Polyomavirus-associated nephropathy: update on antiviral strategies

Novel ways to monitor immunosuppression in pediatric kidney transplant recipients-underlying concepts and emerging data

After pediatric kidney transplantation, immunosuppressive therapy is given to avoid acute and chronic rejections. However, the immunosuppression causes an increased risk of severe viral complications and bacterial infections and is associated with serious side effects. It is therefore crucial to achieve the optimal individual balance between over- and under-immunosuppression and thereby avoid unnecessary exposure to immunosuppressive drugs. In routine use, steering of immunosuppressants is performed primarily by monitoring of trough levels that mirror pharmacokinetics (although not, however, pharmacodynamics). Other diagnostic and prognostic markers to assess the individual intensity of immunosuppression are missing. Potential methods to determine immune function and grade of immunosuppression, such as analysis of the torque teno virus (TTV) load, QuantiFERON Monitor®, and ImmuKnow® as well as virus-specific T cells (Tvis), are currently being evaluated. In some studies TTV load, QuantiFERON Monitor® and ImmuKnow® were associated with the risk for post-transplant rejections and infections, but randomized controlled trials after pediatric kidney transplantation are not available. Post-transplant monitoring of Tvis levels seem to be promising because Tvis control virus replication and have been shown to correlate with virus-specific as well as general cellular immune defense, which represents the individual’s susceptibility to infections. Additional Tvis-monitoring provides an innovative opportunity to personalize the antiviral management and the dosing of the immunosuppressive therapy after pediatric kidney transplantation to avoid unnecessary therapeutic interventions and identify over-immunosuppression.

Leflunomide an immunomodulator with antineoplastic and antiviral potentials but drug-induced liver injury: A comprehensive review

Leflunomide (LF) represents the prototype member of dihydroorotate dehydrogenase (DHODH) enzyme inhibitors. DHODH is a mitochondrial inner membrane enzyme responsible for catalytic conversion of dihydroorotate into orotate, a rate-limiting step in the de novo synthesis of the pyrimidine nucleotides. LF produces cellular depletion of pyrimidine nucleotides required for cell growth and proliferation. Based on the affected cells the outcome can be attainable as immunosuppression, antiproliferative, and/or the recently gained attention of the antiviral potentials of LF and its new congeners. Also, protein tyrosine kinase inhibition is an additional mechanistic benefit of LF, which inhibits immunological events such as cellular expansion and immunoglobulin production with an enhanced release of immunosuppressant cytokines. LF is approved for the treatment of autoimmune arthritis of rheumatoid and psoriatic pathogenesis. Also, LF has been used off-label for the treatment of relapsing-remitting multiple sclerosis. However, LF antiviral activity is repurposed and under investigation with related compounds under a phase-I trial as a SARS CoV-2 antiviral in cases with COVID-19. Despite success in improving patients' mobility and reducing joint destruction, reported events of LF-induced liver injury necessitated regulatory precautions. LF should not be used in patients with hepatic impairment or in combination with drugs elaborating a burden on the liver without regular monitoring of liver enzymes and serum bilirubin as safety biomarkers. This study aims to review the pharmacological and safety profile of LF with a focus on the LF-induced hepatic injury from the perspective of pathophysiology and possible protective agents.

The Role of HLA and KIR Immunogenetics in BK Virus Infection after Kidney Transplantation

BK virus (BKV) is a polyomavirus with high seroprevalence in the general population with an unremarkable clinical presentation in healthy people, but a potential for causing serious complications in immunosuppressed transplanted patients. Reactivation or primary infection in kidney allograft recipients may lead to allograft dysfunction and subsequent loss. Currently, there is no widely accepted specific treatment for BKV infection and reduction of immunosuppressive therapy is the mainstay therapy. Given this and the sequential appearance of viruria-viremia-nephropathy, screening and early detection are of utmost importance. There are numerous risk factors associated with BKV infection including genetic factors, among them human leukocyte antigens (HLA) and killer cell immunoglobulin-like receptors (KIR) alleles have been shown to be the strongest so far. Identification of patients at risk for BKV infection would be useful in prevention or early action to reduce morbidity and progression to frank nephropathy. Assessment of risk involving HLA ligands and KIR genotyping of recipients in the pre-transplant or early post-transplant period might be useful in clinical practice. This review summarizes current knowledge of the association between HLA, KIR and BKV infection and potential future directions of research, which might lead to optimal utilization of these genetic markers.

Diagnostics, treatment, and immune response in BK polyomavirus infection after pediatric kidney transplantation

After pediatric kidney transplantation BK polyomavirus (BKPyV) infections are associated with an increased risk of graft loss by BKPyV-associated nephropathy (BkPyVAN). However, suitable prognostic markers for the individual outcome of BKPyV infections are missing and the management of therapeutic interventions remains a challenge to the success of pediatric kidney transplantation. This review gives an overview on current diagnostic and therapeutic strategies in the field of BKPyV infections after pediatric kidney transplantation. Methods determining the individual immune response to BKPyV are described and their usability is discussed. There is growing evidence that BKPyV-specific T cells (BKPyV-Tvis) may serve as prognostic markers in order to steer immunosuppressive therapy in pediatric kidney recipients with BKPyV viremia in future. Prospective randomized trials in viremic kidney recipients comparing Tvis-steered therapeutic intervention with standard reduction of immunosuppression are needed before implementation of BKPyV-Tvis monitoring in routine care of BKPyV infections.

