Polyomavirus BK replication in de novo kidney transplant patients receiving tacrolimus or cyclosporine: a prospective, randomized, multicenter study

Total nephroureterocystectomy and urethrectomy due to urothelial carcinoma associated with the BK polyomavirus infection after kidney transplantation: a case report with literature review

Background

BK polyomavirus (BKPyV) infection after kidney transplantation is an important cause of graft failure among kidney transplant recipient and may cause malignant tumor, although the association between BKPyV infection and malignant tumor has been controversial yet.

Case presentation

We report a case of a 39-year-old-male kidney transplantation (KTx) recipient with urine BKPyV replication who developed a graft pelvic tumor with the positive Simian virus 40 large T antigen (SV40 TAg). The patients received a living-related KTx from his 65-year-old mother. A protocol biopsy at 14 months after KTx showed BKPyV-associated nephropathy. Therefore, the dose of immunosuppressants was reduced, resulting in improved BKPyV viremia, but viruria persisted. About 117 months after KTx, urine cytology showed atypical cells suspicious for malignancy. Cystoscopy revealed a tumor on the neck of the bladder. Transurethral resection of the bladder tumor (TUR-BT) was performed; however, the diagnosis of malignancy was not confirmed at that time. Six months after the TUR-BT, urine cytology showed atypical cells definite for malignancy. Computed tomography and retrograde pyelography showed no evidence of urinary tract tumor and metastasis. Subsequently, total nephroureterocystectomy and urethrectomy were performed. Histological examination of the graft ureter revealed a high-grade urothelial carcinoma, with glandular differentiation, pT1. Immunohistochemically, the tumor showed positivities for SV40 TAg and p53, along with increased Ki67 labeling cells were increased. By contrast, nonneoplastic cells were negative for SV40 TAg. At the time of writing the present manuscript, the patient is free from recurrence or residual tumor and being closely monitored without additional therapy, 32 months after the surgery.

Conclusion

The relationship between BKPyV infection after KTx and bladder carcinogenesis remains to be elucidated. However, when the KTx recipients who continue to have BKPyV infection for a long time are treated, the possibility of risk factors for renourinary carcinoma should always be carefully considered.

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.

Analysis of risk factors influencing the BK polyomavirus replication in patients with ESRD waiting for kidney transplantation

BACKGROUND

Since the pre-transplant status affects the renal transplantation success and ultimately the survival rate, identifying the probable risk factors that increase the chance of BK virus replication in end-stage renal disease patients can be included in proposing proper surveillance guidelines during pre and post-transplantation.

METHODS

A descriptive cross-sectional study was performed by collecting plasma samples from 192 ESRD patients undergoing hemodialysis for at least 3 months. Quantitative Real-time PCR assay was used to detect and measure the BK viral load. Demographic and clinical characteristics of the patients who had BK viremia were documented.

RESULTS

14 (7.3%) out of our 192 participants had BK virus viremia (95%CI 4.2%-11.6%). Demographic characteristics including etiology of ESRD and underlying diseases, mean duration and frequency of dialysis, co-infection with HBV and HCV did not affect the virus replication, since the difference between patients with BK virus viremia and BK virus negative individuals was not statistically significant. However, the statistical significance of the mean age of men with BKV and without BK virus viremia was found (OR: 3.42, P = 0.02 95%CI 0.86-13.61). Also, multiple regression analyses of some other parameters revealed that old age, high body mass index and male gender can be predictive factors of BK virus viremia in ESRD patients.

CONCLUSION

Based on our findings, elderly male had higher chance of being exposed to BK virus viremia. Some other demographic characteristics such as a high BMI, old age and gender (male) can increase the risk of BK viremia in patients with ESRD prior to kidney transplantation.

Persistent BK polyomavirus-DNAemia may warrant cystoscopy to rule out urologic carcinoma: A case report and review of the literature

There is minimal literature describing the clinical workup of patients with persistent BKPyV-DNAemia despite aggressive immunosuppressive reduction. We present a case herein of persistent BKPyV-DNAemia with significant discordance of BK viruria level in a kidney transplant recipient found to have bladder carcinoma. Based on our findings, we recommend evaluating the urine of patients with persistent BKPyV-DNAemia for BK viruria. If there is significant discordance in the level of BKPyV-DNAemia and viruria, cystoscopy should be pursued to rule out bladder or uroepithelial malignancies.

Renal Allograft Biopsies with Polyomavirus BK Nephropathy: Turin Transplant Center, 2015-19

Background: In kidney transplant patients, polyomavirus-associated nephropathy (PVAN) represents a serious complication; the key factor for the development of PVAN is immunosuppression level and modulation of anti-rejection treatment represents the first line of intervention. Allograft biopsy and histology remain the criterion standard for diagnosing PVAN. Methods: All consecutive renal biopsies with the diagnosis of PVAN carried out at the University Hospital City of Health and Science of Turin over a five-years period were studied. Renal allograft biopsy was performed due to renal function alterations associated to medium-high polyomavirus BK (BKV)-DNA levels on plasma specimen. Results: A total of 21 patients underwent a first biopsy to diagnose a possible BKV nephropathy, in 18, a second biopsy was made, in eight, a third biopsy, and finally, three underwent the fourth renal biopsy; following the results of each biopsies, immunosuppressant agents dosages were modified in order to reduce the effect of PVAN. Conclusions: In this study, the clinical and histological features of 21 kidney transplant recipients with BKV reactivation and development of PVAN are described. To date, the only treatment for PVAN consists in the reduction of immunosuppressive agents, constantly monitoring viral load.

BK Polyomavirus-Specific CD8 T-Cell Expansion In Vitro Using 27mer Peptide Antigens for Developing Adoptive T-Cell Transfer and Vaccination

BACKGROUND

BK polyomavirus (BKPyV) remains a significant cause of premature kidney transplant failure. In the absence of effective antivirals, current treatments rely on reducing immunosuppression to regain immune control over BKPyV replication. Increasing BKPyV-specific CD8 T cells correlate with clearance of BKPyV DNAemia in kidney transplant patients. We characterized a novel approach for expanding BKPyV-specific CD8 T cells in vitro using 27mer-long synthetic BKPyV peptides, different types of antigen-presenting cells, and CD4 T cells.

METHODS

Langerhans cells and immature or mature monocyte-derived dendritic cells (Mo-DCs) were generated from peripheral blood mononuclear cells of healthy blood donors, pulsed with synthetic peptide pools consisting of 36 overlapping 27mers (27mP) or 180 15mers (15mP). BKPyV-specific CD8 T-cell responses were assessed by cytokine release assays using 15mP or immunodominant 9mers.

RESULTS

BKPyV-specific CD8 T cells expanded using 27mP and required mature Mo-DCs (P = .0312) and CD4 T cells (P = .0156) for highest responses. The resulting BKPyV-specific CD8 T cells proliferated, secreted multiple cytokines including interferon γ and tumor necrosis factor α, and were functional (CD107a+/PD1-) and cytotoxic.

