Diagnosis Of BK Virus Nephropathy Research Articles

Protocol biopsy of kidney allograft enables early detection of BK virus nephropathy to preserve kidney allograft function.

The Banff Working Group has updated the histological classification of BK virus nephropathy (BKVN), highlighting the importance of early detection. However, an early detection strategy for BKVN using biopsy has not yet been established. Our investigation aimed to assess the efficacy of protocol biopsy for the diagnosis of BKVN. We performed a retrospective cohort study of 314 patients who had undergone kidney transplantation between 2006 and 2021. Kidney allograft biopsies were performed as part of a protocol biopsy at 3 months and 1 year post-transplantation. Following the diagnosis of BKVN, the immunosuppressant dose was reduced. Twelve patients (3.8%) were diagnosed with BKVN by biopsy. Most diagnoses are established during the early stages of BKVN (polyomavirus nephropathy class 1 in six, class 2 in five, and class 3 in one). Following the reduction in immunosuppressant dose, kidney allograft function did not deteriorate in any patients. Additionally, test for BK virus DNA in the blood was negative. All but one patient demonstrated histological resolution of BKVN, and the other had a very slight positivity for the simian virus 40 large T antigen. The median follow-up time after BKVN diagnosis was 6 years. One patient developed de novo donor-specific antibody and subclinical acute antibody-mediated rejection that was successfully cured. Our analysis indicates that protocol biopsy may enable the early detection of BKVN, resulting in the preservation of kidney function.

Development of a Bak gene based standard curve for absolute quantification of BK virus in real time quantitative PCR assay and noninvasive diagnosis of BK virus nephropathy in kidney allograft recipients

BackgroundBK virus nephropathy (BKVN) is a frequent and serious post-transplant complication and undermines realization of the full benefits of kidney transplantation. We developed a Bak amplicon-based standard curve for absolute quantification of BKV VP1 mRNA copy number in the real time quantitative PCR (RT-qPCR) assay and investigated the performance characteristics of this novel assay. MethodsWe determined analytical specificity, sensitivity, and precision of our 73 bp mouse Bak amplicon based standard curve for absolute quantification of BKV VP1 mRNA in RT-qPCR assays. The diagnostic accuracy of the Bak standard curve in the RT-qPCR assay for the noninvasive diagnosis of BKVN in human kidney allograft recipients was investigated by quantification of BKV VP1 mRNA copy number in 192 urine samples matched to 192 kidney allograft biopsies from 155 unique kidney allograft recipients. Intraclass correlation coefficients (ICC) were calculated for the threshold cycles (Ct) and BKV VP1 mRNA copy number observed in the RT-qPCR assay with the Bak standard curve or the BKV standard curve. ResultsPerformance characteristics of the Bak amplicon-based RT-qPCR assay were exceptional with a slope of −3.291, Y-intercept of 38.60, R2 value of 1.00, efficiency of 101% and error of 0.014. Amplification was specific for the Bak amplicon. Intra assay standard deviation (SD) was 0.08 or less and inter assay SD was 0.11 or less for 31 cycles or less of amplification of the Bak amplicon. Receiver operating characteristic (ROC) curve analysis of BKV VP1 mRNA copy number in 192 biopsy matched urines yielded an area under the ROC of 0.982 (95% CI, 0.964 to 0.999, P < 0.0001) for discriminating patients with BKVN biopsies from patients without BKVN biopsies. The striking identity in the measurement of BKV VP1 mRNA copy numbers in the Bak amplicon-based RT-qPCR assay and in the BKV amplicon-based RT-qPCR assay was shown by an ICC of 1.00 when the Cts were compared, and an ICC of 0.99 when the log10 BKV VP1 mRNA copy numbers were compared. ConclusionsBak standard curve for absolute quantification of BKV VP1 mRNA copy number in the RT-qPCR assay demonstrated high efficiency, short and long-term precision and analytical specificity. BKVN was diagnosed with high accuracy. Our new findings, viewed in the light of our earlier demonstration that absolute quantification of a panel of mRNAs encoding immunoregulatory proteins is feasible with the Bak amplicon-based RT-qPCR assays, suggest that the Bak standard curve could serve as a universal calibrator for absolute quantification of transcripts in RT-qPCR assays and help reduce the workload, costs and eliminate contamination of genes of interest by repeated amplification of gene specific standard curves.

