BK virus nephritis after renal transplantation

A comparative analysis of clinical outcomes between conversion to mTOR inhibitor and calcineurin inhibitor reduction in managing BK viremia among kidney transplant patients

BK virus-associated nephropathy (BKVAN) exerts a substantial impact on allograft survival, however, the absence of robust clinical evidence regarding treatment protocols adds to the complexity of managing this condition. This study aimed to compare the two treatment approaches. The study population consisted of patients who underwent kidney transplantation between January 2016 and June 2020 at two tertiary hospitals in Korea. Patients diagnosed with BK viremia were evaluated based on their initial viral load and the treatment methods. The 'Reduction group' involved dose reduction of tacrolimus while the 'Conversion group' included tacrolimus discontinuation and conversion to sirolimus. A total of 175 patients with an initial viral load (iVL) ≥ 3 on the log10 scale were evaluated within two iVL intervals (3-4 and 4-5). In the iVL 4-5 interval, the Reduction group showed potential effectiveness in terms of viral clearance without statistically significant differences. However, within the iVL 3-4 interval, the Reduction group demonstrated superior viral clearance and a lower incidence of biopsy-proven acute rejection (BPAR) than the Conversion group. The renal function over 12 months after BKV diagnosis showed no statistically significant difference. Reducing tacrolimus compared to converting to mTORi would be a more appropriate treatment approach for BK viral clearance in kidney transplantation. Further research is warranted in a large cohort of patients.

Optimizing the approach to monitoring allograft inflammation using serial urinary CXCL10/creatinine testing in pediatric kidney transplant recipients

BACKGROUND

Urinary CXCL10/creatinine (uCXCL10/Cr) is proposed as an effective biomarker of subclinical rejection in pediatric kidney transplant recipients. This study objective was to model implementation in the clinical setting.

METHODS

Banked urine samples at a single center were tested for uCXCL10/Cr to validate published thresholds for rejection diagnosis (>80% specificity). The positive predictive value (PPV) for rejection diagnosis for uCXCL10/Cr-indicated biopsy was modeled with first-positive versus two-test-positive approaches, with accounting for changes associated with urinary tract infection (UTI), BK and CMV viremia, and subsequent recovery.

RESULTS

Seventy patients aged 10.5 ± 5.6 years at transplant (60% male) had n = 726 urine samples with n = 236 associated biopsies (no rejection = 167, borderline = 51, and Banff 1A = 18). A threshold of 12 ng/mmol was validated for Banff 1A versus no-rejection diagnosis (AUC = 0.74, 95% CI = 0.57-0.92). The first-positive test approach (n = 69) did not resolve a clinical diagnosis in 38 cases (55%), whereas the two-test approach resolved a clinical diagnosis in the majority as BK (n = 17/60, 28%), CMV (n = 4/60, 7%), UTI (n = 8/60, 13%), clinical rejection (n = 5/60, 8%), and transient elevation (n = 18, 30%). In those without a resolved clinical diagnosis, PPV from biopsy for subclinical rejection is 24% and 71% (p = .017), for first-test versus two-test models, respectively. After rejection treatment, uCXCL10/Cr level changes were all concordant with change in it-score. Sustained uCXCL10/Cr after CMV and BK viremia resolution was associated with later acute rejection.

CONCLUSIONS

Urinary CXCL10/Cr reliably identifies kidney allograft inflammation. These data support a two-test approach to reliably exclude other clinically identifiable sources of inflammation, for kidney biopsy indication to rule out subclinical rejection.

Case report: JC polyomavirus nephropathy in simultaneous heart-kidney transplantation: the role of viral-specific in situ hybridization staining

Introduction

JC polyomavirus (JCPyV) is a ubiquitous virus that can be latent in the brain and the kidney. It is the etiologic agent responsible for progressive multifocal leukoencephalopathy, a fatal, demyelinating disease of the central nervous system, and rarely causes polyomavirus nephropathy in immunocompromised kidney transplant recipients.

Case description

We present the first case of JCPyV nephropathy in a simultaneous heart-kidney transplant patient, where viral-specific in situ hybridization staining of the kidney tissue was utilized to confirm the diagnosis. The patient was diagnosed 6 years after simultaneous heart-kidney transplantation and was treated with immunosuppression reduction and intravenous immunoglobulin.

Discussion

JCPyV nephropathy should be considered in the differential diagnosis of kidney allograft injury, particularly, with suggestive light microscopy histologic features in the absence of BK polyomavirus viremia and/or viruria. In addition to obtaining JCPyV PCR in the blood, in situ hybridization staining may have a utility in confirming the diagnosis. To date, we lack effective JCPyV-specific therapies, and prompt initiation of immunosuppression reduction remains the mainstay of treatment.

Delayed Graft Function Among Kidney Transplant Recipients Is Associated With an Increased Risk of Urinary Tract Infection and BK Viremia

Background

Delayed graft function (DGF) among deceased donor kidney transplant recipients (DDKTRs) is a well-known risk factor for allograft rejection, decreased graft survival, and increased cost. Although DGF is associated with an increased risk of rejection, it is unclear whether it also increases the risk of infection.

Methods

We reviewed all adult DDKTRs at our center between 2010 and 2018. The primary outcomes of interest were BK viremia, cytomegalovirus viremia, pneumonia, and urinary tract infection (UTI) within the first year of transplant. Additional analysis was made with censoring follow-up at the time of allograft rejection.

