Human polyoma virus in renal allograft biopsies: morphological findings and correlation with urine cytology

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.

Characterization of Herpesviridae Family Members, BK Virus, and Adenovirus in Children and Adolescents with Nephrotic Syndrome

Since the significance of viral infections in children and adolescents with nephrotic syndrome (NS) is yet to be defined, this study intended to estimate the occurrence, pattern, and outcomes of some DNA viral infections in children with NS.

METHODS

A prospective study was conducted to determine the genome identification of the viruses Epstein-Barr (EBV), human cytomegalovirus (HCMV), human herpesvirus 6 (HHV-6 type A and type B) and 7 (HHV-7), polyomavirus (BKV), and human adenovirus (HAdV) in plasma and urine samples of pediatric patients with NS.

RESULTS

A total of 35 patients aged 1 to 18 years with NS and under immunosuppressant drugs participated in the study. Plasma and urine samples were collected at regular intervals during a median follow-up of 266 days (range 133-595), and DNA was analyzed to detect the selected DNA viruses. Eleven patients (31.4%) had active virus infections, and patterns were classified as coinfection, recurrent, and consecutive. Of these, six patients (54.5%) presented viral coinfection, six (54.5%) viral recurrence, and seven patients (63.3%) had viral consecutive infection. Ten of the eleven patients with active infection had a proteinuria relapse (91%) and eight (72.7%) were hospitalized (p = 0.0022). Active HCMV infection was the most frequent infection and was observed in six patients (54.5%), three of the eleven patients (27.2%) had suspected HCMV disease in the gastrointestinal tract, and one had HHV-7 coinfection. The frequency of other infections was: 9% for HHV-6, 45.5% for BKV, 27.3% for HHV-7, 18.2% for EBV, and 18.2% for HAdV.

CONCLUSION

viral infections, especially HCMV, can be an important cause of morbidity and nephrotic syndrome relapse in children.

BK polyomavirus infection: more than 50 years and still a threat to kidney transplant recipients

BK polyomavirus (BKPyV) is a ubiquitous human polyomavirus and a major infection after kidney transplantation, primarily due to immunosuppression. BKPyV reactivation can manifest as viruria in 30%-40%, viremia in 10%-20%, and BK polyomavirus-associated nephropathy (BKPyVAN) in 1%-10% of recipients. BKPyVAN is an important cause of kidney graft failure. Although the first case of BKPyV was identified in 1971, progress in its management has been limited. Specifically, there is no safe and effective antiviral agent or vaccine to treat or prevent the infection. Even in the current era, the mainstay approach to BKPyV is a reduction in immunosuppression, which is also limited by safety (risk of de novo donor specific antibody and rejection) and efficacy (graft failure). However, recently BKPyV has been getting more attention in the field, and some new treatment strategies including the utilization of viral-specific T-cell therapy are emerging. Given all these challenges, the primary focus of this article is complications associated with BKPyV, as well as strategies to mitigate negative outcomes.

Lessons from Polyomavirus Immunofluorescence Staining of Urinary Decoy Cells

Decoy cells that can be detected in the urine sediment of immunosuppressed patients are often caused by the uncontrolled replication of polyomaviruses, such as BK-Virus (BKV) and John Cunningham (JC)-Virus (JCV), within the upper urinary tract. Due to the wide availability of highly sensitive BKV and JCV PCR, the diagnostic utility of screening for decoy cells in urine as an indicator of polyomavirus-associated nephropathy (PyVAN) has been questioned by some institutions. We hypothesize that specific staining of different infection time-dependent BKV-specific antigens in urine sediment could allow cell-specific mapping of antigen expression during decoy cell development. Urine sediment cells from six kidney transplant recipients (five males, one female) were stained for the presence of the early BKV gene transcript lTag and the major viral capsid protein VP1 using monospecific antibodies, monoclonal antibodies and confocal microscopy. For this purpose, cyto-preparations were prepared and the BK polyoma genotype was determined by sequencing the PCR-amplified coding region of the VP1 protein. lTag staining began at specific sites in the nucleus and spread across the nucleus in a cobweb-like pattern as the size of the nucleus increased. It spread into the cytosol as soon as the nuclear membrane was fragmented or dissolved, as in apoptosis or in the metaphase of the cell cycle. In comparison, we observed that VP1 staining started in the nuclear region and accumulated at the nuclear edge in 6-32% of VP1⁺ cells. The staining traveled through the cytosol of the proximal tubule cell and reached high intensities at the cytosol before spreading to the surrounding area in the form of exosome-like particles. The spreading virus-containing particles adhered to surrounding cells, including erythrocytes. VP1-positive proximal tubule cells contain apoptotic bodies, with 68-94% of them losing parts of their DNA and exhibiting membrane damage, appearing as "ghost cells" but still VP1⁺. Specific polyoma staining of urine sediment cells can help determine and enumerate exfoliation of BKV-positive cells based on VP1 staining, which exceeds single-face decoy staining in terms of accuracy. Furthermore, our staining approaches might serve as an early readout in primary diagnostics and for the evaluation of treatment responses in the setting of reduced immunosuppression.

Importance of Follow-Up Biopsies in the Prediction of Renal Allograft Survival Following Polyomavirus-Associated Nephropathy

OBJECTIVES

Allograft biopsy is the gold standard for diagnosing polyomavirus-associated nephropathy. We aimed to establish the effects of histopathologic findings proposed by the Banff Polyomavirus Working Group on graft outcome. We also aimed to understand the clinical importance of follow-up biopsies for patients with polyomavirus-associated nephropathy.

MATERIALS AND METHODS

Our study included 22 patients with polyomavirus-associated nephropathy. All biopsies were classified according to the latest Banff Polyomavirus Working Group classification. Follow-up biopsies of all patients were evaluated in detail.

RESULTS

The mean interval between polyomavirus-associated nephropathy and transplant was 10 ± 1.6 months. Of 22 patients, biopsy revealed stage 1 in 3 (13.6%), stage 2 in 17 (77.3%), and stage 3 in 2 patients (9.1%). Fourteen patients (63.6%) had polyomavirus viral load 3, 5 (22.7%) had polyomavirus viral load 2, and 3 had polyomavirus viral load 1. Among patients included in analyses, 18.2% had antibody-mediated rejection and 27.2% had T-cell-mediated rejection simultaneously with polyomavirus-associated nephropathy. Graft loss increased with increasing polyomavirus-associated nephropathy class and polyomavirus viral load (P = .015 and P = .002, respectively). The mean time of graft survival decreased with increasing degree of tubulitis, interstitial inflammation, plasma infiltration, and neutrophil infiltration. Patients with interstitial fibrosis, glomerular polyoma, and cortical plus medullar involvement showed earlier graft loss. Follow-up biopsies showed that diffuse interstitial fibrosis or persistent inflam-mation negatively influenced graft loss.