Viral Diagnostics

This chapter discusses recent developments in diagnostics for cytomegalovirus (CMV), Epstein-Barr virus (EBV), BK virus (BKV), community respiratory viruses (CRVs), parvovirus, hepatitis viruses, HIV, and other viral agents of importance in solid organ and hematopoietic stem cell transplantation.

Infection in Kidney Transplantation

Infection is an important cause of morbidity and mortality after kidney transplantation. It has been estimated that 70% of kidney transplant recipients will experience an infection episode within the first 3 years after transplantation (Dharnidharka et al. 2007). After cardiovascular disease, infection is the second leading cause of death in recipients with allograft function (Snyder et al. 2009). The immunosuppressive therapy required to prevent organ rejection places the kidney transplant recipient at increased risk for donor-derived, nosocomial, and community-acquired infections as well as reactivation of latent pathogens. Pretransplant screening, immunizations, and optimal antibacterial and antiviral prophylaxis can help to reduce the impact of infection. Awareness of the approach to infection in the transplant recipient including diagnostic and management strategies is essential to optimizing outcomes.

BK Virus-associated Hemorrhagic Cystitis in Patients with Allogeneic Hematopoietic Cell Transplantation: Report of Three Cases

BK viras is a human polyoma viras. It is acquired in early childhood and remains life-long latent in the genitourinary system. BK virus replication is more common in receiving immunosuppressive therapy receiving patients and transplant patients. BK virus could cause hemorrhagic cystitis in patients with allogeneic stem cell transplantation. Hemorrhagic cystitis is a serious complication of hematopoietic stem cell transplantation. Hemorrhagic cystitis could cause morbidity and long stay in the hospital. Diagnosis is more frequently determined by the presence of BK virus DNA detected with quantitative or real-time PCR testing in serum or plasma and less often in urine. The reduction of immunosuppression is effective in the treatment of BK virus infection. There are also several agents with anti-BK virus activity. Cidofovir is an active agent against a variety of DNA viruses including poliomyoma viruses and it is a cytosine nucleotide analogue. Intravenous immunoglobulin IgG (IVIG) also includes antibodies against BK and JC (John Cunningham) viruses. Hereby, we report three cases of hemorrhagic cystitis. Hemorrhagic cystitis developed in all these three cases of allogeneic stem cell transplantation due to acute myeloid leukemia (AML). BK virus were detected as the cause of hemorrhagic cystitis in these patients. Irrigation of the bladder was performed. Then levofloxacin 1 x750 mg intravenous and IVIG 0.5 gr/kg were started. But the hematuria did not decreased. In the first case, treatment with leflunomide was started, but patient died due to refractory AML and severe graft-versus-host disease after 4th day of leflunamide and levofloxacin treatments. Cidofovir treatment and the reduction of immunosuppressive treatment decreased the BK virus load and resulted symptomatic improvement in the second case. Initiation of cidofovir was planned in the third case. Administration of cidofovir together with the reduction of immunosuppression in the treatment of hemorrhagic cystitis associated with BK virus in allogeneic stem cell transplant recipients could be a good option.

Anion homeostasis is important for non-lytic release of BK polyomavirus from infected cells

BK polyomavirus (BKPyV) is a member of a family of potentially oncogenic viruses, whose reactivation can cause severe pathological conditions in transplant patients, leading to graft rejection. As with many non-enveloped viruses, it is assumed that virus release occurs through lysis of the host cell. We now show the first evidence for a non-lytic release pathway for BKPyV and that this pathway can be blocked by the anion channel inhibitor DIDS. Our data show a dose-dependent effect of DIDS on the release of BKPyV virions. We also observed an accumulation of viral capsids in large LAMP-1-positive acidic organelles within the cytoplasm of cells upon DIDS treatment, suggesting potential late endosome or lysosome-related compartments are involved in non-lytic BKPyV release. These data highlight a novel mechanism by which polyomaviruses can be released from infected cells in an active and non-lytic manner, and that anion homeostasis regulation is important in this pathway.

BK Virus Nephropathy in Kidney Transplantation: An Approach Proposal and Update on Risk Factors, Diagnosis, and Treatment

BK virus belongs to Polyomaviridae family; it causes 95% of nephropathy cases related to polyomavirus, with the other 5% caused by JC virus. Nephropathy jeopardizes graft function, causing a premature failure of the graft in 1%-10% of patients with kidney transplants. Nowadays, antiviral effective treatment is unknown, which is why blood and urine screening of renal transplantation patients has become the most important recommendation to guide the decrease of immunosuppression, and the only proven method to decrease poor outcomes. Different interventions, such as cidofovir, leflunomide, fluoroquinolones, and intravenous immunoglobulin, have been attempted with no improvement at all. This review aims to summarize the most relevant features of BK virus, historical issues, transmission mechanisms, risk factors, and therapeutic interventions.