The clinical significance of BK viremia and the effect of cyclosporine and/or mizoribine on BK virus infection

IntroductionThe diagnosis of BK virus nephropathy is based on renal biopsy findings, and the diagnosis of presumptive BK virus nephropathy is made by sustained plasma BK virus DNA loads of > 4 log10 copies/ml. However, the BK virus plasma viral load cutoff of 4 log10 copies/ml may underestimate the diagnosis of BK virus nephropathy. In this study, we evaluated the clinical significance of BK viremia in kidney transplant recipients. Patients and MethodsFrom January 2010 to November 2015, we experienced 8 kidney transplant recipients who developed BK viremia. We retrospectively analyzed these recipients, focusing on the plasma BK viral load at onset of BK viremia, time to BK viremia after transplantation, frequency of BK virus nephropathy, and our treatment for BK viremia. ResultsThe median plasma BK virus polymerase chain reaction at the diagnosis of BK viremia was 1600 copies/ml (370–9400 copies/ml). The median time to BK viremia after transplantation was 10.9 months (1.4–67.9 months). Three patients were associated with BK virus nephropathy on biopsy. Clearance of BK viremia was observed in all of these cases after intervention. ConclusionsOur study demonstrated that intervention in BK viremia with a viral load of < 4 log10 copies/ml may be needed to prevent the development of graft dysfunction and BK virus nephropathy in kidney transplant recipients.

Urinary exosomal viral microRNA as a marker of BK virus nephropathy in kidney transplant recipients.

ObjectiveBkv-miR-B1-5p, one of the microRNAs encoded by BK virus, was recently reported to be elevated in the blood among the patients with BK virus nephropathy (BKVN). Urinary exosome was suggested to be a possible source of biomarker for kidney diseases, but it was unknown whether it could contain viral microRNA as well as human microRNAs. The aim of this study was to evaluate whether urinary exosomal BK viral microRNA were expressed during replication and could be used to diagnose BKVN in kidney transplant recipients.Materials and methodsIn a cross-sectional multicenter study, we collected and analyzed 458 graft biopsies from 385 kidney transplant recipients. Urine samples were collected at the time of graft biopsy, and microRNAs in urinary exosome were measured once. For 13 patients with BKVN and 67 age, sex-matched kidney transplant recipients, we measured BK viral microRNA B1-5p, 3p and human microRNA-16 in urinary exosomal fraction and compared the diagnostic value with BK viral load in plasma and urine.ResultsPathology proven BKVN was diagnosed in 13 patients (2.8%). High levels of bkv-miR-B1-5p and bkv-miR-B1-3p were shown in all patients with BKVN. Meanwhile, plasma BK viral load assay (cut-off value of ≥ 4.0 log10 copies/mL) showed false negative in 3 cases and urinary BK viral load assay (cut-off value of ≥ 7.0 log10 copies/mL) showed false negative in 1 case among these 13 patients. The receiver operator characteristics curve analysis for bkv-miR-B1-5p and bkv-miR-B1-5p/miR-16 showed excellent discriminative power for the diagnosis of BKVN, with area under the curve values of 0.989 and 0.985, respectively.ConclusionsThis study suggests that urinary exosomal bkv-miR-B1-5p and bkv-miR-B1-5p/miR-16 could be surrogate markers for the diagnosis of BKVN.

Native kidney BK virus nephropathy associated with acute lymphocytic leukemia

Polyoma BK virus nephropathy is a common complication after renal transplantation and is rarely seen in non-renal transplant recipients. There are only a couple of case reports of BK virus nephropathy in native kidneys in non-transplant patients, including a recent report of a 73-year-old patient with chronic lymphatic leukemia. A variety of treatment options, including leflunomide and cidofovir, were reported in these patients. Here we report the case of a 10-year-old boy with acute lymphatic leukemia who presented with non-oliguric hypertensive acute kidney injury at the 12th maintenance cycle of his chemotherapy. The workup supported the clear diagnosis of BK virus nephropathy with tubulointerstitial changes, and the patient responded favorably to intravenous immunoglobulin therapy. Pediatric nephrologists need to consider BK virus nephropathy as a differential diagnosis of acute kidney injury in immunocompromised non-transplant patients.

Silver-enhanced In Situ Hybridization for Detection of Polyomavirus DNA in Patients With BK Virus Nephropathy

BK virus nephropathy is not an infrequent complication of renal transplantation associated with high rates of graft loss. Although antibodies against SV40 antigen detect different viruses of the polyomavirus family, immunohistochemistry is widely used to confirm the diagnosis of BK virus nephropathy in renal biopsies. Here we aimed to validate the novel silver-enhanced in situ hybridization (SISH) technique for the automated detection of BK virus in renal transplant biopsies. Two different patient cohorts were included. Twenty-nine consecutive patients suspicious for BK virus infection were investigated by SISH and chromogenic in situ hybridization. An additional 26 renal biopsies positive by SV40 immunohistochemistry from 19 patients were analyzed by SISH. Polyomavirus DNA serum levels, as determined by nested PCR analysis, were available for all of these patients. The presence of BK virus DNA in renal tubular cells was identified in 5 of the suspicious cases by both, SISH and chromogenic in situ hybridization . One additional patient was only positive in the SISH. In the second cohort, SISH was positive in all SV40 positive biopsies, but SISH signals were less extensive than SV40 immunohistochemistry. Our results show that the BK virus SISH is an ancillary tool for the detection of polyomavirus DNA in renal biopsies using bright-field microscopy. However, its diagnostic value in comparison with standard immunohistochemistry seems to be limited.

