BK Virus Replication Research Articles

Neutralizing Antibodies Targeting BK Polyomavirus: Clinical Importance and Therapeutic Potential for Kidney Transplant Recipients.

Most of the world's adult population is latently infected by the BK polyomavirus. It causes asymptomatic infection in healthy individuals but emerged as a threat to kidney transplant recipients because of virus-associated nephropathy caused by immunosuppressive therapy. In these conditions, when a functional cellular response is impaired by immunosuppression, neutralizing antibodies may play a major role because they can directly prevent infection of target cells, independently of cell-mediated immunity, by binding to the viral particles. Studying the contribution of anti-BK virus neutralizing antibodies in viral control has long been hampered by the lack of convenient in vitro models, but major progress has been made in the past decade. The four BK virus genotypes have been demonstrated to behave as distinct serotypes. A low recipient neutralizing antibody titer against the donor's serotype before kidney transplant has been significantly associated with BK virus replication after transplant. Different mechanisms exploited by the BK virus to evade neutralizing antibodies have been described. Recent studies also support the potential benefit of administering intravenous Igs or monoclonal neutralizing antibodies as a therapeutic strategy, and more interestingly, this could also be used as preventive or preemptive therapy before advanced kidney damage has occurred. Besides, neutralizing antibodies could be induced by vaccination. In this review, we summarize accumulated knowledge on anti-BK virus neutralizing antibodies as well as their clinical importance and therapeutic potential for kidney transplant recipients.

Acute Kidney Injury and BK Polyomavirus in Urine Sediment Cells.

Polyomaviruses are widespread, with BK viruses being most common in humans who require immunosuppression due to allotransplantation. Infection with BK polyomavirus (BKV) may manifest as BK virus-associated nephropathy and hemorrhagic cystitis. Established diagnostic methods include the detection of polyomavirus in urine and blood by PCR and in tissue biopsies via immunohistochemistry. In this study, 79 patients with pathological renal retention parameters and acute kidney injury (AKI) were screened for BK polyomavirus replication by RNA extraction, reverse transcription, and virus-specific qPCR in urine sediment cells. A short fragment of the VP2 coding region was the target of qPCR amplification; patients with (n = 31) and without (n = 48) a history of renal transplantation were included. Urine sediment cell immunofluorescence staining for VP1 BK polyomavirus protein was performed using confocal microscopy. In 22 patients with acute renal injury, urinary sediment cells from 11 participants with kidney transplantation (KTX) and from 11 non-kidney transplanted patients (nonKTX) were positive for BK virus replication. BK virus copies were found more frequently in patients with AKI stage III (n = 14). Higher copy numbers were detected in KTX patients having experienced BK polyoma-nephropathy (BKPyVAN) in the past or diagnosed recently by histology (5.6 × 109-3.1 × 1010). One patient developed BK viremia following delayed graft function (DGF) with BK virus-positive urine sediment. In nonKTX patients with BK copies, decoy cells were absent; however, positive staining of cells was found with epithelial morphology. Decoy cells were only found in KTX patients with BKPyVAN. In AKI, damage to the tubular epithelium itself may render the epithelial cells more permissive for polyoma replication. This non-invasive diagnostic approach to assess BK polyomavirus replication in urine sediment cells has the potential to identify KTX patients at risk for viremia and BKPyVAN during AKI. This method might serve as a valuable screening tool for close monitoring and tailored immunosuppression decisions.

Longitudinal viral kinetic study of BK virus in renal transplant patients - A single-center study in Sri Lanka

BackgroundThere is a strong association between high-level BK viraemia and the development of BK virus-associated nephropathy. Therefore, understanding the kinetics of BK virus replication following transplantation would be helpful in predicting high-level viraemia and the development of BKVAN. ObjectivesThis study was aimed to assess the incidence of BKV infection and the BK viral kinetics among renal transplant recipients in their first year following the transplant. MethodsThis study was a retrospective descriptive study involving renal transplant recipients treated at National Hospital, Kandy, Sri Lanka. The patients were recruited from January 2018 to December 2019 and their demographic details and quantitative BKV PCR assay results were analysed during the first year following transplantation. Results297 patients were transplanted during the study period wherein, males predominated with 78.1% and 43.67 years old being the mean age (IQR: 35.50–53.0). The cumulative incidence of BK viraemia was 24.9% (n = 74). The mean age of the cohort with BK viraemia was 44.4 years (IQR: 36–54). Twenty percent (n = 13) of the female population had BKV viraemia, while 26.29% (n = 61) of the male population. Among patients with BK viraemia 12 had significant viraemia of 104IU/ml giving a cumulative incidence of significant viraemia was 4.04% and 10 of them (83.33%) had low levels of viraemia before showing significant viraemia. ConclusionThe presence of low-level viraemia in 83% of patients with significant viraemia proves the value of early routine screening to predict the development of significant BK viraemia and to take preventive measures.

