Presence of urinary Haufen accurately predicts polyomavirus nephropathy

Polyomavirus nephropathy: quantitative urinary polyomavirus-Haufen testing accurately predicts the degree of intrarenal viral disease

BACKGROUND

A qualitative highly predictive urinary test for polyomavirus nephropathy (PVN) is the PV-Haufen test. This article evaluates whether a quantitative PV-Haufen analysis, that is, the number of PV-Haufen shed per milliliter urine, predicts PVN disease grades and the severity of intrarenal PV replication.

METHODS

Polyomavirus-Haufen were counted in 40 urine samples from patients with biopsy-proven definitive PVN. The number of PV-Haufen was correlated with both histologic PVN disease grades 1 to 3 and the number of SV40-T-expressing cells as indicators of intrarenal PV replication in corresponding renal allograft biopsies (manual counts and automated morphometry). Findings from quantitative PV-Haufen analyses were compared to conventional laboratory test results, that is, BK viremia (quantitative polymerase chain reaction [PCR]) and BK viruria (quantitative PCR and decoy cell counts).

RESULTS

Polyomavirus-Haufen counts showed excellent correlation (α0.77-0.86) with the severity of intrarenal PV replication and disease grades. In particular, low PV-Haufen numbers strongly correlated with early PVN grade 1 and minimal intrarenal expression of SV40-T antigen (P < 0.001). In comparison, BK viremia and viruria levels by PCR showed only modest correlations with histologic SV40-T expression (α0.40-0.49) and no significant correlation with disease grades or minimal intrarenal PV replication. No correlations were seen with urinary decoy cell counts. In contrast to conventional quantitative PCR assays or decoy cell counts, quantitative urinary PV-Haufen testing accurately reflects the severity of PV replication, tissue injury, and PVN disease grades.

CONCLUSIONS

Quantitative PV-Haufen testing is a novel noninvasive approach to patient management for the diagnosis and prediction of PVN disease grades and monitoring of disease course during therapy.

Different risk factor profiles distinguish early-onset from late-onset BKV-replication

Two of three reactivations of latent BKV-infection occur within the first 6 months after renal transplantation. However, a clear differentiation between early-onset and late-onset BKV-replication is lacking. Here, we studied all kidney transplant recipients (KTRs) at our single transplant center between 2004 and 2012. A total of 103 of 862 KTRs were diagnosed with BK viremia (11.9%), among which 24 KTRs (2.8%) showed progression to BKV-associated nephropathy (BKVN). Sixty-seven KTRs with early-onset BKV-replication (65%) and 36 KTRs with late-onset BKV-replication (35%) were identified. A control group of 598 KTRs without BKV-replication was used for comparison. Lymphocyte-depleting induction, CMV-reactivation, and acute rejection increased the risk of early-onset BKV-replication (P < 0.05). Presensitized KTRs undergoing renal retransplantation were those at increased risk of late-onset BKV-replication (P < 0.05). Among KTRs with BK viremia, higher doses of mycophenolate increased the risk of progression to BKVN (P = 0.004). KTRs with progression to BKVN showed inferior allograft function (P < 0.05). KTRs with late-onset BK viremia were more likely not to recover to baseline creatinine after BKV-replication (P = 0.018). Our data suggest different risk factors in the pathogenesis of early-onset and late-onset BKV-reactivation. While a more intensified immunosuppression is associated with early-onset BKV-replication, a chronic inflammatory state in presensitized KTRs may contribute to late-onset BKV-replication.

BK virus nephropathy is not always alone

INTRODUCTION

BK virus associated allograft nephropathy (BKVAN) is an important cause of allograft lost that often occurs in the first year of transplantation. The state of over immunosuppression also predispose these patients to various opportunistic viral infection Objectives: This research aimed to study the renal transplanted patients for BK viremia and BKVAN.

PATIENTS AND METHODS

This observational study was conducted between January 2013 to December 2014 to study the renal transplanted patients for BK viremia and BKVAN. In our center patients received combination of de-sensitization therapy including antithymocyte globulin (ATG), rituximab (RITU), basiliximab, therapeutic plasma exchange, and methylprednisolone (MTP), in high risks or only MTP therapy in immunologically low risk patients.

