Monitoring the progress of BK virus associated nephropathy in renal transplant recipients

Intraepithelial Inclusions on Urinalysis Screening among COVID-19 Cases: Are they Covicytes?-A Hospital-Based Cohort Study with Narrative Review

Title

"Intraepithelial inclusions on urinalysis screening among COVID-19 cases: Are they Covicytes?-A hospital-based cohort study with narrative review."

Context

Coronavirus disease 2019 (COVID-19)-associated delayed acute kidney injury (AKI) is often reported in subsequent waves of the pandemic. Early intervention and regular follow-up influence the outcome and inhibit progression into chronic kidney disease (CKD). This is the first study to identify urinary cytomorphological abnormalities (Covicytes) and predict COVID-19-associated delayed AKI with a narrative review of the possible etiologies for intraepithelial inclusions.

Settings and Design

A hospital-based cohort study with a narrative review.

Material and Methods

Screening urinalysis to assess the cytomorphology of epithelial cells (ECs) and inclusions in Leishman and periodic acid-Schiff (PAS)-stained smears by two independent pathologists was performed in reverse transcriptase polymerase chain reaction (RT-PCR)-confirmed COVID-19 cases at a tertiary care center.

Statistical Analysis

Basic statistical tools were used for descriptive statistical analysis, and data were expressed in mean, proportion, and frequency.

Results

Cytomorphological abnormalities (48/188) were predominant among adult males. Leukocyturia (39/48) with positive nitrite test (28/39), high ECs (27/48) and squamous cell-to-tubular EC (SC:TEC) ratio, intraepithelial intracytoplasmic inclusions predominantly in TECs (Covicytes), and multiple well-visualized, perinuclear PAS-negative neutrophilic vacuoles (17/39) were found. The association with preexisting diabetes (31/48), hypertension (10/48), and disease severity was noted.

Conclusions

This study reported COVID-19-associated urinary cytomorphological abnormalities and interesting unique inclusions (Covicytes) that may be a result of underlying inflammatory changes, reactive hyperplasia, degenerative changes, or defective endocytosed vacuoles. The possible etiologies for renal inclusions were reviewed. We recommend compulsory baseline and follow-up urinary cytology screening for all COVID-19-suspected patients to detect and predict delayed AKI before clinical and biochemical manifestation during disease endemicity.

Antivirals against human polyomaviruses: Leaving no stone unturned

Human polyomaviruses (HPyVs) encompass more than 10 species infecting 30%-90% of the human population without significant illness. Proven HPyV diseases with documented histopathology affect primarily immunocompromised hosts with manifestations in brain, skin and renourinary tract such as polyomavirus-associated nephropathy (PyVAN), polyomavirus-associated haemorrhagic cystitis (PyVHC), polyomavirus-associated urothelial cancer (PyVUC), progressive multifocal leukoencephalopathy (PML), Merkel cell carcinoma (MCC), Trichodysplasia spinulosa (TS) and pruritic hyperproliferative keratinopathy. Although virus-specific immune control is the eventual goal of therapy and lasting cure, antiviral treatments are urgently needed in order to reduce or prevent HPyV diseases and thereby bridging the time needed to establish virus-specific immunity. However, the small dsDNA genome of only 5 kb of the non-enveloped HPyVs only encodes 5-7 viral proteins. Thus, HPyV replication relies heavily on host cell factors, thereby limiting both, number and type of specific virus-encoded antiviral targets. Lack of cost-effective high-throughput screening systems and relevant small animal models complicates the preclinical development. Current clinical studies are limited by small case numbers, poorly efficacious compounds and absence of proper randomized trial design. Here, we review preclinical and clinical studies that evaluated small molecules with presumed antiviral activity against HPyVs and provide an outlook regarding potential new antiviral strategies.

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.