CONCLUSIONS

Synthetic 27mP permit expanding BKPyV-specific CD8 T-cell responses when pulsing mature Mo-DCs in presence of CD4 T cells, suggesting novel and safe approaches to vaccination and adoptive T-cell therapies for patients before and after kidney transplantation.

BK virus-associated nephropathy in a lung transplant patient: case report and literature review

BACKGROUND

BK virus-associated nephropathy (BKVAN) is a relatively common cause of renal dysfunction in the first six months after renal transplantation. It arises from reactivation of the latent and usually harmless BK virus (BK virus) due to immunosuppression and other factors including some that are unique to renal transplantation such as allograft injury. BKVAN is much rarer in non-renal solid organ transplantation, where data regarding diagnosis and management are extremely limited.

CASE PRESENTATION

We report a case of a 58-year-old man found to have worsening renal dysfunction nine months after bilateral sequential lung transplantation for chronic obstructive pulmonary disease (COPD). He had required methylprednisolone for acute allograft rejection but achieved good graft function. Urine microscopy and culture and renal ultrasound were normal. BK virus PCR was positive at high levels in urine and blood. Renal biopsy subsequently confirmed BKVAN. The patient progressed to end-stage renal failure requiring haemodialysis despite reduction in immunosuppression, including switching mycophenolate for everolimus, and the administration of intravenous immunoglobulin (IVIG).

CONCLUSIONS

This very rare case highlights the challenges presented by BK virus in the non-renal solid organ transplant population. Diagnosis can be difficult, especially given the heterogeneity with which BKV disease has been reported to present in such patients, and the optimal approach to management is unknown. Balancing reduction in immunosuppression against prevention of allograft rejection is delicate. Improved therapeutic options are clearly required.

A case-control study to assess the role of polyomavirus in transplant complications: Where do we stand?

PURPOSE

The study's aim was to assess whether polyomavirus DNAemia screening was associated with different outcomes in patients with positive viremia compared with negative viremia.

METHODS

Case-control retrospective study of patients with polyomavirus DNAemia (viremia > 1000 copies/mL) matched 1:1 with controls. Control group consists of the patient who received a transplant immediately before or after each identified case and did have nil viremia.

FINDING

Ultimately, 120 cases of BK polyomavirus (BKPyV) were detected and matched with 130 controls. Of these, 54 were adult kidney transplant recipients (KTRs), 43 were pediatric KTRs, and 23 were undergoing hemato-oncologic therapy, of which 20 were undergoing hematopoietic stem cell transplantation. The odds ratio (OR) for overall risk of poorer outcomes in cases versus controls was 16.07 (95% CI: 5.55-46.54). The unfavorable outcome of switching the immunosuppressive drug (ISD) (14/40,35%) was no different from that of those treated with reduced ISD doses (31/71, 43.6%, P = .250). Acute rejection or graft-versus-host disease, previous transplant, and intensity of immunosuppression (4 ISDs plus induction or conditioning) were risk factors for BKPyV-DNAemia (OR: 13.96, 95% CI: 11.25-15.18, P < .001; OR: 6.14, 95% CI: 3.91-8.80, P < .001; OR: 5.53, 95% CI: 3.37-7.30, P < .001, respectively).

CONCLUSIONS

Despite viremia screening, dose reduction, and change in therapeutic protocol, patients with positive BKPyV-DNAemia present poorer outcomes and unfavorable results.

Polyomavirus and cytomegalovirus infections are risk factors for grafts loss in simultaneous pancreas and kidney transplant

BACKGROUND

Published literature on predictors of polyomavirus (BKV) and cytomegalovirus (CMV) infections in simultaneous pancreas and kidney (SPK) transplant and their impact on allograft outcomes remain sparse. We hypothesize that BKV and CMV viremia infections decrease allograft survival in SPK. Identifying modifiable predictors of BKV and CMV may help tailor immunosuppression and improve allograft survival.

METHODS

All SPK recipients at our institution between January 2000 and April 2016 were included (n = 757). Thirty-nine recipients had BKV only and 25 had CMV only, and infection occurred at median follow-up times of 217 and 163 days, respectively. Event density sampling was used to match recipients with BKV or CMV to up to 10 recipients without infection by age, sex, and HLA mismatch status, and these were followed for a median of 4.3 years after infection.

RESULTS

Older age (HR 1.49 for each decade; 95% CI: 0.95, 2.35; P = .083) and tacrolimus use (HR 20.6; 95% CI: 2.37, 179.53; P = .006) were associated with increased incidence of BKV, but not CMV, infection. Both BKV and CMV infections were associated with increased risk of allograft failure for both pancreas (BKV [HR 2.17; 95% CI 1.47, 3.208; P = .000], CMV [HR 1.7; 95% CI 1.077, 2.687; P = .023]) and kidney (BKV [HR 2.65; 95% CI 1.765, 3.984; P = .000], CMV [HR 2.07; 95% CI 1.295, 3.308; P = .002]).

CONCLUSION

Older age at time of transplant and tacrolimus may help predict BKV infection in SPK recipients.

Epidemiology of and Risk Factors for BK Polyomavirus Replication and Nephropathy in Pediatric Renal Transplant Recipients: An International CERTAIN Registry Study

BACKGROUND

BK polyomavirus-associated nephropathy (BKPyVAN) constitutes a serious cause of kidney allograft failure, but large-scale data in pediatric renal transplant recipients and a comprehensive analysis of specific risk factors are lacking.

METHODS

We analyzed the data of 313 patients in the Cooperative European Pediatric Renal Transplant Initiative Registry, with an observation period of 3.3 years (range, 1-5). The net state of immunosuppressive therapy was assessed by the modified Vasudev score.

RESULTS

Presumptive BKPyVAN (defined as sustained [>3 wk] high-level BK viremia >10 copies/mL) within 5 years posttransplant occurred in 49 (15.8%) of 311 patients, and biopsy-proven BKPyVAN in 14 (4.5%) of 313. BKPyV viremia was observed in 115 (36.7%) of 311 patients, of whom 11 (9.6%) of 115 developed viremia late, that is, after the second year posttransplant. In 6 (12.5%) of 48 patients with high-level viremia and in 3 (21.4%) of 14 with BKPyVAN, this respective event occurred late. According to multivariable analysis, BKPyV viremia and/or BKPyVAN were associated not only with a higher net state of immunosuppression (odds ratio [OR], 1.3; P < 0.01) and with tacrolimus-based versus ciclosporin-based immunosuppression (OR, 3.6; P < 0.01) but also with younger recipient age (OR, 1.1 per y younger; P < 0.001) and obstructive uropathy (OR, 12.4; P < 0.01) as primary renal disease.

CONCLUSIONS

Uncontrolled BKPyV replication affects a significant proportion of pediatric renal transplant recipients and is associated with unique features of epidemiology and risk factors, such as young recipient age, obstructive uropathy, and overall intensity of immunosuppressive therapy. BKPyV surveillance should be considered beyond 2 years posttransplant in pediatric patients at higher risk.