CONCLUSIONS

The Banff Polyomavirus Working Group's schema significantly correlated with graft outcome. Early detection of polyomavirus-associated nephro-pathy and subsequent detection of persistent inflammation and interstitial fibrosis and tubular atrophy in follow-up biopsies and modification of immunosuppressive therapy can successfully prevent graft loss.

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

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

Acitretin and Retinoic Acid Derivatives Inhibit BK Polyomavirus Replication in Primary Human Proximal Renal Tubular Epithelial and Urothelial Cells

Small-molecule drugs inhibiting BK polyomavirus (BKPyV) represent a significant unmet clinical need in view of polyomavirus-associated nephropathy or hemorrhagic cystitis, which complicate 5% to 25% of kidney and hematopoietic cell transplantations. We characterized the inhibitory activity of acitretin on BKPyV replication in primary human renal proximal tubular epithelial cells (RPTECs). Effective inhibitory concentrations of 50% (EC₅₀) and 90% (EC₉₀) were determined in dilution series measuring BKPyV loads, transcripts, and protein expression, using cell proliferation, metabolic activity, and viability to estimate cytotoxic concentrations and selectivity indices (SI). The acitretin EC₅₀ and EC₉₀ in RPTECs were 0.64 (SI₅₀, 250) and 3.25 μM (SI₉₀, 49.2), respectively. Acitretin effectively inhibited BKPyV replication until 72 h postinfection when added 24 h before infection until 12 h after infection, but decreased to <50% at later time points. Acitretin did not interfere with nuclear delivery of BKPyV genomes, but it decreased large T-antigen transcription and protein expression. Acitretin did not inhibit the initial round of BKPyV replication following transfection of full-length viral genomes, but it affected subsequent rounds of reinfection. Acitretin also inhibited BKPyV replication in human urothelial cells and in Vero cells, but not in COS-7 cells constitutively expressing Simian virus 40 (SV40) large T antigen. Retinoic acid agonists (all-trans retinoic acid, 9-cis retinoic acid [9-cis-RA], 13-cis-RA, bexarotene, and tamibarotene) and the RAR/RXR antagonist RO41-5253 also inhibited BKPyV replication, pointing to an as-yet-undefined mechanism. IMPORTANCE Acitretin selectively inhibits BKPyV replication in primary human cell culture models of nephropathy and hemorrhagic cystitis. Since acitretin is an approved drug in clinical use reaching BKPyV-inhibiting concentrations in systemically treated patients, further studies are warranted to provide data for clinical repurposing of retinoids for treatment and prevention of replicative BKPyV-diseases.

BK polyomavirus-pathogen, paradigm and puzzle

BK virus is a polyomavirus with seroprevalence rates of 80% in adults. Infection is usually acquired during childhood, and the virus is benign or pathologic depending on immune status. The virus reactivates in immunodeficiency states, mostly among transplant (either kidney or bone marrow) recipients. There are approximately 15 000 renal transplants every year in the USA, of which 5-10% develop BK polyomavirus nephropathy; 50-80% of patients who develop nephropathy go on to develop graft failure. BK virus is associated with BK polyomavirus nephropathy, ureteral stenosis, late-onset hemorrhagic cystitis, bladder cancer and other nonlytic large T-expressing carcinomas. The renal spectrum begins with viruria and can end with graft failure. The clinical spectrum and outcomes vary among transplant patients. New noninvasive diagnostic methods, such as urinary polyomavirus Haufen detected by electron microscopy, are currently under study. Treatment is primarily directed at decreasing immunosuppression but may be associated with graft rejection. Repeat transplantation is encouraged as long as viral clearance in plasma prior to transplant is accomplished. There remain no definitive data regarding the utility of transplant nephrectomy.

Routine immunohistochemistry study for polyomavirus BK nephropathy in transplanted kidney biopsies, is it recommended?

BACKGROUND

Early diagnosis and treatment of Polyomavirus BK Nephropathy (PVBKN) is a challenging issue in the management of patients with kidney transplantation. Currently, histopathologic diagnosis is the gold standard method for diagnosis of PVBKN. However, typical viral inclusions may not be found in early stages of the PVBKN and should, instead, be diagnosed using immunohistochemistry (IHC) study. There is no clear consensus about routine IHC tests in the pathologic evaluation of transplanted kidney biopsy samples.

MATERIAL AND METHODS

The current study was conducted on transplanted kidney biopsy samples, since 2016 to 2019. The patients who have presented with new onset of allograft dysfunction, at least 2 weeks after transplantation surgery, were included in our study. All these biopsy samples were evaluated with routine renal biopsy stains as well as IHC for SV40 (Simvian Virus 40) antigen. The identification of typical nuclear virus inclusion body and any nuclear positive staining on IHC (≥1+ positive result) were considered as definite evidence of PVBKN. Sensitivity, specificity, Positive Predictive and Negative Predictive Values (PPV and NPV) of histopathologic assessment without IHC study were evaluated.

RESULTS

Among 275 included cases, 18 (6.5%) patients with PVBKN were diagnosed. In patients with PVBKN, typical viral inclusions were detected in 14 samples (77.7%), on primary histopathological examination. However, virus-infected cells were identified just after IHC study in 4 (22.2%) of patients. Sensitivity, Specifity, PPV and NPV of morphologic histopathological assay without IHC for detection of PVBKN was 77.7, 100, 100 and 98.4% respectively.

CONCLUSION

Routine IHC study for SV40 in all transplanted kidney biopsy samples with new onset of allograft dysfunction, will enhance the diagnostic sensitivity of early stage disease detection.