P8.122: Tacrolimus Dose Reduction as an Effective Therapeutic Approach to the Patients With Active BK Virus Replication And Nephrotoxicity

Background: BK viral nephropathy (BKVN) affects a significant proportion of kidney grafts in the early post-transplant period and often leads to functional failure of these grafts. The intensity of immunosuppressive therapy plays a significant role in the activation of BK viral (BKV) replication. Methods: 457 per-protocol biopsies of kidney grafts were performed in a group of 161 newly transplanted patients. The incidence of histological signs of tacrolimus nephrotoxicity as a manifestation of excessive immunosuppression was calculated using the Calcineurin Inhibitor Nephrotoxicity Score (CINS). In case of detection of simultaneous toxicity and substantial BKV replication, the dose of tacrolimus and/or mycophenolate was reduced and the effect on the inhibition of BKV activation and regression of toxic changes were compared. In parallel, we studied the effect of pre-emptive reduction of tacrolimus dose on the development of BKV replication in isolated detections of toxicity during the subsequent period. Results: The reduction of tacrolimus and mycophenolate dose in patients with histological evidence of toxicity and significant BKV replication was associated with an early and significant decrease in the BKV plasma load compared to isolated mycophenolate reduction (P = 0.023), significant decrease in CINS (P = 0.001) and better functional parameters at the end of this one-year follow-up (P = 0.024). A pre-emptive dose reduction of tacrolimus in case of toxicity evidence led to a marked reduction in the incidence of substantial BKV viremia during the subsequent period. Conclusions: The reduction of tacrolimus and mycophenolate dose in patients with histologically verified tacrolimus nephrotoxicity represents a more effective approach to attenuate significant BKV replication than a single-dose reduction of mycophenolate, including the regression of toxic changes. Pre-emptive tacrolimus dose reduction in case of toxicity signs is associated with a lower incidence of significant BKV replication during the first year after transplantation, without increasing the risk of acute rejection. Supported by MH CZ – DRO (FNOl, 00098892) and by grant IGA_LF_2022_03.

Efficacy of Cidofovir in Treatment of BK Virus Induced Hemorrhagic Cystitis in Post Allogeneic Hematopoietic Cell Transplant Recipients