Results

A total of 1512 DDKTRs were included, of whom 468 (31%) had DGF. As expected, several recipient, donor, and baseline immunological characteristics differed by DGF status. After adjustment, DGF was significantly associated with an increased risk of BK viremia (hazard ratio: 1.34; 95% confidence interval, 1.0-1.81; P = 0.049) and UTI (hazard ratio: 1.70; 95% confidence interval, 1.31-2.19; P < 0.001) but not cytomegalovirus viremia or pneumonia. Associations were similar in models censored at the time of rejection.

Conclusions

DGF is associated with an increased risk of early infectious complications, mainly UTI and BK viremia. Close monitoring and appropriate management are warranted for better outcomes in this unique population.

The Tacrolimus Concentration/Dose Ratio Does Not Predict Early Complications After Kidney Transplantation

Early-on post kidney transplantation, there is a high risk of graft rejection and opportunistic viral infections. A low tacrolimus concentration/dose (C/D) ratio as a surrogate marker of fast tacrolimus metabolism has been established for risk stratification 3 months post-transplantation (M3). However, many adverse events occurring earlier might be missed, and stratification at 1 month post-transplantation (M1) has not been investigated. We retrospectively analyzed case data from 589 patients who had undergone kidney transplantation between 2011 and 2021 at three German transplant centers. Tacrolimus metabolism was estimated by use of the C/D ratio at M1, M3, M6, and M12. C/D ratios increased substantially during the year, particularly between M1 and M3. Many viral infections and most graft rejections occurred before M3. Neither at M1 nor at M3 was a low C/D ratio associated with susceptibility to BKV viremia or BKV nephritis. A low C/D ratio at M1 could not predict acute graft rejections or impaired kidney function, whereas at M3 it was significantly associated with subsequent rejections and impairment of kidney function. In summary, most rejections occur before M3, but a low C/D ratio at M1 does not identify patients at risk, limiting the predictive utility of this stratification approach.

Pancreatic insufficiency as a complication of type 1 diabetes causing enteric hyperoxaluria in a transplant kidney

A kidney transplant recipient with a medical history of type 1 diabetes mellitus (T1DM) presents to the clinic with an acute kidney injury (AKI) and diarrhoea. Kidney biopsy found deposition of focal oxalate crystals, and further investigation revealed a raised 24-hour urinary oxalate and reduced faecal elastase. Therefore, we present a case of acute oxalate nephropathy (AON) secondary to enteric hyperoxaluria as a result of pancreatic insufficiency caused by T1DM. T1DM is a common cause of end-stage renal failure and exocrine pancreatic insufficiency. Therefore, AON secondary to enteric hyperoxaluria should be considered in patients with a transplant AKI. Earlier testing of 24-hour urinary oxalate and faecal elastase could generate diagnosis before biopsy results and allow commencement of pancreatic replacement therapy earlier to avoid permanent loss of kidney function.

How to Deal With Kidney Retransplantation-Second, Third, Fourth, and Beyond

Kidney transplantation is the best health option for patients with end-stage kidney disease. Ideally, a kidney transplant would last for the lifetime of each recipient. However, depending on the age of the recipient and details of the kidney transplant, there may be a need for a second, third, fourth, or even more kidney transplants. In this overview, the outcome of multiple kidney transplants for an individual is presented. Key issues include surgical approach and immunologic concerns. Included in the surgical approach is an analysis of transplant nephrectomy, with indications, timing, and immunologic impact. Allograft thrombosis, whether related to donor or recipient factors merits investigation to prevent it from happening again. Other posttransplant events such as rejection, viral illness (polyomavirus hominis type I), recurrent disease (focal segmental glomerulosclerosis), and posttransplant lymphoproliferative disease may lead to the need for retransplantation. The pediatric recipient is especially likely to need a subsequent kidney transplant. Finally, noncompliance/nonadherence can affect both adults and children. Innovative approaches may reduce the need for retransplantation in the future.

A systematic review and meta-analysis of enzyme-linked immunosorbent spot (ELISPOT) assay for BK polyomavirus immune response monitoring after kidney transplantation

BK virus (BKV) infection after kidney transplantation can cause BKV nephropathy (BKVAN) resulting in graft dysfunction and allograft loss. The treatment for BKVAN is reduction of the immunosuppressive load which increases the risk of kidney transplant rejection. There is no biomarker to monitor BKV activity besides BK viral load. The value of the Enzyme-Linked Immunosorbent Spot (ELISPOT) assay as a tool to monitor the recipient's anti-BKV immune response after transplantation was investigated systematically. Electronic databases, including MEDLINE, Scopus, and the Cochrane Central Register of Controlled Trials were searched for studies of ELISPOT evaluating the immune response against BKV. BKV status was categorized as "active BKV infection" and as "resolving BKV infection". Random-effects model meta-analysis was performed to determine the diagnostic performance of the ELISPOT assay, after stratifying patients into groups based on positive and negative ELISPOT results. One-hundred twenty-seven articles were identified of which nine were included. Patients with negative ELISPOT had an increased risk of having active BKV replication (odds ratio of 71.9 (95%-CI 31.0-167.1). Pooled sensitivity was 0.95 (95%-CI 0.89-0.98) and specificity was 0.88 (95%-CI 0.78-0.94). The standardized mean difference of the number of IFN-γ producing cells between patients with active BKV infection compared with patients who had resolving BKV infection was -2.09 (95%-CI -2.50, -1.68). The ELISPOT assay is a useful tool for BKV risk assessment and in combination with BKV load may support clinicians in guiding immunosuppressive therapy in patients with BKV replication.