Relationship between 2-Hour Tacrolimus Concentrations and Clinical Outcomes in Long Term Kidney Transplantation

Background: Tacrolimus is routinely monitored using trough concentrations, however, recent data have suggested that area under the curve (AUC) provides better correlation with toxicity and efficacy. Area under the curve is cumbersome to measure, but studies have demonstrated that surrogate time points such as 2-hour concentrations are well correlated with AUC. Methods: This is a single center, retrospective study of adult kidney transplant recipients with 2-hour tacrolimus concentrations measured over three years post-transplant. The primary outcome was to determine the difference in serum creatinine (Scr) in those with 2-hour tacrolimus concentrations greater than 20 ng/mL versus those less than or equal to 20 ng/mL. Results: A total of 150 kidney transplant recipients were included. The mean Scr and glomerular filtration rate were 1.49 ± 1.01 mg/dL and 59 ± 23.2 mL/min/1.73 m2, respectively, for the entire cohort. The rate of donor specific antibody formation was 2% and 8% experienced biopsy-proven rejection. The rate of cytomegalovirus viremia was 2% and BK viremia was 13%. There was no significant difference in kidney function over 36 months for the groups specified a priori. Conclusions: Long-term outcomes of maintaining tacrolimus 2-hour concentrations over 20 ng/mL is favorable with minimal opportunistic infections.

Immunosuppression, BK polyomavirus infections, and BK polyomavirus-specific T cells after pediatric kidney transplantation

BACKGROUND

After kidney transplantation, immunosuppressive therapy increases risk of BK polyomavirus-associated nephropathy (BKPyVAN). Outcomes of BKPyV viremia are various and prognostic markers are missing. The impact of different immunosuppressive regimens on BKPyV infections is currently under discussion.

METHODS

We analyzed immunosuppressive therapy and BKPyV-specific cellular immunity to distinguish patients at risk of BKPyVAN from those with self-limiting viremia for purposes of risk-stratified BKPyV management. In a retrospective analysis, 46 pediatric kidney recipients with BKPyV viremia were analyzed with regard to duration of BKPyV viremia and immunosuppressive therapy; in addition, in 37/46 patients, BKPyV-specific CD4 and CD8 T cells were measured.

RESULTS

Nine patients showed persistent BKPyV viremia and BKPyVAN, and required therapeutic intervention, while 37 patients had asymptomatic, self-limiting viremia. At onset of viremia, 78% of patients with persistent viremia and BKPyVAN were treated with tacrolimus, whereas tacrolimus therapy was significantly less frequent in patients with self-limiting viremia (14%). The majority of patients with transient, self-limiting viremia received cyclosporine A (81%) and/or mTOR inhibitors (81%). Patients with persistent BKPyV viremia and BKPyVAN showed lack of BKPyV-specific CD4 and CD8 T cells (6/6), whereas the majority of patients with self-limiting viremia (27/31) had detectable BKPyV-specific CD4 and/or CD8 T cells ≥ 0.5 cells/μl (p < 0.001).

CONCLUSIONS

These results indicate that tacrolimus enhances risk of BKPyVAN with need of therapeutic intervention, whereas under cyclosporine A and mTOR inhibitors, the majority of pediatric kidney recipients showed self-limiting viremia. In patients at risk of BKPyV infections, combination of cyclosporine A and mTOR inhibitor may be advantageous.

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.

Combination of calcineurin and mTOR inhibitors in kidney transplantation: a propensity score analysis based on current clinical practice

INTRODUCTION

The TRANSFORM study demonstrated that an immunosuppression based on a combination of calcineurin inhibitors and de-novo mTOR inhibitors (mTORi) is safe and effective in kidney transplant recipients. However, data that validate this approach in clinical practice are currently missing.

MATERIALS AND METHODS

Analysis of 401 kidney transplant recipients transplanted from June 2013 to December 2016. All patients received tacrolimus with prednisone in combination with either mycophenolate (n = 186) or mTORi (either everolimus or sirolimus, n = 215). A propensity score to receive mTORi was calculated based on the inverse probability of treatment weighting (IPTW) from the following parameters: age and sex of donor and recipient, BMI, previous transplants, diabetes, cPRA, dialysis before transplantation, dialysis vintage, type of donor, ABO-incompatibility, HLA-mismatches, induction and ischemia time. Median follow-up was 2.6 [1.9; 3.7] years.

RESULTS

Cox-regression analysis suggests good results for mTORi versus MPA in terms of 1-year biopsy-proven acute rejection (BPAR, P = 0.063), 1-year graft loss (P = 0.025) and patient survival (P < 0.001). Results observed for BPAR and graft failure were largely attributed to those patients that would have been excluded by the TRANSFORM because of some exclusion criteria (52.9% of the population, P = 0.003 for 1-year BPAR and P = 0.040 for graft loss). In patients who met selection criteria for TRANSFORM, no effect of treatment for BPAR or graft failure was observed, while the beneficial effect on overall survival persisted.

CONCLUSIONS

In a real-life setting, a protocol based on de-novo mTORi with tacrolimus and prednisone could be employed as a standard immunosuppressive regimen and was associated with good outcomes.

JC polyomavirus-specific antibody responses in pediatric kidney transplant recipients

BKPyV is widely recognized in KTRs, but little is known about rates of primary and secondary JCPyV exposure in pediatric KTRs. We evaluated JCPyV exposure in pediatric KTRs using antibody responses in the first 12 months post-transplant. Of 46 children transplanted between 2009 and 2014, 6 lacked any samples for serologic testing, leaving 40 KTRs for study. JCPyV-specific IgG and IgM antibodies were measured using a normalized VLP ELISA. Significant JCPyV exposure was defined as IgG seroconversion, increasing IgG levels of >0.5 nOD units, or IgM detection. Of 40 recipients (median age 3.2 years), 11 (27.5%) were seropositive, 20 (50%) seronegative for JCPyV-IgG, while 9 (22.5%) had no specimen at the time of transplantation, but were confirmed as seronegative in post-transplant samples. Of 29 (72.5%) at risk, JCPyV-IgG seroconversion occurred in 15/29 (51.7%) including JCPyV-IgM in 6 patients (20.7%). Two patients (6.9%) developed only JCPyV-IgM. Among JCPyV-IgG-positive KTRs, six (12.5%) had significant IgG increases. Altogether 23 of 40 patients (57.5%) had serological evidence of primary or secondary JCPyV exposure. In these patients, kidney function tended to be lower during the 2 years of follow-up, but only one patient lost the graft due to JCPyV nephropathy. Thus, JCPyV exposure is common in pediatric KTR and may present serologically as primary or secondary infection. Although only one case of JC-PyVAN occurred, a trend toward lower renal function was seen. Dedicated studies of larger cohorts are warranted to define impact of JCPyV in pediatric KTR.

