BK Virus Nephropathy: Prevalence, Impact and Management Strategies

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.

Protocolized polyoma BK viral load monitoring and high-dose immunoglobulin treatment in children after kidney transplant

Background

BKPyV virus nephropathy (BKPyVAN) is diagnosed in 5%-16% of pediatric renal transplant recipients (PRTR) and preceded by BKPyV-viruria and DNAemia. Despite the risk of irreversible transplant damage associated with BKPyVAN, evidence-based consensus guidelines for BKPyVAN prevention are still lacking. In this retrospective study, we examined the safety and efficacy of high-dose intravenous immunoglobulin (HD-IVIG) therapy for prevention of BKPyVAN in PRTR with significant BKPyV-viruria/DNAemia.

Methods

Between January 2013 and December 2022, all PRTR under our care underwent routine urine and blood testing for BKPyV viral load, using specific polymerase chain reaction (PCR). BKPyV DNAemia, with <103 copies/mL, with BKPyV viruria <107 copies/mL, with no evidence of BKPyVAN, were managed with 50% dose reduction of mycophenolate mofetil (MMF). Patients showing no decline in BKPyV viral load within two months of MMF dose reduction were managed with HD-IVIG (2 g/kg).

Results

Seventy patients were recruited during a ten-year period and 31/70 patients (44%) demonstrated significant post-transplantation BKPyV-viruria/DNAemia, while 13/31 (42%) patients were unresponsive to MMF dose reduction, and were administered HD-IVIG. Of these, 12/13 (92%) patients achieved BKPyV viral clearance within six months from completion of HD-IVIG therapy and 1/13 patient (8%) was unresponsive to HD-IVIG therapy, showing increased BKPyV viral load. There were no major adverse events associated with HD-IVIG, and none of our patients developed BKPyVAN during the study period.

Conclusions

Prophylactic HD-IVIG therapy in PRTR with significant BKPyV-viruria/DNAemia unresponsive to MMF dose reduction is safe and might be effective in preventing BKPyVAN. Our findings remain to be established by large-scale prospective studies.

A Rare Cause of Encephalopathy Post Renal Transplant: BK Polyoma Virus Encephalitis

BK polyoma virus (BKV) belongs to Polyomaviridae family. It is a double-stranded DNA virus. Only a few cases of BKV-associated neurological disease in renal transplant recipients have been reported. BKV related central nervous system (CNS) infection may often remain unrecognized in immunocompromised patients. Here, we are reporting a case of BKV encephalitis post renal transplantation for the awareness of all physicians regarding this entity.

Stepwise Reduction of Mycophenolate Mofetil with Conversion to Everolimus for the Treatment of Active BKV in Kidney Transplant Recipients: A Single-Center Experience in Vietnam

Background: No specific antiviral drug can effectively treat BKV reactivation after kidney transplantation. Thus, we evaluated stepwise-reduced immunosuppression to treat BKV reactivation. Methods: 341 kidney-transplant recipients were monitored for BKV infection (BKV-viremia, BKV-viruria). Positive samples with a significant virus load were nested PCR-genotyped in the VP1 region. In 97/211 patients presenting BKV viremia ≥104 copies/mL and/or BKV viruria ≥107 copies/mL, or BKV-nephropathy immunosuppression (i.e., mycophenolate mofetil [MMF]) was reduced by 50%. If viral load did not decrease within 28 days, MMF dose was further reduced by 25%, although calcineurin-inhibitor (CNI) therapy remained unchanged. If BKV viral load did not decrease within another 28 days, MMF was withdrawn and replaced by everolimus combined with reduced CNIs. Results: Only 41/97 BKV (+) cases completed the 6-month follow-up. Among these, 29 (71%) were in the BKV-I group and 12 (29%) were in BKV-IV. BKV viruria and BKV viremia were significantly decreased from 9.32 to 6.09 log10 copies/mL, and from 3.59 to 2.45 log10 copies/mL (p < 0.001 and p = 0.024, respectively). 11/32 (34.4%) patients were cleared of BKV viremia; 2/32 (6.3%) patients were cleared of BKV in both serum and urine, and 9/9 (100%) only had BKV viruria but did not develop BKV viremia. eGFR remained stable. No patient with BKV-related nephropathy had graft loss. There was a significant inverse relationship between changes in eGFR and serum BKV load (r = −0.314, p = 0.04). Conclusions: This stepwise immunosuppressive strategy proved effective at reducing BKV viral load in kidney transplant recipients that had high BKV loads in serum and/or urine. Renal function remained stable without rejection.

BK Virus Infection and BK-Virus-Associated Nephropathy in Renal Transplant Recipients

Poliomavirus BK virus (BKV) is highly infective, causing asymptomatic infections during childhood. After the initial infection, a stable state of latent infection is recognized in kidney tubular cells and the uroepithelium with negligible clinical consequences. BKV is an important risk factor for BKV-associated diseases, and, in particular, for BKV-associated nephropathy (BKVN) in renal transplanted recipients (RTRs). BKVN affects up to 10% of renal transplanted recipients, and results in graft loss in up to 50% of those affected. Unfortunately, treatments for BK virus infection are restricted, and there is no efficient prophylaxis. In addition, consequent immunosuppressive therapy reduction contributes to immune rejection. Increasing surveillance and early diagnosis based upon easy and rapid analyses are resulting in more beneficial outcomes. In this report, the current status and perspectives in the diagnosis and treatment of BKV in RTRs are reviewed.

