Different risk factor profiles distinguish early-onset from late-onset BKV-replication

Prevalence of JC and BK Polyomavirus Infection in Patients with Chronic Kidney Disease in the State of Pará, Brazil

The polyomaviruses that infect humans, JC virus (JCV) and BK virus (BKV), can establish persistent infections in the cells that make up the renal system, causing nephritis and BKV-associated nephropathy in up to 10% of renal transplant patients, and of these, 90% lose the graft and return for hemodialysis. This study aimed to determine the prevalence of polyomaviruses (PyV) in the population with chronic kidney disease (CKD), classified into three groups (conservative, dialysis, and transplanted) and a control group. Urine samples were collected from 290 individuals, including 202 patients with CKD and 88 from the control group. PyV screening was performed by PCR amplification of a fragment of the VP1 region, and the JCV and BKV species were distinguished through enzymatic digestion with the restriction endonuclease BamHI from the amplification of a TAg region. All amplification products were visualized on a 3% agarose gel. The prevalence of PyV infection was correlated with clinical-epidemiological variables using the chi-squared and Fisher's exact tests. In the group with CKD, the prevalence of PyV was 30.2%, a higher rate being observed in conservative patients (36.66%; 22/60), followed by dialysis patients (30.48%; 25/82), and transplanted patients (20%; 12/60). In the control group, the prevalence was 46.59% (41/88). The differentiation between species revealed that JCV was present in 77.8% and BKV in 22.2% of the group with CKD. The prevalence of infection was higher in male patients (59.32%), whose most common pathology was systemic arterial hypertension (35.59%). In the group of transplanted patients, there was a statistically significant association between infection and the use of the immunosuppressant azathioprine (p = 0.015). The prevalence of PyV infection was higher in the control group than in the group with CKD, being predominant in males and in patients with systemic arterial hypertension.

Risk factors and outcome of concurrent and sequential multiviral cytomegalovirus, Epstein-Barr virus, BK virus, adenovirus and other viral reactivations in transplantation

PURPOSE OF REVIEW

Reactivation of viral infections occurs frequently in immunosuppressed populations, particularly in solid organ (SOT) or allogeneic haematopoietic cell (HCT) transplant patients. Concurrent and sequential multivirus infections are common, yet risk factors and outcomes remain unclear. This review aims to identify the patients vulnerable to multivirus infections and characterize the impact of increased viral burden to formulate prevention and treatment strategies.

RECENT FINDINGS

Incidences of up to 89% in SOT and 36% in HCT have been reported for two viruses, and 32% in SOT and 28% in HCT for at least three viruses. Risk factors appear related to an increased burden of immunosuppression, with most viral coinfections occurring within 12 months of transplantation. Direct viral complications such as cytomegalovirus disease are more frequent in coinfected patients, with documented prolonged duration of viraemia, higher viral load and increased end-organ disease. Graft dysfunction, acute rejection and graft-vs.-host disease (GVHD) have also been associated. Increased mortality is reported in the HCT population.

SUMMARY

Multivirus infections occur in a significant proportion of transplant patients and is linked to immunosuppressive burden. There is increasing evidence that this leads to worse graft and patient outcomes. Further prospective studies are required to further comprehensively characterise viral epidemiology, mechanisms and treatment strategies to ameliorate this risk.

Monitoring of blood immunosuppressant concentrations and lymphocyte activation for predicting viral infections following kidney transplantation: A pilot study