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

BACKGROUNDS

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

METHODS

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

RESULTS

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

CONCLUSION

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

Prospective Study of Long Noncoding RNA, MGAT3-AS1, and Viremia of BK Polyomavirus and Cytomegalovirus in Living Donor Renal Transplant Recipients

Introduction

Viremia after renal transplantation is a major cause of morbidity and mortality and treatment opportunities are limited. Tests to determine the increased risk for viremia would be preferable.

Methods

In a prospective, single-center study, we conducted follow-up of 163 renal transplant recipients after incident living donor renal transplantation. We determined a long noncoding RNA, β-1,4-mannosylglycoprotein 4-β-N-acetylglucosaminyltransferase-antisense1 (MGAT3-AS1/beta-actin ratio), in peripheral blood mononuclear cells. Viremia of BK polyomavirus and cytomegalovirus was diagnosed with more than 1000 plasma copies/ml within the first 3 postoperative months. The MGAT3-AS1/beta-actin ratio was assessed before viremia was determined.

Results

Receiver operator characteristics curve analysis showed a median MGAT3-AS1/beta-actin ratio cutoff value of 4.45 × 10^–6 to indicate viremia after transplantation. Samples for 11 of 66 renal transplant recipients (17%) with MGAT3-AS1/beta-actin ratios below 4.45 × 10^–6 showed viremia of BK polyomavirus and cytomegalovirus compared with only 6 of 97 renal transplant recipients (6%) with higher MGAT3-AS1/beta-actin ratios (odds ratio [OR]: 3.03; 95% confidence interval [CI]: 1.06–8.67 by Fisher exact test). Furthermore, samples for 6 of 66 renal transplant recipients (9%) with MGAT3-AS1/beta-actin ratios below 4.45 × 10^–6 showed BK polyomavirus viremia compared with none of 97 renal transplant recipients (0%) with higher MGAT3-AS1/beta-actin ratios (OR: 20.95; 95% CI, 1.16–378.85 by Fisher exact test). Multivariate logistic regression analysis confirmed that MGAT3-AS1/beta-actin ratios below the cutoff level remained significantly associated with viremia after transplant. Lower MGAT3-AS1/beta-actin ratios occurred with rituximab-containing induction therapy.

Conclusions

A low MGAT3-AS1/beta-actin ratio indicates an increased risk for viremia of BK polyomavirus and cytomegalovirus in living donor renal transplant recipients.

Low-dose cidofovir and conversion to mTOR-based immunosuppression in polyomavirus-associated nephropathy

BACKGROUND

Polyomavirus-associated nephropathy (PVAN) remains a relevant complication following kidney transplantation with allograft loss rates of up to 50%. Reduction in overall immunosuppression is a cornerstone of therapy, whereas no specific antiviral regimen has shown conclusive benefit to date. The present case series demonstrates the efficacy of a dual therapeutic approach with low-dose cidofovir and conversion to mTOR-based immunosuppression in PVAN.

METHODS

Patients with biopsy-proven PVAN having received low-dose cidofovir (0.25 mg/kg) according to the Tübingen Cidofovir Protocol and been converted to mTOR-based immunosuppression were analyzed retrospectively.

RESULTS

Twenty-three patients with a median follow-up of 2.24 [IQR 1.55-5.01] years were included in the analysis. Median time to PVAN diagnosis was 268 [IQR 153-869] days after transplantation. Polyomavirus clearance from plasma was achieved in 78% of patients after a median of 118 [IQR 76-293] days. Of the 23 patients, nine patients (39%) lost their allograft function during follow-up, but only three of these (13%) due to PVAN. Fourteen patients (61%) stabilized or improved allograft function. The cidofovir protocol allowed for specific antiviral therapy without adverse nephrotoxicity, even in patients with low allograft function.

CONCLUSIONS

Low-dose cidofovir and conversion to mTOR-based immunosuppression allow for effective virus clearance and preservation of allograft function in a high proportion of patients with PVAN and progressive allograft dysfunction and may prolong allograft survival in these patients.

Excellent outcome after desensitization in high immunologic risk kidney transplantation

Introduction

HLA-incompatible (HLAi) and ABO-incompatible (ABOi) kidney transplantation (KT) has been on the increase over the last decade. However, there are wide variations in outcomes from these procedures. In this study we evaluated the graft and patient outcomes in incompatible KT and non-sensitized KT.

Methods

Patients who underwent KT between January 2012 and April 2018 were enrolled and reviewed. We divided kidney transplant recipients (KTRs) into five groups as follows: HLAi (n = 50); ABOi (n = 65); HLAi+ABOi (n = 5); control (n = 428); and living-donor control (LD control, n = 218). We compared the risk of rejection, graft function, graft survival, and patient survival between incompatible KTRs and control/LD control KTRs.

Results

Although the incidence of active antibody-mediated rejection in HLAi group tends to be higher than in control and LD control groups (6.0% vs. 2.8%, P = 0.20; 6.0% vs. 3.7%, P = 0.44, respectively), the rejection-free survival, graft survival, and patient survival were not significantly different from those of the control and LD control groups in all three incompatible KT groups (all P>0.05). Graft function during the study period was also not different between incompatible KTRs and control/LD control groups (both P>0.05). Using Cox regression analysis, neither HLAi nor ABOi were risk factors for graft failure. Some infectious diseases such as urinary tract infection and cytomegalovirus infection were more common in the HLAi group than in the control/LD control group (both P<0.05), but only one infection-related death occurred in HLAi KTRs. Infection risks were similar in the ABOi and HLAi+ABOi groups compared to controls.