Evaluation of leflunomide for the treatment of BK viremia and biopsy proven BK nephropathy; a single center experience

BACKGROUND

BK virus reactivation is a significant complication following renal transplantation that can result in graft failure. Reduction of immunosuppression and substitution of leflunomide for mycophenolate mofetil (MMF) has been used to treat this entity.

OBJECTIVES

To evaluate the use of leflunomide in BK viremia (BKV) and biopsy proven BK nephropathy (BKN) in kidney and kidney-pancreas transplant recipients.

PATIENTS AND METHODS

We retrospectively reviewed 28 kidney and kidney-pancreas transplant recipients who had received leflunomide for BKV from January 2006 to November 2012. Demographics, time to BKV diagnosis, biopsy findings, rejection episodes, and laboratory data were recorded.

RESULTS

The average (mean ± SD) time to BKV from time of transplant was 316.1 ± 368.0 days (62-1708 days). At time of diagnosis, 64% of patients had their maintenance immunosuppression reduced. The indications for leflunomide administration were; BKV and biopsy proven acute rejection (BPAR) (50%), biopsy proven BKN (18%), or persistent BKV (25%). Therapeutic levels (50-100 mcg/mL) were achieved in only 54% of patients, and 60% of them had required a leflunomide dose of at least 60 mg/day. BK virus was cleared from the serum on average of 151 ± 145.2 days (17-476 days). At study commencement, 29% of patients had remained on leflunomide due to persistent BKV.

CONCLUSIONS

In our study, most patients required at least a 60 mg daily dose of leflunomide to achieve therapeutic levels and to clear the virus compared to the standard 40 mg daily dose. Delaying therapy may result in progressive BKV and BKN.

Impact of HMG-CoA reductase inhibitors on the incidence of polyomavirus-associated nephropathy in renal transplant recipients with human BK polyomavirus viremia

BACKGROUND

Up to 20% of renal transplant recipients (RTR) will develop human BK polyomavirus (BKPyV) viremia. BKPyV viremia is a pre-requisite of polyomavirus-associated nephropathy (PyVAN). Risk of BKPyV infections increases with immunosuppression. Currently, the only effective therapy against PyVAN is reductions in immunosuppression, but this may increase the risk of rejection. In vitro data have shown that pravastatin dramatically decreased caveolin-1 expression in human renal proximal tubular epithelial cells (HRPTEC) and suppressed BKPyV infection in these cells. Based on these data, we postulated that statin therapy may prevent the progression of BKPyV viremia to PyVAN.

PATIENTS AND METHODS

A multicenter, retrospective study was conducted in adult RTR transplanted between July 2005 and March 2012. All patients with documented BKPyV viremia (viral load >500 copies/mL on 2 consecutive tests) were included. Group I consisted of patients taking a statin before the BKPyV viremia diagnosis (n = 32), and Group II had no statin exposure before or after the BKPyV viremia diagnosis (n = 36). The primary endpoint was the incidence of PyVAN.

RESULTS

Demographic data, transplant characteristics, and the degree of immunosuppression (i.e., induction/maintenance therapies, rejection treatment) were similar between the groups, with the exception of more diabetics in Group I. The incidence of PyVAN was comparable between the 2 groups (Group I = 28.1% vs. Group II = 41.7%; P = 0.312).

CONCLUSIONS

Despite the proven in vitro effectiveness of pravastatin preventing BKPyV infection in HRPTEC, statins at doses maximized for cholesterol lowering, in RTR with BKPyV viremia, did not prevent progression to PyVAN.

Conversion to a sirolimus-based regimen is associated with lower incidence of BK viremia in low-risk kidney transplant recipients

BACKGROUND

BK viral nephropathy is an increasingly recognized cause of early allograft loss in kidney transplantation. This study aimed to determine whether a sirolimus (Sir)-based calcineurin inhibitor-sparing regimen is associated with a lower incidence of BK viremia.

METHODS

This was a single-center retrospective study. Patients were either on tacrolimus (Tac)-based or on Sir-based immunosuppression. Conversion from Tac to Sir occurred at or after 3 months if patients were <62 years of age, had calculated panel reactive antibodies of <20%, and did not have acute early rejection.

RESULTS

Incidence of clinically significant BK viremia was 17.9% in the Tac group and 4.3% in the Sir group. Cox regression multivariate analysis showed that male gender (hazard ratio [HR] = 2.87) and switch to Sir (HR = 0.333) impacted the incidence of BK viremia. Kaplan-Meier analysis showed a higher BK-free survival in the Sir group. A trend was seen toward shorter time to resolution of BK viremia and lower peak viremia in the Sir group. Patients on Sir had a higher estimated glomerular filtration rate at each time point; 34% of patients discontinued Sir because of side effects.

CONCLUSION

Conversion to Sir-based maintenance immunosuppression at or about 3 months after kidney transplantation correlates with a lower incidence of BK viremia.