The current standard pharmacokinetic monitoring of immunosuppressive therapy does not consider inter- and intra-individual differences in the biological response to multidrug immunosuppressive therapy. The authors evaluated the blood levels of the immunosuppressive drugs IL-2 and IFN-γ in circulating lymphocytes as surrogate indicators of the development of viral infections after living kidney transplantation. This single-center prospective study included 20 kidney transplant recipients who underwent living-donor transplantation at the Mie University Hospital. All the study participants received tacrolimus, mycophenolic acid, methylprednisolone, and basiliximab. The area under the concentration curves (AUCs) of blood tacrolimus and serum mycophenolic acid were measured 1 day prior to transplantation and on post-transplantation days (PTD) for up to 5 months. IL-2 and IFN-γ levels in circulating lymphocytes were measured simultaneously. One recipient experienced an acute graft rejection. Although the AUC of tacrolimus at PTD 7 was significantly higher in the virus-infected group than that in the non-infected group, the AUC of mycophenolic acid did not differ significantly between the 2 groups. The expression levels of IFN-γ+ NK, IFN-γ+ CD4+ T, and CD8+ T cells in the infected group also tended to be higher than those in the noninfected group. During the study period, there was a clear difference in the expression of IFN-γ+ CD8+ T cells, which increased significantly during or after infection. Circulating IFN-γ+ CD8+ T cell counts may serve as promising biomarkers for predicting opportunistic viral infections early after kidney transplantation.

Risk factors and outcomes of BK viremia among deceased donor kidney transplant recipients based on donor characteristics

INTRODUCTION

BK polyomavirus (BKV) is a common infection among kidney transplant recipients (KTR). Risk factors and outcomes based on donor characteristics remain largely unknown.

METHODS

In this study, we aimed to analyze the impact of donor factors through a paired kidney analysis. We included 289 pairs of adult deceased donor transplants (578 KTRs total); each pair had received kidneys from the same donor. Recipient pairs were divided into three groups: "no BK group" if neither KTR developed BK viremia (n = 336), "discordant" if the only one did (n = 176), and "concordant" if both did (n = 66). Acute rejection (AR), graft failure, and BK nephropathy (BKN) were outcomes of interest.

RESULTS

Donors in the concordant group were younger, had lower kidney donor profile index (KDPI), and were less likely to be donor after circulatory death (DCD). In multivariate analyses, KTRs who had a donor with a higher body mass index (BMI) (hazard ratio (HR): 0.97; 95% confidence interval (CI): 0.95-0.99; p = .009) were less likely to develop BKV. Concordance was not associated with AR (HR: 0.83; 95% CI: 0.51-1.34; p = .45), graft failure (HR: 1.77; 95% CI: 0.42-7.50; p = .43), or BKN (HR: 1.02; 95% CI: 0.51-2.03; p = .96).

DISCUSSION

Our study suggests lower donor BMI is associated with BKV infection, and concordance or discordance between paired kidney recipients is not associated with poor outcomes.

Intravenous immunoglobulins do not prove beneficial to reduce alloimmunity among kidney transplant recipients with BKV-associated nephropathy

Reduced immunosuppression during BKV-DNAemia has been associated with T-cell mediated rejection (TCMR), de novo donor-specific antibodies (DSA) and antibody-mediated rejection (ABMR). Intravenous immunoglobulins (IVIG) may reduce alloimmunity. We studied 860 kidney transplant recipients (KTRs) for the development of BKV-DNAuria and BKV-DNAemia (low-level <10 000 IE/ml, high-level >10 000 IE/ml). 52/131 KTRs with high-level BKV-DNAemia received IVIG. The HLA-related immunological risk was stratified by the Predicted Indirectly Recognizable HLA Epitopes (PIRCHE) algorithm. BKV-DNAuria only was observed in 86 KTRs (10.0%), low-level BKV-DNAemia in 180 KTRs (20.9%) and high-level BKV-DNAemia in 131 KTRs (15.2%). KTRs with low-level BKV-DNAemia showed significantly less TCMR compared to KTRs with high-level BKV-DNAemia (5.2% vs. 25.5%; P < 0.001) and no BKV-replication (13.2%; P = 0.014), lowest rates of de novo DSA (21.3%), ABMR (9.2%) and flattest glomerular filtration rate (GFR) slope (-0.8 ml/min). KTRs with low-level BKV-DNAemia showed significantly higher median (interquartile range) total PIRCHE if they developed TCMR [100.22 (72.6) vs. 69.52 (49.97); P = 0.020] or ABMR [128.86 (52.99) vs. 69.52 (49.96); P = 0.005]. Administration of IVIG did not shorten duration of BKV-DNAemia (P = 0.798) or reduce TCMR, de novo DSA and ABMR (P > 0.05). KTRs with low-level BKV-DNAemia showed best protection against alloimmunity, with a high number of PIRCHE co-determining the remaining risk. The administration of IVIG, however, was not beneficial in reducing alloimmunity.