Conclusion

Our results showed favorable outcomes for incompatible KT after desensitization. Although desensitization therapy for incompatible KT has improved access to transplantation for KT candidates with high immunological risk, more clinical data are clearly needed.

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.

BK virus characterisation among HIV-1-Infected individuals and its association with immunosuppression

Purpose

BK virus (BKV) is an opportunistic pathogen which causes significant morbidity and mortality in individuals who are immunodeficient. We aimed to quantitate and characterise BKV and to correlate with the degree of immunosuppression among human immunodeficiency virus (HIV)-1-infected individuals.

Methods

BKV DNA detection was carried out using an in-house quantitative real-time polymerase chain reaction on paired whole-blood and urine samples collected from 187 antiretroviral therapy (ART)-naïve HIV-1-infected individuals and 93 healthy individuals who served as controls. Sequencing was performed for a proportion of high BK viral load (VL) samples to observe non-coding control region (NCCR) rearrangements.

Results

BKV positivity in urine was 25.6% among HIV-infected individuals and 10.7% in control individuals (P = 0.03). The BK VL showed a significant negative correlation with CD4+ T-cell counts, a positive correlation with WHO clinical staging and no significant correlation with HIV-1 VL. Of 42 BKVs from urine samples sequenced, two showed rearrangements without clinically severe disease or high VL. Their NCCR and VP1 sequence-based genotyping revealed genotype I. In a small subset of individuals (n = 8) on ART who were being followed up, six individuals showed either decrease or complete clearance of virus with ART.

Conclusion

There was a higher frequency of BK viruria in HIV-1-infected individuals than among healthy controls and the positivity correlated with the degree of immunosuppression. There was no association of high VL with NCCR rearrangements in urine.

Validated Models of Immune Response to Virus Infection

Viruses are a main cause of disease worldwide and many are without effective therapeutics or vaccines. A lack of understanding about how host responses work to control viral spread is one factor limiting effective management. How different immune components regulate infection dynamics is beginning to be better understood with the help of mathematical models. These models have been key in discriminating between hypotheses and in identifying rates of virus growth and clearance, dynamical control by different host factors and antivirals, and synergistic interactions during multi-pathogen infections. A recent focus in evaluating model predictions in the laboratory and clinic has illuminate the accuracy of models for a variety of viruses and highlighted the critical nature of theoretical approaches in virology. Here, I discuss recent model-driven exploration of host-pathogen interactions that have illustrated the importance of model validation in establishing the model's predictive capability and in defining new biology.

Nucleic Acid Tests for BK Polyomavirus Is Critical in Renal Transplant Recipients

This study evaluates the incidence of BK polyomavirus (BKV) and prognosis of BKV infection in kidney transplant recipients (KTRs) who received transplantation in our hospital before and after regular BKV nucleic acid test (NAT) was implemented.

METHODS

The study included 74 KTRs who received a single kidney either from standard- or expanded-criteria deceased donor between March 2011 and March 2017. BKV NATs were regularly checked in 26 patients (group 1) in the first posttransplant year in accordance with current guidelines since NAT was implemented in our laboratory in 2014. We retrospectively compared 48 KTRs (group 2) who either received NAT when necessary in another laboratory or were not checked before 2014.

RESULTS

There was no significant difference in patient characteristics between groups. BKV viruria were confirmed in 8 of 26 (30.8%) group 1 patients, whereas only 2 of 48 (4.2%) BKV infections were confirmed in group 2. None of the BKV(+) KTRs in group 1 developed BK polyomavirus-associated nephropathy (BKVAN), whereas 2 BKV(+) patients (100%) of group 2 developed BKVAN, which indicates renal function deterioration and biopsy-validated nephropathy. There was no significant difference in graft survival and renal function between the 2 groups.

CONCLUSIONS

The risk of BKV infection is considerably higher in KTRs using NAT. Because there is no approval treatment, early diagnosis of BKV infection and early reduction of immunosuppression agents is critical for KTRs. Implementation of regular BKV NAT is mandatory before BKVAN and malignant neoplasms develop.

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.

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

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

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

Background

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

Methods

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

Results

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

Conclusion

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

BK Virus-Associated Nephropathy: Current Situation in a Resource-Limited Country

BACKGROUND

Data on BK virus-associated nephropathy (BKVAN) and treatment strategy in a resource-limited country are scarce. This study aimed to evaluate epidemiology of BKVAN and its situation in Thailand.

METHODS

A retrospective analysis was conducted among adult kidney transplant recipients at Ramathibodi Hospital from October 2011 to September 2016. Patients' demographic data, information on kidney transplantation, immunosuppressive therapy, cytomegalovirus and BK virus infections, and allograft outcomes were retrieved and analyzed.

RESULTS

This study included 623 kidney transplant recipients. Only 327 patients (52.49%) received BK virus infection screening, and 176 of 327 patients had allograft dysfunction as a trigger for screening. BKVAN was identified in 39 of 327 patients (11.93%). Deceased donor transplantation and cytomegalovirus infection were associated with a higher risk of BKVAN (odds ratio = 2.2, P = .024, 95% confidence intervals [1.1, 4.43], and odds ratio = 2.6, P = .006, 95% confidence intervals [1.29, 5.26], respectively). BKVAN patients were at significantly higher risk for allograft rejection (P < .001) and allograft failure (P = .036). At the end of the study, 4 graft losses were documented (12.12%).

