Leflunomide treatment for polyomavirus BK-associated nephropathy after kidney transplantation

BK Polyomavirus in Pediatric Renal Transplantation-What We Know and What We Do Not

BK polyomavirus (BKPyV) is still a real threat in the management of kidney transplantation. Immunosuppressive treatment disrupts the equilibrium between virus replication and immune response, and uncontrolled BKPyV replication leads to nephropathy (BKPyV nephropathy). The first evidence of BKPyV reactivation in transplant recipients is the detection of viral shedding in urine, which appears in 20% to 60% of patients, followed by BKPyV viremia in 10-20% of kidney transplant recipients. BKPyV nephropathy eventually occurs in 1-10% of this population, mainly within the first 2 years post-transplantation, causing graft loss in about half of those patients. Few data exist regarding the pediatric population and we focus on them. In this paper, we review the existing diagnostic methods and summarize the evidence on the role of BKPyV humoral and cellular immunity in modulating the clinical course of BKPyV infection and as potential predictors of the outcome. We look at the known risk factors for BKPyV nephropathy in the immunosuppressed patient. Finally, we propose a sensible clinical attitude in order to screen and manage BKPyV infection in kidney transplant children.

The Second International Consensus Guidelines on the Management of BK Polyomavirus in Kidney Transplantation

BK polyomavirus (BKPyV) remains a significant challenge after kidney transplantation. International experts reviewed current evidence and updated recommendations according to Grading of Recommendations, Assessment, Development, and Evaluations (GRADE). Risk factors for BKPyV-DNAemia and biopsy-proven BKPyV-nephropathy include recipient older age, male sex, donor BKPyV-viruria, BKPyV-seropositive donor/-seronegative recipient, tacrolimus, acute rejection, and higher steroid exposure. To facilitate early intervention with limited allograft damage, all kidney transplant recipients should be screened monthly for plasma BKPyV-DNAemia loads until month 9, then every 3 mo until 2 y posttransplant (3 y for children). In resource-limited settings, urine cytology screening at similar time points can exclude BKPyV-nephropathy, and testing for plasma BKPyV-DNAemia when decoy cells are detectable. For patients with BKPyV-DNAemia loads persisting >1000 copies/mL, or exceeding 10 000 copies/mL (or equivalent), or with biopsy-proven BKPyV-nephropathy, immunosuppression should be reduced according to predefined steps targeting antiproliferative drugs, calcineurin inhibitors, or both. In adults without graft dysfunction, kidney allograft biopsy is not required unless the immunological risk is high. For children with persisting BKPyV-DNAemia, allograft biopsy may be considered even without graft dysfunction. Allograft biopsies should be interpreted in the context of all clinical and laboratory findings, including plasma BKPyV-DNAemia. Immunohistochemistry is preferred for diagnosing biopsy-proven BKPyV-nephropathy. Routine screening using the proposed strategies is cost-effective, improves clinical outcomes and quality of life. Kidney retransplantation subsequent to BKPyV-nephropathy is feasible in otherwise eligible recipients if BKPyV-DNAemia is undetectable; routine graft nephrectomy is not recommended. Current studies do not support the usage of leflunomide, cidofovir, quinolones, or IVIGs. Patients considered for experimental treatments (antivirals, vaccines, neutralizing antibodies, and adoptive T cells) should be enrolled in clinical trials.

BK viral infection: A review of management and treatment

BK viral infection remains to be a challenging post-transplant infection, which can result in kidney dysfunction. The mainstay approach to BK infection is reduction of immunosuppression. Alterations in immunosuppressive regimen with minimization of calcineurin inhibitors, use of mechanistic target of rapamycin inhibitors, and leflunomide have been attempted with variable outcomes. Over the past few years, investigators have explored potential therapeutic options for BK infection. Fluoroquinolone prophylaxis and treatment was found to have no benefit in kidney transplant recipients. The utility of cidofovir is limited by its nephrotoxicity. Intravenous immunoglobulin is becoming a popular option for treatment and prophylaxis for BK infection, as it increases the neutralizing antibody titers against the most common BK virus serotypes. Virus-specific T cell therapy is an emerging treatment option for BK viremia. In this review, we will explore management and therapeutic options for BK infection and recent evidence available in literature.