Clinical features of BK-polyomavirus and cytomegalovirus co-infection after kidney transplantation

BK polyomavirus (BKPyV) and cytomegalovirus (CMV) are the main viral pathogens affecting the graft and recipient outcome after allogenic kidney transplantation. It has recently been found that infection with both viruses has a greater impact on kidney graft function than a single infection. We retrospectively analyzed a cohort of 723 recipients who received kidney transplantation between 2007 and 2015 after living and postmortal donation for differences in risk and outcome parameters regarding BKPyV (DNAemia) and CMV (CMV DNAemia) co-infection compared to sole viremias and to patients without viremia. Of all kidney allograft recipients in our cohort, 8.2% developed co-infection with BKPyV DNAemia and CMV DNAemia, 15.1% showed BKPyV viremia alone and 25.2% sole CMV DNAemia. Acute rejection was closely linked with co-infection (multivariable analysis, p = 0.001). Despite the fact that the estimated glomerular filtration rate of patients with co-infection was noticeably reduced compared to patients with BKV or CMV infection alone, transplant survival and patient survival were not significantly reduced. Co-infection with BKPyV and CMV in kidney transplanted patients is significantly associated with inferior allograft function. Since co-infection is strongly associated with acute rejection, co-infected individuals should be considered a risk collective.

The Role of HLA and KIR Immunogenetics in BK Virus Infection after Kidney Transplantation

BK virus (BKV) is a polyomavirus with high seroprevalence in the general population with an unremarkable clinical presentation in healthy people, but a potential for causing serious complications in immunosuppressed transplanted patients. Reactivation or primary infection in kidney allograft recipients may lead to allograft dysfunction and subsequent loss. Currently, there is no widely accepted specific treatment for BKV infection and reduction of immunosuppressive therapy is the mainstay therapy. Given this and the sequential appearance of viruria-viremia-nephropathy, screening and early detection are of utmost importance. There are numerous risk factors associated with BKV infection including genetic factors, among them human leukocyte antigens (HLA) and killer cell immunoglobulin-like receptors (KIR) alleles have been shown to be the strongest so far. Identification of patients at risk for BKV infection would be useful in prevention or early action to reduce morbidity and progression to frank nephropathy. Assessment of risk involving HLA ligands and KIR genotyping of recipients in the pre-transplant or early post-transplant period might be useful in clinical practice. This review summarizes current knowledge of the association between HLA, KIR and BKV infection and potential future directions of research, which might lead to optimal utilization of these genetic markers.

Functional immune monitoring of BK Virus and donor-specific T-cell effector immune responses to guide treatment decision-making after kidney transplantation; an illustrative case report and literature review

Differential diagnosis between Polyoma virus associated-nephropathy (PVAN) and T-cell mediated rejection (TCMR) might be challenging, as respective treatment approaches are totally opposite. Here we report the illustrative case of a kidney transplant recipient with PVAN who developed a persistent acute TCMR after full abrogation of viral infection through immunosuppression modulation. By simultaneous functional immune monitoring of BKV and donor-specific T-cell responses using IFN-γELISPOT assay, we retrospectively demonstrated the predominant effector mechanisms responsible of allograft injury and thus, potential guidance for treatment decision-making. Furthermore, the evidence of an efficient T-cell alloimmunity abrogation accompanied by a sustained anti-viral response after sirolimus addition, promotes the potential benefit of converting patients to an mTOR-based immunosuppression in case of PVAN.