Introduction:BK virus associated hemorrhagic cystitis (BK-HC) is a common complication after allogeneic hematopoietic stem cell transplantation (allo-HCT), with incidence up to 70%. BK virus is a widely prevalent non-encapsulated DNA human polyomavirus which latently infects the uroepithelium and reactivates during immunosuppression. While its pathogenesis is not yet clearly elucidated, BK-HC is associated with factors related to transplant procedure (myeloablative conditioning regimen), graft source (unrelated donor, HLA mismatching), onset of acute graft-versus-host disease, and high-level urinary BK viral replication. Symptomatic and supportive measures have been the standard of care for many years for this difficult-to-treat complication. Treatments that have been trialed include antivirals, antibiotics, and immunomodulatory agents. Cidofovir is a nucleotide analog of cytosine that is active against various DNA viruses with growing evidence as a therapeutic option for BK-HC. The aim of the present retrospective study is to assess the safety profile and efficacy of intravenous and intravesical cidofovir in allo-HCT patients with BK-HC.Methods:We conducted a retrospective study of the allo-HCT patient cohort from January 2010 until March 2017 in a single center in Ontario, Canada. All patients who underwent allo-HCT and received cidofovir for symptomatic BK-HC (hematuria with BK viruria and/or viremia) were included. Electronic charts were reviewed for patient characteristics, cidofovir prescription data, clinical outcomes, and toxicities. BK-HC severity was graded as: Grade 1 (microscopic hematuria), Grade 2 (macroscopic hematuria), Grade 3 (macroscopic hematuria with clots), Grade 4 (impaired renal function). Clinically efficacy was assessed at the end of cidofovir treatment as: Complete Response (CR) - complete symptom remission, Partial Response (PR) - downgrading of severity, or No Response - unchanged or worsening severity. The primary outcome was response to cidofovir, as defined by PR or CR. Secondary outcomes include overall survival, BK virus levels (both urine and blood), and renal toxicity (increase Cr > 30 µmol/L).Results:Twelve allo-HCT patients (6 male, 6 female; median age 49) with BK-HC were treated with cidofovir at our center. The majority of transplants were from 10/10 HLA matched related donors and complicated by acute GVHD and CMV viremia. Median time to BK-HC was 82 days (23-762 days), with an initial clinical grade of 3 (50%) or 4 (50%). All patients had BK viruria, whereas 2 did not have BK viremia. Prior therapies were received by most patients, specifically ciprofloxacin (75%) or leflunomide (17%). Cidofovir administration was via intravenous (33%), intravesical (58%), or both modalities (8%). Median cumulative dose was 10 mg/kg (1-37 mg/kg) across a median of 2 doses (1-21 doses) with a median of 3.25 days (1-30 days) between doses. Mean BK-HC grade decreased significantly by 1.8 (3.5 pre-cidofovir, 1.7 post-cidofovir, p<0.01). Overall, 66% of patients had response to cidofovir (CR=4, PR=4), with similar response rates between intravenous (66%) and intravesical (62%) administration. Two patients had reemergence of BK-HC after showing an initial response. Over the study period, 67% of patients died. Renal toxicity was experienced by 33% of patients; 3 patients had acute kidney injury (2 receiving intravesical, 1 receiving both modalities). Further complications included keratitis, Fanconi's syndrome, and pseudomonal sepsis after intravesical administration.Discussion:In our retrospective institutional review, a majority of patients achieved at least partial remission after cidofovir treatment with similar response rates between intravesical and intravenous administration. While the rate of CR was lower in our study (33%) than previous studies (60-100%), only severe BK-HC cases were included. Nonetheless, there was an overall significant reduction in BK-HC severity with cidofovir administration. While avoidance of systemic toxicity is a purported benefit of intravesical instillation, amongst patients receiving intravesical cidofovir, acute kidney injury as a possible complication needs to be considered. While cidofovir may be an efficacious therapy for BK-HC, albeit with potential demonstrated toxicities, further prospective trials are needed. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

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.

Monitoring of gene expression in tacrolimus‐treated de novo renal allograft recipients facilitates individualized immunosuppression: Results of the IMAGEN study

Calcineurin inhibitors (CNI) have a small therapeutic window, and drug monitoring is required. Pharmacokinetic monitoring does not correlate sufficiently with clinical outcome. Therefore, the expression of nuclear factor of activated T cells (NFAT)-regulated genes in the peripheral blood has been suggested as a potentially useful immune monitoring tool to optimize CNI therapy. NFAT-regulated gene expression (RGE) was evaluated in renal allograft recipients as predictive biomarker to detect patients at risk of acute rejection or infections. NFAT-RGE (interleukin-2, interferon-γ, granular-macrophage colony-stimulating factor) was evaluated by quantitative real-time polymerase chain reaction in whole blood samples at day 7, day 14, month 1, 3, and 6 after transplantation in 64 de novo renal allograft recipients from 3 European centres. Immunosuppression consisted of tacrolimus (Tac), mycophenolic acid, and corticosteroids. Tac concentrations (C0 and C1.5) correlated inversely with NFAT-RGE (P <.01). NFAT-RGE showed a high interindividual variability (1-61%). Patients with high residual gene expression (NFAT-RGE ≥30%) were at the increased risk of acute rejection in the following months (35 vs. 5%, P =.02), whereas patients with low residual gene expression (NFAT-RGE <30%) showed a higher incidence of viral complications, especially cytomegalovirus and BK virus replication (52.5 vs. 10%, P =.01). NFAT-RGE was confirmed as a potential noninvasive early predictive biomarker in the immediate post-transplant period to detect patients at risk of acute rejection and infectious complications in Tac-treated renal allograft recipients. Monitoring of NFAT-RGE may provide additional useful information for physicians to achieve individualized Tac treatment.