RESULTS

Of total number of 26 patients (20-52 years, M/F 17/9), seven patients received ATG and seven patient received intensive desensitizing protocols, BKVAN and BK viremia happened in three and two patients in above groups subsequently, only one patient developed BKVAN in low risk group. We also observed; cytomegalovirus (CMV) and parvovirus B19 infection and hemophagocytic syndrome (HPS), thrombotic microangiopathy (TMA) and endocarditis in our patients with BKVAN and BK viremia.

CONCLUSION

Awareness about the possibility of BK virus nephropathy and appropriate immunosuppression minimization are crucial components of management. Consideration of other opportunistic infections and specific syndromes are also very important.

Polyomavirus nephropathy: quantitative urinary polyomavirus-Haufen testing accurately predicts the degree of intrarenal viral disease

BACKGROUND

A qualitative highly predictive urinary test for polyomavirus nephropathy (PVN) is the PV-Haufen test. This article evaluates whether a quantitative PV-Haufen analysis, that is, the number of PV-Haufen shed per milliliter urine, predicts PVN disease grades and the severity of intrarenal PV replication.

METHODS

Polyomavirus-Haufen were counted in 40 urine samples from patients with biopsy-proven definitive PVN. The number of PV-Haufen was correlated with both histologic PVN disease grades 1 to 3 and the number of SV40-T-expressing cells as indicators of intrarenal PV replication in corresponding renal allograft biopsies (manual counts and automated morphometry). Findings from quantitative PV-Haufen analyses were compared to conventional laboratory test results, that is, BK viremia (quantitative polymerase chain reaction [PCR]) and BK viruria (quantitative PCR and decoy cell counts).

RESULTS

Polyomavirus-Haufen counts showed excellent correlation (α0.77-0.86) with the severity of intrarenal PV replication and disease grades. In particular, low PV-Haufen numbers strongly correlated with early PVN grade 1 and minimal intrarenal expression of SV40-T antigen (P < 0.001). In comparison, BK viremia and viruria levels by PCR showed only modest correlations with histologic SV40-T expression (α0.40-0.49) and no significant correlation with disease grades or minimal intrarenal PV replication. No correlations were seen with urinary decoy cell counts. In contrast to conventional quantitative PCR assays or decoy cell counts, quantitative urinary PV-Haufen testing accurately reflects the severity of PV replication, tissue injury, and PVN disease grades.

CONCLUSIONS

Quantitative PV-Haufen testing is a novel noninvasive approach to patient management for the diagnosis and prediction of PVN disease grades and monitoring of disease course during therapy.

Polyomavirus BK-encoded microRNA suppresses autoregulation of viral replication

Polyomavirus BK (BKV) infection is an important cause of renal allograft failure. Viral microRNAs are known to play a crucial role in viral replication. This study investigated the expression of BKV-encoded microRNAs (miR-B1) in patients with polyomavirus-associated nephropathy (PVAN) and their role in viral replication. Following BKV infection in renal proximal tubular cells, the 3p and 5p miR-B1 levels were significantly increased. Cells transfected with the vector containing the miR-B1 precursor (the miR-B1 vector) showed a significant increase in expression of 3p and 5p miR-B1 and decrease in luciferase activity of a reporter containing the 3p and 5p miR-B1 binding sites, compared to cells transfected with the miR-B1-mutated vector. Transfection of the miR-B1 expression vector or the 3p and 5p miR-B1 oligonucleotides inhibited expression of TAg. TAg-enhanced promoter activity and BKV replication were inhibited by miR-B1. In contrast, inhibition of miR-B1 expression by addition of miR-B1 antagomirs or silencing of Dicer upregulated the expression of TAg and VP1 proteins in BKV-infected cells. Importantly, patients with PVAN had significantly higher levels of 3p and 5p miR-B1 compared to renal transplant patients without PVAN. In conclusion, we demonstrated that (1) miR-B1 expression was upregulated during BKV infection and (2) miR-B1 suppressed TAg-mediated autoregulation of BKV replication. Use of miR-B1 can be evaluated as a potential treatment strategy against BKV infection.