Beyond Cytomegalovirus and Epstein-Barr Virus: a Review of Viruses Composing the Blood Virome of Solid Organ Transplant and Hematopoietic Stem Cell Transplant Recipients

Viral primary infections and reactivations are common complications in patients after solid organ transplantation (SOT) and hematopoietic stem cell transplantation (HSCT) and are associated with high morbidity and mortality. Among these patients, viral infections are frequently associated with viremia. Beyond the usual well-known viruses that are part of the routine clinical management of transplant recipients, numerous other viral signatures or genomes can be identified in the blood of these patients. The identification of novel viral species and variants by metagenomic next-generation sequencing has opened up a new field of investigation and new paradigms. Thus, there is a need to thoroughly describe the state of knowledge in this field with a review of all viral infections that should be scrutinized in high-risk populations. Here, we review the eukaryotic DNA and RNA viruses identified in blood, plasma, or serum samples of pediatric and adult SOT/HSCT recipients and the prevalence of their detection, with a particular focus on recently identified viruses and those for which their potential association with disease remains to be investigated, such as members of the Polyomaviridae, Anelloviridae, Flaviviridae, and Astroviridae families. Current knowledge of the clinical significance of these viral infections with associated viremia among transplant recipients is also discussed. To ensure a comprehensive description in these two populations, individuals described as healthy (mostly blood donors) are considered for comparative purposes. The list of viruses that should be on the clinicians' radar is certainly incomplete and will expand, but the challenge is to identify those of possible clinical significance.

Glomerular Parietal Epithelial Cells Infection Is Associated With Poor Graft Outcome in Kidney Transplant Recipients With BK Polyomavirus-Associated Nephropathy

BACKGROUND

The purpose of this study was to investigate the effect of BK polyomavirus (BKPyV infection of glomerular parietal epithelial cells (GPECs) on graft outcome in kidney transplant recipients with BKPyV-associated nephropathy (BKPyVAN).

METHODS

A total of 152 kidney transplant recipients with BKPyVAN were divided into 31 with (GPEC-positive group) and 121 without (GPEC-negative group) BKPyV-infected GPECs. Clinicopathological characteristics and allograft survival were compared between the groups.

RESULTS

The GPEC-positive group had more patients with advanced-stage BKPyVAN than the GPEC-negative group (P < .001). At the last follow-up, the GPEC-positive group had a significantly higher serum creatinine level than the GPEC-negative group. The graft loss rate in the GPEC-positive group was higher than that in the GPEC-negative group (32.3% vs 12.4%; P = .008). Kaplan-Meier analysis showed that the graft survival rate in the GPEC-positive group was lower than that in the GPEC-negative group (log-rank test, P = .004). Multivariate Cox regression analysis demonstrated that BKPyV infection of GPECs was an independent risk factor for graft survival (hazard ratio, 3.54; 95% confidence interval, 1.43-8.76; P = .006).

CONCLUSIONS

GPEC infection in patients with BKPyVAN indicates more-severe pathological damage and a rapid decline in renal function. BKPyV infection of GPECs is an independent risk factor for allograft loss.

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.

Cytomegalovirus Viremia after Living and Deceased Donation in Kidney Transplantation

Despite screening, effective anti-viral drugs and risk-balanced prophylaxis, cytomegalovirus (CMV) remains a major cause of morbidity in transplant patients. The objective of this study was to retrospectively analyze the risk factors associated with CMV viremia after kidney transplantation in a large European cohort with standardized valganciclovir prophylaxis in the present era. A special focus was placed on the comparison of living and postmortal donation. We conducted a longitudinal observational study involving 723 adult patients with a total of 3292 patient-years who were transplanted at our center between 2007 and 2015. Valganciclovir prophylaxis was administered over 100 days for CMV+ donors (D) or recipients (R), over 200 days for D+/R−, and none in D−/R−. A CMV+ donor, rejection episodes, and deceased donor transplantation were identified to be associated with increased incidences of CMV viremia. Although we did not find a reduced overall survival rate for patients with CMV viremia, it was associated with worse graft function. Since we observed a relevant number of CMV infections despite prescribing valganciclovir prophylaxis, a pre-emptive strategy in patients with (suspected) adherence restrictions could be favored. Our data can help transplant physicians educate their patients about their individual CMV risk and choose the most appropriate CMV treatment approach.