BK Polyomavirus Nephropathy in Kidney Transplantation: Balancing Rejection and Infection

BK polyomavirus nephropathy (BKVN) and allograft rejection are two closely-associated diseases on opposite ends of the immune scale in kidney transplant recipients. The principle of balancing the immune system remains the mainstay of therapeutic strategy. While patient outcomes can be improved through screening, risk factors identification, and rapid reduction of immunosuppressants, a lack of standard curative therapy is the primary concern during clinical practice. Additionally, difficulty in pathological differential diagnosis and clinicopathology’s dissociation pose problems for a definite diagnosis. This article discusses the delicate evaluation needed to optimize immunosuppression and reviews recent advances in molecular diagnosis and immunological therapy for BKVN patients. New biomarkers for BKVN diagnosis are under development. For example, measurement of virus-specific T cell level may play a role in steering immunosuppressants. The development of cellular therapy may provide prevention, even a cure, for BKVN, a complex post-transplant complication.

An application of the 2018 Banff Classification for BK polyomavirus-associated nephropathy in renal transplantation

BACKGROUND

There is still a lack of a recognized morphological classification of BK viral nephropathy (BKVN) which can better reflect the clinical manifestations and prognosis.

METHODS

We retrospectively analyzed the data of 53 patients with BKVN in our center from January 2011 to December 2018 and evaluated the new Banff 2018 classifications' predictive value for the graft prognosis.

RESULTS

The period between transplantation and BKVN diagnosis lasted for 10.3 months (IQR, 5.3-21.9 months). The main reason (92.5%) for puncture was the increase of blood serum creatinine. Of the 53 patients diagnosed with BKVN, 100% were positive for urinary BK virus-DNA, and the viral load was 1.4 × 10⁸  copies/mL (IQR, 3.7 × 10⁴ -1.3 × 10¹¹  copies/mL); 75.5% were positive for blood BK virus-DNA, and the viral load was 3.3 × 10⁴  copies/mL (IQR, 0-2.8 × 10⁷  copies/mL). There were five cases in class 1, 31 cases in class 2, and 17 cases in class 3; the viral load of urine BK was 3.3 × 10⁸ , 1.4 × 10⁸ , and 6.3 × 10⁷  copies/mL (P > .05); the viral load of blood BK was 3.3 × 10⁴ , 3.3 × 10⁴ , and 3.3 × 10⁴  copies/mL (P > .05); the 1-year graft survival rates were 100%, 90.3%, and 52.9%, respectively (P < .05).

CONCLUSION

BKVN mostly occurs within 1 year after transplantation. There is no correlation between BK virus load in hematuria and pathological damage at the time of diagnosis. The 2018 Banff Classification for BKVN can better indicate the prognosis of graft.

Total nephroureterocystectomy and urethrectomy due to urothelial carcinoma associated with the BK polyomavirus infection after kidney transplantation: a case report with literature review

Background

BK polyomavirus (BKPyV) infection after kidney transplantation is an important cause of graft failure among kidney transplant recipient and may cause malignant tumor, although the association between BKPyV infection and malignant tumor has been controversial yet.

Case presentation

We report a case of a 39-year-old-male kidney transplantation (KTx) recipient with urine BKPyV replication who developed a graft pelvic tumor with the positive Simian virus 40 large T antigen (SV40 TAg). The patients received a living-related KTx from his 65-year-old mother. A protocol biopsy at 14 months after KTx showed BKPyV-associated nephropathy. Therefore, the dose of immunosuppressants was reduced, resulting in improved BKPyV viremia, but viruria persisted. About 117 months after KTx, urine cytology showed atypical cells suspicious for malignancy. Cystoscopy revealed a tumor on the neck of the bladder. Transurethral resection of the bladder tumor (TUR-BT) was performed; however, the diagnosis of malignancy was not confirmed at that time. Six months after the TUR-BT, urine cytology showed atypical cells definite for malignancy. Computed tomography and retrograde pyelography showed no evidence of urinary tract tumor and metastasis. Subsequently, total nephroureterocystectomy and urethrectomy were performed. Histological examination of the graft ureter revealed a high-grade urothelial carcinoma, with glandular differentiation, pT1. Immunohistochemically, the tumor showed positivities for SV40 TAg and p53, along with increased Ki67 labeling cells were increased. By contrast, nonneoplastic cells were negative for SV40 TAg. At the time of writing the present manuscript, the patient is free from recurrence or residual tumor and being closely monitored without additional therapy, 32 months after the surgery.

Conclusion

The relationship between BKPyV infection after KTx and bladder carcinogenesis remains to be elucidated. However, when the KTx recipients who continue to have BKPyV infection for a long time are treated, the possibility of risk factors for renourinary carcinoma should always be carefully considered.

Advances in BK Virus Complications in Organ Transplantation and Beyond

Reactivation of BK virus (BKV) remains a dreaded complication in immunosuppressed states. Conventionally, BKV is known as a cause for BKV-associated nephropathy and allograft dysfunction in kidney transplant recipients. However, emerging studies have shown its negative impact on native kidney function and patient survival in other transplants and its potential role in diseases such as cancer. Because BKV-associated nephropathy is driven by immunosuppression, reduction in the latter is a convenient standard of care. However, this strategy is risk prone due to the development of donor-specific antibodies affecting long-term allograft survival. Despite its pathogenic role, there is a distinct lack of effective anti-BKV therapeutics. This limitation combined with increased morbidity and health care cost of BKV-associated diseases add to the complexity of BKV management. While summarizing recent advances in the pathogenesis of BKV-associated nephropathy and its reactivation in other organ transplants, this review illustrates the limitations of current and emerging therapeutic options and provides a compelling argument for an effective targeted anti-BKV drug.

Possibility of BKV-Associated Nephropathy in Hospitalized Burn Patients

Although renal failure in burn patients results from some defined reasons, there are various causes which are still unclear. BK virus is a human polyomavirus, which, in case of reactivation, can cause late-onset renal dysfunction and cystitis among immunodeficient patients such as transplant, pregnant, diabetic, and HIV patients. Regarding the related challenges, Polyomavirus BK (BKV), as a ubiquitous virus, is considered as one of the potential threats in the occurrence of Polyomavirus-associated nephropathy (PAN). Hypovolemia, occurring due to the weakness of the immune system, may be regarded as the major reason for the possibility of PAN as a risk factor in burn patients. Accordingly, this study was designed to evaluate the reactivation of BKV as a probable risk factor for renal failure or a problem in the future life of burn patients. This case-control study was conducted from October 2014 to September 2016, during which 270 patients were admitted to the burn unit. The patients were divided into two groups of case and control according to the inclusion criteria, and 20 patients were assigned to each group. The serum samples were first assessed for BKV-IgG and then were quantified by specific quantitative real-time polymerase chain reaction for BKV load. Positive samples were assessed for changes in noncoding regulatory region (NCRR) compared to Archetype strain by PCR sequencing method. Amplified sequences were analyzed for NCRR arrangement while the reactivation was assessed through these changes in NCRR. In both groups, patients were seropositive for BKV-IgG. Eight patients (40%) in the case group and two patients (10%) in the control group were found to be positive for BKV DNA with a load of ≥1000 and ≥100 copies/ml, respectively. There was a significant association between BKV DNA and kidney injury in the case group. The NCRR of DNA-positive samples had a large rearrangement compared to standard strain, but they showed relatively high similarity. Compared with other patients, burn patients are among the most susceptible ones to PAN, which can be considered as a major risk factor in the treatment of burn patients and optimizing their therapy.