Deciphering the Prognostic and Predictive Value of Urinary CXCL10 in Kidney Recipients With BK Virus Reactivation.

BK virus (BKV) replication increases urinary chemokine C-X-C motif ligand 10 (uCXCL10) levels in kidney transplant recipients (KTRs). Here, we investigated uCXCL10 levels across different stages of BKV replication as a prognostic and predictive marker for functional decline in KTRs after BKV-DNAemia. uCXCL10 was assessed in a cross-sectional study (474 paired urine/blood/biopsy samples and a longitudinal study (1,184 samples from 60 KTRs with BKV-DNAemia). uCXCL10 levels gradually increased with urine (P-value < 0.0001) and blood BKV viral load (P < 0.05) but were similar in the viruria and no BKV groups (P > 0.99). In viremic patients, uCXCL10 at biopsy was associated with graft functional decline [HR = 1.65, 95% CI (1.08–2.51), P = 0.02], irrespective of baseline eGFR, blood viral load, or BKVN diagnosis. uCXL10/cr (threshold: 12.86 ng/mmol) discriminated patients with a low risk of graft function decline from high-risk patients (P = 0.01). In the longitudinal study, the uCXCL10 and BKV-DNAemia trajectories were superimposable. Stratification using the same uCXCL10/cr threshold at first viremia predicted the subsequent inflammatory response, assessed by time-adjusted uCXCL10/cr AUC (P < 0.001), and graft functional decline (P = 0.03). In KTRs, uCXCL10 increases in BKV-DNAemia but not in isolated viruria. uCXCL10/cr is a prognostic biomarker of eGFR decrease, and a 12.86 ng/ml threshold predicts higher inflammatory burdens and poor renal outcomes.

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

BackgroundSince the pre-transplant status affects the renal transplantation success and ultimately the survival rate, identifying the probable risk factors that increase the chance of BK virus replication in end-stage renal disease patients can be included in proposing proper surveillance guidelines during pre and post-transplantation. MethodsA descriptive cross-sectional study was performed by collecting plasma samples from 192 ESRD patients undergoing hemodialysis for at least 3 months. Quantitative Real-time PCR assay was used to detect and measure the BK viral load. Demographic and clinical characteristics of the patients who had BK viremia were documented. Results14 (7.3%) out of our 192 participants had BK virus viremia (95%CI 4.2%–11.6%). Demographic characteristics including etiology of ESRD and underlying diseases, mean duration and frequency of dialysis, co-infection with HBV and HCV did not affect the virus replication, since the difference between patients with BK virus viremia and BK virus negative individuals was not statistically significant. However, the statistical significance of the mean age of men with BKV and without BK virus viremia was found (OR: 3.42, P = 0.02 95%CI 0.86–13.61). Also, multiple regression analyses of some other parameters revealed that old age, high body mass index and male gender can be predictive factors of BK virus viremia in ESRD patients. ConclusionBased on our findings, elderly male had higher chance of being exposed to BK virus viremia. Some other demographic characteristics such as a high BMI, old age and gender (male) can increase the risk of BK viremia in patients with ESRD prior to kidney transplantation.

Intravenous immunoglobulin as a preventive strategy against BK virus viremia and BKV-associated nephropathy in kidney transplant recipients-Results from a proof-of-concept study.

BK virus (BKV) replication occurs frequently in kidney transplant recipients (KTR), potentially leading to BKV-associated nephropathy (BKVAN) and graft loss. Patients with high titers of BKV-neutralizing antibodies (NAbs) are protected against BKV replication, and intravenous immunoglobulin (IVIg) infusion can increase NAb titers. We investigated whether early IVIg administration prevents BKV replication in patients with low NAb titers (<4 log10 against the BKV-specific genotype). Based on NAb titers on the day of transplantation, KTR followed in the Strasbourg University Hospital (n=174) were retrospectively divided into the following 3 risk categories for BKV replication: (1) patients with low NAb titers ("high-risk") who received IVIg for the first 3 posttransplant months (n=44), (2) patients with low NAb titers ("high-risk") who did not undergo IVIg treatment (n=41), and (3) patients with high NAb titers ("low-risk") who did not receive IVIg (n=89). At 12 posttransplant months, the incidence of BKV viremia in the high-risk group treated with IVIg (6.8%) was similar to that observed in the low-risk group (10.1%) and markedly lower than that of the untreated high-risk group (36.6%; P<.001). Similar results were observed with regard to BKVAN. We conclude that IVIg may be a valuable strategy for preventing BKV replication.