BK virus infection: an update on diagnosis and treatment

BK virus, first isolated in 1971, is a significant risk factor for renal transplant dysfunction and allograft loss. Unfortunately, treatment options for BK virus infection are limited, and there is no effective prophylaxis. Although overimmunosuppression remains the primary risk factor for BK infection after transplantation, male gender, older recipient age, prior rejection episodes, degree of human leukocyte antigen mismatching, prolonged cold ischemia time, BK serostatus and ureteral stent placement have all been implicated as risk factors. Routine screening for BK has been shown to be effective in preventing allograft loss in patients with BK viruria or viremia. Reduction of immunosuppression remains the mainstay of BK nephropathy treatment and is the best studied intervention. Laboratory-based methods such as ELISPOT assays have provided new insights into the immune response to BK and may help guide therapy in the future. In this review, we will discuss the epidemiology of BK virus infection, screening strategies, treatment options and future research directions.

Currently recommended BK virus (BKV) plasma viral load cutoff of ≥4 log10/mL underestimates the diagnosis of BKV-associated nephropathy: a single transplant center experience

BACKGROUND

BK virus (BKV)-associated nephropathy (BKVAN) is a major cause of renal dysfunction and graft loss in renal transplant recipients. Monitoring plasma BK viral load (BKVL) is the recommended screening tool to predict BKVAN. American Society of Transplantation (AST) guidelines define a BKVL of ≥4 log10/mL (10,000 copies) as presumptive BKVAN and recommend reduction in immunosuppression. We evaluated the clinical sensitivity of the quantitative BKV DNA assay in predicting risk for BKVAN using the AST-recommended BKVL cutoff.

METHODS

In a retrospective, single-center study, all patients who underwent renal transplant at Henry Ford Hospital from January 2008 to August 2011 were analyzed (n = 490). Plasma BKVL Assay A (commercial large T antigen-based polymerase chain reaction [PCR]) was done in all patients. Renal biopsy was done if there was a rise in serum creatinine ≥0.5 mg from baseline. BKVAN was confirmed by biopsy. As a subset to this study, from the same cohort, data for a set of 20 consecutive Assays A and B (in-house VP1-based PCR assay) from 15 patients over a period of 3 months were collected. Differences in physicians' clinical decision-making (CDM) were analyzed between the 2 assays using chi-square test.

RESULTS

A total of 413 patients met the inclusion criteria, of which 222 patients had BK viremia. Among the 248 patients who had a renal biopsy done, 31 (12.5%) were found to have BKVAN. Eleven of the 31 (35%) patients had BKVL consistently <4 log10/mL, and thus were not diagnosed to have BKVAN using the AST-recommended BKVL cutoff of ≥4 log10/mL. A total of 8 patients lost their graft owing to BKVAN, including 3 patients with BKVL <4 log10/mL. Using a cutoff point of plasma BKVL of ≥4 log10/mL, the sensitivity, specificity, positive predictive value, and negative predicative value of the PCR Assay A for the diagnosis of biopsy-proven BKVAN were 64.5%, 98.4%, 87.0%, and 94.5%, respectively, and for the diagnosis of presumptive nephropathy were found to be 76.6%, 99.4%, 95.8%, and 96.4%, respectively. In the second part of the study, presumptive nephropathy was detected in 8 samples using Assay A and 14 samples using Assay B. Six samples in Assay A would have led to no changes in the CDM in terms of reduction in immunosuppression. Kidney biopsy was carried out in 5 patients, 4 of whom had BKVAN and had Assay B log count of ≥5. If Assay A had been used in CDM, BKVAN would have been missed in 1 patient.

CONCLUSION

Utilizing the current AST guideline cutoff of ≥4 log10 /mL, the PCR Assay A underestimated the diagnosis of BKVAN. Urgent standardization of the various BKVL assays and establishment of universal cutoff points is imperative to avoid BKVAN-related graft loss.