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.

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.

Incidence, risk factors, and outcome of BK polyomavirus infection after kidney transplantation

BACKGROUND

Polyomavirus-associated nephropathy is a leading cause of kidney allograft failure. Therapeutic options are limited and prompt reduction of the net state of immunosuppression represents the mainstay of treatment. More recent application of aggressive screening and management protocols for BK-virus infection after renal transplantation has shown encouraging results. Nevertheless, long-term outcome for patients with BK-viremia and nephropathy remains obscure. Risk factors for BK-virus infection are also unclear.

AIM

To investigate incidence, risk factors, and outcome of BK-virus infection after kidney transplantation.

METHODS

This single-centre observational study with a median follow up of 57 (31-80) mo comprises 629 consecutive adult patients who underwent kidney transplantation between 2007 and 2013. Data were prospectively recorded and annually reviewed until 2016. Recipients were periodically screened for BK-virus by plasma quantitative polymerized chain reaction. Patients with BK viral load ≥ 1000 copies/mL were diagnosed BK-viremia and underwent histological assessment to rule out nephropathy. In case of BK-viremia, immunosuppression was minimized according to a prespecified protocol. The following outcomes were evaluated: patient survival, overall graft survival, graft failure considering death as a competing risk, 30-d-event-censored graft failure, response to treatment, rejection, renal function, urologic complications, opportunistic infections, new-onset diabetes after transplantation, and malignancies. We used a multivariable model to analyse risk factors for BK-viremia and nephropathy.

RESULTS

BK-viremia was detected in 9.5% recipients. Initial viral load was high (≥ 10000 copies/mL) in 66.7% and low (< 10000 copies/mL) in 33.3% of these patients. Polyomavirus-associated nephropathy was diagnosed in 6.5% of the study population. Patients with high initial viral load were more likely to experience sustained viremia (95% vs 25%, P < 0.00001), nephropathy (92.5% vs 15%, P < 0.00001), and polyomavirus-related graft loss (27.5% vs 0%, P = 0.0108) than recipients with low initial viral load. Comparison between recipients with or without BK-viremia showed that the proportion of patients with Afro-Caribbean ethnicity (33.3% vs 16.5%, P = 0.0024), panel-reactive antibody ≥ 50% (30% vs 14.6%, P = 0.0047), human leukocyte antigen (HLA) mismatching > 4 (26.7% vs 13.4%, P = 0.0110), and rejection within thirty days of transplant (21.7% vs 9.5%; P = 0.0073) was higher in the viremic group. Five-year patient and overall graft survival rates for patients with or without BK-viremia were similar. However, viremic recipients showed higher 5-year crude cumulative (22.5% vs 12.2%, P = 0.0270) and 30-d-event-censored (22.5% vs 7.1%, P = 0.001) incidences of graft failure than control. In the viremic group we also observed higher proportions of recipients with 5-year estimated glomerular filtration rate < 30 mL/min than the group without viremia: 45% vs 27% (P = 0.0064). Urologic complications were comparable between the two groups. Response to treatment was complete in 55%, partial in 26.7%, and absent in 18.3% patients. The nephropathy group showed higher 5-year crude cumulative and 30-d-event-censored incidences of graft failure than control: 29.1% vs 12.1% (P = 0.008) and 29.1% vs 7.2% (P < 0.001), respectively. Our multivariable model demonstrated that Afro-Caribbean ethnicity, panel-reactive antibody > 50%, HLA mismatching > 4, and rejection were independent risk factors for BK-virus viremia whereas cytomegalovirus prophylaxis was protective.

