BK virus associated nephropathy in renal transplantation: where do we stand

BK virus is an increasingly identified complication in renal allograft recipients. During the last decade, the use of potent immunosuppressive medications has led to reemergence of this virus. Despite the paucity of randomized trials, we have come a long way in the knowledge of BK virus associated nephropathy. This review highlights the epidemiological, pathogenic, pathological, and clinical aspects of BK virus. It summarizes advances made in prophylaxis and treatment strategies to curtail this virus in an era of modern immunosuppression. The old word of wisdom- prevention is better than cure- might be relevant in context of BK virus prophylaxis with flouroquinolones in years to follow.

Chemical methodology as a source of small-molecule checkpoint inhibitors and heat shock protein 70 (Hsp70) modulators

Unique chemical methodology enables the synthesis of innovative and diverse scaffolds and chemotypes and allows access to previously unexplored "chemical space." Compound collections based on such new synthetic methods can provide small-molecule probes of proteins and/or pathways whose functions are not fully understood. We describe the identification, characterization, and evolution of two such probes. In one example, a pathway-based screen for DNA damage checkpoint inhibitors identified a compound, MARPIN (ATM and ATR pathway inhibitor) that sensitizes p53-deficient cells to DNA-damaging agents. Modification of the small molecule and generation of an immobilized probe were used to selectively bind putative protein target(s) responsible for the observed activity. The second example describes a focused library approach that relied on tandem multicomponent reaction methodologies to afford a series of modulators of the heat shock protein 70 (Hsp70) molecular chaperone. The synthesis of libraries based on the structure of MAL3-101 generated a collection of chemotypes, each modulating Hsp70 function, but exhibiting divergent pharmacological activities. For example, probes that compromise the replication of a disease-associated polyomavirus were identified. These projects highlight the importance of chemical methodology development as a source of small-molecule probes and as a drug discovery starting point.

[Cytomegalovirus and BK polyomavirus infection after renal transplantation]

Cytomegalovirus (CMV) and BK polyomavirus (BKV) infections have been described in a high percentage of renal transplant patients and are known to cause various complications in renal transplantation. They are closely related to immunosuppressive therapy and implicated in the progression of graft failure. This review focuses on the clinical aspects of CMV and BKV infection after renal transplantation, optimal monitoring, and recent preventive measures and interventions to improve graft function and recipient survival.

Aggressive immunosuppression minimization reduces graft loss following diagnosis of BK virus-associated nephropathy: a comparison of two reduction strategies

BACKGROUND AND OBJECTIVES

BK virus-associated nephropathy (BKVAN) has emerged as a leading cause of kidney graft loss, with no known predictors for graft loss and no consensus regarding treatment other than reduction of immunosuppression.

DESIGN, SETTING, PARTICIPANTS AND MEASUREMENTS

A single-center retrospective analysis was performed of all cases of BKVAN from 1999 to 2005 for clinical predictors of graft loss, with evaluation of the impact of immunosuppression withdrawal (3-drug to 2-drug immunosuppression) within the first month versus reduction of immunosuppression.

RESULTS

Of 910 kidney transplants, 35 (3.8%) cases of BKVAN were diagnosed at a median of 15 months after transplant (range, 5.5 to 90 months after transplant), 16 (46%) of which progressed to graft failure at a median of 11 months (range, 2 to 36 months) after diagnosis. Depleting antibody induction was a significant risk factor for graft loss on univariate analysis, whereas early drug withdrawal (<1 mo following diagnosis) protected against graft loss. On multivariate analysis, these findings were independent predictors of graft outcomes. Additionally, when patients were comanaged by referring nephrologists and the transplant center before the diagnosis of BKVAN, the risk of graft loss was 11-fold higher (P = 0.03) than if patients were managed solely by the transplant center.

CONCLUSIONS

Increased awareness and early diagnosis of BKVAN, with aggressive tapering of immunosuppression once established, is critical to preserve kidney graft function. Early drug withdrawal to low-dose two-drug therapy maintenance may be preferable to a general reduction of agents.

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 (> or = 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.

Successful pregnancy in renal transplant recipient with previous known polyomavirus nephropathy

Pregnancy after renal transplantation has become increasingly common. Studies in non-immunocompromised patients have shown that pregnant women have increased susceptibility to infection or reactivation of latent virus such as BK virus. To what extent a renal transplant recipient is at risk for reactivation of polyoma virus during pregnancy remains unknown. We hereby report successful pregnancy outcome in a renal transplant recipient with a known history of BK virus nephropathy treated with cidofovir i.v. To our knowledge, this is the first published experience with a successful pregnancy in renal transplant recipients with known history of polyomavirus-associated nephropathy.