An in-house assay for BK polyomavirus quantification using the Abbott m2000 RealTime system

BK polyomavirus (BKPyV) quantification is useful for monitoring renal transplant patient response to therapy. The Abbott m2000 RealTime System employed by some clinical laboratories to perform US Food and Drug Administration-approved assays can also be used to develop in-house assays such as the one presented here. This study aimed to validate an in-house quantitative real-time PCR assay targeting the BKPyV major capsid VP1 gene for assessment of viral load using the Abbott m2000 RealTime System. BKPyV load was measured in 95 urine and plasma samples previously tested for BKPyV by one of three laboratories (46 BKPyV-positive samples consisting of 35 plasma and 11 urine samples; 49 samples negative for BKPyV consisting of 47 plasma and two urine samples). Two additional plasma specimens from the College of American Pathologists proficiency testing survey were also analysed. Precision studies were performed by diluting a high-viral-titre patient sample into BKPyV-negative pooled plasma to create high-positive (6.16 log10 copies ml(-1)) and low-positive (3.16 log10 copies ml(-1)) samples. For precision studies of inter-assay variability, a high-positive (7.0 log10 copies ml(-1)) and a low-positive (3.0 log10 copies ml(-1)) sample were measured in 20 separate runs. The assay's limit of quantification and limit of detection were 2.70 and 2.25 log10 copies ml(-1), respectively. The assay was linear from 2.70 to 9.26 log10 copies ml(-1). Of the 48 known positives, 43 were detected as positive, with three reported by the reference laboratory as values lower than the limit of detection. Two known positives at 3.27 and 3.80 log10 copies ml(-1) tested negative by the m2000 BKPyV assay. Of the 49 known negative samples, 48 were negative by the m2000 BKPyV load assay, with one sample confirmed positive by a reference laboratory. Qualitative analysis prior to discrepancy testing demonstrated a sensitivity of 89.58 % and a specificity of 97.96 %. Precision studies demonstrated inter-assay coefficients of variation of 0.63 % (high positive) and 4.38 % (low positive). Genotyping was performed on 22 patient samples, of which 21 (95.45 %) were type I and one (4.55 %) was type II. In conclusion, the m2000 BKPyV viral load assay sensitivity, specificity, linear range, precision and cost effectiveness make it an attractive methodology for clinical laboratories using the Abbott m2000 RealTime System.

The impact of surveillance and rapid reduction in immunosuppression to control BK virus-related graft injury in kidney transplantation

We prospectively screened 609 consecutive kidney (538) and kidney-pancreas (71) transplant recipients for BK viremia over a 4-year interval using polymerase chain reaction viral load detection and protocol kidney biopsies. We found that BK viremia is common at our center: total cases 26.7%, cases during first year 21.3% (mean 4 months), and recipients with ≥ 10 000 copies/ml 12.3%. We found few predictive clinical or demographic risk factors for any BK viremia or viral loads ≥ 10,000 copies/ml, other than prior treatment of biopsy confirmed acute rejection and/or higher immunosuppressive blood levels of tacrolimus (P = 0.001) or mycophenolate mofetil (P = 0.007). Viral loads at diagnosis (<10 000 copies/ml) demonstrated little impact on graft function or survival. However, rising copy numbers demand early reductions in immunosuppressive drug doses of at least 30-50%. Viral loads >185 000 copies/ml at diagnosis were predictive of BK virus-associated nephropathy (BKVAN; OR: 113.25, 95% CI: 17.22-744.6, P < 0.001). Surveillance for BK viremia and rapid reduction of immunosuppression limited the incidence of BKVAN to 1.3%. The addition of leflunomide or ciprofloxacin to immunosuppressive dose reduction did not result in greater rates of viral clearance. These data support the role of early surveillance for BK viremia to limit the impact on transplant outcome, although the most effective schedule for screening awaits further investigation.

BK polyomavirus in solid organ transplantation

The human BK polyomavirus (BKV) is the major cause of polyomavirus-associated nephropathy (PyVAN) putting 1-15% of kidney transplant patients at risk of premature allograft failure, but is less common in other solid organ transplants. Because effective antiviral therapies are lacking, screening kidney transplant patients for BKV replication in urine and blood has become the key recommendation to guide the reduction of immunosuppression in patients with BKV viremia. This intervention allows for expanding BKV-specific cellular immune responses, curtailing of BKV replication in the graft, and clearance of BKV viremia in 70-90% patients. Postintervention rejection episodes occur in 8-12%, most of which are corticosteroid responsive. Late diagnosis is faced with irreversible functional decline, poor treatment response, and graft loss. Adjunct therapies such as cidofovir, leflunomide and intravenous immunoglobulins have been used, but the benefit is not documented in trials. Retransplantation after PyVAN is largely successful, but requires close monitoring for recurrent BKV viremia.