The Importance of Kidney Medullary Tissue for the Accurate Diagnosis of BK Virus Allograft Nephropathy.

The published tissue adequacy requirement of kidney medulla for BK virus allograft nephropathy diagnosis lacks systematic verification and competes against potential increased procedural risks from deeper sampling. We evaluated whether the presence of kidney medulla improved the diagnostic rate of BK nephropathy in 2244 consecutive biopsy samples from 856 kidney transplants with detailed histologic and virologic results. Medulla was present in 821 samples (37%) and correlated with maximal core length (r=0.35; P<0.001). BK virus allograft nephropathy occurred in 74 (3% overall) but increased to 5% (42 of 821) with medulla compared with 2% (32 of 1423) for cortical samples (P<0.001). Biopsy medulla was associated with infection after comprehensive multivariable adjustment of confounders, including core length, glomerular number, and number of cores (adjusted odds ratio, 1.81; 95% confidence interval, 1.02 to 3.21; P=0.04). In viremic cases (n=275), medulla was associated with BK virus nephropathy diagnosis (39% versus 19% for cortex; P<0.001) and tissue polyomavirus load (Banff polyomavirus score 0.64±0.96 versus 0.33±1.00; P=0.006). Biopsy medulla was associated with BK virus allograft nephropathy using generalized estimating equation (odds ratio, 2.04; 95% confidence interval, 1.05 to 3.96; n=275) and propensity matched score comparison (odds ratio, 2.24; 95% confidence interval, 1.11 to 4.54; P=0.03 for 156 balanced pairs). Morphometric evaluation of Simian virus 40 large T immunohistochemistry found maximal infected tubules within the inner cortex and medullary regions (P<0.001 versus outer cortex). Active BK virus replication concentrated around the corticomedullary junction can explain the higher detection rates for BK virus allograft nephropathy with deep sampling. The current adequacy requirement specifying targeting medulla can be justified to minimize a missed diagnosis from undersampling.

P1759NEPHROTOXICITY OF CALCINEURIN INHIBITORS AS A RISK FACTOR FOR BK VIRUS REPLICATION AFTER KIDNEY TRANSPLANTATION

Abstract Background and Aims BK virus nephropathy (BKVN) represents a serious complication of kidney transplantation and is responsible for significant percentage of transplanted kidneys prematurely terminating their function. Its occurrence is considered a complication of immunosuppressive therapy and is closely related to its intensity. The aim of our prospective study was to evaluate the incidence of subclinical and clinically manifest nephrotoxicity of calcineurin inhibitors (CI) in repeated protocol kidney graft biopsies as a manifestation of excessive immunosuppression and to evaluate its relationship to the PCR confirmed active BKV replication and bioptically proven BKVN during the first year after transplantation. Method In a group of 161 newly transplanted patients we prospectively evaluated 457 consecutive protocol renal biopsies performed within the first year after transplantation. Using the CI nephrotoxicity score, the incidence of nephrotoxicity was monitored. Findings were correlated with laboratory (PCR) and histological evidence of active BK virus (BKV) replication and BKVN. Results When compared to the normal histology, nephrotoxicity was associated with more frequent significant BKV viraemia and viruria (P = 0.02 and P = 0.01, respectively) and more common occurrence of BKVN. The persistence of toxicity in the subsequent biopsy proved to be a negative risk factor of significant BKV viraemia and viruria (P = 0.03 and P = 0.01, respectively), independently of the initial BKV status of the monitored groups. Toxicity could also be used as a predictor of significant viraemia and viruria (P = 0.02 and P = 0.01, respectively) even in the absence of viral replication at the time of initial biopsy. Conclusion Early histological detection of CI nephrotoxicity followed by pre-emptive CI dose reduction might prevent significant BKV reactivation in the risky first posttransplant year. The evaluation whether a regression of histological signs of nephrotoxicity after a CI dose reduction leads to a reduction in BKV replication, and whether a more frequent occurrence of rejection does not complicate further posttransplant course, will be the subject of our further investigation. Supported by grant of Ministry of Health, Czech Republic DRO (FNOL 00098892) – 87-68.