Anterior pelvic exenteration and synchronous bilateral nephroureterectomy for BK polyoma virus induced urothelial carcinoma of the bladder: A case report

BK polyoma virus (BKV) is a known risk factor for the development of urothelial carcinoma. There is currently limited data on the management of BKV-induced urothelial carcinoma (BUC) of the bladder, with available data limited to case reports. It remains debatable whether radical cystectomy (RC) with removal of the native urinary tract or RC alone is the most optimal management for BUC of the bladder. BKV-induced urothelial carcinoma is rare, and its management is challenging in immunocompromised patients such as that of post-transplant patients. This case report provides additional insight into a rare disease, the management of which still lacks established guidelines and remains debatable.

The effect of BK polyomavirus large T antigen on CD4 and CD8 T cells in kidney transplant recipients

Human BK polyomavirus (BKPyV) can affect the machinery of the host cell to induce optimal viral replication or transform them into tumor cells. Reactivation of BKPyV happens due to immunosuppression therapies following renal transplantation which might result in BK polyomavirus nephropathy (BKPyVAN) and allograft loss. The first protein that expresses after entering into host cells and has an important role in pathogenicity is the Large T antigen (LT-Ag). In this review tries to study the molecular and cellular inter-regulatory counteractions especially between CD4 and CD8 T cells, and BKPyV LT-Ag may have role in nephropathy after renal transplantation.

BK Polyomavirus Infection and Risk Factors in Pediatric Patients Undergoing Kidney Transplant

OBJECTIVES

BK polyomavirus infection is a critical complication affecting graft survival after kidney transplant. We aimed to determine the frequency, the effect on graft function, and the risk factors of BK polyomavirus infection in pediatric kidney transplant patients.

MATERIALS AND METHODS

We retrospectively reviewed data of 144 pediatric patients (female/male: 67/77; 0-18 years of age) who received kidney transplants in the past 10 years at our center. Demographic/ laboratory data, kidney failure etiologies, donor types, and immunosuppressive treatments were recorded. Patients were grouped as those with and without BKV infection, with groups compared in terms of transplant age, sex, kidney failure etiology, donor type, immunosuppressive treatments, presence of ureteral stents, acute rejection episodes, accompanying viral infections, glomerular filtration rate, and graft loss rate.

RESULTS

Twelve patients (8.3%) had BK polyomavirus infection. All 12 patients had viruria (8.3%), 8 (5.5%) had viremia, and 4 (2.8%) had BK polyomavirus nephropathy. Two patients (1.4%) had graft loss because of BK polyomavirus nephropathy. When patients with and without infection were compared, no significant differences were found in terms of sex, transplant age, donor type, presence of a ureteral stent, acute rejection, graft loss, or immunosuppressive treatment (P > .05). Rates of congenital anomalies of the kidney and urinary tract were 30.3% and 66.6% in those without and with BK polyomavirus infection, respectively (P < .05). The group positive for BK polyomavirus had a significantly higher incidence of cytomegalovirus infection versus the group without infection (P < .05). Glomerular filtration rate values at years 1 and 3 were similar between groups (P > .05).

CONCLUSIONS

Frequency of BK polyomavirus nephropathy in pediatric patients undergoing kidney transplant in our center was consistent with data from other centers. Graft loss can be prevented by early detection and treatment through close periodic control and adequate evaluation of risk factors.

BK Polyomavirus-Biology, Genomic Variation and Diagnosis

The BK polyomavirus (BKPyV), a representative of the family Polyomaviridae, is widespread in the human population. While the virus does not cause significant clinical symptoms in immunocompetent individuals, it is activated in cases of immune deficiency, both pharmacological and pathological. Infection with the BKPyV is of particular importance in recipients of kidney transplants or HSC transplantation, in which it can lead to the loss of the transplanted kidney or to haemorrhagic cystitis, respectively. Four main genotypes of the virus are distinguished on the basis of molecular differentiation. The most common genotype worldwide is genotype I, with a frequency of about 80%, followed by genotype IV (about 15%), while genotypes II and III are isolated only sporadically. The distribution of the molecular variants of the virus is associated with the region of origin. BKPyV subtype Ia is most common in Africa, Ib-1 in Southeast Asia, and Ib-2 in Europe, while Ic is the most common variant in Northeast Asia. The development of molecular methods has enabled significant improvement not only in BKPyV diagnostics, but in monitoring the effectiveness of treatment as well. Amplification of viral DNA from urine by PCR (Polymerase Chain Reaction) and qPCR Quantitative Polymerase Chain Reaction) is a non-invasive method that can be used to confirm the presence of the genetic material of the virus and to determine the viral load. Sequencing techniques together with bioinformatics tools and databases can be used to determine variants of the virus, analyse their circulation in populations, identify relationships between them, and investigate the directions of evolution of the virus.