN), BKV genotypes' evolution and anti-BKV humoral response are not well established. We aim to analyze BKV replication and genetic evolution following transplantation, and characterize concomitant anti-BKV-VP1 humoral response.

METHODS

We retrospectively analyzed 32 cases of biopsy-proven BKVN. Stored plasma and kidney biopsies were tested for BKV viral load, and VP1 sequencing performed on positive samples. BKV-VP1 genotype-specific neutralizing antibodies (NAbs) titers were determined at transplantation and BKVN.

RESULTS

At the time of BKVN diagnosis, BKV viral load was 8.2 log₁₀ IU/10⁶ cells and 5.4 log₁₀ IU/mL in kidney and plasma, respectively. VP1 sequencing identified the same BKV-subtype in both compartments in 31/32 cases. At the time of transplantation, 8/20 (40%) of biopsies tested positive for BKV detection, whereas concomitant BKV viremia was negative. VP1 sequencing identified a different subtype compared to BKVN in 5/6 of these samples. This was confirmed following transplantation: 8 patients had a BKV+ biopsy before BKV viremia, and VP1 sequencing identified a different subtype compared to BKVN in all of them. After the onset of BKV viremia and prior to BKVN diagnosis, the BKV subtype in BKV+ plasma and kidney biopsy was the same as the one isolated at BKVN. BKV-VP1 NAbs titers were significantly higher at the time of BKVN compared to transplantation (p = .0031), with similar titers across genotypes.

CONCLUSION

Altogether, our data suggest that among some KTR with BKVN, the BKV genotype from the donor may not be responsible for BKVN pathogenesis.

Genotypes and Variants of BKPyV in Organ Donors after Brain Death

Kidney transplantation from a donor with latent BKPyV might be the cause of serious complications, such as BK virus-associated nephropathy. The aim of the study was to determine the prevalence of BKPyV infection in donors after brain death (DBDs), to analyse the molecular variation of BKPyV and to compare clinical and inflammation parameters of DBDs infected with various genotypes of BKPyV. BKPyV was investigated in blood and urine samples of 103 DBDs using PCR followed by sequencing and bioinformatic analysis, and the viral load was assessed by qPCR. Clinical parameters, including cellular markers of inflammation were assessed. The results confirm high prevalence of BKPyV (48%),and genotype IV (49%) over genotype I (43%) and the co-infection with genotypes I and IV in 8.2%. Viral load ranged from 102 to 107 copies/mL, with an average of 1.92 × 106 copies/mL. No specific markers for BKPyV infection were detected among the parameters tested. Infection with genotype I may be associated with the adverse impact on thekidney function, while infection with genotype IV was associated with the anemia Not only the viral load but also the genotype of BKPyV may have an impact on the course of infection.

A cluster of BK polyomavirus-associated hemorrhagic cystitis after allogeneic hematopoietic stem cell transplantation

BACKGROUND

BK polyomavirus (BKV) can cause hemorrhagic cystitis (HC) in immunocompromised patients after hematopoietic stem cell transplantation (HSCT). It remains unclear whether nosocomial BKV infections occur. During a 9-month period, an increase in BKV-associated HC (BKV-HC) cases was observed at our institution.

AIM

The BKV-HC cluster population was compared with populations of HSCT patients from before and after the BKV-HC cluster to evaluate whether nosocomial BKV transmission had occurred.

METHODS

A retrospective analysis was carried out to assess the risk of patients developing BKV-HC after HSCT. The background data of the cluster patients were compared with those of the patients who underwent HSCT before or after the cluster, and the collected BKV isolates were serotyped.

RESULTS

BKV-HC involving grade ≥2 hematuria occurred in six of 15 HSCT recipients during a 9-month period. The incidence of BKV-HC was significantly higher in this period than in the other periods (p = 0.0014). There were no significant differences in the patients' background data between the cluster and non-cluster periods, including in terms of risk factors for BKV-HC. Serotype analyses of BKV revealed that the BKV detected in the urine samples from four of the six BKV-HC patients belonged to subtype Ic. The gene sequences of these four BKV exhibited >99.5% homology.

CONCLUSION

Our study suggests that nosocomial BKV infections may occur after HSCT. Although many cases of BKV-HC are caused by the reactivation of a latent virus, it is necessary to employ appropriate hygiene measures when cases of BKV-HC occur.