Risk Factors for the Development of BK Virus Nephropathy in Renal Transplant Recipients

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.

BK Polyomavirus Nephropathy in Kidney Transplantation: Balancing Rejection and Infection

BK polyomavirus nephropathy (BKVN) and allograft rejection are two closely-associated diseases on opposite ends of the immune scale in kidney transplant recipients. The principle of balancing the immune system remains the mainstay of therapeutic strategy. While patient outcomes can be improved through screening, risk factors identification, and rapid reduction of immunosuppressants, a lack of standard curative therapy is the primary concern during clinical practice. Additionally, difficulty in pathological differential diagnosis and clinicopathology’s dissociation pose problems for a definite diagnosis. This article discusses the delicate evaluation needed to optimize immunosuppression and reviews recent advances in molecular diagnosis and immunological therapy for BKVN patients. New biomarkers for BKVN diagnosis are under development. For example, measurement of virus-specific T cell level may play a role in steering immunosuppressants. The development of cellular therapy may provide prevention, even a cure, for BKVN, a complex post-transplant complication.

Risk factors for progression from low level BK dnaemia to unfavorable outcomes after BK management via immunosuppressive reduction

BACKGROUNDS

Effective management of BK viremia (BKPyV-DNAemia) in kidney transplant recipients (KTRs) involves regular monitoring and adjustment of immunosuppression. With this strategy, the majority of patients will clear BK or have ongoing, but non-significant, low-level BKPyV-DNAemia. However, despite adjustments, some will develop more severe sequelae of BK including BKPyV-DNAemia >5 log₁₀ copies/mL and BK nephropathy, and others may develop de novo DSA (dnDSA) or acute rejection (AR).

METHODS

This was a single-center study of KTRs transplanted at the University of Wisconsin-Madison between 01/01/2015 and 12/31/2017. In this study, we sought to elucidate characteristics associated with the progression of BKPyV-DNAemia to unfavorable outcomes after decreasing immunosuppressive medications for the management of BK viremia as described in consensus guidelines.

RESULTS

A total of 224 KTRs fulfilled our selection criteria; 118 (53%) resolved or had persistent low DNAemia, 64 (28%) had severe BK/nephropathy, and 42 (19%) developed dnDSA or AR. In multivariable analysis, female gender (HR: 2.05; 95% CI: 1.08-3.90; P = .02); previous rejection (HR: 2.90; 95% CI: 1.04-8.12; P = .04), and early infection (HR: 0.81; 95% CI: 0.72-0.90; P < .001) were associated with the development of severe BK/nephropathy. Conversely, non-depleting induction at transplant (HR: 2.06; 95% CI: 1.03-4.11; P = .03), HLA mismatches >3 (HR: 2.27; HR: 1.01-5.06; P = .04), and delayed graft function (HR: 4.14; 95% CI: 1.12-15.28; P = .03) were associated with development of dnDSA and/or rejection.

CONCLUSION

Our study suggests that almost half of KTRs with BKPyV-DNAemia managed by our immunosuppressant adjustment protocol progress unfavorably. Identification of these risk factors could assist the frontline clinician in creating an individualized immunosuppressive modification plan potentially mitigating negative outcomes.

The Impact of Different Induction Immunosuppressive Therapy on Long-Term Kidney Transplant Function When Measured by Iothalamate Clearance

Background

Improvement in short-term outcomes after kidney transplant has been achieved by using different induction and maintenance therapeutic approaches. Long-term outcomes have not matched the expectations of the transplant stakeholders. Our study aimed to address the early impact of induction agents on long-term outcome of kidney transplant when measured by iothalamate clearance.

Methods

All adult kidney transplant recipients between January of 2012 and December of 2016 were reviewed. Six hundred forty-nine patients were divided into three groups based on the induction agent (basiliximab, alemtuzumab, and thymoglobulin). Protocoled 4 months and 48 months kidney allograft function evaluations with iothalamate clearance test were compared among the three groups.

Results

Patients who received basiliximab were significantly older with no difference among African American and Caucasians. The 48 months assessment showed significant decline in median iothalamate clearance in basiliximab group at 49 mL/min vs. alemtuzumab group 64.8 mL/min and thymoglobulin 60 mL/min with P = 0.007. The basiliximab group developed a significant higher proteinuria measured by spot urine to creatinine ratio at 48 months.

Conclusions

The use of basiliximab as an induction agent for kidney transplant is associated with significant decline in kidney function 4 years post transplantation when measured by iothalamate clearance.