Synthesis and structure–activity relationships of small molecule inhibitors of the simian virus 40 T antigen oncoprotein, an anti-polyomaviral target

Polyomavirus infections are common and relatively benign in the general human population but can become pathogenic in immunosuppressed patients. Because most treatments for polyomavirusassociated diseases nonspecifically target DNA replication, existing treatments for polyomavirus infection possess undesirable side effects. However, all polyomaviruses express Large Tumor Antigen (T Ag), which is unique to this virus family and may serve as a therapeutic target. Previous screening of pyrimidinone–peptoid hybrid compounds identified MAL2-11B and a MAL2-11B tetrazole derivative as inhibitors of viral replication and T Ag ATPase activity (IC50 of ~20-50 μM. To improve upon this scaffold and to develop a structure–activity relationship for this new class of antiviral agents, several iterative series of MAL2-11B derivatives were synthesized. The replacement of a flexible methylene chain linker with a benzyl group or, alternatively, the addition of an ortho-methyl substituent on the biphenyl side chain in MAL2-11B yielded an IC50 of 50 μM, which retained antiviral activity. After combining both structural motifs, a new lead compound was identified that inhibited T Ag ATPase activity with an IC50 of 50 μM. We suggest that the knowledge gained from the structure–activity relationship and a further refinement cycle of the MAL2-11B scaffold will provide a specific, novel therapeutic treatment option for polyomavirus infections and their associated diseases.

Allograft adenovirus nephritis

We present an uncommon case of allograft adenovirus tubulointerstitial nephritis in a 63-year-old male 6 weeks following cadaveric renal transplantation for end-stage renal failure secondary to hypertensive nephrosclerosis. The patient presented with acute onset of fevers, dysuria, haematuria and diarrhoea with acute graft dysfunction. A renal biopsy demonstrated necrotizing tubulointerstitial nephritis with viral cytopathic changes and no evidence of rejection. Adenovirus was identified as the pathogen. Treatment involved the reduction in the patient's usual immunosuppression, intravenous immunoglobulin, piperacillin-tazobactam and ganciclovir. We present the clinical and pathological findings of necrotizing adenoviral nephropathy, highlighting the importance of considering this diagnosis in renal transplant recipients presenting with interstitial nephritis in the setting of a systemic illness.

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.

BK virus nephropathy developing after renal transplantation and its treatment with ciprofloxacin: a case report

BK virus nephropathy (BKVN) is among the most important problems in renal transplant recipients. This report presented an assessment of treatment with a fluoroquinolone antibiotic, ciprofloxacin, for 6 months in a 21-year-old male patient who developed BKVN after transplantation. Ciprofloxacin treatment reduced the viral load and improved the clinical findings.

Contrasting patterns of viral load response in transplant recipients with BK polyomavirus DNAemia on leflunomide therapy

BACKGROUND

Reduction in immunosuppression is considered the therapy of proven benefit for BKV infection in renal transplantation, but the use of leflunomide has also been reported. It was observed at this center that the patterns of viral load response while on leflunomide appear to fall into two distinct types.

METHODS

Medical records of 22 kidney and kidney-pancreas recipients at a single center who received leflunomide therapy for BKV DNAemia were reviewed. Information was collected on demographics, BKV viral loads, other antiviral therapy, immunosuppressive drug levels and doses, adverse effects, and graft and patient outcomes.

RESULTS

Eighteen of 22 cleared BKV viremia, and 12 of 22 had preserved allograft function; only two graft losses occurred in the screening era among leflunomide-treated patients. Two patterns of viral load reduction were observed, termed the "smooth" and the "zigzag" pattern, which differed in mean time to clear of BKV DNA (2.9 vs. 19.5 months, p = 0.0073). Graft preservation was correlated with lower serum creatinine (SCr) at the start of leflunomide therapy.

CONCLUSIONS

Long courses and "zigzag" fluctuations in viral load can occur in patients who eventually clear BKV on leflunomide with preserved allograft function. Intermittent increases in viral load do not necessarily portend therapeutic failure. Although the utility of leflunomide is still debated in the transplant community, this information may be useful to clinicians who choose to use it in selected patients.

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.

Leflunomide inhibits the apoptosis of human embryonic lung fibroblasts infected by human cytomegalovirus

BACKGROUND

The immunomodulatory drug leflunomide (LEF) is frequently used for treating human cytomegalovirus (HCMV), but its antiviral mechanism is still unclear. In this study,we therefore investigated the effects of the active LEF metabolite A771726 on the HCMV lifecycle in human embryonic lung fibroblasts. We clarified the mechanism of LEF antiviral infection, and provide a new way to treat immune dysfunction patients with HCMV infection.

METHODS

The experiment was divided into four groups: the control group, the HCMV group, the ganciclovir+HCMV group as well as the LEF+HCMV group. MTT was used for assessment of the cell inhibitory rate. Apoptosis was measured by staining with fluorescein isothiocyanate Annexin V and propidium iodide. Statistical significance was determined by paired t-test using SPSS software.