CONCLUSION

Current treatment of BK-virus infection offers sub-optimal results. Initial viremia is a valuable parameter to detect patients at increased risk of nephropathy. Panel-reactive antibody > 50% and Afro-Caribbean ethnicity are independent predictors of BK-virus infection whereas cytomegalovirus prophylaxis has a protective effect.

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).

Clinical characteristics and outcomes of late-onset BK virus nephropathy in kidney and kidney-pancreas transplant recipients

BACKGROUND

BK virus nephropathy (BKPyVAN) is a major complication in kidney transplant recipients (KTR) and typically occurs within 1 year of transplant. Guidelines vary in recommendations for BKPyV screening beyond 1 year. A systematic characterization of risk factors and outcomes of late-onset (>1 year) BKPyVAN has not previously been reported.

METHODS

We retrospectively compared characteristics and outcomes of early- (<1 year) and late-onset BKPyVAN (definitive [biopsy-confirmed] or presumptive [plasma BKPyV >10 000 copies/mL]) in a cohort of 671 KTR and simultaneous kidney-pancreas transplant (SPK) recipients between 2008 and 2013 at a single US transplant center. Proportions were compared using Chi-square or Fisher's exact test with P < .05 considered significant.

RESULTS

BKPyVAN was diagnosed in 96 (14.3%) patients (proven 16.7%, presumptive 83.3%): 79 (82.3%) early- and 17 (17.7%) late-onset. The proportion with late-onset BKPyVAN was significantly higher among SPK than KTR (4 of 7 [57.1%] vs 13 of 89 [14.6%], P = .017). Late-onset represented "de novo" infection (no BKPyV detection within the first year) in 14 (82.4%) and progression of earlier lower grade BKPyV reactivation in 3 (17.6%). Clinical outcomes were similar for early- and late-onset BKPyVAN (P > .05 all comparisons). In a pooled analysis of prior studies of BKPyVAN in SPK recipients, 62.9% (17 of 27) were late-onset.

CONCLUSION

A significant proportion of BKPyVAN is late-onset, especially among SPK recipients, and supports a longer duration of BKPyV monitoring for SPK recipients than recommended in some guidelines.

BK polyomavirus infection after renal transplantation: Surveillance in a resource-challenged setting

BACKGROUND

There is a paucity of data available about BK polyomavirus (BKPyV) infection after renal transplantation (RTX) in resource-limited countries with a predominantly living-donor, ABO-compatible RTX program. We aimed to assess BKPyV infection in such patients in a public hospital in India.

METHODS

We prospectively evaluated plasma BKPyV replication in 62 patients at 1, 3, 6, 9, and 12 months after RTX. Sustained significant BK viremia (SSBKV) was defined as significant viremia (≥10 000 copies/mL) detected ≥2 times, and BKPyV-associated nephropathy (BKVAN) as histologic changes of BKVAN with BK viremia with/without graft dysfunction.

RESULTS

All patients underwent RTX without requiring desensitization. Incidence of BK viremia was: 17.7%, 41.9%, 16.1%, 25.8%, and 17.7% at 1, 3, 6, 9, and 12 months, respectively. Of 62 patients, 64.5% had BKPyV viremia during the study, 32.2% had significant viremia, all except one detected in the first 6 months. Nine (14.5%) patients had SSBKV. There was no biopsy-proven BKVAN. At the end of 1 year, mean serum creatinine was higher and graft dysfunction was significantly more common in patients with SSBKV compared to those without SSBKV.

CONCLUSION

Transient BK viremia is common in low/intermediate immunologic risk RTX recipients in India, with a peak occurring at 3-6 months. Most clear their viremia by 12 months. Graft dysfunction seems to be more frequent in patients with SSBKV, although BKVAN is uncommon on biopsy in these patients.