Diagnostic utility of urine cytology in detection of decoy cells in renal transplant patients: Report of five cases and review of literature

BK polyoma virus (PV) is one of the commonest post-transplant viral infections, affecting approximately 15% of renal transplantation recipients, leading to graft failure in more than half of cases. The epithelial cells with polyoma viral inclusions in urine cytology specimens are termed "decoy cells" to caution pathologists not to misdiagnose these cells as cancer cells. The infected cells in urinary sediments are characterized by enlarged nucleus, basophilic intranuclear homogenous inclusions, and ground glass chromatin, which may cause diagnostic error in urine cytology. We report five cases of renal transplant patients, in which urine sample was positive for decoy cells. Routine urine cytology of post renal transplant patients with worsening renal function is a useful screening procedure to rule out PV reactivation, before ascertaining transplant rejection. Its cost-effectiveness in addition to the short processing time makes it an invaluable tool in the evaluation of transplant recipients with symptoms suggestive of graft rejection.

BK Polyomavirus-associated nephropathy managed by screening policy in a real-life setting

BACKGROUND

BK polyomavirus-associated nephropathy (PyVAN) is an important complication after kidney transplantation. Prevalence ranges from 1% to 10%, and graft loss occurs in approximately 50% of the cases. There is no effective treatment, so early viral detection with immunosuppression tapering is the current strategy to prevent PyVAN.

AIMS

To verify the frequency of PyVAN in a single center and evaluate the response to immunosuppressive adjustments through graft survival analysis.

METHODS

Retrospective evaluation of a cohort of kidney transplant recipients with biopsy-proven PyVAN, compared with no-PyVAN patients regarding clinical aspects, immunosuppression, and graft survival over at least 2 years.

RESULTS

There were 1404 kidney transplants analyzed in the study period, 58 with biopsy-proven PyVAN. Cumulative incidence was 4.1%. Median time from transplantation to PyVAN diagnosis was 6 (1-41) months. PyVAN was associated with recipient male gender (P = .041) and deceased donation (P = .005). Graft survival was inferior for PyVAN compared to no-PyVAN patients, 81.8% vs 75.2%, P = .019. Thirteen (22.4%) PyVAN patients lost their grafts, nine (15.5%) losses attributed to BKPyV infection. Three patients with BKPyV-associated graft losses were submitted to a successful second kidney transplant, with no evidence of viral replication during follow-up.

CONCLUSION

PyVAN still is an important cause of kidney graft failure. Even though implementing active vigilance and immunosuppressive adjustment, this real-life single-center study demonstrated inferior graft survival in PyVAN patients compared to non-PyVAN.

Conversion From Mycophenolates to Mizoribine Is Associated With Lower BK Virus Load in Kidney Transplant Recipients: A Prospective Study

BACKGROUND

BK virus allograft nephropathy (BKVAN) is a graft-threatening complication after kidney transplantation. Current consensus regarding the prevention of BKVAN is to screen for BK viremia and to treat sustained BK viremia through reducing immunosuppression. This study assessed the effect of conversion from mycophenolates to mizoribine (MZR) on the prevention of BK viremia in kidney transplant recipients.

METHODS

De novo kidney transplant recipients were screened for BK viruria. Sustained high levels of BK viruria (>10⁷ copies/mL) were treated by switching from mycophenolates to MZR. The reduction and clearance of BK viruria and viremia were evaluated.

RESULTS

Fifty kidney transplant recipients with high levels BK viruria were enrolled, including 11 recipients with BK viremia. After 6 months of MZR therapy, only 3 recipients still had high levels of BK viruria. The clearance rate of BK viremia was 100%. One episode of acute rejection occurred (2.0%) and was reversed by steroid administration. The serum uric acid level of the recipients was similar before and after switching to MZR, but the proportion of recipients receiving uric acid-reducing drugs increased significantly after 3 months of MZR therapy (19/50 vs 31/50; P = .02). No new cases of BK viremia were observed after conversion to MZR.

CONCLUSION

Conversion from mycophenolates to MZR in kidney transplant recipients with sustained high levels of BK viruria was associated with reduction of BK viruria and clearance of BK viremia. This may be an effective approach to prevent BK viremia and BKVAN.

ECIL guidelines for the prevention, diagnosis and treatment of BK polyomavirus-associated haemorrhagic cystitis in haematopoietic stem cell transplant recipients

Objectives

To define guidelines for BK polyomavirus (BKPyV)-associated haemorrhagic cystitis (BKPyV-HC) after paediatric and adult HSCT.

Methods

Review of English literature and evidence-based recommendations by expert consensus.

Results

BKPyV-HC occurs in 8%-25% of paediatric and 7%-54% of adult recipients undergoing allogeneic HSCT. Diagnosis requires the triad of cystitis, macro-haematuria and high urine BKPyV loads >7 log10 copies/mL, and exclusion of other relevant aetiologies. BKPyV viraemia is frequent and may serve as a more specific semiquantitative follow-up marker. No randomized controlled trials are available to inform antiviral prophylaxis or treatment. However, hyper-hydration and/or bladder irrigation showed limited prophylactic value. Fluoroquinolones are not effective for prophylaxis or treatment, but rather increase antibiotic resistance. Hyperbaric oxygen or fibrin glue is marginally effective based on small case series from correspondingly equipped centres. Although cidofovir has been reported to improve and/or reduce BKPyV viraemia or viruria, the current data do not support its regular use.

Conclusions

BKPyV-HC remains a disabling unmet clinical need in HSCT that requires novel approaches supported by proper clinical trials.