RESULTS

The results of the study showed that cell proliferation was significantly inhibited by HCMV at 24 hours and 48 hours. With increasing HCMV concentration, the value-added inhibition of the cells was significantly decreased compared with the control group, and was statistically significant (P<0.01). Ganciclovir can increase proliferation of cells infected with HCMV; compared with the control group it was statistically significant (P<0.05). Meanwhile, with LEF treatment cell proliferation was significantly improved at 24 hours and 48 hours, with statistical significance (P<0.05). The apoptosis rate of human embryonic lung fibroblasts infected with HCMV increased significantly at 24 hours, 48 hours and 72 hours, and as time goes on the apoptosis rate increases statistically significantly (P<0.01) compared with the control group The apoptosis rate of the HCMV infection group decreased by adding LEF,and was statistically significant (P<0.05).

CONCLUSIONS

In this study we show that LEF is an exciting new drug for cytomegalovirus infection. LEF significantly inhibited HCMV infection-induced apoptosis and proliferation, playing an important role in the treatment of patients infected by HCMV. In this study we explored the potential usefulness of LEF for cytomegalovirus infection and found it to be a cost-effective new treatment for cytomegalovirus infection that deserves further study.

A screen for modulators of large T antigen's ATPase activity uncovers novel inhibitors of Simian Virus 40 and BK virus replication

New polyomaviruses are continually being identified, and it is likely that links between this virus family and disease will continue to emerge. Unfortunately, a specific treatment for polyomavirus-associated disease is lacking. Because polyomaviruses express large Tumor Antigen, TAg, we hypothesized that small molecule inhibitors of the essential ATPase activity of TAg would inhibit viral replication. Using a new screening platform, we identified inhibitors of TAg's ATPase activity. Lead compounds were moved into a secondary assay, and ultimately two FDA approved compounds, bithionol and hexachlorophene, were identified as the most potent TAg inhibitors known to date. Both compounds inhibited Simian Virus 40 replication as assessed by plaque assay and quantitative PCR. Moreover, these compounds inhibited BK virus, which causes BKV Associated Nephropathy. In neither case was host cell viability compromised at these concentrations. Our data indicate that directed screening for TAg inhibitors is a viable method to identify polyomavirus inhibitors, and that bithionol and hexachlorophene represent lead compounds that may be further modified and/or ultimately used to combat diseases associated with polyomavirus infection.

Fluoroquinolones inhibit HCV by targeting its helicase

BACKGROUND

HCV has infected >170 million individuals worldwide. Effective therapy against HCV is still lacking and there is a need to develop potent drugs against the virus. In the present study, we have employed two culture models to test the activity of fluoroquinolone drugs against HCV: a subgenomic replicon that is able to replicate independently in the cell line Huh-8 and the Huh-7 cell culture model that employs cells transfected with synthetic HCV RNA to produce the infectious HCV particles. Fluoroquinolones have also been shown to have inhibitory activity against certain viruses, possibly by targeting the viral helicase. To tease out the mechanism of the antiviral activity of fluoroquinolones, their effect on HCV NS3 helicase protein was also tested.

METHODS

Huh-7 cells producing the HCV virion as well as Huh-8 cells were grown in the presence or absence of 12 different fluoroquinolones. Afterwards, Huh-7 and Huh-8 cells were lysed and viral RNA was extracted. The extracted RNA was reverse transcribed and quantified by real-time quantitative PCR. Fluoroquinolones were also tested on purified NS3 protein in a molecular-beacon-based in vitro helicase assay.

RESULTS

To varying degrees, all of the tested fluoroquinolones effectively inhibited HCV replication in both Huh-7 and Huh-8 culture models. The inhibition of HCV NS3 helicase activity was also observed with all 12 of the fluoroquinolones.

CONCLUSIONS

Fluoroquinolones inhibit HCV replication possibly by targeting the HCV NS3 helicase. These drugs hold promise for the treatment of HCV infection.

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

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

Polyomavirus BK neutralizing activity in human immunoglobulin preparations

BACKGROUND

Polyomavirus BK (BKV) infection can cause nephropathy in the allograft kidney. No well-established drug treatment is available at this time. Human intravenous immunoglobulins (IVIG) have been used as an empiric therapy without proof of effectiveness.

METHODS

We tested five lots of commercially available IVIG preparations from two different suppliers for polyomavirus neutralizing activity. BKV and mouse polyomavirus were used to infect human and murine host cells, respectively, with or without prior treatment with IVIG. Neutralization activity was measured by quantitation of viral DNA after 7 days in culture.

RESULTS

Coincubation of BKV but not mouse polyomavirus with clinically relevant concentrations of IVIG derived from healthy and hepatitis B vaccinated subjects caused more than 90% inhibition of viral DNA yield after 7 days in culture. Consistent with a direct neutralizing mechanism, this effect was significantly diminished if viral infection was performed in immunoglobulin pretreated cells or if immunoglobulin treatment was delayed 2 hr after addition of infectious virus.

CONCLUSION

Human IVIG preparations contain BKV neutralizing antibodies. Data on neutralizing capacity of these antibodies are presented to aid dose exploration in clinical trials seeking to validate the use of IVIG in patients with BKV infection.