Detection of BK polyomavirus after kidney transplantation: a comparison of urine electron microscopy with plasma polymerase chain reaction

BK polyomavirus (BKV) infection continues to be a significant source of allograft dysfunction in kidney transplant recipients. The optimal screening method to detect BKV remains undetermined. In this retrospective analysis of 347 consecutive kidney transplant recipients, we compare the diagnostic and screening performance of urine electron microscopy (EM) with plasma polymerase chain reaction (PCR) in testing for BKV, using biopsy-proved polyomavirus-associated nephropathy (PVAN) as the gold standard. Sixty-nine of 347 recipients had a positive screening test for BKV infection. Twenty-nine patients underwent biopsy, and 11 were diagnosed with PVAN. Sensitivity rates of urine EM and plasma PCR were 88% and 100%, respectively. Specificity rates of urine EM and plasma PCR were 91% and 78%. There was no statistical difference in the operating characteristics of the two tests. The majority of both plasma PCR and urine EM tests were positive in the six months prior to a diagnostic biopsy confirming PVAN. In those patients who had evidence of BKV infection but did not have PVAN, the percentage of positive screening tests decreased with aggressive lowering of immunosuppression. We conclude that urine EM and plasma PCR both function well in screening for BKV infection and in the diagnosis of PVAN. There is an opportunity to detect viral replication, lower immunosuppression, and to prevent PVAN in this population.

BK polyoma virus nephropathy in the native kidney

BACKGROUND

While BK polyoma virus nephropathy (PVN) is a well-recognized cause of renal allograft dysfunction, PVN of native kidneys is likely under-recognized.

METHODS

We present the pathologic features, risk factors and outcomes of eight cases of PVN in native kidneys.

RESULTS

The cohort included eight males aged 16-73 years (mean 47.4) with an immunocompromised state (mean duration 3.15 years) attributable to: hematologic malignancies (n = 6), for which three had undergone bone marrow transplant; lung transplant (n = 1) and combined tuberculosis and diabetes (n = 1). Seven patients were receiving specific immunosuppressive therapies. Patients were biopsied for acute kidney injury (AKI) with rise in mean creatinine levels from baseline 1.6 to 2.8 mg/dL. Pathology showed BK PVN with characteristic intranuclear inclusions staining positive for SV40 T antigen and negative for JC virus (JCV), with positive serum and/or urine PCR for BK virus. One patient had focal medullary JCV co-infection. Two patients also had renal infiltration by chronic lymphocytic leukemia (CLL). Six patients received specific therapy directed to PVN (cidofovir or leflunomide). Follow-up ranged from 2 to 20 (mean 10) months. Despite marked decrease in serum BK viral copy numbers, creatinine continued to rise in six cases (mean 3.7 mg/dL in four, requiring dialysis in two) and three patients died of malignancy, opportunistic infection or renal failure. Advanced histologic stage of PVN, ineffective antiviral therapy, co-morbidities and persistent immunocompromised state likely contributed to the poor outcomes.

CONCLUSION

A high level of suspicion in immunocompromised patients is needed to diagnose PVN in an early stage that may respond more favorably to antiviral therapy.

Incidence and outcomes of BK virus allograft nephropathy among ABO- and HLA-incompatible kidney transplant recipients

BACKGROUND AND OBJECTIVES

ABO-incompatible kidney transplant recipients may have a higher incidence of BK virus allograft nephropathy (BKVAN) compared with ABO-compatible recipients. It is unclear whether HLA-incompatible recipients share this risk or whether this phenomenon is unique to ABO-incompatible recipients. DESIGN, SETTING, PARTICIPATION, MEASUREMENTS: This study analyzed adult incompatible kidney transplant recipients from 1998 to 2010 (62 ABO-incompatible and 221 HLA-incompatible) and identified patients in whom BKVAN was diagnosed by biopsy (per protocol or for cause). This was a retrospective analysis of a prospectively maintained database that compared BKVAN incidence and outcomes between ABO- and HLA-incompatible recipients, respectively. BKVAN link to rejection and graft accommodation phenotype were also explored. The Johns Hopkins Institutional Review Board approved this study.