P1762THE EFFECT OF IMMUNOSUPPRESSIVE THERAPY ON THE CLINICAL FOLLOW-UP OF BK VIRUS IN KIDNEY TRANSPLANT RECIPIENTS

Abstract Background and Aims BK virus nephropathy occurs in up to 10% of kidney transplant recipients and can result in graft loss. The reactivation of BK virus is largely asymptomatic, and routine surveillance especially in the first 12-24 months after transplant is necessary for early recognition and intervention. Reduced immunosuppression and antiviral treatment in the early stages may be effective in stopping BK virus replication. This study is designed to investigate the effect of management in immunosuppressive therapy on BK virus titers and graft functions in our kidney transplant group. Method A total of 370 kidney transplant recipients between the ages of 18-69 years and receiving a triple immunosuppressive therapy (Tacrolimus+Mycophenoloic Acid+Prednisolone) were included in the study. Demographic characteristics, BK virus titers, serum creatinine and immunosuppressive drug (Tacrolimus, Everolimus) levels were measured at regular intervals in the first 24 months. Among these patients 43 of them were found to have BK virus positivity. At the time of the detection of BK virus positivity, patients were divided into three groups regarding the change in the immunosuppressive protocols: Group I: Tacrolimus + Everolimus + Prednisolone, Group II: Everolimus + Prednisolone, Group III: Tacrolimus + Prednisolone. BK virus titers and graft functions of all three groups were compared with each other. SPSS 15 for Windows was used for statistical analysis. Results The mean age of the patients was 45.3 years, and the mean duration of transplantation was 16.3 months at the time of the BK virus positivity. During the follow-up, mean Tacrolimus levels were found to be in their highest value (14.1 ng/mL) in the posttransplant three months while BK virus titer reached the highest value (1.1x106 copies/ml) in the posttransplant seven to nine months. Increased creatinine values two months after BK virus positivity were strongly correlated (p = 0.02, p = 0.008, p = 0.05, p = 0.002 at 6th, 9th, 12th and 24th months, respectively). A significant decrease in BK virus titers was observed in all three groups due to reductions in immunosuppressive treatment protocol (p = 0.005, p = 0.003, p = 0.028, in groups I, II, III respectively). Conclusion Our study favors the benefits of the prospective screening for BK virus to identify early viral replication, permit intervention, and prevent progression to nephropathy or allograft loss. The best studied treatment for BK viremia and nephropathy is careful reduction of immunosuppression

BK virus–specific T-cell immune reconstitution after allogeneic hematopoietic cell transplantation

AbstractClinical disease caused by BK virus reactivation is a frequent complication of allogeneic hematopoietic cell transplantation (HCT). Because of the lack of effective antiviral agents, BK virus–specific T cells are emerging as a potential therapy for BK virus disease, but the immune response to BK virus after allogeneic HCT has not been well characterized. Our study describes reconstitution of BK virus–specific T-cell immunity in 77 adult patients after HCT. All patients had urinary symptoms, and urine was tested for BK virus replication; 33 patients were positive for BK virus (cases), and 44 were negative (controls). In BK virus cases, the median time to first positive test was 75 days (range, 2-511). BK virus cases had lower CD4 T-cell counts 3 to 9 months after transplant, but CD8 T-cell counts were similar in cases and controls. BK virus–specific T cells were identified by cytokine flow cytometry in cryopreserved samples collected prospectively. BK virus–specific CD4 T cells producing T helper 1 (Th1) cytokines recovered quickly after HCT. BK virus–specific T cells were detected more frequently in patients with BK virus reactivation at most time points, and CD4 T cells producing Th1 cytokines were more frequent than BK virus–specific cytolytic CD8 T cells. Early detection of interferon-γ+ and cytolytic BK virus–specific CD4 T cells was associated with lower rates of hematuria among cases. Overall, our study describes recovery of BK virus–specific T cells after HCT and the distinct roles for BK virus–specific T cells in the development and resolution of clinical symptoms.