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.

Leflunomide treatment for polyomavirus BK-associated nephropathy after kidney transplantation

Polyomavirus-associated nephropathy (PVAN) affects 1-10% of kidney-transplant (KT) patients, with graft failure/loss in approximately 90% of cases. Reducing immunosuppression is the key treatment option, but addition of leflunomide may improve BK Virus (BKV) clearance and graft survival. In a prospective open-labeled study, 12 KT patients with biopsy-proven PVAN were treated with reduced immunosuppression and leflunomide. BKV viremia and graft function were followed. PVAN was diagnosed at 6 months (3-192) post-transplant; median serum creatinine concentration (sCC) was 189 micromol/l (92-265). After 16 months (8-30) of follow-up, the sCC was 150 micromol/l (90-378, NS). Renal function improved in six cases (50%), remained stable in two (16.6%) and deteriorated in four (33.4%), with graft loss in two (17%). Clearance of BKV viremia was observed in five (42%) cases. Side effects included anemia in six cases leading to leflunomide withdrawal in two patients, and mild thrombocytopenia. In KT patients diagnosed with PVAN, leflunomide plus reduced immunosuppression improved graft function in 66.6%, cleared BKV viremia in 42%, and resulted in side effects in 17%. This limited efficacy contrasts with other reports and falls short of expectation. We conclude that active screening, earlier diagnosis and intervention remain the cornerstones of treatment.

Dual infection with polyomavirus BK and acyclovir-resistant herpes simplex virus successfully treated with cidofovir in a bone marrow transplant recipient

A hematopoietic stem cell transplant recipient developed a mucosal herpes simplex virus-1 (HSV-1) infection while under acyclovir (ACV) treatment (HSV was later shown to be resistant to ACV). Concomitantly, the patient presented a hemorrhagic cystitis (HC) due to polyomavirus BK, for which intravenous cidofovir (CDV) was prescribed. The patient benefited from the broad-spectrum anti-DNA virus activity of CDV, and not only the HC resolved without signs of nephrotoxicity but also the HSV-1 lesions disappeared. This is the first report describing the effect of CDV on 2 simultaneous and unrelated DNA viral infections in an immunosuppressed transplant recipient. In addition, we describe here that this HSV-1 isolate possesses a unique phenotype and genotype.

Ureteric and urethral stenosis: a complication of BK virus infection in a pediatric renal transplant patient

Viral infections remain an Achilles heel in solid organ transplant. In recent years, incidence of BK virus infection in the kidney transplant population is on rise. BK virus is known to cause severe renal dysfunction, ureteric stenosis, and hemorrhagic cystitis in renal transplant patients. Most of the reviews and prospective studies on BKV nephropathy pertain to the adult population. Although ureteral stenosis is known to occur in BK infection, urethral stenosis is not being reported in the literature. In this report, we describe a case of BKV nephropathy in a 16-yr-old male presenting with ureteric and urethral stenosis. To our knowledge this is the first case report of its kind in a pediatric transplant population.

Intravesikale Cidofovir – Instillationstherapie bei Polyomavirus-assoziierter hämorrhagischer Zystitis nach Knochenmarktransplantation

Viral infections of the urogenital tract are a potential problem in patients taking immunosuppressive medication. We report a 14 year old male patient with hemorrhagic cystitis who had undergone bone marrow transplantation for the treatment of acute lymphoblastic leukemia. Attempts at coagulation as well as instillation treatment and continuous bladder irrigation were not sufficient to stop bleeding. Sequential to these procedures, local instillation with cidofovir into the bladder was started to treat a suspected infection with polyomavirus and the gross hematuria stopped within a few days.