BK Polyomavirus Virus Glomerular Tropism: Implications for Virus Reactivation from Latency and Amplification during Immunosuppression

BK polyomavirus (BKPyV), or BKV infection, is ubiquitous and usually non-pathogenic, with subclinical infections in 80–90% of adults worldwide. BKV infection is often associated with pathology in immunocompromised individuals. BKV infection often is associated with renal impairment, including ureteral stenosis, hemorrhagic cystitis, and nephropathy. BKV infection is less commonly associated with pneumonitis, retinitis, liver disease, and meningoencephalitis. BKV is known to replicate, establish latency, undergo reactivation, and induce clinical pathology in renal tubular epithelial cells. However, recent in vitro studies support the notion that BKV has expanded tropism-targeting glomerular parenchymal cells of the human kidney, which could impact glomerular function, enhance inflammation, and serve as viral reservoirs for reactivation from latency during immunosuppression. The implications of BKV expanded tropism in the glomerulus, and how specific host and viral factors that would contribute to glomerular inflammation, cytolysis, and renal fibrosis are related to BKV associated nephropathy (BKVAN), have not been explored. The pathogenesis of BKV in human glomerular parenchymal cells is poorly understood. In this review, I examine target cell populations for BKV infectivity in the human glomerulus. Specifically, I explore the implications of BKV expanded tropism in the glomerulus with regard viral entry, replication, and dissemination via cell types exposed to BKV trafficking in glomerulus. I also describe cellular targets shown to be permissive in vitro and in vivo for BKV infection and lytic replication, the potential role that glomerular parenchymal cells play in BKV latency and/or reactivation after immunosuppression, and the rare occurrence of BKV pathology in glomerular parenchymal cells in patients with BKVAN.

Cytomegalovirus prevention strategies and the risk of BK polyomavirus viremia and nephropathy

Polyomavirus BK (BKV) is the cause of polyomavirus-associated nephropathy resulting in premature graft loss. There are limited data regarding the role of cytomegalovirus (CMV) infection and its prevention in developing BKV viremia and PVAN. In a prospective study, we analyzed 207 consecutive renal transplant recipients previously enrolled in 2 randomized trials evaluating different CMV prevention regimens with routine screening for BKV and CMV. Of these, 59 received valganciclovir and 100 valacyclovir prophylaxis; 48 patients were managed by preemptive therapy. At 3 years, the incidence of BKV viremia and PVAN was 28% and 5%, respectively. CMV DNAemia developed in 55% and CMV disease in 6%. Both BKV viremia (42% vs 23% vs 21%, P = .006) and PVAN (12% vs 2% vs 2%, P = .011) were increased in patients treated with valganciclovir prophylaxis compared to valacyclovir and preemptive therapy. Using multivariate Cox proportional hazard regression, valganciclovir prophylaxis was independent predictor of BKV viremia (hazard ratio [HR] = 2.38, P = .002) and PVAN (HR = 4.73, P = .026). In contrast, the risk of subsequent BKV viremia was lower in patients with antecedent CMV DNAemia (HR = 0.50, P = .018). These data suggest valganciclovir prophylaxis may be associated with increased risk of BKV viremia and PVAN. CMV DNAemia did not represent a risk for BKV.

Viral infections and immune reconstitution interaction after pediatric allogenic hematopoietic stem cell transplantation

Background: Viral infections are a major cause of morbidity and mortality after hematopoietic stem cell transplantation (HSCT). Although immune suppression plays a central role, the literature shows conflicting results on interplay between post-transplant immune reconstitution (IR) and viral infections. Methods: We prospectively studied viral infections and IR in 30 pediatric patients undergoing allogenic HSCT, with a follow-up time of 24 months. In total, 1337 blood (CMV, EBV, HHV-6, ADV and BKV) and urine (BKV and JCV) virus samples were analyzed. IR including B-cells (CD19+), T cells (CD3+, CD4+, CD8+) and NK-cells were measured. Clinical outcomes included overall survival (OS), non-relapse mortality (NRM), graft-versus-host disease (GVHD) and occurrence of blood culture positive bacterial infections. Results: We found BKV reactivation to be most frequent, 47% of the children had viremia and 77% viruria. The frequencies of CMV, HHV-6 and adeno viremia were 37%, 37% and 6%, respectively. Viremias beyond 3 months post-HSCT were uncommon. Factors such as GVHD, use of steroids, EBV and CMV infections and pre-transplant irradiation affected IR. No specific viral infection or IR related factor was associated to OS or NRM. Conclusions: Viral infections and IR interact in a bi-directional manner. Accordingly, close follow-up of both IR and viral loads is warranted.

Intravenous Immunoglobulin Administration Significantly Increases BKPyV Genotype-Specific Neutralizing Antibody Titers in Kidney Transplant Recipients

BK polyomavirus (BKPyV)-associated nephropathy (BKPyVAN) is one of the major causes of kidney graft dysfunction, and there are no BKPyV-specific antiviral therapies available. BKPyV neutralizing antibodies (NAbs) play key roles in protecting against BKPyV replication and represent a potential therapeutic or preventive strategy. In this study, we evaluated NAb titers in intravenous immunoglobulin (i.v. Ig) preparations and in kidney transplant recipients (KTR) before and after i.v. Ig administration. NAb titers directed against major BKPyV genotypes were measured using a BKPyV pseudovirion system. Thirty-three KTR receiving high (1 g/kg of body weight/day; n = 17) or low (0.4 g/kg/day; n = 16) i.v. Ig doses were included. Median NAb titers in i.v. Ig preparations ranged from 5.9 log₁₀ 50% inhibitory concentration (IC₅₀) for genotype I to 4.1 log₁₀ IC₅₀ for genotype IV. A mean of 90% of patients (range, 88% to 100%) displaying low or negative BKPyV NAb titers against genotype I reached 4 log₁₀ IC₅₀ after the first i.v. Ig administration. This value was reached by a mean of 44% (range, 13% to 83%) and 19% (range, 0% to 38%) of patients against genotype II and genotype IV, respectively. The benefit of i.v. Ig administration persisted until the following course of treatment (day 22 ± 7 days) for genotypes I and II, and no cumulative effect was observed through the three doses. Our findings demonstrate that i.v. Ig administration results in a significant increase in BKPyV NAb titers in KTR. These in vitro and in vivo pharmacokinetic data provide the rationale for a proof-of-concept study investigating the efficacy of i.v. Ig for the prevention of BKPyV infection in KTR.

Reducing calcineurin inhibitor first for treating BK polyomavirus replication after kidney transplantation: long-term outcomes

BACKGROUND

Reducing immunosuppression is the mainstay of treating BK polyomavirus (BKPyV) viraemia after kidney transplantation, but the best approach, efficacy and impact are undefined. We established a standard operating procedure (SOP) treating BKPyV viraemia based on first reducing calcineurin inhibitor ('CNI first'). The aim of this study was to investigate long-term outcomes in 644 consecutive transplantations using this SOP.

METHODS

Patients were monitored for active BKPyV infection by urinary decoy cells and, if positive, by BKPyV viraemia. In case of sustained BKPyV viraemia >1000 copies/mL, immunosuppression was reduced stepwise according to the SOP. Patients were classified as 'no decoy cells' [n = 432 (66%)], 'decoy cells/no viraemia' [n = 107 (17%)] and 'viraemia' [n = 105 (17%)].