RESULTS

Risk for BKVAN was greater among ABO-incompatible than HLA-incompatible patients (17.7% versus 5.9%; P=0.008). Of BKVAN cases, 42% were subclinical, diagnosed by protocol biopsy. ABO-incompatibility and age were independent predictors for BKVAN on logistic regression. C4d deposition without histologic features of glomerulitis and capillaritis (graft accommodation-like phenotype) on 1-year biopsies of ABO-incompatible patients with and without BKVAN was 40% and 75.8%, respectively (P=0.04). Death-censored graft survival (91%) and serum creatinine level among surviving kidneys (1.8 mg/dl) were identical in ABO- and HLA-incompatible patients with BKVAN (median, 1399 and 1017 days after transplantation, respectively).

CONCLUSIONS

ABO-incompatible kidney recipients are at greater risk for BKVAN than HLA-incompatible kidney recipients. ABO-incompatible recipients not showing the typical graft accommodation-like phenotype may be at heightened risk for BKVAN, but this observation requires replication among other groups.

Detection of BK virus in urine from renal transplant subjects by mass spectrometry

Background

The diagnosis and management of BK virus (BKV) reactivation following renal transplantation continues to be a significant clinical problem. Following reactivation of latent virus, impaired cellular immunity enables sustained viral replication to occur in urothelial cells, which potentially leads to the development of BKV-associated nephropathy (BKVAN). Current guidelines recommend regular surveillance for BKV reactivation through the detection of infected urothelial cells in urine (decoy cells) or viral nucleic acid in urine or blood. However, these methods have variable sensitivity and cannot routinely distinguish between different viral subtypes. We therefore asked whether mass spectrometry might be able to overcome these limitations and provide an additional non-invasive technique for the surveillance of BKV and identification of recipients at increased risk of BKVAN.

Results

Here we describe a mass spectrometry (MS)-based method for the detection of BKV derived proteins directly isolated from clinical urine samples. Peptides detected by MS derived from Viral Protein 1 (VP1) allowed differentiation between subtypes I and IV. Using this approach, we observed an association between higher decoy cell numbers and the presence of the VP1 subtype Ib-2 in urine samples derived from a cohort of 20 renal transplant recipients, consistent with the hypothesis that certain viral subtypes may be associated with more severe BKVAN.

Conclusions

This is the first study to identify BK virus proteins in clinical samples by MS and that this approach makes it possible to distinguish between different viral subtypes. Further studies are required to establish whether this information could lead to stratification of patients at risk of BKVAN, facilitate distinction between BKVAN and acute rejection (AR), and ultimately improve patient treatment and outcomes.

Clinical role of the renal transplant biopsy

Percutaneous needle core biopsy is the definitive procedure by which essential diagnostic and prognostic information on acute and chronic renal allograft dysfunction is obtained. The diagnostic value of the information so obtained has endured for over three decades and has proven crucially important in shaping strategies for therapeutic intervention. This Review provides a broad outline of the utility of performing kidney graft biopsies after transplantation, highlighting the relevance of biopsy findings in the immediate and early post-transplant period (from days to weeks after implantation), the first post-transplant year, and the late period (beyond the first year). We focus on how biopsy findings change over time, and the wide variety of pathological features that characterize the major clinical diagnoses facing the clinician. This article also includes a discussion of acute cellular and humoral rejection, the toxic effects of calcineurin inhibitors, and the widely varying etiologies and characteristics of chronic lesions. Emerging technologies based on gene expression analyses and proteomics, the in situ detection of functionally relevant molecules, and new bioinformatic approaches that hold the promise of improving diagnostic precision and developing new, refined molecular pathways for therapeutic intervention are also presented.

The BK virus in renal transplant recipients-review of pathogenesis, diagnosis, and treatment

The BK virus, a DNA virus from the Polyomavirus group, represents an opportunistic infection of immunosuppressed transplant recipients. Though the virus was discovered approximately 40 years ago, the emergence of BK virus nephropathy since 1995 onwards, with associated high graft loss rates, has revolutionized renal transplantation medicine. Kidney transplant professionals realized that the consequences of over-immunosuppression were as severe as the consequences of under-immunosuppression and we entered the era of immunosuppressive minimization. Despite this recognition, the optimal testing type for BK virus infections and frequency of testing are hotly debated. Similarly, optimal treatment strategies remain sources of intense controversy. The authors review the current strategies of screening, diagnosis, and possible treatment, and also review the amount and quality of evidence in favor or against. Similarities and differences between cytomegalovirus, Epstein-Barr virus, and BV virus, the three major viral infections in kidney transplantation, are highlighted.