The therapeutic effect of switching from tacrolimus to low-dose cyclosporine A in renal transplant recipients with BK virus nephropathy

Background: There is no effective therapy for BK virus (BKV) nephropathy (BKVN). Cyclosporine A (CsA) has a lower immunosuppressive effect than tacrolimus. In vitro studies have shown that CsA inhibits BKV replication. The present study aimed to evaluate the effectiveness of switching from tacrolimus to low-dose CsA in renal transplant recipients with BKVN. Methods: Twenty-four patients diagnosed with BKVN between January 2015 and December 2016 were included. Tacrolimus was switched to low-dose CsA, and patients were followed for 24 months. Primary end points were BKV clearance in blood and graft. Secondary end points were urine specific gravity, serum creatinine, and graft loss. Results: The viremia in all patients cleared at a mean of 2.7 ± 2.0 months after switching to CsA. Urine specific gravity at 3 months after switching to CsA increased significantly compared with that at diagnosis (P=0.002). The timing and trend of urine specific gravity increase was consistent with the timing and trend of blood and urine viral load decrease. Repeated biopsies at a median of 11.2 months (range: 9.1-12.5 months) after switching to CsA showed that 8 patients (42.1%) were negative for BKV, and 11 patients (58.9%) had a decrease in BKV load (P<0.001). There was no statistical difference in the serum creatinine level between the time of diagnosis and 24 months of CsA therapy (P=0.963). The graft survival rate was 100%. Only two patients (8.3%) suffered from acute rejection. Conclusion: Switching from tacrolimus to low-dose CsA may be an effective therapy for BKVN.

Infection-Induced Kidney Diseases

Infection induced kidney diseases are of concern for clinicians because timely detection and treatment of infections may cure or limit the extent of injury inflicted by microorganisms causing the infections. Infections can cause kidney injury by either direct invasion, or indirectly by immune mediated mechanisms, which manifest as post-infectious glomerulonephritis, or infection-related glomerulonephritis. Clinical manifestations may be acute or chronic depending on the microorganisms, endemic/epidemic nature and source of infection. All microbials virus, bacteria, mycobacteria, fungus, and protozoa have been implicated in kidney diseases either causing direct kidney injuries or immune-mediated injuries. Infection control practices in large parts of world is limited by poverty, social behavior, high population density, deforestation, inadequate access to safe drinking water, and poor health care facilities. Although, antimicrobials and vaccinations have successfully eradicated and cured many infectious diseases; however injudicious antimicrobial use and emergence of resistant organisms complicated the disease severity like secondary renal amyloidosis with chronic persistent infection. Re-emergence of various infections has been a recent pattern in developed world leading to uncertain diagnostic challenges, and association with kidney diseases.

BK Virus Infection in Kidney Transplantation: A Case for Early Intervention

The prognosis for renal allograft survival in a patient with BK virus–associated nephropathy is distressing because nearly 50% of affected grafts are lost. With these statistics in mind, attempting clinical intervention before BK virus disease develops seems appropriate. Noninvasive screening tools such as tests to detect decoy cells in urine can enable diagnosis of BK viral infection in its early stages. Although it is not entirely clear which patients with BK infection will have BK disease develop, it may be possible to intervene in this early warning period to prevent the further development of BK virus–associated nephropathy. We present a case of a 50-year-old man in whom asymptomatic BK viruria developed 6 weeks after he received a non-HLA matched kidney from a deceased donor. This BK viruria was accompanied, subsequently, by an unexplained increase in serum creatinine level 2 months after transplantation. Following a change in his immunosuppressive regimen as therapy for presumed renal allograft dysfunction associated with BK viral infection, the decoy cells in his urine disappeared and his creatinine levels stabilized.

BK Virus Nephropathy in Heart Transplant Recipients

Polyomavirus-associated nephropathy (PVAN) has become an important cause of kidney failure in kidney transplant recipients. PVAN is reported to affect 1% to 7% of kidney transplant recipients, leading to premature transplant loss in approximately 30% to 50% of diagnosed cases. PVAN occurring in the native kidneys of solid-organ transplant recipients other than kidney only recently has been noted. We report 2 cases of PVAN in heart transplant recipients, which brings the total of reported cases to 7. We briefly review the literature on the hypothesized causes of PVAN in kidney transplant recipients and comment on whether these same mechanisms also may cause PVAN in other solid-organ transplant recipients. PVAN should be considered in the differential diagnosis when evaluating worsening kidney function. BK viremia surveillance studies of nonkidney solid-organ recipients should be conducted to provide data to assist the transplantation community in deciding whether regular monitoring of nonkidney transplant recipients for BK viremia is indicated.