Adverse Drug Events after Kidney Transplantation

Introduction: Kidney transplantation stands out as the optimal treatment for patients with end-stage kidney disease, provided they meet specific criteria for a secure outcome. With the exception of identical twin donor-recipient pairs, lifelong immunosuppression becomes imperative. Unfortunately, immunosuppressant drugs, particularly calcineurin inhibitors like tacrolimus, bring about adverse effects, including nephrotoxicity, diabetes mellitus, hypertension, infections, malignancy, leukopenia, anemia, thrombocytopenia, mouth ulcers, dyslipidemia, and wound complications. Since achieving tolerance is not feasible, patients are compelled to adhere to lifelong immunosuppressive therapies, often involving calcineurin inhibitors, alongside mycophenolic acid or mTOR inhibitors, with or without steroids. Area covered: Notably, these drugs, especially calcineurin inhibitors, possess narrow therapeutic windows, resulting in numerous drug-related side effects. This review focuses on the prevalent immunosuppressive drug-related side effects encountered in kidney transplant recipients, namely nephrotoxicity, post-transplant diabetes mellitus, leukopenia, anemia, dyslipidemia, mouth ulcers, hypertension, and viral reactivations (cytomegalovirus and BK virus). Additionally, other post-kidney-transplantation drugs such as valganciclovir may also contribute to adverse events such as leukopenia. For each side effect, we propose preventive measures and outline appropriate treatment strategies.

Therapeutic strategies against BK polyomavirus infection in kidney transplant recipients: Systematic review and meta-analysis

BACKGROUND

The selection of antiviral therapy for BK polyomavirus (BKPyV) infection has been extensively debated. Our study aimed to assess the efficacy and safety of various treatments for BKPyV infection.

METHODS

We searched PubMed, EMBASE, and Web of Science databases for relevant studies regarding drug treatments for BKPyV viremia/DNAemia published between January 1, 1970 and September 30, 2022. Two independent authors screened the published studies, extracted pertinent data, and evaluated their methodological quality. A meta-analysis was performed using the RevMan software version 4.2.2.

RESULTS

A total of 33 published studies involving 986 patients were included in the meta-analysis. Overall, therapeutic interventions comprised immunosuppression reduction alone or in combination with leflunomide, intravenous immunoglobulin (IVIG), cidofovir, or mTOR inhibitor (mTORi) therapy. The meta-analysis revealed that the efficacy of immunosuppression reduction alone for serum BKPyV clearance was 68% (95% confidence interval [CI]: 0.58-0.77; I2 = 78%). Moreover, the efficacy of immunosuppression reduction in combination with leflunomide, cidofovir, IVIG, or mTORi therapy for serum BKPyV clearance was 61% (95% CI: 0.47-0.74; I2 = 83%), 71% (95% CI: 0.63-0.78; I2 = 0), 87% (95% CI: 0.82-0.93; I2 = 45%), and 80% (95% CI: 0.59-1.00; I2 = 58%), respectively. Compared to immunosuppression reduction alone, immunosuppression reduction combined with IVIG therapy offered a statistically significant benefit in serum BKPyV clearance (P < 0.01) with minimal adverse reactions, whereas other adjunctive drug treatments did not demonstrate considerable effects.

CONCLUSIONS

Reducing immunosuppression remains the primary approach for treating BKPyV infection. Although the combination treatment with IVIG proved to be most effective, other agents might offer varied antiviral advantages of high heterogeneity, which should be substantiated in future long-term randomized controlled trials.

Infections after organ transplantation and immune response

Organ transplantation has provided another chance of survival for end-stage organ failure patients. Yet, transplant rejection is still a main challenging factor. Immunosuppressive drugs have been used to avoid rejection and suppress the immune response against allografts. Thus, immunosuppressants increase the risk of infection in immunocompromised organ transplant recipients. The infection risk reflects the relationship between the nature and severity of immunosuppression and infectious diseases. Furthermore, immunosuppressants show an immunological impact on the genetics of innate and adaptive immune responses. This effect usually reactivates the post-transplant infection in the donor and recipient tissues since T-cell activation has a substantial role in allograft rejection. Meanwhile, different infections have been found to activate the T-cells into CD₄⁺ helper T-cell subset and CD₈⁺ cytotoxic T-lymphocyte that affect the infection and the allograft. Therefore, the best management and preventive strategies of immunosuppression, antimicrobial prophylaxis, and intensive medical care are required for successful organ transplantation. This review addresses the activation of immune responses against different infections in immunocompromised individuals after organ transplantation.