Histological Evolution of BK Virus-Associated Nephropathy: Importance of Integrating Clinical and Pathological Findings

Long-term clinicopathological studies of BK-associated nephropathy (PyVAN) are not available. We studied 206 biopsies (71 patients), followed 3.09 ± 1.46 years after immunosuppression reduction. The biopsy features (% immunostain for PyV large T ag + staining and inflammation ± acute rejection) were correlated with viral load dynamics and serum creatinine to define the clinicopathological status (PyVCPS). Incidence of acute rejection was 28% in the second biopsy and 50% subsequently (25% mixed T cell-mediated allograft rejection (TCMR) + antibody-mediated allograft rejection (AMR); rejection overall affected 38% of patients (>50% AMR). Graft loss was 15.4% (0.8-5.3 years after PyVAN); 76% had complete viral clearance (mean 28 weeks). The only predictors of graft loss were acute rejection (TCMR p = 0.008, any type p = 0.07), and increased "t" and "ci" in the second biopsy (p = 0.006 and 0.048). Higher peak viremia correlated with poorer viral clearance (p = 0.002). Presumptive and proven PyVAN had similar presentation, evolution, and outcome. Late PyVAN (>2 years, 9.8%) justifies BK viremia evaluation at any point with graft dysfunction and/or biopsy evaluation. This study describes the histological evolution of PyVAN and corresponding clinicopathological correlations. Although the pathological features overall reflect the viral and immunological interactions, the PyVAN course remains difficult to predict based on any single feature. Appropriate clinical management requires repeat biopsies and determination of the PyVCPS at relevant time points, for corresponding personalized immunosuppression adjustment.

Pilot Study of Early Monitoring Using Urinary Screening for BK Polyomavirus as a Strategy for Prevention of BKV Nephropathy in Kidney Transplantation

BACKGROUND

Urine monitoring programs represent an important strategy for early diagnosis of reactivation of BK polyomavirus (BKV) in kidney transplant recipients. This study analyzes a BKV urine screening model in kidney transplant patients.

METHODS

Urinary screening for BKV reactivation was performed by urinary decoy cell and polymerase chain reaction (PCR) tests in samples from 32 consecutive kidney transplant patients, collected in a 6-month follow-up period. PCR in plasma samples and BKV immunohistochemical studies to assess BKV renal disease, if a kidney biopsy was indicated, were performed.

RESULTS

The urinary screening for BKV among 32 renal receptors was positive in 18 patients (56%) by the concomitant use of the decoy cells and/or qualitative PCR at some time during the study period. Transfusion before transplantation was significantly associated with urinary decoy cell positive screening (odds ratio = 11; 95% confidence interval = 1.47 to 82.4; P < .05); and so was male sex (odds ratio = 2.02; 95% confidence interval = 1.07 to 3.83; P < .05). The clinical management of screening positive cases consisted of decreasing or changing the immunosuppression regimen. Sixteen renal biopsies were performed. Immunohistochemistry for SV40 T antigen was negative in all biopsies. After 1 year of follow-up, no patient developed BKV-associated nephropathy, and there was no difference in renal function between patients positive and negative for BKV urinary screening.

CONCLUSIONS

Early urinary monitoring is effective in detection of BKV replication and represents a good strategy to minimize the deleterious effects caused by the presence of the virus on preservation of graft function.

Incidence of BK polyomavirus infection after kidney transplantation is independent of type of immunosuppressive therapy

BACKGROUND

BK polyomavirus (BKV) infection and BKV nephropathy (BKVN) are risk factors for allograft function and survival.