Evaluation of fluoroquinolones for the prevention of BK viremia after renal transplantation

BACKGROUND AND OBJECTIVES

Nearly 30% of renal transplant recipients develops BK viremia, a prerequisite for BK nephropathy. Case reports have evaluated treatment options for BK virus, but no controlled studies have assessed prophylactic therapies. Fluoroquinolone antibiotics were studied for prevention of BK viremia after renal transplantation.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This retrospective analysis evaluated adult renal transplant recipients with at least one BK viral load (blood) between 90 and 400 days after transplantation. Six to 12 months of co-trimoxazole was used for Pneumocystis prophylaxis. In sulfa-allergic/-intolerant patients, 6 to 12 months of atovaquone with 1 month of a fluoroquinolone was used. Fluoroquinolones can inhibit BK DNA topoisomerase. The two groups studied were those that received 30 days of levofloxacin or ciprofloxacin after transplantation and those that did not. The primary endpoint was BK viremia rates at 1 year. Of note, of the 160 patients not receiving fluoroquinolone prophylaxis, 40 received a fluoroquinolone for treatment of a bacterial infection within 3 months after transplantation. Subgroup analysis evaluating these 40 patients against the 120 who had no exposure to fluoroquinolones was completed.

RESULTS

A 1-month fluoroquinolone course after transplantation was associated with significantly lower rates of BK viremia at 1 year compared with those with no fluoroquinolone. In the subgroup analysis, exposure to fluoroquinolone for treatment of bacterial infections within 3 months after transplantation was associated with significantly lower 1-year rates of BK viremia.

CONCLUSIONS

This analysis demonstrates that fluoroquinolones are effective at preventing BK viremia after renal transplantation.

A rapid and simple high-performance liquid chromatography assay for the leflunomide metabolite, teriflunomide (A77 1726), in renal transplant recipients

Leflunomide (Arava), a drug with immunosuppressive and antiviral effects, is being used in renal transplant recipients, primarily for its action against BK polyomavirus (BKV), which affects 1% to 10% of renal transplant recipients and often causes failure of grafted kidneys. Leflunomide effects are solely due to an active metabolite, teriflunomide (formerly A77 1726). Trough blood concentrations of teriflunomide exceeding 40 microg/mL (148 micromol/L) are associated with progressive clearance of BKV. Toxic effects become increasingly apparent at higher concentrations. We have developed a rapid, simple, and robust high-performance liquid chromatography (HPLC) method for therapeutic monitoring of teriflunomide in renal transplant recipients. Sample preparation is rapid, and each HPLC separation takes about 7 minutes. Intraday and interday coefficients of variation were 1.5% or less and 5.6% or less, respectively. The method was linear to 200 microg/mL (740 micromol/L), which is well above teriflunomide concentrations that are likely to be observed.

The significance of renal C4d staining in patients with BK viruria, viremia, and nephropathy

Peritubular capillary C4d staining in allograft kidney is an important criterion for antibody-mediated rejection. Whether BK virus infection can result in complement activation is not known. We studied 113 renal allograft biopsies from 52 recipients with a history of BK virus activation. The samples were classified into four groups according to the concurrent detection of BK virus DNA in urine, plasma, and/or biopsy: BK-negative (n=37), viruria (n=53), viremia (n=7), and nephropathy (n=16) groups. The histological semiquantitative peritubular capillary C4d scores in the viremia (0.3+/-0.8) and BK nephropathy (0.6+/-0.9) groups were lower than those in the BK-negative group (1.2+/-1.1, P=0.05 and P=0.06, respectively) and the viruria group (1.2+/-1.1, P=0.04 and P=0.06, respectively). Diffuse or focal peritubular capillary C4d staining was present in 9/76 (12%) and 14/76 (19%) of all samples with concurrent BK virus reactivation (viruria, viremia, and nephropathy). The diagnosis of antibody-mediated rejection could be established in 7/9 (78%) and 5/14 (36%) of these samples, respectively. Diffuse tubular basement membrane C4d staining was restricted to BK nephropathy cases (4/16, 25%). Semiquantitative tubular basement membrane C4d scores were higher in BK nephropathy (1.2+/-1.3) compared with BK-negative (0.05+/-0.3, P=0.017) and viruria (0.0+/-0.0, P=0.008) groups. Bowman's capsule C4d staining was more frequent in BK nephropathy (5/16) compared with the aforementioned groups (2/36 (P=0.023) and 4/51 (P=0.03), respectively). Within the BK nephropathy group, samples with tubular basement membrane stain had more infected tubular epithelial cells (12.1+/-7.6% vs 4.4+/-5.0%, P=0.03) and a trend toward higher interstitial inflammation scores. In conclusion, peritubular capillary C4d staining remains a valid marker for the diagnosis of antibody-mediated rejection in the presence of concurrent BK virus infection. A subset of biopsies with BK nephropathy shows tubular basement membrane C4d staining, which correlates with marked viral cytopathic effect.