A multivalent polyomavirus vaccine elicits durable neutralizing antibody responses in macaques

In 2019, there were about 100,000 kidney transplants globally, with more than a quarter of them performed in the United States. Unfortunately, some engrafted organs are lost to polyomavirus-associated nephropathy (PyVAN) caused by BK and JC viruses (BKPyV and JCPyV). Both viruses cause brain disease and possibly bladder cancer in immunosuppressed individuals. Transplant patients are routinely monitored for BKPyV viremia, which is an accepted hallmark of nascent nephropathy. If viremia is detected, a reduction in immunosuppressive therapy is standard care, but the intervention comes with increased risk of immune rejection of the engrafted organ. Recent reports have suggested that transplant recipients with high levels of polyomavirus-neutralizing antibodies are protected against PyVAN. Virus-like particle (VLP) vaccines, similar to approved human papillomavirus vaccines, have an excellent safety record and are known to induce high levels of neutralizing antibodies and long-lasting protection from infection. In this study, we demonstrate that VLPs representing BKPyV genotypes I, II, and IV, as well as JCPyV genotype 2 produced in insect cells elicit robust antibody titers. In rhesus macaques, all monkeys developed neutralizing antibody titers above a previously proposed protective threshold of 10,000. A second inoculation, administered 19 weeks after priming, boosted titers to a plateau of ≥ 25,000 that was maintained for almost two years. No vaccine-related adverse events were observed in any macaques. A multivalent BK/JC VLP immunogen did not show inferiority compared to the single-genotype VLP immunogens. Considering these encouraging results, we believe a clinical trial administering the multivalent VLP vaccine in patients waiting to receive a kidney transplant is warranted to evaluate its ability to reduce or eliminate PyVAN.

BK Polyomavirus-Induced Nephropathy in Native Kidney

BK polyomavirus has been well-studied as an opportunistic infection in immunocompromised kidney transplant patients. In the majority of the population, BK polyomavirus establishes a lifelong infection in renal tubular and uroepithelial cells; however, in an immunocompromised state, the virus can reactivate and can lead to BK polyomavirus-associated nephropathy (BKN). In this case, the patient was a 46-year-old male with a past medical history of HIV, compliant with antiretroviral therapy (ART), and B-cell lymphoma treated with chemotherapy. The patient presented with worsening kidney function of unknown etiology. This prompted further assessment with a kidney biopsy. Kidney biopsy findings were consistent with BKN. In the literature, BKN has been studied in renal transplant patients; however, it rarely involves native kidneys.

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

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

Polyoma BK Virus in Kidney Transplant Recipients: Screening, Monitoring, and Management

Polyomavirus BK virus (BKPyV) infection is an important complication of kidney transplantation and allograft failure. The prevalence of viremia is 10%-15%, compared with BK-associated nephropathy (BKPyVAN) at 3%-5%. Given that there are no effective antiviral prophylaxis or treatment strategies for BKPyVAN, active screening to detect BKPyV viremia is recommended, particularly during the early posttransplant period. Immunosuppression reduction to allow viral clearance may avoid progression to severe and irreversible allograft damage. The frequency and duration of screening are highly variable between transplant centers because the evidence is reliant largely on observational data. While the primary treatment goals center on achieving viral clearance through immunosuppression reduction, prevention of subsequent acute rejection, premature graft loss, and return to dialysis remain as major challenges. Treatment strategies for BKPyV infection should be individualized to the recipient's underlying immunological risk and severity of the allograft infection. Efficacy data for adjuvant therapies including intravenous immunoglobulin and cidofovir are sparse. Future well-powered and high-quality randomized controlled trials are needed to inform evidence-based clinical practice for the management of BKPy infection.