RESULTS

At 6-years post-transplant, graft survival was ∼84%, the clinical rejection rate was ∼25% and they were not different among the three groups (P = 0.14; P = 0.91). The median estimated glomerular filtration rate at the last follow-up was similar (range 49-53 mL/min, P = 0.08). Of 105 viraemic patients, 101 (96%) cleared BKPyV viraemia. In 39% of patients, viraemia clearance followed a tacrolimus reduction. A reduction of mycophenolic acid was required in 43% and discontinuation in 3%. No short-term graft loss was directly attributable to BKPyV-associated nephropathy. After a median follow-up of 5 years after clearance of BKPyV viraemia, 11/101 patients (11%) developed clinical rejection: 7 (7%) T-cell-mediated rejection and 4 (4%) antibody-mediated rejection (ABMR).

CONCLUSIONS

Immunosuppression reduction based on 'CNI first' leads to similar long-term outcomes in patients with/without BKPyV viraemia and is associated with a low risk for ABMR after clearance of BKPyV viraemia. Randomized trials are needed to compare the risks and benefits of immunosuppression reduction strategies in kidney transplant patients with BKPyV viraemia.

BK virus histopathologic disease severity does not predict allograft outcome in renal transplant recipients

AIMS

BK polyomavirus nephropathy (BKPyVN) is an important cause of allograft failure after renal transplantation. Despite early screening for the virus, allograft loss from BKPyVN is still experienced in up to 14% of all renal transplant recipients. The aim of this study was to investigate the association between BKPyVN histopathologic disease severity and allograft outcome at our center.

METHODS

Kidney transplant recipients who had undergone transplantation between 2002 and 2014 with biopsy proven BKPyVN were eligible for this retrospective study. Each biopsy was re-evaluated by a single pathologist blinded to the clinical data and scored according to the Banff criteria for rejection and BKPyVN. Serum creatinine and BK viral load at the time of biopsy diagnosis as well as allograft outcomes to include allograft survival and serum BK viremia resolution were collected for each recipient to determine if BK virus histopathologic disease severity could predict allograft outcome.

RESULTS

Twenty cases of BKPyVN were identified from 1031 total renal transplants performed. There was no statistical association between allograft loss and BKPyVN histopathology (p = 0.49). There was also no statistical association between BKPyVN histopathology and BK viral load at the time of biopsy diagnosis (p = 0.38) or serum BK viremia resolution (p = 0.16).

CONCLUSIONS

BKPyVN histopathology does not appear to be useful in predicting renal allograft outcome in those recipients diagnosed with BKPyVN which is in contrast to some previously published data.

Management of BK-virus infection - Swedish recommendations

BK-virus (BKV) associated nephropathy (BKVAN) and BKV associated haemorrhagic cystitis (HC) are complications of BKV infection/reactivation in renal and allogeneic haematopoietic stem cell transplantation (HSCT) patients, respectively. The task of how to manage these diseases was given to the chair by the Swedish Reference Group for Antiviral Therapy (RAV). After individual contributions by members of the working group, consensus discussions were held in a meeting on 23 January 2018 arranged by RAV. Thereafter, the recommendations were published in Swedish on November 2018. The current translation to English has been approved by all co-authors. High BKV serum levels suggest an increased risk for BKVAN and potential graft failure. For detection of BKVAN, careful monitoring of BKV DNA levels in serum or plasma is recommended the first year after renal transplantation and when increased creatinine serum levels of unknown cause are observed. Notably, a renal biopsy is mandatory for diagnosis. To reduce the risk for progression of BKVAN, there is no specific treatment, and tailored individual decrease of immunosuppression is recommended. For BKV-HC, BKV monitoring is not recommended, since BK-viruria frequently occurs in HSCT patients and the predictive value of BKV in plasma/serum has not been determined. However, the risk for BKV-HC is higher for patients undergoing myeloablative conditioning, having an unrelated, HLA-mismatched, or a cord blood donor, and awareness of the increased risk and early intervention may benefit the patients. Also for BKV-HC, no specific therapy is available. Symptomatic treatment, e.g. forced diuresis and analgesics could be of use.

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.

BK virus: Current understanding of pathogenicity and clinical disease in transplantation

BK polyomavirus (BKV) is an important cause of graft loss in renal transplant recipients that continues to pose a significant challenge to clinicians due to its frequently unpredictable onset, persistence, and the lack of effective antiviral agents or prevention strategies. This review covers our current understanding of epidemiology, viral transmission and disease progression, and treatment and prevention strategies that have been used to manage this disease.

The therapeutic effect of switching from tacrolimus to low-dose cyclosporine A in renal transplant recipients with BK virus nephropathy

Background: There is no effective therapy for BK virus (BKV) nephropathy (BKVN). Cyclosporine A (CsA) has a lower immunosuppressive effect than tacrolimus. In vitro studies have shown that CsA inhibits BKV replication. The present study aimed to evaluate the effectiveness of switching from tacrolimus to low-dose CsA in renal transplant recipients with BKVN. Methods: Twenty-four patients diagnosed with BKVN between January 2015 and December 2016 were included. Tacrolimus was switched to low-dose CsA, and patients were followed for 24 months. Primary end points were BKV clearance in blood and graft. Secondary end points were urine specific gravity, serum creatinine, and graft loss. Results: The viremia in all patients cleared at a mean of 2.7 ± 2.0 months after switching to CsA. Urine specific gravity at 3 months after switching to CsA increased significantly compared with that at diagnosis (P=0.002). The timing and trend of urine specific gravity increase was consistent with the timing and trend of blood and urine viral load decrease. Repeated biopsies at a median of 11.2 months (range: 9.1-12.5 months) after switching to CsA showed that 8 patients (42.1%) were negative for BKV, and 11 patients (58.9%) had a decrease in BKV load (P<0.001). There was no statistical difference in the serum creatinine level between the time of diagnosis and 24 months of CsA therapy (P=0.963). The graft survival rate was 100%. Only two patients (8.3%) suffered from acute rejection. Conclusion: Switching from tacrolimus to low-dose CsA may be an effective therapy for BKVN.

Conversion From Mycophenolates to Mizoribine Is Associated With Lower BK Virus Load in Kidney Transplant Recipients: A Prospective Study

BACKGROUND

BK virus allograft nephropathy (BKVAN) is a graft-threatening complication after kidney transplantation. Current consensus regarding the prevention of BKVAN is to screen for BK viremia and to treat sustained BK viremia through reducing immunosuppression. This study assessed the effect of conversion from mycophenolates to mizoribine (MZR) on the prevention of BK viremia in kidney transplant recipients.

METHODS

De novo kidney transplant recipients were screened for BK viruria. Sustained high levels of BK viruria (>10⁷ copies/mL) were treated by switching from mycophenolates to MZR. The reduction and clearance of BK viruria and viremia were evaluated.