Prospective monitoring of BK virus reactivation in renal transplant recipients in North India

BACKGROUND

BK nephropathy (BKN) is an important complication of renal transplantation with a reported incidence between 1% and 10% in different parts of the world. Early diagnosis is important to plan early therapeutic strategies. The epidemiology and evolution of BKN is relatively unknown in India and hence, the present study has been designed to prospectively monitor the activation of BK virus (BKV) in renal transplant recipients in India.

PATIENTS AND METHODS

In this study, 32 renal allograft recipients were prospectively monitored with protocol biopsies of allografts, BKV DNA load in plasma, and viral particles in urine by electron microscopy (EM) on day 1, and at 1, 3, and 6 months. Additionally, the baseline BKV DNA load in plasma was quantitated in 21 corresponding donors.

RESULTS

On follow-up in 32 recipients, 9.7%, 23.8%, 19.2%, and 13.3% of patients showed viral profiles by EM at day 1, 1 month, 3 months, and 6 months, respectively. BKV DNA positivity in plasma was 25.8%, 42.9%, 15.4%, and 20% at day 1, 1 month, 3 months, and 6 months, respectively, with mean BKV copy number/mL plasma of 1796, 1029, 2611, and 3318, respectively. A total of 15.7% (17/108) urine samples of 32 renal recipients were positive by urine EM. Out of 100 protocol biopsies, none developed histologically demonstrable cytopathic effects of BKN, although 8% biopsies were SV-40 large T antigen (SV-40 T Ag) positive. By quantitative real-time polymerase chain reaction assay, 27/108 (25%) of recipients' plasma samples were positive for BKV. Peak viremia and viruria occurred at 1-3 months post transplantation. The baseline viremia in donors was predictive of viremia positivity in the post-transplantation period at 1 month. Twenty-four episodes of graft dysfunction were attributed mainly to rejection.

CONCLUSION

The study shows a total of 15.7% and 25% urine and plasma samples were positive for BKV at any time during a 6-month follow-up. The highest incidence of BK viruria and viremia occurred at 1 month. In protocol biopsies, focal positivity of SV-40 T Ag was seen in 8% biopsies.

Monthly screening for BK viremia is an effective strategy to prevent BK virus nephropathy in renal transplant recipients

BACKGROUND

BK polyomavirus virus (BKV) nephropathy (BKVN) is the most common viral infection that affects renal allografts. Because a specific antiviral therapy is lacking, BKVN may result in graft dysfunction and/or loss. We prospectively analyzed whether monthly nucleic acid testing (NAT) for BKV replication in blood and immediate reduction of immunosuppression (IS) could prevent BKVN.

METHODS

NAT was performed at monthly intervals for 6 months and then at 12 months in 119 de novo renal transplant recipients. In viremic patients (presumptive BKVN), a graft biopsy was systematically performed and IS was immediately reduced.

RESULTS

BKV viremia occurred in 13 (10.9%) patients after a median time of 90 days (23-241); 77% of patients were viremic before month 4. After reduction of IS, viral load was undetectable in 11 patients, remained low in 1, and continued to increase in 1 patient who developed definitive BKVN despite reduction of IS, and finally returned to dialysis 6 months after transplantation.

CONCLUSION

BKV infection is an early complication. Monthly NAT in blood during the first 6 months and immediate reduction of IS in viremic patients almost completely prevent definitive BKVN.

Validation of noninvasive diagnosis of BK virus nephropathy and identification of prognostic biomarkers

BACKGROUND

BK virus nephropathy (BKVN) may cause renal allograft dysfunction and failure. The gold standard test is kidney biopsy, which is invasive and costly. A noninvasive, accurate biomarker for diagnosis of BKVN and prognostication of allograft function after BKVN infection may improve allograft survival.