Utilization of vero cells for primary and chronic BK virus infection

BK virus (BKV) nephropathy has a poor prognosis for renal allograft survival with 30% to 60% risk of allograft loss over 1 year. In the past decade, BKV nephropathy has occurred in 1% to 10% of renal transplant patients, with higher rates observed in patients with increased immunosuppression exposure and renal allograft injury. Vero cells (Green monkey kidney cell origin) were optimized for BKV primary and chronic infection inclusive of culture requirements for 60-day growth and monolayer confluence. Quantification of BKV replication in the culture supernatant (SN) and cells was by real-time polymerase-chain reaction (PCR) using the Roche Lightcycler 2.0. Primary BKV infection of Vero cells is achieved by 2 hour incubation with 6.5 x 10(5) BKV copies with subsequent washing of cells leading to steady-state cellular infection of 10(2) to 10(3) BKV copies. Primary infection is demonstrated within 7 to 10 days by a >10-fold increase of BKV copies in SN. Thereafter, a BKV viral load reduction in SN to a chronic/latent level (<10(2) BKV copies in SN) is observed by 14 days. Vero cells with chronic low-level BKV infection (10(2)-10(3) BKV copies in cells) exhibited reactivation (>10(5) BKV copies in SN) in >72% of late culture wells after 40 days. Vero cells can accommodate primary and chronic BKV infection followed by viral reactivation in late culture. The performance characteristics of 3 different pathogenic BKV strains obtained from patients with BKV nephropathy had infectivity profiles that correlated well the relative clinical profile in this Vero cell culture system.

Prevalence and clinical course of BK virus nephropathy in pancreas after kidney transplant patients

The influence of BK virus nephropathy (BKVN) in pancreas after kidney (PAK) transplantation is unclear. A retrospective analysis of PAK transplants performed at our center was conducted to determine the impact of BKVN. Among 40 PAK transplants performed using sequential immunosuppression, four patients developed BKVN, as defined by a >20% rise in serum creatinine and BK viremia (BK plasma load >4 log copies/mL), at a median of 19 months following PAK. In all four patients, treatment of BKVN consisted of reduction in tacrolimus, cessation of mycophenolate mofetil, and introduction of leflunomide. With this approach, two patients experienced improvement or stabilization of renal function. The remaining two patients progressed to dialysis dependence despite treatment. Plasma BK load < or =5 log copies/mL was associated with graft preservation. Gender, age, delay between transplants, cumulative Thymoglobulin dose, and type of kidney donor were not associated with BK virus infection. Pancreas graft rejection or dysfunction was not observed with the above immunosuppression modification. Mean amylase and lipase > or =6 months following BKVN treatment remained normal. BKVN is an important cause of kidney allograft loss in PAK patients. Screening and early treatment of BKVN may enable preservation of kidney and pancreas grafts.

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.

Management of infections by the human polyomavirus JC: past, present and future

Progressive multifocal leukoencephalopathy is a fatal demyelinating disease caused by infection of oligodendrocytes by the human polyomavirus known as JC virus. Over the past 10 years, the disease has been documented almost exclusively in AIDS patients, who constitute a rapidly growing population of immunosuppressed individuals. More recently, progressive multifocal leukoencephalopathy has also been described in patients undergoing solid organ or cell transplant, as a result of immunosuppressive therapy to avoid graft rejection. Although there are several reports of successful treatment of progressive multifocal leukoencephalopathy, large-scale prospective trials have been few, and with mixed results. As more is discovered about the biology of JC virus infection and advances are made in targeted parenchymal delivery of therapeutic agents, there is hope for the development of an effective therapy for progressive multifocal leukoencephalopathy.

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.

[Polyomavirus BK-associated nephropathy after kidney transplantation]

Polyomavirus BK (BKV) infection has been lately recognized as a major cause of renal allograft dysfunction. BKV-related interstitial nephropathy (PVAN) may affect 1-10% of renal allograft recipients, occurring more frequently in the first 6 months after transplantation. Progression to irreversible allograft failure has been observed in up to 45% of all cases; thanks to increased PVAN awareness and improved diagnostic techniques, the rate of graft loss has lowered, more consistently in centres with active screening and intervention programs. PVAN pathogenesis is characterized by multiple synergizing factors, among which immunodepression plays a key role. PVAN diagnosis requires the evaluation of a renal biopsy showing polyomavirus cytopathic changes and confirming BKV through an ancillary technique such as immunohistochemistry. Given the focal nature of the disease, early diagnosis may be difficult to obtain. Thus, quantification of BKV-DNA in plasma has been suggested as surrogate marker for PVAN. To date, given the lack of controlled trials, there is no consensus on a 'standard' management of PVAN. However, evidence based on reported observations suggests that a step-wise reduction of immunosuppression, preceded by pulsed steroids in case of coexistent acute rejection, may improve outcomes. Additional options may be represented by drugs with antiviral activity, such as cidofovir, leflunomide or quinolones. Application of a preventive treatment based on viremia monitoring has been recently proposed.