RESULTS

Fifty kidney transplant recipients with high levels BK viruria were enrolled, including 11 recipients with BK viremia. After 6 months of MZR therapy, only 3 recipients still had high levels of BK viruria. The clearance rate of BK viremia was 100%. One episode of acute rejection occurred (2.0%) and was reversed by steroid administration. The serum uric acid level of the recipients was similar before and after switching to MZR, but the proportion of recipients receiving uric acid-reducing drugs increased significantly after 3 months of MZR therapy (19/50 vs 31/50; P = .02). No new cases of BK viremia were observed after conversion to MZR.

CONCLUSION

Conversion from mycophenolates to MZR in kidney transplant recipients with sustained high levels of BK viruria was associated with reduction of BK viruria and clearance of BK viremia. This may be an effective approach to prevent BK viremia and BKVAN.

The detection of BKPyV genotypes II and IV after renal transplantation as a simple tool for risk assessment for PyVAN and transplant outcome already at early stages of BKPyV reactivation

BACKGROUND

After reactivation the BK-polyomavirus (BKPyV) associated nephropathy (PyVAN) is observed in 1-10% of renal transplant recipients, of which up to 80% undergo graft failure. BKPyV reactivation after renal transplantation was associated with donor-derived serotypes against which the recipient has no immunological protection. However, PyVAN risk assessment seroactivity testing is a time-consuming and cost intensive process.

OBJECTIVES

Since BKPyV serotypes can be attributed to distinct genotypes I to IV, in the present study we retrospectively analyzed whether a simple PCR-based BKPyV genotyping assay might be a fast and inexpensive method to assess the risk for PyVAN and transplant outcome already at early stages of BKPyV reactivation.

STUDY DESIGN

56 patients who were renal transplanted and tested positive for BKPyV viremia were included into the study. The BKPyV-VP1-coding sequences were PCR-amplified, sequenced, and subjected to genotyping. For group specific analysis patients were grouped in genotype I (n = 46) and a second group including genotype II and IV (n = 10) and associated with their clinical outcomes.

RESULTS

The most abundant genotype I was detected in 46 of 56 (82%) patients, however, in the genotype II and IV group PyVAN was twice as frequent as compared to the genotype I group 24 months after transplantation (8 of 10 (80%) vs. 17 of 46 (37%); p = 0.001). Accordingly, graft failure was significantly more frequent in the genotype II and IV group (3 of 10 (30%) vs. 2 of 46 (4%); p = 0.007).

CONCLUSION

PCR-based BKPyV genotyping might represent a fast and inexpensive method to assess the risk for PyVAN and transplant outcome already at early stages of BKPyV reactivation even if matched samples of the donor are not available.

Effect of polyoma viremia on 3-year allograft kidney function

BACKGROUND

Polyoma viremia is associated with damage to renal tubular and urothelial cells. This may imply that a certain level of viremia, even cleared thereafter, could be associated with long-term renal dysfunction.

METHODS

We, retrospectively, analyzed 390 first renal transplants adult recipients (≥18 years) who were monitored for BK viremia in the first 12 months and evaluated estimated GFR (MDRD-4 equation) at 1 month and at the last follow-up (959 ± 392 days).

RESULTS

One hundred and ninety-nine patients (51%) developed at least one positive viremia: 105 (53%) low viremia (<10⁴  copies/mL), 36 (18%) high viremia (4 × 10⁴  > viremia ≥ 10⁴  copies/mL) and 58 (15%) viremia (≥4 × 10⁴  copies/mL) consistent with polyoma virus associated nephropathy (PyVAN). Out of these 58 patients, 24 (6%) developed bx-proven (SV40+) PyVAN and 34(8.7%) presumptive PyVAN (SV40-). Baseline characteristics, immunosuppression, KDRI, rejection episodes, etc., did not differ among groups but there were more deceased donors and ATG induction therapy in the high viremia group. At last follow-up, all patients in the low, high viremia and presumptive PyVAN (except 2) had cleared BK viremia. Bx-proven PyVAN led to 14 graft losses, 10 due to PyVAN. In the presumptive PyVAN there was only one graft loss registered as due to PyVAN. eGFR, at 1 month after KTx, did not differ among groups (51 ± 22 vs 48 ± 24 vs 45 ± 27 vs 43 ± 18 vs 46 ± 22 mL/min/1.73 m² ), for no, low and high viremia as well for presumptive PyVAN and bx-proven PyVAN groups, respectively. At the last follow-up, eGFR did not differ between the no, low, and high viremia compared to baseline and to each other but was statistically lower in the presumptive and bx-proven PyVAN (38 ± 15 and 17 ± 7 mL/min/1.73 m² ) either compared to baseline or to the other groups.

CONCLUSIONS

This study shows that low and high levels of BK viremia do not lead to GFR changes although very high viremia levels, compatible with presumptive or bx-proven PyVAN, even if cleared thereafter, lead to allograft damage and decreased GFR.

CD4+ T Cell Immune Response to VP1 and VP3 in BK Virus Infected Recipients of Renal Transplantation

OBJECTIVE

To investigate the characteristics of BK virus (BKV) specific cellular immune response in the recipients who have early infection with BKV after renal transplantation.

METHODS

The recipients of renal allografts (n = 30) were divided into groups of BK virus nephropathy (BKVN), viruria, and viremia. The BKV load was observed with real-time fluorescence quantitative polymerase chain reaction in urine and blood every three months. The values of serum creatinine (SCr) were detected. The peripheral blood mononuclear cells (PBMCs) were cultivated with overlapping peptide pool containing BKV structural proteins VP1, VP2, and VP3, and regulatory proteins large tumor antigen (LT-Ag) and small tumor antigen (st-Ag), to stimulate in vitro specific cellular immunoresponse. Flow cytometry was used to measure the proliferation of CD3+/CD4+/CD8+ T and interferon [INF]-γ/interleukin [IL]-2/tumor necrosis factor [TNF]-α T cell subsets.

RESULTS

The BKV infection increased SCr values in recipients of renal transplantation. CD4+ T cells were dominant (>90%) in the in vitro cellular immunoresponse to VP1, VP2, VP3, LT-Ag, and st-Ag. At the presence of viremia and BKVN, IL-2/IFN-γ+/TNF-α+ CD4+ T cells showed significantly decreased in vitro cellular immunoresponse to VP1, VP2, and VP3 (p < 0.05), but insignificantly changed to LT-Ag and st-Ag (p > 0.05). For the cases of viruria and viremia, IL-2/IFN-γ+/TNF-α+ CD4+ T cells showed significantly higher in vitro cellular immunoresponse to VP1, VP2, and VP3 than to LT-Ag and st-Ag (p < 0.05). The immunogenicity of VP1 and VP3 was significantly higher than that of VP2 (p < 0.05).

CONCLUSIONS

The BKV infection increases SCr values, and CD4+ T cells are dominant in the in vitro BKV specific cellular immunoresponse in the recipients of renal transplantation. Viremia significantly decreased the immunoresponse to VP1, VP2, and VP3. There is the significantly stronger immunoresponse to VP1 and VP3 when compared with that to VP2, LT-Ag, and st-Ag, suggesting that VP1 and VP3 may be the major targets for the BKV specific immune response.