Validation of Noninvasive Diagnosis of BK Virus Nephropathy and Identification of Prognostic Biomarkers

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. 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. 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). 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.

Immunosuppressive agents as risk factors for BK virus nephropathy: an overview and update

Important of the field: BK virus has emerged as an important cause of graft dysfunction and failure in renal transplant recipients. Risk factors for BK virus nephropathy (BKN) are not well established, but evidence suggests that it is the result of a complex interplay between multiple donor- and recipient-related factors.Areas covered in this review: The purpose of this article is to review the current understanding on the effect of various immunosuppressive agents on BK viral replication and the results of different reported immunosuppression reduction protocols.What the reader will gain: The intensity of overall immunosuppression has been accepted as a major risk factor for the development of BKN. We review the data regarding the contribution of different anti-rejection agents to the risk of BK virus-induced graft injury.Take home message: Although reduction in immunosuppression on detection of BK viral replication appears to be the most successful means in preserving allograft function, data are emerging that support the stronger association of the disease with tacrolimus, in contrast to mycophenolate compounds. Therefore, initial dose reduction for tacrolimus may be more beneficial than this anti-metabolite preemptively or after diagnosis of BKN.

Comparison of Detecting Methods of BK Virus Infection in Patients with Renal Allograft Recipients

Background : BK virus nephropathy (BKVN) is an emerging problem as a consequence of the use of potent immunosuppressive agents. Because optimal detection methods for the diagnosis of BKVN are required clinically, we compared the results of renal allograft biopsy, urine cytology, and urine and blood viral loads. Methods : Four hundred sixty two case notes from 2004 to 2009 at Seoul St. Mary’s Hospital were reviewed. During that period, 286 cases of urine cytology for decoy cells, 938 cases of urine BKV reverse transcription-polymerase chain reaction (RT-PCR), and 1,029 cases of blood BKV RT-PCR were performed. All diagnostic methods were performed in 85 cases. Results : A histological diagnosis of BKVN was made in 2.4% of cases (11/462). Urine cytology for decoy cells was positive in 26.2% (75/286). BKV RT-PCR revealed viruria in positivity of 22.1% (207/938) and viremia in 5.2% (54/1,029). In cases of BKVN, the sensitivities of urine and blood BKV RT-PCR were all 100% and the specificities were 69% and 94.5%, respectively. In cases with positive urine decoy cells, the sensitivities of urine and blood BKV RT-PCR were 50% and 27.7%, with specificities of 77.7% and 100%, respectively. Conclusions : BKV screening by RT-PCR assays may be a clinically useful noninvasive test to identify renal recipients with concurrent BKVN.

BK Virus Nephropathy Due to KOM-3 Strain

Interstitial nephritis caused by BK polyomavirus is an important complication of kidney transplantation. A diagnosis of BK virus nephropathy is established by a combination of characteristic histological, immunostaining, and ultrastructural findings. We report the first documented case of BK virus nephropathy caused by the KOM-3 strain in a patient after kidney transplantation. The biopsy specimen showed the characteristic histological and ultrastructural findings of BK virus, but was negative on immunostaining with a monoclonal antibody directed against BK virus large T antigen (LTag). Kidney tissue was subjected to polymerase chain reaction amplification using BK virus LTag-specific primers followed by DNA sequencing. Sequence results showed 100% homology to the KOM-3 strain, which has a 4-amino acid deletion in the C terminus of LTag compared with the reference sequence DUN strain. This deletion can explain the negative immunostaining results because the monoclonal antibody is directed against an epitope in this region. The patient lost his graft 2 months after diagnosis. Pathologists should be aware of this potential pitfall in interpreting immunostaining for BK virus. The incidence and prognostic implications of KOM-3 strain require additional studies.

Association of treatment with 15‐deoxyspergualin and BK virus nephropathy in kidney allograft recipients