METHODS

We tested the diagnostic accuracy of our previously reported cutoff value of 6.5x10(5) BKV viral capsid protein 1 (VP-1) mRNA/ng RNA in urinary cells (Ding et al., Transplantation 2002; 74: 987) using an independent cohort (n=89). We also examined whether urinary cell mRNA profiles obtained at the time of BKVN diagnosis identified patients at risk of subsequent decline in graft function.

RESULTS

BKVN was accurately diagnosed (sensitivity of 100% and specificity of 97%) using our previously reported cutoff value. Levels of granzyme B (GB) mRNA (P=0.002) and proteinase inhibitor (PI)-9 mRNA (P=0.01) in urinary cells were higher in BKVN patients with a subsequent decline in renal function (n=8) compared with patients with stable function (n=10), and were positively associated (GB, P=0.01; PI-9, P=0.04) with rise in serum creatinine from the time of BKVN diagnosis to 12 months after diagnosis. GB levels in the BKVN patients with a decline in renal function were similar to those in the acute rejection group (n=11, P>0.05), but higher than the normal biopsy group (n=36, P<0.001); levels in BKVN patients with stable function were lower than those in the acute rejection group (P<0.01) and not significantly different from the normal biopsy group (P>0.05).

CONCLUSIONS

Noninvasive diagnosis of BKVN and prognostication of renal allograft function after BKVN diagnosis are feasible by measurement of transcripts for BKV viral capsid protein 1 (VP-1), GB, and PI-9 in urine.

Viral Haufen are urinary biomarkers of polyomavirus nephropathy: New diagnostic strategies utilizing negative staining electron microscopy

Haufen, i.e. discrete three-dimensional cast-like polyomavirus aggregates in the urine, mark polyoma BK-virus nephropathy (BKN) with positive and negative predictive values of greater than 95%. They are novel diagnostic biomarkers of BKN, an important infectious complication post kidney transplantation. Here, we describe technical details of Haufen detection by negative staining electron microscopy. We studied more than 400 urine samples from over 180 patients and developed easy-to-follow protocols for optimal specimen preservation and preparation, including sample clarification and concentration. We detail diagnostic clues to detect Haufen and illustrate pitfalls, including "Haufen-look-alikes," which can hamper the interpretation. Urinary Haufen detection by negative staining electron microscopy is a new application of an old, well-established diagnostic technique. The protocols described here are useful for pathologists and electron microscopists to search for Haufen in voided urine samples, to predict BKN noninvasively, and to help clinicians managing renal allograft recipients.

Human polyoma viruses and disease with emphasis on clinical BK and JC

Polyoma viruses are ubiquitous infecting many different mammalian species including humans. There are five known human polyoma viruses. JC virus and BK virus are two polyoma viruses identified nearly three decades ago. Recently WU, KI and Merkel cell polyoma viruses have been isolated from humans. The exact role of these three newly discovered viruses in human disease is not known. Most human polyoma disease is caused by BK and JC viruses which are usually acquired in childhood. Approximately 50-80% of humans have seropositivity to these viruses. Clinically apparent diseases in immunocompetent hosts are extremely rare. These viruses remain latent possibly in the lymphoid organs, neuronal tissue, and kidney and under the circumstances of severe immunosuppression both these viruses reactivate. Neurotropic JC virus reaches the brain and causes progressive multifocal leukoencephalopathy, a demyelinating disease of the central nervous system with a high mortality rate. BK virus is urotheliotropic and its reactivation causes a form of interstitial nephritis, known as BK or polyoma virus associated nephropathy which is associated with high graft loss if not recognized early. There are no known effective antiviral agents for any of the polyoma viruses.

Modern uses of electron microscopy for detection of viruses

Electron microscopy, considered by some to be an old technique, is still on the forefront of both clinical viral diagnoses and viral ultrastructure and pathogenesis studies. In the diagnostic setting, it is particularly valuable in the surveillance of emerging diseases and potential bioterrorism viruses. In the research arena, modalities such as immunoelectron microscopy, cryo-electron microscopy, and electron tomography have demonstrated how viral structural components fit together, attach to cells, assimilate during replication, and associate with the cellular machinery during replication and egression. These studies provide information for treatment and vaccine strategies.