Development and validation of multiplex real-time PCR assays for rapid detection of cytomegalovirus, Epstein-Barr virus, and polyomavirus BK in whole blood from transplant candidates

Transplant recipients are more susceptible to bacterial and viral infections. Cytomegalovirus (CMV), Epstein-Barr virus (EBV), and polyomavirus BK (BK) are risk factors for graft dysfunction. All three of them are latent viruses that can cause serious disease in immunocompromised patients. Mainly qualitative PCR tests are required for diagnosis and quantitative monitoring, which are used to follow the response to transplantation. We developed a multiplex real-time PCR (qPCR) method to detect these viruses during blood screenings of transplant recipients. We also validated analytical and clinical performance tests using the developed multiplex qPCR. The limit of detection (LOD) was 100, 125, and 183 copies/ml for CMV, EBV, and BK, respectively. These results had high linearity (R² = 0.997) and reproducibility (CV range, 0.95-2.38%, 0.52-3.32%, and 0.31-2.45%, respectively). Among 183 samples, we detected 8 samples that were positive for CMV, while only 6 were positive for EBV, and 3 were positive for BK. Therefore, the viral infection prevalence in transplant candidates was 4.40% for CMV, 3.29% for EBV, and 1.64% for BK. This multiplex qPCR method should be used widely for diagnosing and monitoring latent viral infections in transplant recipients.

The Banff Working Group Classification of Definitive Polyomavirus Nephropathy: Morphologic Definitions and Clinical Correlations

Polyomavirus nephropathy (PVN) is a common viral infection of renal allografts, with biopsy-proven incidence of approximately 5%. A generally accepted morphologic classification of definitive PVN that groups histologic changes, reflects clinical presentation, and facilitates comparative outcome analyses is lacking. Here, we report a morphologic classification scheme for definitive PVN from the Banff Working Group on Polyomavirus Nephropathy, comprising nine transplant centers in the United States and Europe. This study represents the largest systematic analysis of definitive PVN undertaken thus far. In a retrospective fashion, clinical data were collected from 192 patients and correlated with morphologic findings from index biopsies at the time of initial PVN diagnosis. Histologic features were centrally scored according to Banff guidelines, including additional semiquantitative histologic assessment of intrarenal polyomavirus replication/load levels. In-depth statistical analyses, including mixed effects repeated measures models and logistic regression, revealed two independent histologic variables to be most significantly associated with clinical presentation: intrarenal polyomavirus load levels and Banff interstitial fibrosis ci scores. These two statistically determined histologic variables formed the basis for the definition of three PVN classes that correlated strongest with three clinical parameters: presentation at time of index biopsy, serum creatinine levels/renal function over 24 months of follow-up, and graft failure. The PVN classes 1-3 as described here can easily be recognized in routine renal biopsy specimens. We recommend using this morphologic PVN classification scheme for diagnostic communication, especially at the time of index diagnosis, and in scientific studies to improve comparative data analysis.

Polyoma virus nephropathy in kidney transplantation

BK virus (BKV) is a polyomavirus that is able to cause renal dysfunction in transplanted grafts via BK virus-associated nephritis (BKVAN). This condition was mis-diagnosed in the past due to clinical and histopthological similarities with acute rejection. Due to the prevalence of the virus in the population, it is an important pathogen in this context, and so it is important to understand how this virus functions and its' relationship with the pathogenesis of BKVN. Screening for BKV often reveals viruria and/or viremia, which then manifests as BKVN, which can be asymptomatic or result in clinical features namely renal dysfunction. The pathogenesis of BKV infection is still unclear and needs to be further investigated; nevertheless there are a variety of hypotheses that indicate that there are a host of factors that play important roles. Treatments for BKVAN include a reduction in immunosuppression, the use of antiviral therapy or the combination of both treatment options.

Inhibition of Retrograde Transport Limits Polyomavirus Infection In Vivo

PyVs can cause significant morbidity and mortality in immunocompromised individuals. No clinically efficacious anti-PyV therapeutic agents are available. A recently identified inhibitor of retrograde transport, Retro-2^cycl, blocks movement of PyV virion-containing vesicles from early endosomes to the endoplasmic reticulum, an early step in the PyV life cycle. Retro-2^cycl and its derivatives have been shown to inhibit infection by human PyVs in tissue culture. Here, we demonstrate that a derivative of Retro-2^cycl, Retro-2.1, reduces infection by MuPyV in the kidneys of acutely infected mice. Mimicking the common clinical scenario of PyV resurgence, we further show that MuPyV levels increase in the kidneys of immunocompromised, persistently infected mice and that this increase is inhibited by Retro-2.1. These data provide the first evidence for control of a natural PyV infection in vivo by administration of an inhibitor of retrograde transport.

Polyomaviruses (PyVs) silently infect most humans, but they can cause life-threatening diseases in immunocompromised individuals. The JC polyomavirus (JCPyV) induces progressive multifocal leukoencephalopathy, a severe demyelinating disease in multiple sclerosis patients receiving immunomodulatory therapy, and BK polyomavirus (BKPyV)-associated nephropathy is a major cause of kidney allograft failure. No effective anti-PyV agents are available. Several compounds have been reported to possess anti-PyV activity in vitro, but none have shown efficacy in clinical trials. Productive PyV infection involves usurping the cellular retrograde vesicular transport pathway to enable endocytosed virions to navigate to the endoplasmic reticulum where virion uncoating begins. Compounds inhibiting this pathway have been shown to reduce infection by simian virus 40 (SV40), JCPyV, and BKPyV in tissue culture. In this study, we investigated the potential of Retro-2.1, a retrograde transport inhibitor, to limit infection by mouse polyomavirus (MuPyV) in vivo. We found that Retro-2.1 significantly reduced MuPyV levels in the kidney during acute infection without affecting renal function or the MuPyV-specific CD8 T cell response. To approximate the clinical setting of PyV resurgence in immunocompromised hosts, we showed that antibody-mediated depletion of T cells in persistently infected mice elevated MuPyV levels in the kidney and that Retro-2.1 blunted this increase in virus levels. In summary, these data indicate that inhibition of retrograde vesicular transport in vivo controls infection in a natural PyV mouse model and supports development of these compounds as potential therapeutic agents for individuals at risk for human PyV-associated diseases.