BK polyomavirus viremia and antibody responses of pediatric kidney transplant recipients in Finland

BACKGROUND

BKPyV is an important cause of premature graft failure after KT. Most clinical studies describe BKPyV infection in adult KT patients. We studied the prevalence of post-transplant BKPyV viremia, serology, and graft function in pediatric KT recipients.

METHODS

Forty-six pediatric patients transplanted between 2009 and 2014 were followed up for BKPyV DNAemia by plasma PCR for median 2.3 (range: 1-6) years. BKPyV-specific antibodies were retrospectively analyzed using virus-like particle ELISA. GFR was measured annually by ⁵¹ Cr-EDTA clearance, and serum samples were screened for DSAs by Luminex assay.

RESULTS

BKPyV viremia was demonstrated in nine patients at a median of 6 months post-KT. Early BKPyV viremia at 3 months post-KT associated with decreased concomitant GFR and tendency for decreased subsequent graft function. Three of nine patients with BKPyV viremia developed DSA, all against class II antigens. PyVAN developed to four patients and responded to judicious reduction in IS. One graft was lost later due to ABMR. BKPyV-IgG was found in 18 of 31 patients (58%) tested at transplantation, and seven recipients seroconverted after transplantation with a significant increase in IgG levels with IgM. Finally, BKPyV-IgG was detectable in 31 of 40 patients (78%) at the end of the study.

CONCLUSIONS

Post-transplant BKPyV viremia in pediatric KT patients may alter graft function and contribute to progression of chronic allograft injury. BKPyV-IgG predicts past exposure. Low or absent BKPyV-specific antibody levels were seen pretransplant in 42% of tested patients, but were not predictive of prolonged replication or poor outcome.

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.

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.

Kidney transplant recipients with polycystic kidney disease have a lower risk of post-transplant BK infection than those with end-stage renal disease due to other causes

BACKGROUND

Polyomavirus-associated nephropathy is associated with high risk of kidney allograft loss. Whether the cause of native end-stage renal disease influences the risk of BK infection is unclear.

METHODS

A retrospective, single-center study of 2741 adult kidney transplant recipients between 1994 and 2014 was performed. Recipients had end-stage renal disease due to polycystic kidney disease (PKD, n = 549), diabetes mellitus (DM, n = 947), hypertension (HTN, n = 442), or glomerulonephritis (GN, n = 803).

RESULTS

A total of 327 recipients (12%) developed post-transplant BK viremia over a median follow-up time of 5 years. The incidence rate of BK viremia was lowest in patients with PKD (1.46 per 100 person-years) compared to other causes of ESRD (DM = 2.06, HTN = 2.65, and GN = 2.01 per 100 person-years). A diagnosis of PKD was associated with a lower risk of post-transplant BK viremia (adjusted HR (95% CI) = 0.67 (0.48-0.95), P = 0.02). BK nephropathy was significantly less common in patients with PKD (0.21 per 100 person-years) compared to those with HTN (0.80 per 100 person-years, P ≤ 0.001). Among patients with PKD, the risk of BK viremia was lower in patients with nephrectomy, compared to those without nephrectomy (adjusted HR (95% CI) = 0.42 (0.19-0.92), P < 0.05).

CONCLUSION

ESRD due to PKD is associated with a lower risk of post-transplant BK infection. The renal tubular epithelial cells in PKD are unique; they are in a proliferative but non-differentiated state. Whether this characteristic of renal tubular epithelial cells alters the BK viral reservoir or replication in PKD patients warrants further study.

Risk factors for BK virus viremia and nephropathy after kidney transplantation: A systematic review

In the last 20 years, the management of BK polyomavirus (BKPyV) reactivation in kidney transplant patients has become a true challenge for the transplant community. The only treatment option is based on the early identification of at-risk patients. The number of reported risk factors for BKPyV reactivation has increased markedly in the literature last years, although they are sometimes in an unclear or contradictory manner. Our purpose is to provide a systematic review and meta-analysis of risk factors for BKPyV viremia and nephropathy described in multivariate analyses. The PubMed database was searched for prospective or prospectively-based observational studies on risk factors for BKPyV viremia and/or nephropathy. Our qualitative assessment of risk factors was based on the odds ratios and hazard ratios calculated in multivariate regression analyses. Of the 241 publications screened, 34 were included in the qualitative analysis. In all, 144 and 19 distinct factors were analyzed for BKPyV viremia and for BKPyV nephropathy, respectively. Our evaluation highlighted eight risk factors for BKPyV viremia: a tacrolimus regimen, a deceased donor, a male recipient, a history of previous transplant, age at transplantation, ureteral stent use, delayed graft function, and acute rejection episodes increased the risk of BKV viremia to varying extents. Tacrolimus and acute rejection episodes were also associated with a higher incidence of BKPyV nephropathy. BKPyV reactivation is a serious complication after renal transplantation. With a view to combating this problem, existing data should be published in full, and new prospective international multicenter studies should be performed.

Impact of immune suppressive agents on the BK-Polyomavirus non coding control region

BACKGROUND

Reactivation of the BK-Polyomavirus (BKPyV) can cause a polyomavirus associated nephropathy in approx. 10% of kidney transplant recipients. In these cases, current therapy is based on the reduction of immunosuppression. Since BKPyV-transcription is driven by the Non-Coding-Control-Region (NCCR) we were interested whether NCCR-activity is affected by immunosuppressive agents.

METHODS

Plasma samples from 45 BKPyV-positive patients after renal transplantation were subjected to PCR-analysis. NCCR-amplicons were cloned into a plasmid that allows the quantification of early and late NCCR-activity by tdTomato and eGFP expression, respectively. HEK293T-cells were transfected with the reporter-plasmids, treated with immunosuppressive agents, and subjected to FACS-analysis. In addition, H727-cells were infected with patient derived BKPyV, treated with mTOR-inhibitors, and NCCR activity was analysed using qRT-PCR.

RESULTS

While tacrolimus and cyclosporine-A did not affect NCCR-promoter-activity, treatment with mTOR1-inhibitor rapamycin resulted in the reduction of early, but not late-NCCR-promoter-activity. Treatment with dual mTOR1/2 inhibitors (INK128 or pp242) led to significant inhibition of early, however, concomitantly enhanced late-promoter-activity. In BKPyV infected cells both rapamycin and INK128 reduced early expression, however, INK128 resulted in higher late-mRNA levels when compared to rapamycin treatment.

CONCLUSIONS

Our results demonstrate that mTOR1-inhibitors are able to reduce early-expression of wildtype and rearranged NCCRs, which might contribute to previously described inhibition of BKPyV-replication. Dual mTOR1/2-inhibitors, however, additionally might shift viral early into late-expression promoting synthesis of viral structural proteins and particle production.

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.

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.