CONCLUSIONS

BKVAN was associated with high rate of allograft rejection and failure. However, surveillance of its complications has been underperformed at our facility. Implementing a formal practice guideline may improve allograft outcome in resource-limited countries.

BK viremia is not associated with adverse outcomes in the absence of BK nephropathy

There are limited data regarding the association of different levels of BK viremia and BK nephropathy (BKN), and graft outcomes. We studied the BK plasma PCR levels of all kidney transplant recipients (KTR) transplanted at our institution between 01/01/2006 and 06/30/2014. Patients were divided into groups based on their highest BK plasma PCR level within the first year following transplantation: undetectable, low (<1000 copies/mL), moderate (1000-10 000 copies/mL), high (>10 000-100 000 copies/mL), very high (>100 000 copies/mL), and those that had biopsy-proven BKN. There were a total of 1146 KTR during the study period: 813 with undetectable BK levels and 333 with any detectable BK level (87 with low, 79 with moderate, 88 with high, 34 with very high level BK, and 45 that had BKN). Compared to KTR with an undetectable BK level, incidence of mortality, graft failure, rejections,and infections were not significantly different for those with low, moderate, high, or very high BK level. Patients with BKN had a higher rate of infection and higher rates of total graft failure or death-censored graft failure compared to those with undetectable BK levels. BK viremia in the absence of BKN does not significantly increase the risk of rejection, infections, or graft failure compared to an undetectable BK level.

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.

Which is more nephrotoxic for kidney transplants: BK nephropathy or rejection?

Little data exist comparing outcomes following BK nephropathy (BKN) vs acute rejection. We reviewed outcomes among recipients who had a primary diagnosis of biopsy-proven BKN or rejection between 1 and 18 months post-transplant. There were 96 cases of BKN and 256 cases of rejections. We compared outcomes of BKN with all rejection combined and also with cellular rejection. Seven of 256 (2.7%) patients developed BKN after treatment of rejection. Conversely, 8 of 96 (8.3%) developed rejection after BKN. The eGFR at time of diagnosis in the BKN group (33.7 ± 12.6) was lower than the rejection group (44.8 ± 23.3, P < .001). The eGFR at 6 months after diagnosis of BKN was 32.7 ± 14.9 and for rejection was 48.8 ± 20.7 (P ≤ .001). The mean eGFR at 3 years postdiagnosis was 41.6 ± 18.5 in BKN and 53 ± 21.3 for rejection (P = .001). The graft failure incidence rates were similar between 2 groups. A similar pattern was observed comparing BKN with cellular rejection. While the difference in rate of graft loss between BKN and rejection did not reach statistical significance, kidney function up to 3 years after diagnosis was worse for BKN than for rejection, suggesting that BKN is at least as damaging to kidneys as rejection.

Fluoroquinolones and BK Virus Nephropathy: A Myth or a Reality

BK polyomavirus (BKV) is a challenging problem for the transplant nephrologist. Various strategies have been used to prevent or treat BK virus nephropathy (BKVN). These include reduction in immunosuppression, intravenous immune globulin, cidofovir, leflunomide, and the fluoroquinolone antibiotics. All these agents have their own toxicities. Great interest was shown to use fluoroquinolones to prevent BKVN after its useful experience was reported in bone marrow transplant. Fluoroquinolones being cheap and easily available, attracted nephrologists to use it, for prevention of BKVN. These agents have been shown in vitro studies to be effective. However, there are mixed results about their effectiveness in prevention of BKVN in clinical setting. This review will focus the evidence available for using fluoroquinolones in prevention of BKVN and its usefulness. Furthermore, a way forward to use these agents or not for prevention of BKVN will also be discussed.

Graft loss among renal-transplant recipients with early reduction of immunosuppression for BK viremia

AIM

To review the incidence of graft loss and acute rejection among renal transplant recipients with early reduction of immunosuppression for BK viremia.

METHODS

We performed a retrospective analysis of consecutive de-novo kidney-only transplants from January 2009 to December 2012 to evaluate the incidence of Polyoma-virus associated nephropathy (PyVAN). Recipient plasma was screened for BKV DNA via quantitative polymerase chain reaction (PCR) at months 1, 3, 6, 9 and 12 post-transplant and on worsening graft function. Immunosuppression was reduced at ≥ 3-log copies/mL. Those with viremia of ≥ 4-log copies/mL (presumptive PyVAN) underwent renal transplant biopsy. Presumptive PyVAN (PP) and definitive PyVAN (DP; biopsy-proven) were treated by immunosuppression reduction (IR) only.

RESULTS

Among 319 kidney transplant recipients, the median age was 53 years (range 19-83), 65.8% were male, and 58.9% were white. Biopsy-proven acute rejection was found in 18.5% within 0-168 wk. Death-censored graft loss occurred in 5.3% (n = 17) and graft loss attributable to PyVAN was 0.6% (n = 2). Forty-seven patients were diagnosed with PP (14.7%) and 18 (5.6%) with DP. Graft loss among participants with PyVAN (8.5%) and those without (4.8%) was not significantly different. Deceased donor kidney transplantation (OR = 2.3, 95%CI = 1.1-4.6) and AR (OR = 2.3, 95%CI = 1.2-4.7) were associated with PyVAN in the multivariate analysis. BK viremia between 3 and 4-log copies/mL occurred in 27 patients, all of whom underwent IR. Of these, 16 (59%) never developed PyVAN while 11 (41%) developed PyVAN (4 DP, 7 PP) within a range of 11-39 wk.