BK virus nephropathy (BKVN) has been proposed as an important cause of allograft dysfunction and loss in kidney allograft recipient over the last decade. Intense immunosuppression and tubular injury have been shown to promote the replication of polyomavirus. 15-deoxyspergualin (DSG), an effective immunosuppressive agent, is used as a rescue drug for acute rejection in clinical renal transplantation in Japan. To determine whether DSG is a risk factor for BKVN and outline the relationship among BKVN, DSG, and other risk factors, we analyzed 88 patients who received living-related renal transplantation between January 1999 and April 2003. A total of 114 biopsy specimens from 88 living-related kidney transplantation recipients (performed between January 1999 to April 2003) were retrospectively analyzed. Patients received immunosuppression therapy based on calcineurin inhibitors and corticosteroid [tacrolimus (TAC) 33 and cyclosporin (CyA) 55]. Additionally, mycophenolate mofeteil (MMF) was used in 21 patients; DSG was used in seven patients; and anti-CD3 monoclonal antibody was used in 16 patients. We analyzed the degree of donor/recipient human leucocyte antigen (HLA) compatibility assessed by the number of HLA-A, -B, and -DR-mismatched antigens in 88 patients. The diagnosis of BKVN was made by the light microscopic examination and a positive immunohistochemical staining of anti-40 antibody in biopsy specimens. Patients were divided into two groups of group A (mild histological change) and group B (moderate or severe histological change) to determine the risk factors in different histological staging. The clinical course of two typical patients in different histological stage is described briefly to outline the risk factors of BKVN. We identified seven cases of BKVN (8.0%) from 88 transplanted patients. Significantly higher incidence of combination regimen consisting of TAC and MMF in BKVN group was noticed compared with non-BKVN group (57.1% vs. 9.9%; p = 0.003). BKVN was associated with a significantly higher incidence of DSG administration compared with non-BKVN group (57.1% vs. 3.7%; p </= 0.001). No difference was found in HLA mismatch between BKVN and non-BKVN group. Additionally, a significantly higher incidence of acute rejection episode prior to BKVN diagnosis was found in group B compared with group A (100% vs. 0%; p = 0.002), and the same statistical difference was shown in the number of anti-rejection therapy between group B and group A (100% vs. 0%; p = 0.002). We recognized a significant difference between group B and group A in terms of the combine regimen therapy of TAC with MMF (p = 0.002) and no difference in graft loss rate (p = 0.092), even though it was 50% in group B and was 0% in group A. In this study, our data indicated excessive intense immunosuppression with TAC-MMF is related to the development of BKVN. In addition, we found that anti-rejection therapy, especially with DSG, may accelerate the development of BKVN.

Frequency of BK virus nephropathy in graft dysfunction biopsies

AbstractBackgroundBK virus nephropathy is the most common type of viral disease to occur following renal transplantation. Although its frequency differs according to transplantation center, the rate is between 1.5% and 20%. Diagnosis can be established histologically by renal allograft biopsy. The aim of this study was to determine the frequency of BK virus nephropathy in patients who had had a renal biopsy for graft dysfunction at our center.MethodsBiopsies received in the last 3 years from patients with graft dysfunction were used in the study. We have found the BK virus in biopsies of 5 of 41 patients (11%). All these patients had been treated with immunosuppressive drugs following transplantation surgery. Biopsies were performed because of disturbance of renal function. Only 1 patient had had a urinary examination. Morphological diagnosis of BK virus nephropathy was followed by serological examination.ResultsThe most frequent morphological changes with BK virus infection in our samples were basophilia, nuclear inclusions, and nuclear enlargement on tubular epithelium. Decoy cells were not found in the biopsy from the only patient who had had a urinary examination. Treatment of the patients with BK virus nephropathy with immunosuppressive drugs has been reduced, and antiviral treatment has been started.ConclusionBK virus nephropathy should be kept in mind in the differential diagnosis of transplant rejection and drug toxicity.

Glomerular changes in BK virus nephropathy

This study seeks to define the glomerular changes that are associated with human BK virus nephropathy (BKVN). It is based on histopathologic review of 124 biopsies showing light-microscopic changes of viral nephropathy. The diagnosis of BKVN was confirmed by immunohistochemistry or by in situ hybridization. Histological lesions were scored by the Banff 97 criteria for renal allograft pathology and were correlated with clinical parameters. Viral cytopathic effect in the parietal Bowman’s capsular epithelium was seen in 21/124 (17%) biopsies. Immunohistochemistry showed infection of Bowman’s capsular epithelium in an additional 15/124 (12%) biopsies. Crescents were found in 15/124 (12%) samples. Glomerulitis exceeding grade Banff g1 was only occasionally shown (4/124 = 3% biopsies). Other pathologic lesions documented include mild increase in mesangial matrix in 23% biopsies, aneurysmal dilatation of glomerular capillaries in 28%, ischemic glomerulopathy in 62%, and chronic transplant glomerulopathy graded as mild (cg1) in 62% of biopsies and as moderate (cg2) in 2/124 (1.9%) biopsies. These findings show that infection of the glomerular epithelium cells can occur in a subset of patients with BKVN, most often in biopsies with high viral load in the tubular epithelium. Isolated crescents can occur in BKVN biopsies, but rapidly progressive glomerulonephritis is not observed. Two biopsies showed electron-dense deposits on ultrastructural examination, but a cause and effect relationship to BK virus infection could not be established.