Antivirals for the treatment of polyomavirus BK replication

Antiviral drugs with specific activity against polyomavirus replication have not been developed in the past. This deficiency has become fully apparent with the emergence of polyomavirus-associated nephropathy in kidney-transplant recipients, with a prevalence rate of up to 10%. In most cases, high BK virus replication in tubular epithelial cells causes significant cytopathology, leading to permanently impaired renal allograft function and return to hemodialysis within 6-60 months. In 5-10% of allogenic bone marrow/hematopoietic stem cell transplant recipients, high-level BK virus replication in the ureter/bladder mucosa has been associated with postengraftment hemorrhagic cystitis, which appears to involve significant immunopathology. Thus, in view of the increasing clinical need, a number of drugs have been studied in small case series. We review the antiviral strategies explored to date and specifically discuss available in vivo and in vitro data on cidofovir, leflunomide, fluoroquinolones and intravenous immunoglobulins, regarding mechanism, administration, dosing and outcome and provide a perspective on future therapy options.

Polyomavirus-associated nephropathy

Polyomaviruses BK and JC are ubiquitous viruses with high seroprevalence rates in general population. Following primary infection, polyomaviruses BK and JC persist latently in different sites, particularly in the reno-urinary tract. Reactivation from latency may occur in normal subjects with asymptomatic viruria, while it can be associated to nephropathy (PVAN) in kidney transplantat recipients. PVAN may occur in 1%-10% of renal transplant patients with loss of the transplanted organ in 30% up to 80% of the cases. Etiology of PVAN is mainly attributable to BK virus, although approximately 5% of the cases may be due to JC. Pathogenesis of PVAN is still unknown, although viral replication and the lack of immune control play a major role. Immunosuppression represents the condicio sine qua non for the development of PVAN and the modulation of anti-rejection treatment represents the first line of intervention, given the lack of specific antiviral agents. At moment, an appropriate immunemodulation can only be accomplished by early identification of viral reactivacation by evaluation of polyomavirus load on serum and/or urine specimens, particularly in the first year post-trasplantation. Viro-immunological monitoring of specific cellular immune response could be useful to identify patients unable to recover cellular immunity posttransplantation, that are at higher risk of viral reactivation with development of PVAN. Herein, the main features of polyomaviruses BK and JC, biological properties, clinical characteristics, etiopathogenesis, monitoring and diagnosing of PVAN will be described and discussed, with an extended citation of related relevant literature data.

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.

Treatment of polyomavirus infection in kidney transplant recipients: a systematic review

BACKGROUND.: Polyomavirus-associated nephropathy (PVAN) is an important cause of kidney graft loss but there is no consensus on its management. This study aimed to systematically document all published treatments for PVAN to determine the most effective therapy. METHODS.: A computerized search in MEDLINE, EMBASE, and Cochrane databases (1950-2008) was performed. References from review articles and published abstracts from the American Transplant Congress (2005-2008) were also included. Study selection criteria included (a) population: adult (>18 years) kidney-only, primary or repeat renal transplant recipients; (b) setting: polyoma viruria, viremia or biopsy-proven PVAN or both; and (c) treatment: immunosuppression reduction alone or with adjuvant agents. The primary outcome was graft failure rate, and secondary outcomes included acute rejection rate, elimination of viruria and viremia, graft function, patient survival, and adverse events. RESULTS.: Of 555 identified citations, 40 studies examining the effect of immunosuppression reduction alone or in combination with cidofovir, leflunomide, intravenous immunoglobulin, or ciprofloxacin were included for appraisal. Pooled results found a death-censored graft loss rate of 8/100 patient-years for immunosuppression reduction alone and 8 and 13/100 patient-years for the addition of cidofovir or leflunomide, respectively. CONCLUSIONS.: There does not seem to be a graft survival benefit of adding cidofovir or leflunomide to immunosuppression reduction for the management of PVAN. However, the evidence base is poor and highlights the urgent need for adequately powered randomized trials to define the optimal treatment of this important condition.