Chronic Kidney Allograft Disease: New Concepts and Opportunities

Chronic kidney disease (CKD) is increasing in most countries and kidney transplantation is the best option for those patients requiring renal replacement therapy. Therefore, there is a significant number of patients living with a functioning kidney allograft. However, progressive kidney allograft functional deterioration remains unchanged despite of major advances in the field. After the first post-transplant year, it has been estimated that this chronic allograft damage may cause a 5% graft loss per year. Most studies focused on mechanisms of kidney graft damage, especially on ischemia-reperfusion injury, alloimmunity, nephrotoxicity, infection and disease recurrence. Thus, therapeutic interventions focus on those modifiable factors associated with chronic kidney allograft disease (CKaD). There are strategies to reduce ischemia-reperfusion injury, to improve the immunologic risk stratification and monitoring, to reduce calcineurin-inhibitor exposure and to identify recurrence of primary renal disease early. On the other hand, control of risk factors for chronic disease progression are particularly relevant as kidney transplantation is inherently associated with renal mass reduction. However, despite progress in pathophysiology and interventions, clinical advances in terms of long-term kidney allograft survival have been subtle. New approaches are needed and probably a holistic view can help. Chronic kidney allograft deterioration is probably the consequence of damage from various etiologies but can be attenuated by kidney repair mechanisms. Thus, besides immunological and other mechanisms of damage, the intrinsic repair kidney graft capacity should be considered to generate new hypothesis and potential therapeutic targets. In this review, the critical risk factors that define CKaD will be discussed but also how the renal mechanisms of regeneration could contribute to a change chronic kidney allograft disease paradigm.

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.

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.

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 anti-viral facet of anti-rheumatic drugs: Lessons from COVID-19

The outbreak of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has posed the world at a pandemic risk. Coronavirus-19 disease (COVID-19) is an infectious disease caused by SARS-CoV-2, which causes pneumonia, requires intensive care unit hospitalization in about 10% of cases and can lead to a fatal outcome. Several efforts are currently made to find a treatment for COVID-19 patients. So far, several anti-viral and immunosuppressive or immunomodulating drugs have demonstrated some efficacy on COVID-19 both in vitro and in animal models as well as in cases series. In COVID-19 patients a pro-inflammatory status with high levels of interleukin (IL)-1B, IL-1 receptor (R)A and tumor necrosis factor (TNF)-α has been demonstrated. Moreover, high levels of IL-6 and TNF-α have been observed in patients requiring intensive-care-unit hospitalization. This provided rationale for the use of anti-rheumatic drugs as potential treatments for this severe viral infection. Other agents, such as hydroxychloroquine and chloroquine might have a direct anti-viral effect. The anti-viral aspect of immunosuppressants towards a variety of viruses has been known since long time and it is herein discussed in the view of searching for a potential treatment for SARS-CoV-2 infection.

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.

Viremia Negativization After BK Virus Infection in Kidney Transplantation: A National Bicentric Study

BACKGROUND

BK virus (BKV) infection represents a potentially dreadful complication after kidney transplantation (KT). When BK viremia is detected, the best therapeutic approach remains not entirely clarified. Critical elements of BK viremia treatment are immunosuppression minimization and introduction of drugs like leflunomide, everolimus, and fluoroquinolones. The study aimed to analyze the results of the BK viremia management in 2 collaborative Italian centers.

METHODS

Ten patients undergoing KT in the 2 collaborative Italian centers of Sapienza University of Rome and University of L'Aquila from January 2013 to December 2017 and showing a post-KT diagnosis of BK viremia were retrospectively investigated.

RESULTS

Mean time from KT to BKV positivity was 7 months (range: 1-19 months). At diagnosis, the mean viral load was 683,842 copies/mL (range: 5800-4,052,415 copies/mL), with an average zenith of 2,428,410 copies/mL (range: 6762-18,022,500 copies/mL). In the 5 patients with BKV nephropathy, we observed a switch from antimetabolite to leflunomide (n = 5), a switch from tacrolimus to everolimus (n = 3), or an introduction of fluoroquinolones (n = 3). BKV clearance was achieved in 3 patients.

CONCLUSIONS

Early BKV diagnosis and stepwise minimization of immunosuppression remain the first-line approach in patients with BK viremia. In the presence of BKV nephropathy, a combination of antiviral drugs like leflunomide and fluoroquinolones/everolimus should favor viremia clearance.