Intermediate dose cidofovir does not cause additive nephrotoxicity in BK virus allograft nephropathy

BKVAN has emerged as a major morbidity in kidney transplant recipients. Among treatment options is cidofovir, which can be nephrotoxic. We previously reported that intermediate dose cidofovir could be used without significant nephrotoxicity. We present extended results of the same treatment protocol in a larger cohort and with longer follow up. Diagnosis of BKVAN was based on detection of BK viral DNA from plasma and renal allograft biopsy tissue. All patients received cidofovir (0.25-1 mg/kg/dose) every 2-3 wk. Total number of cidofovir doses ranged from 1 to 18 (mean 8). This report includes eight patients, aged 5-21 yr, treated with intermediate dose cidofovir. Median follow-up was 11 months (range 4-32). Mean fall in reciprocal of serum creatinine (1/sCr) from baseline at BKVAN diagnosis was 64% (range 28-120%). A time-series plot of plasma BK virus PCR and 1/sCr showed marked reduction in viral loads without significant deterioration in 1/sCr from the initial value at BKVAN diagnosis. In this larger series with extended follow up, intermediate dose cidofovir without probenecid for the treatment of BKVAN continues to show stabilization of renal function without progression to renal failure.

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.

Use of leflunomide in the treatment of polyomavirus BK-associated nephropathy

OBJECTIVE

To review the available literature describing the use of leflunomide for the treatment of polyomavirus BK-associated nephropathy (BKVAN) in renal transplant recipients.

DATA SOURCES

Relevant literature was obtained through MEDLINE (1950-May 2008) and Science Citation Index Expanded (1900-May 2008) by using search terms leflunomide, Arava, polyomavirus, polyoma, BK virus, and transplant. Additional articles were identified through a manual search of the reference lists of the articles obtained.

STUDY SELECTION AND DATA EXTRACTION

All articles that were written in English and discussed leflunomide use for BKVAN in renal transplant recipients were evaluated. Case reports and in vitro studies were included in this review.

DATA SYNTHESIS

BKVAN has emerged as a problematic infectious complication with limited treatment options in renal transplant recipients. Leflunomide, used off-label for refractory BKVAN, is postulated to possess both antiviral and immunosuppressive properties. Two in vitro culture studies, 5 case reports/series, 2 retrospective cohort studies, and 3 prospective observational trials that described leflunomide use in BKVAN were identified. Available literature suggests that leflunomide at target blood concentrations of around 40 mg/L, in addition to immunosuppressive reduction, reduces BK viremia/viruria and graft failure, with few dose-limiting adverse events. It is highly recommended that routine complete blood cell counts, hepatic function panels, and drug concentrations be monitored to detect toxicity.

CONCLUSIONS

Leflunomide appears to be promising as adjunctive treatment of BKVAN in renal transplant patients. Due to the lack of controlled randomized trials, however, use of leflunomide as first-line treatment cannot be routinely recommended.

Transforming growth factor-beta-mediated regulation of BK virus gene expression

The increasing prevalence of BK virus (BKV)-associated diseases in immunosuppressed patients has prompted an investigation of the immune response to BKV, especially the role of cytokines in regulating viral replication. We examined the effect of TGF-beta, a cytokine that is stimulated by certain immunosuppressive therapies, on BKV gene expression during lytic infection of renal proximal tubule epithelial cells. Viral gene expression, and specifically the activity of the BKV early promoter, is regulated by TGF-beta in a strain-dependent manner. Promoter activity is upregulated in the presence of TGF-beta for the TU strain of BKV, and not for the Dik, Dunlop, or Proto-2 strains. Using site-directed mutagenesis, we have identified a small segment of the TU promoter that is required for stimulation in response to TGF-beta. These results demonstrate that BKV strains can respond differently to cytokine treatment and suggest that TGF-beta may play a role in the reactivation of BKV.

Repression of BK virus infection of human renal proximal tubular epithelial cells by pravastatin

BACKGROUND

BK virus (BKV), a human polyomavirus, causes BKV nephritis, which often leads to graft loss after renal transplantation. Currently, the only efficient therapy against BKV nephritis seems to be a reduction or change of immunosuppressive agents, but this may increase the inherent risk of rejection. Here, we report the ability of 3-hydroxy-3-methyl-glutaryl coenzyme A reductase inhibitor (statin), which is routinely used to treat hypercholesterolemia, to repress BKV entry pathways in human renal proximal tubular epithelial cells (HRPTEC) and, correspondently, prevent BKV infection.

METHODS

HRPTEC were co-incubated with BKV and pravastatin. Then the percentage of HRPTEC infected with BKV by immunofluorescent analysis and large T-antigen expression which suggested BKV infection by Western blots was assessed in the absence and presence of pravastatin. The distribution of purified and labeled BKV particles in the presence and absence of pravastatin was also investigated.

RESULTS

Both the percentage of BKV infected cells and the large T-antigen expression were significantly decreased in HRPTEC pretreated and co-incubated with pravastatin. However, when pravastatin was added 72 hr after BKV infection it failed to decrease percentage of BKV infected cells. It is likely, that pravastatin's inhibitory effect is explained by depletion of caveolin-1, a critical element of caveolae. BKV enters HRPTEC by caveolar-mediated endocytosis. We provide evidence that pravastatin dramatically decreased caveolin-1 expression in HRPTEC and interfered with internalization of labeled BKV particles.