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.

Polyomavirus BK replication dynamics in vivo and in silico to predict cytopathology and viral clearance in kidney transplants

Fast BK virus (BKV) replication in renal tubular epithelial cells drives polyomavirus-BK-associated nephropathy (PVAN) to premature kidney transplant (KT) failure. BKV also replicates in urothelial cells, but remains asymptomatic in two-thirds of affected KT patients. Comparing 518 day-matched plasma-urine samples from 223 KT patients, BKV loads were approximately 3000-fold higher in urine than in plasma (p < 0.000001). Molecular and quantitative parameters indicated that >95% of urine BKV loads resulted from urothelial replication and <5% from tubular epithelial replication. Fast BKV replication dynamics in plasma and urine with half-lives of <12 h accounted for daily urothelial and tubular epithelial cell loss of 4 x 10(7) and 6 x 10(7), respectively. BKV dynamics in both sites were only partly linked, with full and partial discordance in 36% and 32%, respectively. Viral expansion was best explained by models where BKV replication started in the kidney followed by urothelial amplification and tubular epithelial cell cross-feeding reaching a dynamic equilibrium after approximately 10 weeks. Curtailing intrarenal replication by 50% was ineffective and >80% was required for clearing viremia within 7 weeks, but viruria persisted for >14 weeks. Reductions >90% cleared viremia and viruria by 3 and 10 weeks, respectively. The model was clinically validated in prospectively monitored KT patients supporting >80% curtailing for optimal interventions.

Low-dose Cidofovir for the Treatment of Polyomavirus-Associated Nephropathy: Two Case Reports and Review of the Literature

Background

Polyomavirus-associated nephropathy (PVAN) is a serious complication and cause of graft loss in kidney transplant recipients. In the absence of specific antiviral drugs, early detection of the disease and reduction of immunosuppressive regimen is the cornerstone of therapy. Cidofovir, a nucleoside analogue, has been found to inhibit BK virus (BKV) replication in vitro and has been proposed as treatment of refractory PVAN at low doses; however, its efficacy has never been demonstrated in randomized controlled trials.

Methods

Cidofovir therapy (0.5 mg/kg at a 2-week interval for eight consecutive doses) was initiated in two patients with biopsy-proven PVAN and persistent BKV DNA viraemia (≥10,000 copies/ml despite sustained reduction of the immunosuppressive regimen). In addition to these two case reports, we performed a critical review of the literature on the use of cidofovir in PVAN.

Results

No significant decrease of BKV viral load in blood was observed during cidofovir therapy and in follow-up of the two patients treated with cidofovir. Our literature review identified 21 publications reporting the use of cidofovir for the treatment of PVAN. All were case reports or small series. The efficacy of cidofovir therapy could not be assessed in 17 of these publications because of lack of data or concomitant reduction of immunosuppressive regimen. The four remaining publications were case reports.

Conclusions

In vitro and clinical data to support the efficacy of cidofovir in the treatment of PVAN are currently lacking. More promising compounds should be identified for further clinical studies.

BK virus nephropathy in renal transplant patients in London

BACKGROUND

BK nephropathy (BKN) is an important cause of renal transplant dysfunction, believed to be associated with higher levels of immunosuppression. We assessed the experience of BKN in renal transplant patients in the London region.

METHODS

All six London transplant centers participated and case notes of patients with BKN in 2004 to 2005 were reviewed.

RESULTS

There were 17 cases of BKN, giving an incidence of 2.1%. Median time to diagnosis was 9 months. Median baseline creatinine rose from 150 to 196 mumol/L. At diagnosis, 16 patients were on tacrolimus, 15 on mycophenolate mofetil, and 10 on triple therapy with tacrolimus, mycophenolate mofetil, and prednisolone. Management of BKN involved reducing immunosuppression; cidofovir was used in two patients and methylprednisolone in five for acute rejection. Median follow-up time was 29.2 months. Creatinine returned to baseline in four patients, remained elevated in 12 and one patient lost his graft. The new median baseline creatinine was 216 mumol/L. Eight patients underwent repeat biopsies of which four became negative for BKV and three subsequently cleared the virus on blood and urine polymerase chain reaction and urine decoy cells. Overall, eight patients cleared the virus. None of age, sex, viral load, or biopsy characteristics (Banff ct score, Drachenberg grade, and number of BKV positive cells) were associated with poorer outcome when patients with increase in creatinine of less than 30% (n=7) or more than 30% (n=10) from baseline were compared.