BK viremia and nephropathy in pediatric renal transplant recipients

The renal survival rate of pediatric renal transplant recipients (pRTR) has improved with the use of modern immunosuppressive agents; however, the incidence of post-transplantation viral infection has increased. This study investigated the incidence of BK viremia and BK viral-associated nephropathy (BKVAN) in pRTR. One-hundred-and-thirty-four pRTR were divided into two groups: group 1 (n = 20, 14.9%) comprised those who were prospectively followed with longitudinal analyses after renal transplantation in the time period from May 2007 to June 2008, while group 2 (n = 114, 85.1%) cross-sectional study of those who were transplanted from January 1994 to April 2007. The mean ages at transplantation in groups 1 and 2 were 10.6 ± 4.7 years and 7.8 ± 4.5 years, respectively. BK viremia was detected in four (20.0%) patients in group 1, and seven (6.1%) in group 2 (P = 0.04), with increased incidence associated with induction therapy. The median time to detection of BK viremia after transplantation was 44 days in group 1 and 142 days in group 2. BKVAN was diagnosed in three patients (two in group 1 and one in group 2). All three patients diagnosed with BKVAN were receiving tacrolimus, mycophenolate mofetil, and corticosteroids as maintenance immunosuppression. Reducing immunosuppression resulted in reduced BK viremia. Monitoring for BK viremia and BKVAN is important in pRTR being treated with the current immunosuppressive regimen. The first line of treatment for BK viremia remains careful reduction of immunosuppression and close monitoring of renal allograft function.

BK polyomavirus in solid organ transplantation-Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

The present AST-IDCOP guidelines update information on BK polyomavirus (BKPyV) infection, replication, and disease, which impact kidney transplantation (KT), but rarely non-kidney solid organ transplantation (SOT). As pretransplant risk factors in KT donors and recipients presently do not translate into clinically validated measures regarding organ allocation, antiviral prophylaxis, or screening, all KT recipients should be screened for BKPyV-DNAemia monthly until month 9, and then every 3 months until 2 years posttransplant. Extended screening after 2 years may be considered in pediatric KT. Stepwise immunosuppression reduction is recommended for KT patients with plasma BKPyV-DNAemia of >1000 copies/mL sustained for 3 weeks or increasing to >10 000 copies/mL reflecting probable and presumptive BKPyV-associated nephropathy, respectively. Reducing immunosuppression is also the primary intervention for biopsy-proven BKPyV-associated nephropathy. Hence, allograft biopsy is not required for treating BKPyV-DNAemic patients with baseline renal function. Despite virological rationales, proper randomized clinical trials are lacking to generally recommend treatment by switching from tacrolimus to cyclosporine-A, from mycophenolate to mTOR inhibitors or leflunomide or by the adjunct use of intravenous immunoglobulins, leflunomide, or cidofovir. Fluoroquinolones are not recommended for prophylaxis or therapy. Retransplantation after allograft loss due to BKPyV nephropathy can be successful if BKPyV-DNAemia is definitively cleared, independent of failed allograft nephrectomy.

Clinical utility of leflunomide for BK polyomavirus associated nephropathy in kidney transplant recipients: A multicenter retrospective study

BACKGROUND

BK polyomavirus associated nephropathy (BKPyVAN) is a significant clinical issue in kidney transplant (KT) recipients. No specific therapy is currently available, although treatment with leflunomide may be part of the therapeutic strategy. Here, we sought to examine the impact of leflunomide on the evolution of BKPyVAN.

METHODS

This was an observational retrospective study conducted in 3 French transplant centers. KT recipients who developed BKPyVAN and received leflunomide after failure of other treatment approaches were deemed eligible. Graft function, viral clearance, patient survival, rejection rates, treatment tolerability, and immunosuppression levels served as the main outcome measures.

RESULTS

A total of 55 patients were included. Treatment with leflunomide was started after a mean of 1.4 ± 4.1months  after BKPyVAN diagnosis. Between the introduction of leflunomide and the end of follow-up, creatinine levels increased by 31 ± 118% (P = 0.04), whereas viremia decreased by 79 ± 37% (P < 0.001). Blood viral clearance was observed in 76% of the study patients. Rejection episodes occurred in 33% of the participants. Eleven patients lost their graft (9 of which because of BKPyVAN). Ten patients developed adverse effects and 3 discontinued leflunomide.

CONCLUSION

We cannot conclude about the exact place of leflunomide in the therapeutic strategy of BKPyVAN. It may be a part of the therapy to promote BK polyomavirus clearance in cases of BKPyVAN who fail to improve after immunosuppression lowering alone. Unfortunately, a significant decline in renal function and high rejection rates remain major clinical challenges.

Native kidney BK nephropathy: A case report

BK virus nephropathy (BKN) is uncommonly reported in native kidneys; mostly reported in bone marrow transplant patients. This case report represents an interesting clinical scenario of biopsy-proven BKN in native kidneys, in the presence of more than one million copies/mL of BK virus in serum.