IMPORTANCE PyVs can cause significant morbidity and mortality in immunocompromised individuals. No clinically efficacious anti-PyV therapeutic agents are available. A recently identified inhibitor of retrograde transport, Retro-2^cycl, blocks movement of PyV virion-containing vesicles from early endosomes to the endoplasmic reticulum, an early step in the PyV life cycle. Retro-2^cycl and its derivatives have been shown to inhibit infection by human PyVs in tissue culture. Here, we demonstrate that a derivative of Retro-2^cycl, Retro-2.1, reduces infection by MuPyV in the kidneys of acutely infected mice. Mimicking the common clinical scenario of PyV resurgence, we further show that MuPyV levels increase in the kidneys of immunocompromised, persistently infected mice and that this increase is inhibited by Retro-2.1. These data provide the first evidence for control of a natural PyV infection in vivo by administration of an inhibitor of retrograde transport.

[Concurrence of acute graft rejection and polyomavirus nephropathy: A clinical case]

The paper describes a case of diagnosing acute renal graft rejection concurrent with polyomavirus nephropathy. Histochemical and electron microscopic methods were used to examine biopsy specimens, which showed morphological changes occurring in the allograft, the ultrastructural characteristics of polyomavirus and the features of its spread in kidney tissue structures.

[Clinical and morphological signs of viral damage to a kidney transplant]

AIM

Тo compare morphological changes and results of immunohistochemical (IHC) identification of viruses (polyomaviruses, adenoviruses, and herpesviruses) in the biopsy specimens with their clinical manifestations in recipients of renal transplants.

MATERIAL AND METHODS

Morphological and IHC studies were conducted using 71 needle renal transplant biopsy specimens from patients in the study group and 10 renal biopsy specimens from those in the control group. A number of clinical indicators were estimated.

RESULTS

IHC examination revealed the expression of adenoviral antigens more commonly in patients with posttransplant nephritis than in recipients without nephritis or in control individuals (p<0.05). The association of patient age and time after kidney transplantation with the severity of viral damage was confirmed: graft loss in children occurred within the first months of surgery (p<0.05). Polyomavirus was detected by PCR in patients with the morphological patterns of polyomavirus nephropathy. Determination of HSV-1 and HSV-2 in the biopsy specimens showed no significant associations with morphological changes.

CONCLUSION

By taking into account a variety of factors that influence the development of viral nephritis, morphological and IHC examinations should be combined with evaluation of clinical findings.

Surgical Pathologic Diagnosis

Surgical pathology results can play a crucial role in the management of immunocompromised patients. Here we highlight factors that differ between immunocompromised and immunocompetent hosts, such as variation in inflammatory response. Conditions that are covered include drug reactions, disease within solid organ allografts, immune reconstitution inflammatory syndrome, specific immunodeficiency syndromes, neoplasms related to viral infections, and viral, bacterial, fungal, and parasitic infections. Special techniques including immunohistochemistry, in situ hybridization and molecular detection of pathogen nucleic acid from formalin-fixed, paraffin-embedded tissue are discussed.

Polyomavirus Nephropathy in Kidney Transplantation

Polyomavirus nephropathy has become an important complication in kidney transplantation, with a prevalence of 1% to 8%. Unfortunately, the risk factors for polyomavirus nephropathy and renal allograft loss are not well defined. The definitive diagnosis is made through assessment of a kidney transplant biopsy. Recently, noninvasive urine and serum markers have been used to assist in polyomavirus nephropathy diagnosis and monitoring. Primary treatment is immunosuppression reduction, but must be balanced with the risks of rejection. No antiviral treatments for polyomavirus nephropathy have been approved by the Food and Drug Administration. Although cidofovir has shown in vitro activity against murine polyomaviruses, and has been effective in some patients, it is associated with significant nephrotoxicity. Graft loss due to polyomavirus nephropathy should not be a contraindication to retransplantation; however, experience is limited. This review presents potential risk factors, screening, diagnostic and monitoring methods, therapeutic management, and retransplantation experience for polyomavirus nephropathy.

Characterization of Immunodominant BK Polyomavirus 9mer Epitope T Cell Responses

Uncontrolled BK polyomavirus (BKPyV) replication in kidney transplant recipients (KTRs) causes polyomavirus-associated nephropathy and allograft loss. Reducing immunosuppression is associated with clearing viremia and nephropathy and increasing BKPyV-specific T cell responses in most patients; however, current immunoassays have limited sensitivity, target mostly CD4(+) T cells, and largely fail to predict onset and clearance of BKPyV replication. To characterize BKPyV-specific CD8(+) T cells, bioinformatics were used to predict 9mer epitopes in the early viral gene region (EVGR) presented by 14 common HLAs in Europe and North America. Thirty-nine EVGR epitopes were experimentally confirmed by interferon-γ enzyme-linked immunospot assays in at least 30% of BKPyV IgG-seropositive healthy participants. Most 9mers clustered in domains, and some were presented by more than one HLA class I, as typically seen for immunodominant epitopes. Specific T cell binding using MHC class I streptamers was demonstrated for 21 of 39 (54%) epitopes. In a prospective cohort of 118 pediatric KTRs, 19 patients protected or recovering from BKPyV viremia were experimentally tested, and 13 epitopes were validated. Single HLA mismatches were not associated with viremia, suggesting that failing immune control likely involves multiple factors including maintenance immunosuppression. Combining BKPyV load and T cell assays using immunodominant epitopes may help in evaluating risk and reducing immunosuppression and may lead to safe adoptive T cell transfer.

BK Polyomavirus Replication in Renal Tubular Epithelial Cells Is Inhibited by Sirolimus, but Activated by Tacrolimus Through a Pathway Involving FKBP-12

BK polyomavirus (BKPyV) replication causes nephropathy and premature kidney transplant failure. Insufficient BKPyV-specific T cell control is regarded as a key mechanism, but direct effects of immunosuppressive drugs on BKPyV replication might play an additional role. We compared the effects of mammalian target of rapamycin (mTOR)- and calcineurin-inhibitors on BKPyV replication in primary human renal tubular epithelial cells. Sirolimus impaired BKPyV replication with a 90% inhibitory concentration of 4 ng/mL by interfering with mTOR-SP6-kinase activation. Sirolimus inhibition was rapid and effective up to 24 h postinfection during viral early gene expression, but not thereafter, during viral late gene expression. The mTORC-1 kinase inhibitor torin-1 showed a similar inhibition profile, supporting the notion that early steps of BKPyV replication depend on mTOR activity. Cyclosporine A also inhibited BKPyV replication, while tacrolimus activated BKPyV replication and reversed sirolimus inhibition. FK binding protein 12kda (FKBP-12) siRNA knockdown abrogated sirolimus inhibition and increased BKPyV replication similar to adding tacrolimus. Thus, sirolimus and tacrolimus exert opposite effects on BKPyV replication in renal tubular epithelial cells by a mechanism involving FKBP-12 as common target. Immunosuppressive drugs may therefore contribute directly to the risk of BKPyV replication and nephropathy besides suppressing T cell functions. The data provide rationales for clinical trials aiming at reducing the risk of BKPyV replication and disease in kidney transplantation.