CONCLUSIONS

Our data suggest that pravastatin, acting through depletion of caveolin-1, prevented caveolar-dependent BKV internalization and repressed BKV infection of HRPTEC.

Viral infection after renal transplantation: surveillance and management

Viral infections remain a significant cause of morbidity and mortality following renal transplantation. Although cytomegalovirus is the most common opportunistic pathogen seen in transplant recipients, numerous other viruses have also affected outcomes. In some cases, preventive measures such as pretransplant screening, prophylactic antiviral therapy, or post transplant viral monitoring may limit the impact of these infections. Recent advances in laboratory monitoring and antiviral therapy have improved outcomes. This review will summarize the major viral infections seen following transplant and discuss strategies for prevention and management of these potential pathogens.

Functional characterization of BK virus-specific CD4+ T cells with cytotoxic potential in seropositive adults

BK polyomavirus (BKV) reactivation is associated with a failure of T cell immunity in kidney transplant patients, and may lead to BKV-associated nephropathy (BKVN) and loss of the allograft. BKV reactivation in hematopoietic stem cell transplant recipients is associated with hemorrhagic cystitis. We have investigated T cell responses to overlapping peptide mixtures corresponding to the whole BKV major T antigen (TAg) and major capsid protein (VP1) in peripheral blood mononuclear cell samples from a cohort of healthy BKV-seropositive subjects. The majority of these individuals possessed populations of both CD8(+) and CD4(+) T cells specific for these BKV antigens. After expansion in culture, the majority of the BKV-specific CD4(+) T cells, in addition to expressing CD40L (CD154), secreted both interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha, contained both granzyme A and granzyme B, and degranulated/mobilized CD107 in response to antigen-specific stimulation. These T cells thus represent potentially functional BKV-specific cytotoxic CD4(+) T lymphocytes. Secretion of both TNF-alpha and IFN-gamma by CD154(+)CD4(+) T cells on BKV-specific stimulation was associated with higher levels of granzyme B and a higher proportion of degranulating cells compared with CD154(+)CD4(+) T cells producing only IFN-gamma or neither cytokine. These healthy subjects also harbored populations of functional CD8(+) T cells specific for one or more of three newly defined HLA-A 02-restricted cytotoxic T lymphocyte epitopes within the BKV TAg as well as two HLA-A 02-restricted epitopes within the BKV VP1 we have previously described. The BKV-specific CD4(+) T cells characterized in this study may play a part in maintaining persistent memory T cell responses to the virus and thus contribute to the immune control of BKV in healthy individuals.

Polyomavirus BK infection in blood and marrow transplant recipients

The association of BK virus infection with hemorrhagic cystitis in blood and marrow transplant (BMT) recipients was first demonstrated two decades ago. During this time, therapeutic interventions focused on supportive measures such as hyperhydration, continuous bladder irrigation and topical administration of agents that alter the mucosal surface of the bladder wall. In recent years, PCR amplification of viral DNA in the urine and plasma has solidified the association of BK virus infection with hemorrhagic cystitis, demonstrating that higher urine and plasma viral loads occur in the setting of disease. The evaluation of virus-specific therapy has lagged behind assessment of the viral load and theories of pathogenesis. Extrapolating from successes in the treatment of BK virus nephropathy in the renal transplant population, cidofovir and leflunomide are identified as potential effective agents for the treatment of BK virus-associated hemorrhagic cystitis. The fluoroquinolone antibiotics may prove to be effective as prophylactic agents. Given the manifestation of BK virus infection in organs outside of the urinary tract in an increasing immunocompromised patient population and the availability of potential antiviral agents, therapeutic trials need to progress beyond the small case series in order to improve the morbidity and mortality caused by BK virus-associated hemorrhagic cystitis in the BMT population.

Polyomavirus BK infection in blood and marrow transplant recipients

The association of BK virus infection with hemorrhagic cystitis in blood and marrow transplant (BMT) recipients was first demonstrated two decades ago. During this time, therapeutic interventions focused on supportive measures such as hyperhydration, continuous bladder irrigation and topical administration of agents that alter the mucosal surface of the bladder wall. In recent years, PCR amplification of viral DNA in the urine and plasma has solidified the association of BK virus infection with hemorrhagic cystitis, demonstrating that higher urine and plasma viral loads occur in the setting of disease. The evaluation of virus-specific therapy has lagged behind assessment of the viral load and theories of pathogenesis. Extrapolating from successes in the treatment of BK virus nephropathy in the renal transplant population, cidofovir and leflunomide are identified as potential effective agents for the treatment of BK virus-associated hemorrhagic cystitis. The fluoroquinolone antibiotics may prove to be effective as prophylactic agents. Given the manifestation of BK virus infection in organs outside of the urinary tract in an increasing immunocompromised patient population and the availability of potential antiviral agents, therapeutic trials need to progress beyond the small case series in order to improve the morbidity and mortality caused by BK virus-associated hemorrhagic cystitis in the BMT population.