Common viral infections in kidney transplant recipients

Infectious complications have been considered as a major cause of morbidity and mortality after kidney transplantation, especially in the Asian population. Therefore, prevention, early detection, and prompt treatment of such infections are crucial in kidney transplant recipients. Among all infectious complications, viruses are considered to be the most common agents because of their abundance, infectivity, and latency ability. Herpes simplex virus, varicella zoster virus, Epstein-Barr virus, cytomegalovirus, hepatitis B virus, BK polyomavirus, and adenovirus are well-known etiologic agents of viral infections in kidney transplant patients worldwide because of their wide range of distribution. As DNA viruses, they are able to reactivate after affected patients receive immunosuppressive agents. These DNA viruses can cause systemic diseases or allograft dysfunction, especially in the first six months after transplantation. Pretransplant evaluation and immunization as well as appropriate prophylaxis and preemptive approaches after transplant have been established in the guidelines and are used effectively to reduce the incidence of these viral infections. This review will describe the etiology, diagnosis, prevention, and treatment of viral infections that commonly affect kidney transplant recipients.

Management of BK Polyomavirus Infection in Kidney and Kidney-Pancreas Transplant Recipients: A Review Article

BK virus (BKV) can cause graft dysfunction or failure in kidney transplant recipients and hemorrhagic cystitis in allogeneic hematopoietic stem cell transplant patients. BKV-associated nephropathy (BKVAN) emerged as a common complication in the late 1990s, probably due to the introduction of potent immunosuppressive agents. BKVAN occurred in up to 5% of kidney transplant recipients, with graft failure in up to 70%. Since universal implementation of effective screening and treatment strategies, BKV is no longer a common cause of graft failure; reported graft loss is only 0% to 5%. This article briefly describes BK virology, epidemiology, diagnosis, and management.

Clinical Pharmacokinetic Monitoring of Leflunomide in Renal Transplant Recipients with BK Virus Reactivation: A Review of the Literature

Leflunomide is an immunosuppressive drug with in vitro and initial observational evidence of antiviral activity against BK virus (BKV), a pathogen that causes opportunistic infection upon reactivation in renal transplant recipients. Leflunomide is considered an ancillary option to immunosuppression reduction in the management of BKV reactivation. Plasma or blood concentrations of teriflunomide, the active metabolite of leflunomide, are commonly monitored because of high leflunomide doses being used, known inter-individual variability in pharmacokinetics, and hepatotoxicity risk. However, the utility of clinical pharmacokinetic monitoring for leflunomide is as yet unclear. A literature search of MEDLINE (1946-December 2016), EMBASE (1974-December 2016), the CENTRAL database, and Google Scholar was performed to identify relevant English-language articles. Further articles were identified from references in relevant literature. A previously published 9-step decision-making algorithm was used to assess the available literature and determine the utility of clinical pharmacokinetic monitoring for leflunomide. Teriflunomide is readily measurable in the plasma or blood, but a clear relationship between concentration and efficacy or toxicity is lacking, and its therapeutic range is not well-established. Efficacy and toxicity endpoints such as renal function and BKV clearance can be readily assessed without measuring teriflunomide concentrations. Pharmacokinetic parameters are affected by genetic polymorphisms in cytochrome P450 CYP2C19 and ABCG2 genes. Therefore, routine clinical pharmacokinetic monitoring of leflunomide cannot be recommended based on current available evidence. However, it may provide clinical benefit in difficult situations when patients demonstrate a lack of therapeutic response or exhibit signs of drug toxicity.

BK Virus: A Cause for Concern in Thoracic Transplantation?

Human BK polyomavirus (BKV) infection is poorly documented in heart and lung transplant patients. BK viruria and viremia have been estimated to affect 19% and 5% of heart transplant recipients, respectively. Data are limited, especially for lung transplantation, but the proportion of patients progressing from BK viruria to viremia or BKV-related nephropathy (BKVN) appears lower than in kidney transplantation. Nevertheless, a number of cases of BKVN have been reported in heart and lung transplant patients, typically with late diagnosis and generally poor outcomes. Risk factors for BKV infection or BKVN in this setting are unclear but may include cytomegalovirus infection and anti-rejection treatment. The relative infrequency of BKVN or other BK-related complications means that routine BKV surveillance in thoracic transplantation is not warranted, but a diagnostic workup for BKV infection may be justified for progressive renal dysfunction with no readily-identifiable cause; after anti-rejection therapy; and for renal dysfunction in patients with cytomegalovirus infection or hypogammaglobulinemia. Treatment strategies in heart or lung transplant recipients rely on protocols developed in kidney transplantation, with reductions in immunosuppression tailored to match the higher risk status of thoracic transplant patients.