Anterior Uveitis Associated With Treatment With Intravenous Cidofovir in Kidney Transplant Patients With BK Virus Nephropathy

BACKGROUND

Polyomavirus-associated nephropathy (PVAN) is an important cause of kidney dysfunction and graft loss. Different treatment regimens have been used, including low-dose intravenous cidofovir. Anterior uveitis, a complication of this treatment, has been reported after its use in patients with cytomegalovirus-associated retinitis. We analyzed the incidence and associated risk factors for this disorder in patients with PVAN.

PATIENTS AND METHODS

The study included 14 kidney-transplant patients who had received low doses of cidofovir after being diagnosed with PVAN.

RESULTS

Five (35%) patients developed an episode of anterior uveitis. The mean number of cidofovir doses given was 6.8 +/- 1.6 as compared with 9.1 +/- 2.1 in patients who did not develop the disease. Creatinine clearance at diagnosis of the nephropathy and after terminating treatment was lower in the uveitis patients, who had a graft survival of 40% versus 100% in the patients who did not develop eye involvement. Treatment was suspended in the affected patients, with complete resolution in 80% after the administration of topical corticoids and cycloplegics.

CONCLUSIONS

Anterior uveitis secondary to low-dose treatment with cidofovir is a common complication in patients with PVAN and is associated with the degree of renal involvement. In the absence of larger studies, cidofovir should be used with caution in patients with creatinine clearance below 30 mL/min.

Clinical utility of histological features of polyomavirus allograft nephropathy

BACKGROUND

The purpose of this study was to determine if histological features of polyomavirus allograft nephropathy (PVAN) are associated with the clinical presentation and outcomes of PVAN.

METHODS

We examined the histological features of initial and follow-up biopsies of 20 kidney and kidney-pancreas transplant recipients with PVAN during a time prior to routine surveillance. The subjects' demographics, clinical characteristics, and outcomes were compared based upon classification of histological features of PVAN on initial biopsy.

RESULTS

Diabetes mellitus (45%) and a history of tacrolimus-induced nephrotoxicity (35%) appeared to be prevalent in subjects with PVAN. Although histological severity of PVAN did not predict or correlate with the clinical course of PVAN, subjects with pattern C on initial PVAN biopsy presented later posttransplant, had higher serum creatinine level at presentation, and had significant allograft deterioration at follow-up than subjects with either pattern A or B on initial biopsy. Resolution of PVAN was noted in 60% of follow-up biopsies and occurred more frequently in subjects with pattern B on initial biopsy. Most subjects developed chronic allograft nephropathy after PVAN and viral clearance did not abrogate the progression to chronic allograft nephropathy.

CONCLUSIONS

These data indicate that histologic patterns of PVAN may have clinical correlation to disease presentation and prognosis.

Low incidence of BK virus nephropathy after simultaneous kidney pancreas transplantation

BACKGROUND

BK virus renal allograft nephropathy (BKVAN) in the setting of simultaneous kidney-pancreas transplantation (SKPT) has been inadequately studied and reported. We analyzed our data on the incidence of BKVAN and its outcome in SKPT recipients at University of Pittsburgh Medical Center (UPMC) and affiliated centers and report significant differences compared to previous studies.

METHODS

This study used retrospective review and case studies.

RESULTS

A review of 243 consecutive SKPT recipients from January 1, 1996 to December 31, 2004 identified seven cases (three females; ages = 23-54 yrs) of BKVAN following SKPT (incidence = 2.9%). The immunosuppressive protocols during this period were divided into: Period I (pre-August 2001) with no antibody induction and Period II (post-August 2001) with alemtuzumab or antithymocyte globulin induction with steroid avoidance. One BKVAN case was diagnosed in Period II (incidence = 1.4%). Six of seven patients were treated with intravenous cidofovir (0.20-0.50 mg/kg) every two to four weeks over one to six months. Three patients lost the renal allograft 8-22 months following diagnosis of BKVAN, whereas four patients had prolonged allograft survival. Pancreatic function was well preserved in five; one patient lost the pancreatic function due to surgical complications and one has had partial preservation.

CONCLUSIONS

There was a relatively lower incidence of BKVAN among SKPT patients at our center. Although overall graft loss rate was comparable to other series, BKVAN patients had a slightly prolonged graft life. The BKVAN incidence was further reduced in patients receiving modified immunosuppression with antibody preconditioning. The underlying reasons may include less toxic immunosuppressive protocols, earlier diagnosis and the use of antiviral therapy.