CONCLUSION

The incidence of BKN in this study is comparable with previous studies, with more favorable outcomes. It supports the association of BKN with potent immunosuppression.

Complications post renal transplantation: literature focus on BK virus nephropathy and diagnostic tools actually available

Clinical diagnosis of kidney transplants related illnesses is not a simple task. Several studies were conducted to define diseases and complications after renal transplantation, but there are no comprehensive guidelines about diagnostic tools for their prevention and detection.

The Authors of this review looked for the medical literature and pertinent publications in particular to understand the role of Human Polyomavirus BK (BKV) in renal failure and to recognize analytical techniques for BK virus associated nephropathy (BKVAN) detection.

BK virus nephropathy and kidney transplantation

Nephropathy from BK virus (BKV) infection is an evolving challenge in kidney transplant recipients. It is the consequence of modern potent immunosuppression aimed at reducing acute rejection and improving allograft survival. Untreated BKV infections lead to kidney allograft dysfunction or loss. Decreased immunosuppression is the principle treatment but predisposes to acute and chronic rejection. Screening protocols for early detection and prevention of symptomatic BKV nephropathy have improved outcomes. Although no approved antiviral drug is available, leflunomide, cidofovir, quinolones, and intravenous Ig have been used. Retransplantation after BKV nephropathy has been successful.

Low-dose cidofovir treatment of BK virus-associated hemorrhagic cystitis in recipients of hematopoietic stem cell transplant

In recipients of hematopoietic stem cell transplants (HSCTs), BK virus (BKV) has been associated with late-onset hemorrhagic cystitis (HC). In our institution, HSCT recipients with BKV-associated HC are treated with 1 mg/kg of cidofovir weekly. We identified HSCT recipients with BKV-associated HC, treated with weekly cidofovir. Microbiological response was defined as at least a one log reduction in urinary BKV viral load; clinical response was defined as improvement in symptoms and stability or reduction in the grade of cystitis. Nineteen allogeneic HSCT patients received a mean of 4.5 weekly doses of cidofovir. HC occurred at a mean of 68.7 days after transplant. A clinical response was detected in 16/19 (84%) patients, and 9/19 (47%) had a measurable microbiological response (8/10 nonresponders had a BKV viral load above the upper limit of the assay before treatment). Fourteen out of nineteen (74%) patients had no significant increase in serum creatinine. Five patients with renal dysfunction resolved after completion of the therapy and removal of other nephrotoxic agents. We conclude that weekly low-dose cidofovir appears to be a safe treatment option for BKV-associated HC. Although the efficacy of low-dose cidofovir is not proven, a prospective trial is warranted.

PCR assays for the early detection of BKV infection in 125 Spanish kidney transplant patients

BK virus (BKV) reactivation arises from immunocompromised conditions and can produce a tubulointerstitial nephropathy (BKVN) in kidney transplant recipients (KTR). Approximately 5% of KTR develop BKVN, and about 45% of these lose their graft. Therefore, using molecular tools to test for BKV may be helpful in early detection. A series of 125 Spanish KTR, originating from a single transplant center, were studied in relation to BKV infection in the first post-transplant year. First, we carried out a urinary cytological study, looking for decoy cells as a possible marker of virus replication. Secondly, in all positive cytological samples and in some negative cytological samples (selected at random), we performed qualitative polymerase chain reaction (PCR) assays in serum and urine amplifying two different genome regions (LT and VP1). A transcription control region (TCR)-BK polymorphism sequence analysis was also performed in those BK PCR positive cases. Twenty-three of 125 (18.4%) KTR presented decoy cells in at least one urinary cytological sample. Molecular studies revealed that 10 of 125 (8%) KTR were BK PCR-serum positive cases (seven LT+/VP1- and three LT+/VP1+); and 13 of 40 (32.5%) KTR were BK PCR-urine positive cases (five LT+/VP1- and eight LT+/VP1+). When we compared PCR-urine and cytological results in 40 KTR, only 15% (six cases) revealed simultaneous positivity in both studies. In the context of clinical graft dysfunction, three patients demonstrated BK DNA presence in the renal biopsy. Finally, sequence analysis of the TCR was performed in 13 BK-PCR positive cases determining the AS, JL, WW, and WW-like viral variants. TCR sequence analysis, allows us to demonstrate the possible implication of the donor in BK infection studying four BK-PCR positive patients paired by donor.