METHODS

We retrospectively analyzed BK viremia and BKVN in 348 patients who received a kidney transplantation donated after brain death (n=232) or living donation (n=116) between 2008 and 2013. A total of 266 patients were treated with standard immunosuppression consisting of basiliximab induction, calcineurin inhibitor (CNI), and mycophenolic acid (MPA, n=219) or everolimus (n=47); 82 patients received more intense immunosuppression with lymphocyte depletion, CNI and MPA (n=38) or everolimus (n=44).

RESULTS

BK viremia occurred in 33 (9.5%) patients in the first year and in 7 (2.0%) recipients in the second year after transplantation. BKVN occurred in 4 (1.1%) patients in the first year. Donor and recipient age, diabetes, previous transplantation, and type of transplantation (donated after brain death vs living donation) were not risk factors (P>.05). BK incidence did not differ depending on induction or maintenance immunosuppression.

CONCLUSION

Incidence of BK viremia is independent of recipient characteristics, type of transplantation as well as induction and maintenance immunosuppression.

Influence of tacrolimus metabolism rate on BKV infection after kidney transplantation

Immunosuppression is the major risk factor for BK virus nephropathy (BKVN) after renal transplantation (RTx). As the individual tacrolimus (Tac) metabolism rate correlates with Tac side effects, we hypothesized that Tac metabolism might also influence the BKV infection risk. In this case-control study RTx patients with BK viremia within 4 years after RTx (BKV group) were compared with a BKV negative control group. The Tac metabolism rate expressed as the blood concentration normalized by the daily dose (C/D ratio) was applied to assess the Tac metabolism rate. BK viremia was detected in 86 patients after a median time of 6 (0–36) months after RTx. BKV positive patients showed lower Tac C/D ratios at 1, 3 and 6 months after RTx and were classified as fast Tac metabolizers. 8 of 86 patients with BK viremia had histologically proven BKN and a higher median maximum viral load than BKV patients without BKN (441,000 vs. 18,572 copies/mL). We conclude from our data that fast Tac metabolism (C/D ratio <1.05) is associated with BK viremia after RTx. Calculation of the Tac C/D ratio early after RTx, may assist transplant clinicians to identify patients at risk and to choose the optimal immunosuppressive regimen.

Simultaneous pancreas/kidney transplant recipients present with late-onset BK polyomavirus-associated nephropathy

BACKGROUND

Infections have increased in simultaneous pancreas/kidney transplant recipients (SPKTRs) with BK polyomavirus (BKV)-associated nephropathy (BKVN) being the most important infectious cause of allograft loss. Comparisons of BKVN with kidney transplant recipients (KTRs), however, are lacking.

METHODS

We studied all SPKTRs and KTRs at our transplant centre between 2003 and 2012. Eleven of 106 SPKTs (10.4%) and 21 of 1062 KTRs (2.0%) were diagnosed with BKVN with allograft loss in 1 SPKTR (9.1%) and 2 KTRs (9.5%). A control of 95 SPKTRs without BKVN was used for comparison.

RESULTS

SPKTRs showed an increased incidence of BKVN compared with KTRs (P < 0.001). Onset of BKVN in SPKTRs was significantly later compared with KTRs (P = 0.033). While 67% of KTRs showed early-onset BKVN, 64% of SPKTRs developed late-onset BKVN. Older recipient age and male gender increased the risk of BKVN in SPKTRs (P < 0.05). No differences were observed for patient and allograft survival (P > 0.05). However, SPKTRs with BKVN showed inferior estimated glomerular filtration rate and a higher incidence of de novo donor-specific antibodies compared with SPKTRs without BKVN in long-term follow-up (P < 0.05). SPKTRs showed higher peak BKV loads, a need for more intense therapeutic intervention and were more likely not to recover to baseline creatinine after BKVN (P < 0.05).

CONCLUSIONS

Our results suggest a higher incidence, more severe course and inferior outcome of BKVN in SPKTRs. An increased vulnerability of the allograft kidney due to inferior organ quality may predispose KTRs to early-onset BKVN. In contrast, SPKTRs present with late-onset BKVN in the presence of high-dose immunosuppression.