CONCLUSION

Instituting an early reduction of immunosuppression, in the absence of adjunctive antivirals, is effective at preventing PyVAN and may be associated with a lower incidence of graft-loss without a reciprocal increase in the incidence of acute rejection.

T cell therapies for human polyomavirus diseases

Rapid restoration of virus-specific T immunity via adoptive transfer of ex vivo generated T cells has been proven as a powerful therapy for patients with advanced cancers and refractory viral infections such as cytomegalovirus (CMV) and Epstein-Barr virus (EBV). BK virus (BKV), John Cunningham virus (JCV), and Merkel cell carcinoma virus (MCV) are the members of the rapidly growing human polyomavirus (hPyV) family that commonly infects most healthy humans. These viruses have a clearly established potential for causing severe end-organ damage or malignant transformation, especially in individuals with weakened immunity who are unable to mount or regain endogenous T-cell responses as a result of underlying leukemia or iatrogenic immunosuppression in autoimmunity, bone marrow and solid organ transplant settings. Here we will discuss recent advances in using T-cell-based immunotherapies to save patients suffering from PyV-associated diseases including hemorrhagic cystitis, BKV virus-associated nephropathy, and JC-associated progressive multifocal leukoencephalopathy (PML). We will also review progress in the understanding of Merkel cell carcinoma (MCC) as a virally driven tumor that is amenable to immune intervention and can be targeted with adoptively transferred T cells specific for viral oncoproteins.

Primary Human Renal-Derived Tubular Epithelial Cells Fail to Recognize and Suppress BK Virus Infection

BACKGROUND

BK polyomavirus (BKV)-associated nephropathy is a threat to kidney allograft survival affecting up to 15% of renal transplant patients. Previous studies revealed that tubular epithelial cells (TEC) show a limited response towards BKV infection. Here we investigated the interplay between BKV and TEC in more detail. In particular, we questioned whether BKV suppresses and/or evades antiviral responses.

METHODS

Human primary TEC and peripheral blood mononuclear cells were infected with BKV Dunlop strain or other viruses. Moreover, TEC were stimulated with genomic double-stranded (ds)DNA or IFN. Viral replication and cellular responses were measured using quantitative real time PCR and multiplex assay.

RESULTS

BKV infection of primary human TEC did not induce an antiviral response, whereas infection with influenza A virus, herpes simplex virus 1, or cytomegalovirus induced a strong antiviral response measured by upregulation of interferon-stimulated genes, such as CXCL10 and DAI. In addition, intracellular delivery of dsDNA or stimulation with IFN did elicit a rapid and pronounced response. However, BKV infection did not affect dsDNA-induced gene expression, indicating BKV did not modulate the antiviral response. Prestimulation of primary TEC with IFNα or dsDNA did not hamper replication of BKV, whereas influenza and herpes simplex virus 1 replication were clearly reduced. In contrast, BKV infection of leukocytes did elicit an antiviral response.

CONCLUSIONS

BKV specifically evades innate immunity in TEC and is not susceptible to an intrinsic interferon response, which may facilitate latent presence of the virus in this cell type.

The impact of recipient BKV shedding before transplant on BKV viruria, DNAemia, and nephropathy post-transplant: A prospective study

We previously demonstrated that detectable BKV replication in donor urine pretransplant was significantly associated with post-transplant recipient BKV viremia. In this 4-year prospective study, we assessed whether recipient BKV replication pretransplant was associated with post-transplant viremia/BKV nephropathy. We studied 220 primary adult and pediatric organ transplant recipients for 490 person-years and 2100 clinical visits. BKV viruria was detectable in 28 (16%), 26 adults and two children; and viremia in none pretransplant. Post-transplant viruria occurred in all recipients with pretransplant BKV viruria, significantly more than in recipients without pretransplant viruria on univariate (P<.005) and multivariate analysis including type of organ transplanted and immunosuppression type (P .008). Time to post-transplant viruria was significantly shorter in recipients with pretransplant viruria (P .01). By univariate and multivariate analysis, BKV viruria in recipients pretransplant did not impact post-transplant BKV viremia (P=.97 and .97, respectively) even when stratified by type of organ transplant (kidney P=.6; liver P=.5). The peak serum and urine BKV PCR post-transplant were not significantly different in patients with pretransplant BKV viruria and no one developed BK nephropathy. In conclusion, recipient BKV viruria prior to transplant predicts post-transplant viruria but not viremia or BKV nephropathy.

BK polyomavirus: a review of the virology, pathogenesis, clinical and laboratory features, and treatment

BK polyomavirus (BKPyV) is a non-enveloped, circular dsDNA virus with a genome of approximately 5100 base pairs. It can be divided into four major genotypes, but the effects of different genotypes on clinical disease are uncertain. Primary BKPyV infection is generally acquired asymptomatically in childhood. It establishes low-level persistence in many tissues, particularly the genitourinary tract. Reactivation can lead to severe disease including BKPyV-associated nephropathy confirmed by renal biopsy, hemorrhagic cystitis and meningoencephalitis. Nucleic acid amplification testing of blood and urine is the main diagnostic and prognostic test for BKPyV infection. The treatment of BKPyV infection has concentrated on reduction in immunosuppressive therapy. Recent studies suggest that antiviral drugs have demonstrated only modest benefit, but adoptive T-cell therapies offer potential advances.