Combined association of recipient killer cell immunoglobulin-like haplotype AA and donor HLA-C*07 gene with BK virus associated nephropathy in kidney transplant patients

Kidney transplant recipient killer cell immunoglobulin-like receptors (KIR) genotype and HLA-C status of their donors have been separately associated with BK virus-associated nephropathy (BKVAN) and BK virus infection. Our aim was to determine whether different combinations of recipients KIR genes and donor HLA-C ligands influence the risk of BKVAN. Retrospective case-control study included 23 recipients with BKVAN and 46 recipients with persistently negative BK virus. Donor HLA-C*07 positivity was associated with lower odds for BKVAN, recipients bearing KIR haplotype AA or lacking any activating KIR genes were more frequent in BKVAN while recipient/donor combination HLA-C*07 negative/KIR AA positive was significantly associated with BKVAN. Our study complements and confirms results from several previously published studies, suggesting potential clinical usefulness.

Infectious Complications of Induction Therapies in Kidney Transplantation

Background

Cytomegalovirus (CMV) and BK virus (BKV) are post-transplant opportunistic viral infections that affect patient and graft survival. This study was designed to evaluate the risk of BKV nephropathy and CMV disease in kidney transplant recipients who received induction therapy with ATG or basiliximab.

Material/Methods

We retrospectively analyzed information on 257 adult patients who underwent kidney transplantation between January 2007 and 2017. Patients were categorized into 3 groups according to the induction therapies. The primary endpoint was the onset of CMV disease or biopsy-confirmed BKV nephropathy. The secondary endpoints were biopsy-proven rejection episodes, graft loss, loss to follow-up, and death.

Results

We followed 257 patients for a median of 55.5 months. The incidence of CMV disease was significantly higher in the only ATG group compared to the group without induction treatment (p<0.001). There was no significant difference in the incidence of BKV nephropathy among groups (p>0.05). The dosage of ATG (OR, 10.685; 95% CI, 1.343 5 to 85.009; P=0.025) was independent risk factor for death.

Conclusions

This study demonstrated that a higher dosage of ATG in high-risk patients is associated with an increased risk of CMV disease and patient death, also, reducing the dosage may be a rational strategy for increasing graft and patient’s survival.

Screening for BK Viremia/Viruria and the Impact of Management of BK Virus Nephropathy in Renal Transplant Recipients

OBJECTIVES

The prevalence of BK-induced nephritis in renal transplant recipients is estimated to be 1% to 10%; the rate of graft loss within 1 year is 30% to 65%. We conducted this study to evaluate screening of BK virus in blood and/or urine among renal transplant recipients and to assess the effects of different therapeutic modalities in renal transplant recipients with BK nephropathy.

MATERIALS AND METHODS

Kidney transplant recipients were screened at the time of transplant and then at 1, 2, 3, 6, 9, 12, 18, and 24 months posttransplant. Fiftynine patients were diagnosed with BK virus viremia. Patients were divided into 2 groups according to treatment: group 1 (n = 29) received an active treatment and group 2 (n = 30) received minimized immunosuppression.

RESULTS

Most patients required graft biopsies to confirm diagnosis (86.2% in group 1 vs 50% in group 2; P = .03). Both groups were comparable regarding demographic data. Initial posttransplant graft function was significantly better in group 1 (P = .017); ultimately, there was no significant difference between both groups regarding graft survival (P= .51). Fifty percent of patients had biopsy-proven acute T-cell-mediated rejection before BK virus-associated nephropathy diagnosis (significantly higher in group 1). Serum creatinine levels were significantly better in group 2 at 3, 4, and 5 years after BK nephropathy (P = .001, .017, and .003, respectively).

CONCLUSIONS

The prevalence of BK nephropathy in our renal transplant recipients was 5.9% with a rate of graft loss ranging from 43% to 51%. Regular screening, less intensive immunosuppressive therapy, and early intervention by reduction of immunosuppressive medications are advisable to obtain early diagnosis and to have better outcomes of BK virus-associated nephropathy with antiviral agents.

Cytomegalovirus and Epstein-Barr virus infections among pediatric kidney transplant recipients at a center using universal Valganciclovir Prophylaxis

BACKGROUND

CMV is associated with adverse effects in renal transplant recipients. The objective of this study was to characterize the incidence and timing of CMV and EBV infections in relation to valGCV prophylaxis in a pediatric renal transplant cohort.

METHODS

Retrospective cohort of pediatric renal transplant patients given universal valGCV prophylaxis and universal viral surveillance was evaluated. Demographics, prophylaxis, acute rejection, and CMV and EBV infections were abstracted.