Polyomavirus nephropathy in native kidneys and renal allografts: an update on an escalating threat

Polyomavirus nephropathy, also termed BK-virus nephropathy (BKN) after the main causative agent, the polyoma-BK-virus strain, is a significant complication after kidney transplantation. BKN is the most common viral infection that affects renal allografts with a prevalence of 1-9% on average 8-13 months post surgery. It can also occur sporadically in native kidneys. Viral nephropathy is caused by the (re)activation of latent BK viruses that enter into a replicative cycle under sustained and intensive immunosuppression. Pure productive kidney infections with JC- and SV-40 polyomaviruses are exceptionally rare. BKN is morphologically defined by the presence of intranuclear viral inclusion bodies in epithelial cells and tubular injury, which is the morphological correlate for renal dysfunction. Renal disease can progress through different histologic stages (from early BKN stage A to late fibrotic stage C) that carry prognostic significance; disease stages B and C often result in chronic kidney (allograft) dysfunction and end-stage renal disease. The clinical goal is to diagnose viral nephropathy in disease stage A and to limit chronic renal injury. Strategies to recognize, classify, and manage BKN are critically discussed including ancillary techniques for risk assessment and patient monitoring: (i) urine cytology and the search for so-called 'decoy cells'; (ii) PCR analyses for viral load measurements in the plasma and urine; and (iii) negative staining urine electron microscopy to identify viral particles.

Urine cytology screening for polyoma virus infection following renal transplantation: the Oxford experience

OBJECTIVE

To review the first year of a monthly urine cytology screening service, introduced to identify renal transplant patients at risk of polyoma virus nephropathy (PVN), at an early, potentially treatable, stage.

METHODS AND RESULTS

Monthly urine samples (n = 392) were received from 97/108 transplant recipients in 2005. Of 56 patients with follow-up >6 months, 20% and 9% had significant (>10 decoy cells/cytospin) and non-significant positive cytology, respectively. The first positive urine samples occurred most commonly in the second and third month post-transplantation and patients with significantly positive samples had higher 3-month and 6-month serum creatinine levels than patients with negative urine cytology (p<0.01). Four patients with positive urine cytology had a subsequent positive plasma BK virus PCR; 3/97 patients had biopsy-proven PVN, all in the third month, 1-6 weeks after first positive urine samples.

CONCLUSIONS

Significant PV viruria is common following renal transplantation with onset usually within the first 3 months. Viruria is associated with worse graft function at 3 and 6 months. The time between urine positivity and clinical PVN is short. More frequent early urine screening would be required to achieve clinical benefit.

Negative-staining electron microscopy of the urine for the detection of polyomavirus infections