BK Polyomavirus: Clinical Aspects, Immune Regulation, and Emerging Therapies

BK polyomavirus (BKV) causes frequent infections during childhood and establishes persistent infections within renal tubular cells and the uroepithelium, with minimal clinical implications. However, reactivation of BKV in immunocompromised individuals following renal or hematopoietic stem cell transplantation may cause serious complications, including BKV-associated nephropathy (BKVAN), ureteric stenosis, or hemorrhagic cystitis. Implementation of more potent immunosuppression and increased posttransplant surveillance has resulted in a higher incidence of BKVAN. Antiviral immunity plays a crucial role in controlling BKV replication, and our increasing knowledge about host-virus interactions has led to the development of improved diagnostic tools and clinical management strategies. Currently, there are no effective antiviral agents for BKV infection, and the mainstay of managing reactivation is reduction of immunosuppression. Development of immune-based therapies to combat BKV may provide new and exciting opportunities for the successful treatment of BKV-associated complications.

Nephropathy Evolving Within the First Two Posttransplant Months With No Typical Cytopathic Lesions: Two Cases Presentation

BACKGROUND

We report 2 cases of polyomavirus-associated nephropathy (PyVAN) emerging within the initial 8 posttransplant weeks. These cases were characterized by intraepithelial BK virus replication without typical nuclear inclusions in epithelial cells.

METHODS AND RESULTS

A 70-year-old male recipient of a cadaveric kidney transplant had experienced unsatisfying graft function since the time of transplantation (Tx). One month after Tx, results of a graft biopsy revealed mild tubulointerstitial inflammation. No intraepithelial nuclear inclusions suggestive of viral infection were present at that time. The patient received intravenous methylprednisolone, and the dosage of tacrolimus was increased. Due to a further drop in the glomerular filtration rate, a subsequent kidney biopsy was performed during posttransplant week 10, which revealed lesions typical of PyVAN. Retrospectively performed SV40 staining revealed that intragraft polyomavirus replication was already present on posttransplant day 30. Basic immunosuppression reduction and ciprofloxacin administration were followed by BK viremia elimination, stabilization of graft function, and resolution of PyVAN. In another patient, a 62-year-old male recipient of a cadaveric renal graft, BK viremia was monitored from the time of Tx. Two months after Tx, the patient was found to have a BK viral load of 6 × 4 log(10)/mL. Results of the graft biopsy revealed fully preserved tubular epithelium, but SV40 staining was positive in some of these cells. After basic immunosuppression reduction and introduction of ciprofloxacin, the BK viral load dropped to 1 × log(10)/mL with graft function stabilization.

CONCLUSIONS

PyVAN may emerge as early as 4 weeks after Tx, with near-normal or acute rejection-like graft morphology. The early monitoring of plasma BK viral load, as well as SV40 staining, avoids misdiagnosis of this severe posttransplant complication.

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.

Polyomavirus nephropathy of the native kidney in a patient with rheumatoid arthritis and pulmonary fibrosis

Polyomavirus nephropathy is commonly seen in the renal allograft setting but is uncommon in native kidneys. This paper describes polyomavirus nephropathy that developed in the native kidneys of a patient following immunosuppressive therapy for rheumatoid arthritis/Sjögren's syndrome associated lung disease. The patient presented with dyspnoea and a slow steady rise in serum creatinine. Owing to chronic immunosuppression, calcineurin-inhibitor toxicity was suspected. However, renal biopsy revealed polyomavirus nephropathy. The treatment of choice, lowered immunosuppression, was complicated by exacerbation of the patient's lung disease. This case highlights features of polyomavirus nephropathy in the native kidney, as well as the difficulty in its treatment when immunosuppressive treatment is necessary for medical comorbidities.

BK virus infection: an update on diagnosis and treatment

BK virus, first isolated in 1971, is a significant risk factor for renal transplant dysfunction and allograft loss. Unfortunately, treatment options for BK virus infection are limited, and there is no effective prophylaxis. Although overimmunosuppression remains the primary risk factor for BK infection after transplantation, male gender, older recipient age, prior rejection episodes, degree of human leukocyte antigen mismatching, prolonged cold ischemia time, BK serostatus and ureteral stent placement have all been implicated as risk factors. Routine screening for BK has been shown to be effective in preventing allograft loss in patients with BK viruria or viremia. Reduction of immunosuppression remains the mainstay of BK nephropathy treatment and is the best studied intervention. Laboratory-based methods such as ELISPOT assays have provided new insights into the immune response to BK and may help guide therapy in the future. In this review, we will discuss the epidemiology of BK virus infection, screening strategies, treatment options and future research directions.