Conversion from tacrolimus-mycophenolate mofetil to tacrolimus-mTOR immunosuppression after kidney-pancreas transplantation reduces the incidence of both BK and CMV viremia

BACKGROUND

We sought to determine whether conversion from tacrolimus/mycophenolate mofetil (TAC-MMF) into tacrolimus/mTOR inhibitor (TAC-mTOR) immunosuppression would reduce the incidences of BK and CMV viremia after kidney/pancreas (KP) transplantation.

METHODS

In this single-center review, the TAC-mTOR cohort (n = 39) was converted at 1 month post-transplant to an mTOR inhibitor and reduced-dose tacrolimus. Outcomes were compared to a cohort of KP recipients (n = 40) maintained on TAC-MMF.

RESULTS

At 3 years post-transplant, KP survivals and incidences of kidney/pancreas rejection were equivalent between mTOR and MMF-treated cohorts. (P = ns). BK viremia-free survival was better for the mTOR vs MMF-treated group (P = .004). In multivariate analysis, MMF vs mTOR immunosuppression was an independent risk factor for BK viremia (hazard ratio 12.27, P = .02). Similarly, mTOR-treated recipients displayed better CMV infection-free survival compared to the MMF-treated cohort (P = .01). MMF vs mTOR immunosuppression (hazard ratio 18.77, P = .001) and older recipient age (hazard ratio 1.13 per year, P = .006) were independent risk factors for CMV viremia. Mean estimated GFR and HgbA1c levels were equivalent between groups at 1, 2, and 3 years post-transplantation.

CONCLUSION

Conversion from TAC/MMF into TAC/mTOR immunosuppression after KP transplantation reduced the incidences of BK and CMV viremia with an equivalent risk of acute rejection and similar renal/pancreas function.

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.

Differential T cell response against BK virus regulatory and structural antigens: A viral dynamics modelling approach

BK virus (BKV) associated nephropathy affects 1-10% of kidney transplant recipients, leading to graft failure in about 50% of cases. Immune responses against different BKV antigens have been shown to have a prognostic value for disease development. Data currently suggest that the structural antigens and regulatory antigens of BKV might each trigger a different mode of action of the immune response. To study the influence of different modes of action of the cellular immune response on BKV clearance dynamics, we have analysed the kinetics of BKV plasma load and anti-BKV T cell response (Elispot) in six patients with BKV associated nephropathy using ODE modelling. The results show that only a small number of hypotheses on the mode of action are compatible with the empirical data. The hypothesis with the highest empirical support is that structural antigens trigger blocking of virus production from infected cells, whereas regulatory antigens trigger an acceleration of death of infected cells. These differential modes of action could be important for our understanding of BKV resolution, as according to the hypothesis, only regulatory antigens would trigger a fast and continuous clearance of the viral load. Other hypotheses showed a lower degree of empirical support, but could potentially explain the clearing mechanisms of individual patients. Our results highlight the heterogeneity of the dynamics, including the delay between immune response against structural versus regulatory antigens, and its relevance for BKV clearance. Our modelling approach is the first that studies the process of BKV clearance by bringing together viral and immune kinetics and can provide a framework for personalised hypotheses generation on the interrelations between cellular immunity and viral dynamics.

Identification of potential key protein interaction networks of BK virus nephropathy in patients receiving kidney transplantation

We aim to identify the key protein interaction networks and implicated pathways of BK virus nephropathy (BKVN) via bioinformatic methods. The microarray data GSE75693 of 30 patients with stable kidney transplantation and 15 with BKVN were downloaded and analyzed by using the limma package to identify differentially expressed genes (DEGs). Then the gene ontology (GO) functional enrichment analysis and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were done to investigate the molecular function (MF), biological process (BP), cellular components (CC) and pathways of DEGs. Finally, protein-protein interactions (PPIs) were constructed, and the hub proteins were  identified. As a result, 249 up-regulated genes and 253 down-regulated genes of BKVN patients were selected based on criteria of P > 0.01 and fold change >2.0. GO and KEGG showed that DEGs were mainly located in nucleus and cytosol, and were implicated in the immune responses. In the PPI analysis, 26 up-regulated and 8 down-regulated proteins composed the pivotal interaction network. CXCL10, EGF and STAT1 were identified as hub proteins in BKVN. In conclusion, CXCL10, EGF and STAT1 may induce kidney injuries by promoting inflammation and prohibiting reparation of tissue damage in BKVN.

BK virus as a mediator of graft dysfunction following kidney transplantation

PURPOSE OF REVIEW

BK virus is a significant risk factor for kidney allograft dysfunction and loss among renal transplant recipients. Currently, there is no proven effective treatment except for the reduction of immunosuppression. In this review, we discuss diagnostic challenges and current treatment options for BK in kidney transplant recipients.

RECENT FINDINGS

Antiviral and antibiotic therapies have been employed for BK viraemia with variable efficacy. In addition, novel therapeutic regimens such as adoptive transfer of targeted T cells have been described as possible treatment options for recipients with BK nephropathy. BK can also be seen in the native kidneys of pancreas, heart, lung and liver transplant recipients, suggesting that BK screening measures should be employed to other solid organ transplant recipients.

SUMMARY

Early screening for BK combined with reduction of immunosuppression remains the mainstay of treatment for BK viraemia. New therapeutic advances demonstrate promise in vitro; however, the in-vivo efficacy will be demonstrated by future studies.

Impact of low-level BK polyomavirus viremia on intermediate-term renal allograft function

BACKGROUND

BK polyomavirus (BKPyV)-associated nephropathy (PyVAN) is a significant cause of premature renal transplant failure. High-level BKPyV viremia is predictive for PyVAN; however, low-level BKPyV viremia does not necessarily exclude the presence of PyVAN. As data are limited regarding whether or not low-level BKPyV viremia has an effect on intermediate-term graft outcome, this study analyzes the impact of low-level BKPyV viremia on intermediate-term graft function and outcome compared with high-level viremia and non-viremic patients.

METHODS

All renal transplant patients received follow-up examinations at the Department of Nephrology, University Hospital Essen. Patients were screened for BKPyV viremia and stratified into three groups according to their maximum BKPyV load in serum (low-level viremia, high-level viremia, and no viremia).

RESULTS

In 142 of 213 (67%) patients, BKPyV was never detected in serum; 42 of 213 (20%) patients were found positive for low-level viremia (≤10⁴ copies/mL); and 29 of 213 (13%) patients showed high-level viremia (>10⁴ copies/mL). No significant differences regarding transplant function and graft failure were observed between patients without BKPyV viremia (delta estimated glomerular filtration rate [eGFR] +0.1 mL/min [month 1 vs last visit at month 44]) and patients with low-level BKPyV viremia (delta eGFR -1.7 mL/min). In patients with high-level viremia, transplant function was significantly restricted (delta eGFR -6.5 mL/min) compared with low-level viremia until the last visit at 44 ± 9.7 months after transplantation. Although the graft function and graft loss were worse in the high-level viremia group compared with no viremia (eGFR 37 vs 45 mL/min), the difference was not significant.

CONCLUSIONS

High-level viremia was associated with impaired graft function. In contrast, low-level BKPyV viremia had no significant impact on intermediate-term graft function.