RESULTS

A total of 92 pediatric renal allograft recipients, 2008-2013, were included. One or more viral infections developed in 77/92 (83.7%) of the patients. EBV was the most common in 62/92 (67%) patients, irrespective of valGCV (82% of episodes occurring on valGCV). CMV DNAemia occurred in 30/92 (33%) patients, 14 episodes (47%) occurring on valGCV. Incidence of breakthrough CMV on prophylaxis was 15% and was associated with persistent DNAemia (OR 7.8, CI:1.6-32.9, P < 0.02). CMV tissue-invasive disease was not seen. CMV syndrome occurred in 10% of the cohort, only in CMV D+ patients, and only one symptomatic breakthrough infection required treatment. Out of 92, 21 (23%) had simultaneous co-infections with 2-3 viruses.

CONCLUSIONS

Viral infections in pediatric renal transplant recipients receiving universal valGCV prophylaxis were common. EBV infections were not reduced by valGCV prophylaxis, and nearly half of CMV infections occurred on valGCV. Symptomatic CMV infection while on prophylaxis was rare. valGCV prophylaxis may prevent symptomatic CMV infection but not EBV infection, and frequent CMV surveillance in pediatric renal transplant recipients on prophylaxis may not be necessary.

BKV, CMV, and EBV Interactions and their Effect on Graft Function One Year Post-Renal Transplantation: Results from a Large Multi-Centre Study

Background

BK virus (BKV), Cytomegalovirus (CMV) and Epstein-Barr virus (EBV) reactivations are common after kidney transplantation and associated with increased morbidity and mortality. Although CMV might be a risk factor for BKV and EBV, the effects of combined reactivations remain unknown. The purpose of this study is to ascertain the interaction and effects on graft function of these reactivations.

Methods

3715 serum samples from 540 kidney transplant recipients were analysed for viral load by qPCR. Measurements were performed throughout eight visits during the first post-transplantation year. Clinical characteristics, including graft function (GFR), were collected in parallel.

Findings

BKV had the highest prevalence and viral loads. BKV or CMV viral loads over 10,000 copies·mL⁻¹ led to significant GFR impairment. 57 patients had BKV-CMV combined reactivation, both reactivations were significantly associated (p = 0.005). Combined reactivation was associated with a significant GFR reduction one year post-transplantation of 11.7 mL·min⁻¹·1.73 m⁻² (p = 0.02) at relatively low thresholds (BKV > 1000 and CMV > 4000 copies·mL⁻¹). For EBV, a significant association was found with CMV reactivation (p = 0.02), but no GFR reduction was found. Long cold ischaemia times were a further risk factor for high CMV load.

Interpretation

BKV-CMV combined reactivation has a deep impact on renal function one year post-transplantation and therefore most likely on long-term allograft function, even at low viral loads. Frequent viral monitoring and subsequent interventions for low BKV and/or CMV viraemia levels and/or long cold ischaemia time are recommended.

Fund

Investigator Initiated Trial; financial support by German Federal Ministry of Education and Research (BMBF).

Risk factors for BK virus infection in living-donor renal transplant recipients: a single-center study from China

Objectives: BK virus (BKV) infection has become one of the main complications in renal transplant recipients (RTRs) with the arrival of newer potent immunosuppressive agents. However, reports on the epidemiology of BKV infection and risk factors in Chinese population after renal transplantation are scarce.

Methods: From June 2015 to July 2016, living-donor renal transplant recipients (LDRTRs) who routinely received the quantitative BKV DNA testing of urine and plasma samples using quantitative real-time polymerase chain reaction (PCR) for the first time after transplantation were selected, while dialysis patients and healthy living donors during that period served as controls. Potential variables were compared and analyzed using logistic regression model multivariate analysis to assess the BKV infection related factors in LDRTRs.

Results: Among the 52 LDRTRs identified, BKV DNA was detected in 16 urine samples (30.8%), significantly higher than that of dialysis patients (6.3%) and healthy living donors (4.2%) (p < .001). Nevertheless, no statistically significant difference wax noted between the latter two groups in urine samples (p = .842). Meanwhile, BKV DNA detection in blood samples was all negative in the three groups. Univariate analysis shown tacrolimus (Tac) trough level and lymphocyte percentage were associated with BKV infection in LDRTRs. Multivariate regression analysis also showed Tac trough level (HR, 1.644; p = .03), lymphocyte percentage (HR, 0.878; p = .026) were associated with BKV infection in LDRTRs.

Conclusions: In Chinese population, the incidence of BKV infection increased significantly after living-donor renal transplantation. Significantly increased Tac trough level and decreased lymphocyte percentage might be the risk factors for BKV infection in LDRTRs.