The human polyomavirus BK (BKPyV): virological background and clinical implications

Polyomavirus BK (BKPyV) infects most people subclinically during childhood and establishes a lifelong infection in the renourinary tract. In most immunocompetent individuals, the infection is completely asymptomatic, despite frequent episodes of viral reactivation with shedding into the urine. In immunocompromised patients, reactivation followed by high-level viral replication can lead to severe disease: 1-10% of kidney transplant patients develop polyomavirus-associated nephropathy (PyVAN) and 5-15% of allogenic hematopoietic stem cell transplant patients develop polyomavirus-associated haemorrhagic cystitis (PyVHC). Other conditions such as ureteric stenosis, encephalitis, meningoencephalitis, pneumonia and vasculopathy have also been associated with BKPyV infection in immunocompromised individuals. Although BKPyV has been associated with cancer development, especially in the bladder, definitive evidence of a role in human malignancy is lacking. Diagnosis of PyVAN and PyVHC is mainly achieved by quantitative PCR of urine and plasma, but also by cytology, immunohistology and electron microscopy. Despite more than 40 years of research on BKPyV, there is still no effective antiviral therapy. The current treatment strategy for PyVAN is to allow reconstitution of immune function by reducing or changing the immunosuppressive medication. For PyVHC, treatment is purely supportive. Here, we present a summary of the accrued knowledge regarding BKPyV.

Human polyomavirus reactivation: disease pathogenesis and treatment approaches

JC and BK polyomaviruses were discovered over 40 years ago and have become increasingly prevalent causes of morbidity and mortality in a variety of distinct, immunocompromised patient cohorts. The recent discoveries of eight new members of the Polyomaviridae family that are capable of infecting humans suggest that there are more to be discovered and raise the possibility that they may play a more significant role in human disease than previously understood. In spite of this, there remains a dearth of specific therapeutic options for human polyomavirus infections and an incomplete understanding of the relationship between the virus and the host immune system. This review summarises the human polyomaviruses with particular emphasis on pathogenesis in those directly implicated in disease aetiology and the therapeutic options available for treatment in the immunocompromised host.

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.

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.

Conversion from tacrolimus/mycophenolic acid to tacrolimus/leflunomide to treat cutaneous warts in a series of four pediatric renal allograft recipients

BACKGROUND

The challenge of immunosuppression in pediatric renal transplantation is to balance preventing rejection while avoiding infectious complications. A dermatological complication of immunosuppression is viral warts, which cause significant disfigurement and increase the risk of skin malignancy.

METHODS

We present three pediatric and adolescent renal allograft recipients with multiple, recalcitrant verrucae vulgares lesions and one patient with molluscum contagiosum who were switched from mycophenolate mofetil to leflunomide. Teriflunomide metabolite levels were carefully maintained between 50,000 and 100,000 ng/mL to balance its immunosuppressive and antiviral properties. No adverse events requiring discontinuation of leflunomide were encountered.

RESULTS

Switching from mycophenolate mofetil to leflunomide successfully cleared verrucae vulgares and molluscum lesions in all four renal transplant patients.

CONCLUSIONS

The ability to minimize and even resolve warts can improve quality of life by reducing risk of skin malignancies and emotional distress in solid organ transplant patients. Leflunomide is a potential therapeutic option for posttransplantation patients with skin warts because it serves both as an adjunct to the immunosuppressive regimen and an antiviral agent.

Common infections in kidney transplant recipients

Infections are a major cause of morbidity and mortality in kidney transplant recipients. To some extent, these may be preventable. Careful pretransplant screening, immunization, and post-transplant prophylactic antimicrobials may all reduce the risk for post-transplant infection. However, because transplant recipients may not manifest typical signs and symptoms of infection, diagnoses may be confounded. Furthermore, treatment regimens may be complicated by drug interactions and the need to maintain immunosuppression to avoid allograft rejection. This article reviews common post-transplant infections, including prophylactic, diagnostic, and treatment strategies, providing guidance regarding care of kidney transplant patients with infection.

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.