[Morphological diagnosis of viral damage to a kidney transplant]

Due to the development of organ transplantation and its accompanying immunosuppression, recent years have been marked by the higher incidence of opportunistic viral infections that are of considerable importance among posttransplantation complications. A variety of viral infections, the possibility of their concomitant or subtle course, and the ability to cause life-threatening complications in recipients make relevant the description of existing diagnostic methods. The article summarizes the data available in the literature on the etiology, clinical symptoms, and morphological manifestations of viral infections, such as polyomaviruses, adenoviruses, herpesviruses, including HSV-1, HSV-2, cytomegalovirus (CMV), and Epstein-Barr virus. It describes the principles of differential diagnosis of kidney transplant damage caused by these viruses and that with acute cellular and humoral rejection, which plays an important role due to opposite approaches to treating these diseases.

Simultaneous immunostaining with anti-S100P and anti-SV40 antibodies revealed the origin of BK virus-infected decoy cells in voided urine samples

BACKGROUND

Methods for determining the origin of BK virus (BKV)-infected cells (decoy cells) in clinical urine samples have not been established although they could enhance the diagnosis of BKV infection in immunocompromised patients.

METHODS

We performed simultaneous immunostaining with anti-S100P (a urothelial marker) and anti-SV40 antibodies in 66 clinical urine samples exhibiting SV40 positivity and a decoy-cell appearance on Papanicolaou staining. The clinical voided urine samples included seven cases of renal transplantation, 47 cases of cancer therapy and 12 cases of non-neoplastic disease. SurePath(™) liquid-based cytology was used for the urine samples.

RESULTS

BKV-infected cells were categorized as SV40(+)/S100P(+) and SV40 (+)/S100p(-). SV40(+)/S100P(-) cells were found in 55 cases (83.4%); nine cases (13.6%) carried both SV40(+)/S100P(-) and SV40(+)/S100P(+) cells. The former were identified as BKV infection in renal tubules and the latter in both the renal tubules and urothelial epithelia. The remaining two cases (3.0%) had only SV40(+)/S100P(+) cells of urothelial origin.

CONCLUSION

Simultaneous immunostaining with anti-S100P and anti-SV40 is a useful method for determining the origin of BKV-infected cells in clinical urine samples from immunocompromised patients such as renal transplantation recipients.

Association of interferon gamma gene polymorphisms with BK virus infection among Hispanic renal allograft recipients

BACKGROUND

BK virus nephropathy is one of the most common viral infections that affect up to 10% of renal transplant recipients (RTRs), causing allograft dysfunction and graft loss. Interferon-gamma (IFN-γ) gene polymorphisms have been associated with parvovirus B19, hepatitis C virus, HIV-1/AIDS infection, cytomegalovirus viremia, and disease. IFN-γ is known to have potent inhibitory effects on BK virus gene expression, both at the level of transcription and translation.

METHODS

It was investigated whether IFN-γ polymorphisms are associated with BKV infection. Genotyping of four single-nucleotide polymorphisms located in the IFN-γ gene were performed on DNA collected from a total of 251 RTRs (71 RTRs with BKV infection and 180 without BKV infection).

RESULTS

Analysis of the results showed that IFN-γ (rs12369470) CC genotype was significantly associated with susceptibility to BKV infection (OR: 2.9, 95% CI: 1.29-6.44, P=0.007) while the IFN-γ +874 (rs2435061) TT and (rs2406918) CC genotypes appear to be markers for protection against BKV infection (OR: 0.29, 95% CI: 0.1-0.83, P=0.01 for rs245061; OR: 0.61, 95% CI: 0.4-0.94, P=0.02 for rs24069718). A haplotype analysis using the combination of rs2435061-rs2406918-rs2870953 showed that the A-G-T haplotype was associated with a significantly reduced risk for BKV infection (OR: 0.43, 95% CI: 0.25-0.73, P=0.001).

CONCLUSION

Polymorphisms in the IFN-γ gene may confer certain protection or predisposition for BKV infection.

Immunophenotyping in BK virus allograft nephropathy distinct from acute rejection

Differentiating BK virus nephropathy (BKVN) from acute rejection (AR) is crucial in clinical practice, as both of them have interstitial inflammation in the grafts. The purpose of the study is to describe the inflammatory cellular constituents of BKVN and to determine the clinical utility of immunophenotyping findings in distinguishing BKVN from AR. In addition, the expression of the HLA-DR was investigated. Sixty-five renal allograft recipients were included in this study, including 22 cases of BKVN, 31 cases of AR, and 12 cases of stable allograft. Immunostaining for infiltrating lymphocytes showed that the number of CD20 cells (P < 0.001) and the percentages of CD3 (P < 0.001), CD4 (P = 0.004), CD8 (P = 0.005), and CD20 (P = 0.002) cells were all significantly different between BKVN and AR. Moreover, there were no statistically significant differences in tubule cell HLA-DR expression (P = 0.156). This observation suggests that the number of CD20 cells and the percentages of CD3, CD4, CD8, and CD20 cells in renal biopsies would aid the distinction between BKVN and AR. On the other hand, the presence of HLA-DR upregulation may not only be specific for acute rejection but also be a response to BKVN.

The human polyomaviruses: from orphans and mutants to patchwork family

For almost 40 years, polyomavirus JC and BK were the only known human polyomaviruses but in the last 7 years, increased interest and innovative molecular screening techniques have led to the identification of 10 previously unknown polyomaviruses in humans. Two of these, Merkel cell polyomavirus and Trichodysplasia spinulosa polyomavirus, have also been found to cause disease in immunocompromised patients. Seroprevalence studies indicate that human polyomaviruses are transmitted independently of one another in humans and carry different risks of exposure and reexposure throughout life. The potential coexistence of 12 or more different polyomavirus species in the same host and possibly even in the same organ raises the question of potential interactions. Careful review of polyomavirus biology may facilitate new discoveries concerning these formerly underestimated viral agents and their influence on human health.