Renal association clinical practice guideline in post-operative care in the kidney transplant recipient

These guidelines cover the care of patients from the period following kidney transplantation until the transplant is no longer working or the patient dies. During the early phase prevention of acute rejection and infection are the priority. After around 3-6 months, the priorities change to preservation of transplant function and avoiding the long-term complications of immunosuppressive medication (the medication used to suppress the immune system to prevent rejection). The topics discussed include organization of outpatient follow up, immunosuppressive medication, treatment of acute and chronic rejection, and prevention of complications. The potential complications discussed include heart disease, infection, cancer, bone disease and blood disorders. There is also a section on contraception and reproductive issues.Immediately after the introduction there is a statement of all the recommendations. These recommendations are written in a language that we think should be understandable by many patients, relatives, carers and other interested people. Consequently we have not reworded or restated them in this lay summary. They are graded 1 or 2 depending on the strength of the recommendation by the authors, and AD depending on the quality of the evidence that the recommendation is based on.

BK polyomavirus nephropathy in two kidney transplant patients with distinct diagnostic strategies for BK virus and similar clinical outcomes: two case reports

Background

BK polyomavirus-associated nephropathy is an important cause of post-transplantation renal failure. We present two cases of BK polyomavirus-associated nephropathy who were submitted to contrasting strategies of clinical follow-up to BK polyomavirus reactivation, but progressed to a similar final outcome.

Case presentation

Case 1 is a 37-year-old white man whose graft had never presented a good glomerular filtration rate function, with episodes of tacrolimus nephrotoxicity, and no urinary monitoring for BK polyomavirus; stage B BK polyomavirus-associated nephropathy was diagnosed by biopsy at 14 months post-transplant. Despite clinical treatment (dosage decrease and immunosuppressive drug change), he progressed to stage C BK polyomavirus-associated nephropathy and loss of graft function 30 months post-transplant. Case 2 is a 49-year-old mulatto man in his second renal transplantation who was submitted to cytological urinary monitoring for BK polyomavirus; he presented early, persistent, and massive urinary decoy cell shedding and concomitant tacrolimus nephrotoxicity. Even with decreasing immunosuppression, he developed BK polyomavirus-associated nephropathy 1-year post-transplant. Loss of graft function occurred 15 months post-transplant.

Conclusions

Cytological urinary monitoring was an efficient strategy for monitoring BK virus reactivation. Decoy cell shedding may be related to BK polyomavirus-associated nephropathy when extensive and persistent. The presence of associated tacrolimus nephrotoxicity may be a confounding factor for the clinical diagnosis of BK polyomavirus-associated nephropathy.

The Frequency and Associated Factors for BK Virus Infection in a Center Performing Mainly Living Kidney Transplantations

PURPOSE

BK virus (BKV) nephropathy has increasingly become an important cause of morbidity in renal transplant recipients. We evaluated the frequency and associated factors for BKV infection in a center performing mainly living donor transplantations over a long time period.

METHODS

One hundred consecutive renal transplant patients were included. Quarterly visits were planned to examine urine for decoy cells and to measure the BKV DNA in the blood and urine. Renal biopsy was performed in case of deteriorated allograft function. Serological examinations for BKV immunoglobulin G (IgG) were performed in donors.

RESULTS

Throughout the entire follow-up period, the rates of viruria, viremia, and the positivity of decoy cells were 12%, 6%, and 13%, respectively. The negative and positive predictive values of decoy cells were 93.1% and 69.2%, respectively, for viruria, and 99.2% and 45.5%, respectively, for viremia. Biopsy-proven BKV nephropathy was observed in 1 patient. The BKV IgG was positive in all living donors. Viruria and viremia were associated with deceased donor transplantation, acute rejection, and pulse steroid therapy. In addition, viremia was associated with antithymocyte globulin therapy and a short duration of the posttransplant period.

CONCLUSIONS

The frequency of BKV infection was lower in our transplant unit compared to previous reports. Reduced doses of immunosuppression seem to be the main factor that may explain the reduced frequency. However, an active screening strategy is still of importance for this patient group.

In kidney transplant recipients with BK polyomavirus infection, early BK nephropathy, microvascular inflammation, and serum creatinine are risk factors for graft loss

BACKGROUND

Little information is available on the risk factors for graft loss in kidney transplant recipients with BK polyomavirus (BKPyV) nephropathy (BKVN) in the presence or absence of antibody-mediated rejection (AMR).

METHODS

We examined the risk factors for graft loss in consecutive kidney allograft recipients with biopsy-confirmed BKVN, with or without concomitant AMR.

RESULTS

A total of 1904 kidney transplants were performed at our institution during 2005-2011. Of these, 330 (17.33%) were diagnosed with BKPyV viremia, and 69 were diagnosed with BKVN (3.6%). Eleven patients had a concomitant diagnosis of AMR. Patients with AMR were characterized by significantly higher peak panel-reactive antibody, retransplant rates, and desensitization preconditioning at the time of transplantation, as well as microvascular inflammation (MVI = glomerulitis + peritubular capillaritis), C4d score, and donor-specific antibody at the time of diagnosis (P ≤ 0.01). Treatment with plasma exchange, intravenous immunoglobulin, and cidofovir was more prevalent in this group (P ≤ 0.02). Univariate analyses assessing the risk factors for graft loss in all patients with BKVN, identified an independent association of African-American race, deceased-donor transplantation, serum creatinine (Scr), MVI, and early disease (BKVN within 6 months of transplant) with poor outcomes. Multivariate analyses retained only 3 variables: Scr >2 mg/dL (hazard ratio [HR] = 4.3, 95% confidence interval [CI] 1.9-9.7, P = 0.0004), early BKVN (HR = 2.7, 95% CI 1.3-5.3, P = 0.004), and MVI (HR = 1.8, 95% CI 1.2-2.8, P = 0.008).