Negative-staining electron microscopy (EM) has played a pivotal role in diagnostic virology. It is a rapid technique for viral detection in the urine and can provide an easy means for monitoring viral activity and productive infections. EM of urine for the detection of polyomaviruses has hitherto not been systematically evaluated as a screening tool for renal transplant patients at risk for BK polyomavirus nephropathy (BKN). Here, the authors discuss technical aspects of negative-staining EM of urine (n = 76 samples) and present a simple and rapid protocol for the semiquantitative evaluation of patient samples. In two patient populations (either with (n = 15 samples) or without (n = 15 samples) an established diagnosis of BKN), EM results were compared with two previously established techniques for monitoring polyomavirus activation: (1) cytology for the quantitation of decoy cells, and (2) quantitative PCR assays for the detection of BK virus DNA load levels. In both patient groups, the dynamics of decoy cell shedding by urine cytology closely paralleled free viral particle shedding by EM, and viral load levels as measured by PCR. A trend toward higher readings was observed in patients with BKN (median values, control versus BKN groups: decoy cells 21 versus 50/slide; free virions by EM: 32 versus 66 viral particles/10 high-power fields; PCR: 3.5 x 10(8) versus 5.4 x 10(8) BK virus copies/ml; all differences not statistically significant). The authors conclude that negative-staining EM and the semiquantitative assessment of free viral particles in the urine can be a useful clinical method to identify patients at increased risk for BKN. EM can be used alone or in combination with urine cytology or PCR assays.

Subtype IV of the BK polyomavirus is prevalent in East Asia

BK polyomavirus (BKV) is ubiquitous in human populations, infecting children asymptomatically and then persisting in the kidney. Using either serological or genotyping methods, BKV isolates have been classified into four subtypes (I-IV), with subtype I mainly detected in all countries studied so far. To elucidate the subtype of BKV prevalent in East Asia, we examined BKV-positive urine samples collected from immunocompetent elderly patients in Mongolia, Northeast China, Northwest China, Southeast China, Southwest China, Vietnam and Japan. The 287-bp typing region of the viral genome in each of these samples was PCR-amplified and sequenced, and a phylogenetic tree was constructed. According to the tree, BKV isolates in East Asia were unambiguously classified into subtype I or IV (subtypes II and III were not detected). In Japan, subtype I was mainly detected and subtype IV was rare, whereas in the other regions subtype IV was detected frequently, at rates ranging from 24 to 100%. Thus, East Asia (excluding Japan) is a region in which subtype-IV BKV is prevalent, a finding that requires the view of the geographic distribution of BKV subtypes to be revised. Furthermore, we present evidence that the immunological states of urine donors do not affect the pattern of BKV subtypes.

Polyomavirus-associated nephropathy: update of clinical management in kidney transplant patients

Over the last decade, polyomavirus-associated nephropathy (PVAN) has occurred with increasing frequency after renal transplantation, leading to significant renal dysfunction and graft loss. More than 95% of all cases are caused by the human polyomavirus type 1 called the BK virus. The primary treatment for PVAN is immunosuppression reduction, which must be carefully balanced against increased risks of rejection. Although no validated protocols exist, a first step commonly involves reduction of calcineurin inhibitors with antiproliferative agents by more than one-third, e.g., reaching trough levels of tacrolimus <6 ng/mL, of cyclosporine <150 ng/mL, dosing of mycophenolate mofetil to <1 g/day, and azathioprine <75 mg/day. When rejection is diagnosed together with PVAN, a transient pulse treatment is recommended before subsequent reduction in immunosuppression. No antiviral treatments for PVAN have been approved by the United States Food and Drug Administration. The antiviral drug cidofovir has shown in vitro activity against murine polyomaviruses, and has been used in some patients in lower doses in an effort to minimize the nephrotoxic effects of cidofovir while treating PVAN. Small series of PVAN patients treated with leflunomide, intravenous immune globulin therapy, and fluoroquinolones have also been reported recently.

Kidney transplant function and histological clearance of virus following diagnosis of polyomavirus-associated nephropathy (PVAN)

Polyomavirus-associated nephropathy (PVAN) is managed by reduced immunosuppression with or without antiviral therapy. Data from 55 patients with biopsy-proven PVAN were analyzed for adverse outcomes and influence of baseline variables and interventions. During 20+/-11 months follow-up, the frequencies of graft loss, major and any functional decline were 15%, 24% and 38%, respectively. Repeat biopsies were performed in 45 patients with persistent PVAN in 47%. Low-dose cidofovir, IVIG and cyclosporine conversion were used in 55%, 20% and 55% of patients. No single intervention was associated with improved outcome. Of the variables examined, only degree of interstitial fibrosis at diagnosis was associated with kidney function decline. In contrast, donor source, interstitial fibrosis, proportion of BKV positive tubules and plasma viral load at diagnosis were all associated with failure of histological viral clearance. This retrospective, nonrandomized analysis suggests that: (i) Graft loss within 2 years of PVAN diagnosis is now uncommon, but ongoing functional decline and persistent infection occur frequently. (ii) Low-dose cidofovir, IVIG and conversion to cyclosporine do not abrogate adverse outcomes following diagnosis. (iii) Fibrosis at the time of diagnosis predicts subsequent functional decline. Further elucidation of the natural history of PVAN and its response to individual interventions will require prospective clinical trials.