Long-term prognosis of BK virus-associated nephropathy in kidney transplant recipients

Background

The long-term prognosis of BK virus-associated nephropathy (BKVAN) in kidney transplant recipients (KTRs) is uncertain. We evaluated the long-term prognosis in KTRs with BKVAN and the clinical significance of BKVAN on post-transplant clinical outcome.

Methods

We retrospectively analyzed the medical records of 582 patients who underwent kidney transplant (KT) between 2001 and 2014. We divided the patients into a BKVAN group (15 patients) diagnosed by allograft biopsy and a control group (356 patients).

Results

The incidence of BKVAN was 4.0%, and the mean follow-up duration was 93.1 ± 52.3 months. Median time from KT to BKVAN diagnosis was 5.9 months (interquartile range [IQR], 4.4–8.7). In the BKVAN group, 9 (60.0%) KTRs with combined acute rejection progressed to graft failure, and the median time from BKVAN diagnosis to graft failure was 36.2 months (IQR, 9.7–65.5). Death-censored graft survival rate and patient survival rate in the BKVAN group were significantly lower than those in the control group. BKVAN and rejection were independent risk factors for graft failure. In the subgroup analysis, death-censored graft survival rate of KTRs with BKVAN with acute rejection was significantly worst in comparison with similar patients without BKVAN regardless of acute rejection (P < 0.001).

Conclusion

The long-term prognosis of BKVAN with acute rejection was very poor because of graft failure caused by inadequate treatment for acute rejection considering BKVAN. Therefore, we should carefully monitor the allograft status of KTRs through regular surveillance tests after treatment for BKVAN with acute rejection.

Impact of donor BK polyomavirus replication on recipient infections in living donor transplantation

BACKGROUND

Multiple risk factors for BK polyomavirus (BKPyV) replication after kidney transplantation have been described. Here, we investigated the impact of living donors' urinary BKPyV shedding and recipients' BKPyV antibody status pre-transplant on BKPyV replication during the first year post-transplantation.

METHODS

We assessed a cohort of living kidney donors and their paired recipients (n = 121). All donors were tested before transplantation, and recipients were tested before and after transplantation for BKPyV viruria and viremia. BKPyV-specific serology was assessed in all recipients at transplantation.

RESULTS

Ten of 121 donors (8.3%) had urinary BKPyV shedding pre-transplant, none had viremia. Overall, 33 (27.3%) recipients developed viruria after transplantation: 7 had received a kidney from a donor with BK viruria (7/10 positive donors) and 26 had received a kidney from a donor without BK viruria (26/111 negative donors; P = .0015). Fifteen (12.4%) recipients developed BK viremia after transplantation: 3 received a kidney from a donor with viruria (3/10 positive donors, 30%) and 12 received a kidney from a donor without viruria (12/111 negative donors, 11%; P = .08). One patient developed proven nephropathy. Ninety-one percent of recipients were seropositive for BKPyV. No relationship between recipients' sero-reactivity at transplantation and post-transplant BKPyV replication was observed. Pre-transplant donor urinary shedding was an independent risk factor for post-transplant BKPyV replication.

CONCLUSION

Screening living kidney donors for BKPyV can identify recipients at higher risk for BKPyV replication after transplantation who may benefit from intensified post-transplant screening and treatment strategies.

BK nephropathy in the native kidneys of patients with organ transplants: Clinical spectrum of BK infection

Nephropathy secondary to BK virus, a member of the Papoviridae family of viruses, has been recognized for some time as an important cause of allograft dysfunction in renal transplant recipients. In recent times, BK nephropathy (BKN) of the native kidneys has being increasingly recognized as a cause of chronic kidney disease in patients with solid organ transplants, bone marrow transplants and in patients with other clinical entities associated with immunosuppression. In such patients renal dysfunction is often attributed to other factors including nephrotoxicity of medications used to prevent rejection of the transplanted organs. Renal biopsy is required for the diagnosis of BKN. Quantitation of the BK viral load in blood and urine are surrogate diagnostic methods. The treatment of BKN is based on reduction of the immunosuppressive medications. Several compounds have shown antiviral activity, but have not consistently shown to have beneficial effects in BKN. In addition to BKN, BK viral infection can cause severe urinary bladder cystitis, ureteritis and urinary tract obstruction as well as manifestations in other organ systems including the central nervous system, the respiratory system, the gastrointestinal system and the hematopoietic system. BK viral infection has also been implicated in tumorigenesis. The spectrum of clinical manifestations from BK infection and infection from other members of the Papoviridae family is widening. Prevention and treatment of BK infection and infections from other Papovaviruses are subjects of intense research.