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.

Role of cell-type-specific endoplasmic reticulum-associated degradation in polyomavirus trafficking

BK polyomavirus (BKPyV) is a widespread human pathogen that establishes a lifelong persistent infection and can cause severe disease in immunosuppressed patients. BKPyV is a nonenveloped DNA virus that must traffic through the endoplasmic reticulum (ER) for productive infection to occur; however, it is unknown how BKPyV exits the ER before nuclear entry. In this study, we elucidated the role of the ER-associated degradation (ERAD) pathway during BKPyV intracellular trafficking in renal proximal tubule epithelial (RPTE) cells, a natural host cell. Using proteasome and ERAD inhibitors, we showed that ERAD is required for productive entry. Altered trafficking and accumulation of uncoated viral intermediates were detected by fluorescence in situ hybridization and indirect immunofluorescence in the presence of an inhibitor. Additionally, we detected a change in localization of partially uncoated virus within the ER during proteasome inhibition, from a BiP-rich area to a calnexin-rich subregion, indicating that BKPyV accumulated in an ER subcompartment. Furthermore, inhibiting ERAD did not prevent entry of capsid protein VP1 into the cytosol from the ER. By comparing the cytosolic entry of the related polyomavirus simian virus 40 (SV40), we found that dependence on the ERAD pathway for cytosolic entry varied between the polyomaviruses and between different cell types, namely, immortalized CV-1 cells and primary RPTE cells.

Role of cell-type-specific endoplasmic reticulum-associated degradation in polyomavirus trafficking

BK polyomavirus (BKPyV) is a widespread human pathogen that establishes a lifelong persistent infection and can cause severe disease in immunosuppressed patients. BKPyV is a nonenveloped DNA virus that must traffic through the endoplasmic reticulum (ER) for productive infection to occur; however, it is unknown how BKPyV exits the ER before nuclear entry. In this study, we elucidated the role of the ER-associated degradation (ERAD) pathway during BKPyV intracellular trafficking in renal proximal tubule epithelial (RPTE) cells, a natural host cell. Using proteasome and ERAD inhibitors, we showed that ERAD is required for productive entry. Altered trafficking and accumulation of uncoated viral intermediates were detected by fluorescence in situ hybridization and indirect immunofluorescence in the presence of an inhibitor. Additionally, we detected a change in localization of partially uncoated virus within the ER during proteasome inhibition, from a BiP-rich area to a calnexin-rich subregion, indicating that BKPyV accumulated in an ER subcompartment. Furthermore, inhibiting ERAD did not prevent entry of capsid protein VP1 into the cytosol from the ER. By comparing the cytosolic entry of the related polyomavirus simian virus 40 (SV40), we found that dependence on the ERAD pathway for cytosolic entry varied between the polyomaviruses and between different cell types, namely, immortalized CV-1 cells and primary RPTE cells.

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.

Urinary decoy cell grading and its clinical implications

BACKGROUND

Examination of urine for decoy cells (DCs) is a useful screening test for polyomavirus (PV) activation. We explored the significance of the amount of DCs in persistent shedding, PV nephropathy and acute rejection.

METHODS

A case-controlled study was performed in 88 renal allograft patients who had DCs detected at least once in four or more urine samples.

RESULTS

Fifty one patients were classified into the high-grade shedding group (HG) and 37 patients into the low-grade shedding group (LG) according to DC shedding (≥10 or <10 DCs/10 high power field [HPF]). DC shedding of more than three consecutive months was significantly more prevalent in the HG as compared with their LG counterparts (p<0.0001). Urinary DCs were present for more than one year in 29.4% of the HG and 8.1% of the LG. Real-time polymerase chain reaction for PV was higher in both urine (51.4% vs. 11.1%) and plasma (9.1% vs. 0%) of the HG than the LG. The prevalence of PV nephropathy was higher in the HG than the LG (p=0.019). However, there was no significant difference in the prevalence of acute rejection.

CONCLUSIONS

Shedding of ≥10 DCs/10 HPF is associated with sustained shedding, polymerase chain reaction positivity and PV nephropathy, but not a predictor of acute rejection.

Renal dysfunction by BK virus infection is correlated with activated T cell level in renal transplantation

BACKGROUND

BK virus (BKV) is known to be associated with nephropathy. Here, we investigated the relationships between BKV levels, T-cell activation, and kidney function in kidney transplant recipients.

MATERIALS AND METHODS

In renal transplant patients and controls, urine BKV levels were detected by quantitative real-time PCR, and the percentage of activated T lymphocytes in blood was determined by flow cytometry. The correlations between viral load, activated T cell percentage, and renal function were determined.

RESULTS

Urine BKV viral loads and the activated T cell percentage were significantly elevated in transplant recipients. Correlational analysis indicated that transplant recipients that had BKV levels of more than 10(6) copies/mL and an activated T lymphocyte percentage of less than 20% were likely to have poor renal function.

CONCLUSIONS

Urine BKV levels and the percentage of activated T lymphocytes can be used as clinical indices to optimize the dosage of immunosuppressive drugs.

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.

Quantification of BK viral load in asymptomatic renal allograft recipients

INTRODUCTION

Polyoma BK virus (BKV) has recently been identified to cause renal allograft dysfunction, which manifests as polyomavirus-associated nephropathy (PVAN). However, the presence and level of BKV DNA in renal allograft patients with good and stable renal function have remained undetermined.

METHODS

In this prospective study, serum samples were collected from a total of 45 renal allograft recipients with serum creatinine <155 μmol/L. In 17 patients, whose duration of transplantation was under 2 years, samples were collected at 3-4-month intervals for up to 2 years after transplantation. BK viral load was quantified using quantitative polymerase chain reaction (Q-PCR).

RESULTS

The BK viral load in asymptomatic renal allograft recipients was independent of the duration of transplantation and did not correlate with allograft function. The mean (± SD) level of viremia was 552.80 ± 1931.00 genome copies/mL, with 92.9% of patients having low levels of viremia corresponding to <1 × 10(3) copies/mL. In contrast, patients with proven PVAN had levels in the range of 10(6) copies/mL.

CONCLUSIONS

The prevailing BK viral load in asymptomatic renal allograft patients is quantifiably low. Our findings may guide optimal immunosuppressive modulation in PVAN cases, where judicious manipulation of immunosuppression is required without inciting allograft rejection.