Polymerase Chain Reaction Detection of BK Virus and Monitoring of BK Nephropathy in Renal Transplant Recipients at the University Hospital La Fe

INTRODUCTION

Reactivation of BK infection occurs in immunocompromised hosts causing tubulointerstitial nephropathy (BKVN). Approximately 5% of kidney transplant recipients (KTR) develop BKVN, special half of whom lose their grafts. However, BKVN morphologic diagnosis on a renal biopsy is complicated, because the cytopathic changes can sometimes mimic rejection. Thus, BKV DNA-polymerase chain reaction (PCR) assay on serum, urine, and renal tissue is useful for early detection and monitoring of BKV.

MATERIALS AND METHODS

We performed routine monthly urine cytologies looking for decoy cells as a marker of virus replication. Then, we performed a qualitative PCR on urine and serum in all recipients (independently of positive or negative cytology). We amplified 3 BK viral genome regions, LT (early transcription region) and VP1 (late transcription region) seeking a more accurate virus detection, and the TCR (control transcription region) region to perform a polymorphism sequence analysis to identify the BK genomic variant. Finally, the BKVN diagnosis was confirmed using renal biopsy.

RESULTS

At present, 132 patients have been monitored. Thirteen of 40 (33%) were PCR-urine-positive cases (5 LT+/VP1- and 8 LT+/VP1+), and 10 of 132 (7.5%) were PCR-serum-positive cases (7 LT+/VP1- and 3 LT+/VP1+). When we compared PCR-urine and cytology results, 11 of 40 (27.5%) patients showed a positive cytology, 6 of whom were PCR- urine-positive (1 LT+/VP1- and 5 LT+/VP1+); whereas, 29 patients showed a negative cytology, 7 of whom were PCR-urine-positive(3 LT+/VP1- and 4 LT+/VP1+). Thus, comparison of PCR- urine and cytology results revealed false-positive and false-negative cases. Finally, TCR sequence analysis was performed in 9 patients to identify the BK genomic variants.

CONCLUSION

Testing for BKV DNA in urine and serum is a noninvasive early detection assay and monitoring tool.

Adjuvant low-dose cidofovir therapy for BK polyomavirus interstitial nephritis in renal transplant recipients

BK virus interstitial nephritis (BKVIN) is a serious complication after kidney grafting, necessitating drastic reduction of immunosuppressive therapy in order to enable viral clearance. Despite these measures, progressive graft dysfunction and graft loss occur in the majority of recipients. We diagnosed BKVIN in 21 recipients grafted between 1998 and 2004. Eight of 21 patients were treated with weekly, adjuvant low-dose cidofovir in addition to reduction of immunosuppressive therapy. BKVIN caused irreversible deterioration of graft function in all patients but renal function stabilized after antiviral treatment (creatinine clearance: 51.8-32 mL/min; p=0.001) and no graft loss occurred in cidofovir-treated recipients during 24.8 (8-41) months follow-up. Peak serum cidofovir concentrations were dose-dependent and attained approximately one-tenth of thein vitroEC50 for cidofovir against BK-virus, while pre-treatment with probenecid did not alter peak serum concentrations nor affected the incidence of nephrotoxicity. In fact, no cidofovir-related renal toxicity occurred; few patients had minor transient side effects (nausea, skin rash). In contrast, 9 of 13 patient who received no adjuvant cidofovir therapy lost their graft after median 8 (4-40) months. In this selected group of recipients with BKVIN, the use of adjuvant low-dose cidofovir therapy resulted in prolonged graft survival and stabilized graft function.