CONCLUSIONS

These observations suggest that, in patients with BK infection, early BKVN, Scr >2, and MVI are predictors of poor outcomes. Further studies are needed to determine effective treatment strategies for BKVN, with or without AMR.

Place of mTOR inhibitors in management of BKV infection after kidney transplantation

CONTEXT

BK virus (BKV) viremia and BKV-associated nephropathy (BKVAN) have become a serious nuisance to kidney transplant (KT) patients since the mid-nineties, when the incidence of this disease has increased significantly.

EVIDENCE ACQUISITION

Directory of open access journals (DOAJ), EMBASE, Google Scholar, PubMed, EBSCO, and Web of Science have been searched.

RESULTS

Many hypothesis have been made as to why this phenomenon has developed; it is of general opinion that a more potent immunosuppression is at the core of the problem. The use of the association of tacrolimus (TAC) with mycophenolic acid (MPA) has gained momentum in the same years as the increase in BKV viremia incidence making it seem to be the most likely culprit. m-TOR inhibitors (m-TORIs) have been shown to have antiviral properties in vitro and this fact has encouraged different transplant teams to use these agents when confronted with BKV infection (viremia or nephropathy). However, the results are mitigated. There had been conflicting results for example when converting from TAC-to sirolimus-based immunosuppression in the setting of established BKVAN.

CONCLUSIONS

In order to prevent BKV infection we have to minimize to some extent immunosuppression, but it is not always possible, e.g. in high immunological risk patients. Conversely, we could use m-TORIs associated with low-dose calcineurin inhibitors (CNIs). This could be actually the key to a safe immunosuppression regimen both from the immunological stand point and from the viral one.

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

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

Mechanisms of BK virus infection of renal cells and therapeutic implications

BK virus (BKV) causes BKV nephritis in renal transplant patients and contributes significantly to the increase of probability of graft loss. BKV, being latent in the urogenital tract, is likely to be transported with the donor kidney to recipients and following reactivation replicates in the nucleus of renal epithelial tubular cells. BKV daughter viruses are released and enter other renal epithelial cells to spread infection. There are still a lot of unknown factors about the mechanism and kinetics of BKV infection. The treatment of BKV infection, with exception of reduction in immunosuppression which increases the risk of allograft rejection, is almost exclusively limited to application of anti-viral drugs with rather inconsistent results. The shortcomings of anti-viral therapies demand the understanding of early steps of infection of permissive cells by BK virus in hope that adequate interventional therapies preventing infection of cells with BK virus could be developed. This review describes the BKV entry in target human cells, intracellular trafficking pathways of BKV particles and potential therapeutic implications based on understanding of mechanisms of BKV infection of renal cells.

Impact of HMG-CoA reductase inhibitors on the incidence of polyomavirus-associated nephropathy in renal transplant recipients with human BK polyomavirus viremia

BACKGROUND

Up to 20% of renal transplant recipients (RTR) will develop human BK polyomavirus (BKPyV) viremia. BKPyV viremia is a pre-requisite of polyomavirus-associated nephropathy (PyVAN). Risk of BKPyV infections increases with immunosuppression. Currently, the only effective therapy against PyVAN is reductions in immunosuppression, but this may increase the risk of rejection. In vitro data have shown that pravastatin dramatically decreased caveolin-1 expression in human renal proximal tubular epithelial cells (HRPTEC) and suppressed BKPyV infection in these cells. Based on these data, we postulated that statin therapy may prevent the progression of BKPyV viremia to PyVAN.

PATIENTS AND METHODS

A multicenter, retrospective study was conducted in adult RTR transplanted between July 2005 and March 2012. All patients with documented BKPyV viremia (viral load >500 copies/mL on 2 consecutive tests) were included. Group I consisted of patients taking a statin before the BKPyV viremia diagnosis (n = 32), and Group II had no statin exposure before or after the BKPyV viremia diagnosis (n = 36). The primary endpoint was the incidence of PyVAN.

RESULTS

Demographic data, transplant characteristics, and the degree of immunosuppression (i.e., induction/maintenance therapies, rejection treatment) were similar between the groups, with the exception of more diabetics in Group I. The incidence of PyVAN was comparable between the 2 groups (Group I = 28.1% vs. Group II = 41.7%; P = 0.312).

CONCLUSIONS

Despite the proven in vitro effectiveness of pravastatin preventing BKPyV infection in HRPTEC, statins at doses maximized for cholesterol lowering, in RTR with BKPyV viremia, did not prevent progression to PyVAN.

Polyomavirus-Specific Cellular Immunity: From BK-Virus-Specific Cellular Immunity to BK-Virus-Associated Nephropathy?

In renal transplantation, BK-virus (BKV)-associated nephropathy has emerged as a major complication, with a prevalence of 1-10% and graft loss in >50% of cases. BKV is a member of the polyomavirus family and rarely induces apparent clinical disease in the general population. However, replication of polyomaviruses, associated with significant organ disease, is observed in patients with acquired immunosuppression. Monitoring of specific immunity combined with viral load could be used to individually assess the risk of viral reactivation and virus control. We review the current knowledge on BKV-specific cellular immunity and, more specifically, in immunocompromised patients. In the future, immune-based therapies could allow us to treat and prevent BKV-associated nephropathy.