1764. Use of Intravesical BCG for Treatment of Bladder Cancer in a Renal Transplant Recipient, with Subsequent Resolution of Chronic BK Viremia

BackgroundBK virus-induced nephropathy in renal transplantation is well recognized but its oncogenic potential is less appreciated.MethodsWe report a case of high-grade urothelial tumor in a renal transplant recipient with chronic BK viremia in the absence of BK nephropathy successfully treated with intravesical Bacillus Calmette-Guerin (BCG) instillation. Following BCG therapy, there was also spontaneous clearance of BK viremia.ResultsIn July 2011, Mr. LYY, a 57-year-old Chinese man with end-stage renal failure secondary to chronic glomerulonephritis underwent uncomplicated deceased donor renal transplantation. One year later, he developed persistent high-level BK viremia despite reduction in immunosuppression. He was also treated with a course of ciprofloxacin from January to October 2013, and intravenous immunoglobulin (IVIG) in February 2013, but high-level BK viremia persisted. In spite of this, his graft function was preserved. He was subsequently placed on BK surveillance alone. Chronic BK viremia persisted for the next 5 years with stable graft function. See Figure 1. In February 2018, an incidental urinary bladder nodule was picked up on computed tomography (CT) scan performed for evaluation of urosepsis. Follow-up flexible cystoscopy in May 2018 showed a 1.5 cm papillary tumor over the left superior bladder wall. Transurethral resection of bladder tumor (TURBT) was performed and histopathological examination revealed high-grade papillary urothelial carcinoma. In addition, the biopsy specimen was stained positive for SV40, suggesting the possible association between chronic BK virus replication in the bladder and oncogenesis. Relook TURBT in July 2018 revealed a persistent erythematous patch over the posterior bladder wall. Given the cystoscopic findings, Mr. LYY received a weekly instillation of intravesical BCG for 6 weeks. He tolerated the intravesical BCG treatment with no local or systemic complications. Interestingly, his serum BK viral loads dropped below lower limits of detection thereafter and continued to remain so for the next 4 months.ConclusionWe postulate that the intravesical BCG therapy triggered an immune response that targeted not only the tumor but also the BK virus infection, resulting in successful clearance of chronic BK viremia. Disclosures All authors: No reported disclosures.

Le BK virus en greffe rénale

BK virus (BKV) is a Polyomavirus which was discovered in the 1970s and is one of the major pathogens in kidney transplantation recipients since the use of new powerful immunosuppressive drugs began. Nearly half of kidney transplant patients can develop BKV replication and up to 10 % of them may progress to nephropathy (BKVN) which potentially leads to graft loss. These patients are particularly affected since BKV persists in the reno-urinary tract and can therefore be transmitted from donor to recipient. As no specific antiviral treatement is currently available, the management of BKV infection is based on viral load monitoring and immunosuppressive therapy reduction, which is unsatisfactory due to the risk of graft rejection. This article presents what is currently known on BKV pathophysiology and immune response, and the perspectives in terms of diagnosis, prognosis as well as prevention strategies against BKV infection.

Multiplex analysis of Human Polyomavirus diversity in kidney transplant recipients with BK virus replication

BackgroundWhile the pathogenicity of the two initially identified Human Polyomaviruses (HPyVs), BK Virus (BKPyV) and JC Virus (JCPyV) has been intensely studied, there is only limited data, on whether the occurrence of the recently discovered HPyVs correlates with high level BKPyV replication and progression towards Polyomavirus associated nephropathy (PVAN). MethodsTherefore, we performed a comprehensive longitudinal genoprevalence analysis of 13 HPyVs using a novel multiplex assay including 400 serum and 388 urine samples obtained from 99 kidney transplant recipients (KTRs), grouped by quantitative BKPyV DNA loads and evidence of manifest BKPyV associated disease (histologically verified PVAN, high urinary decoy cell levels and concurrent decrease of renal function). ResultsIn total, 3 different non-BKPyV/JCPyV HPyVs, Human Polyomavirus 9, Merkel Cell Polyomavirus (MCPyV) and Trichodysplasia Spinulosa associated Polyomavirus were detected in 11 blood and 21 urine samples from 21 patients. Although DNAemia of these viruses occurred more frequently during high level BKPyV DNAemia and PVAN, the increase of the detection frequency due to progression of BKPyV replication did not reach statistical significance for blood samples. The positive detection rate of MCPyV in urine, however, was significantly higher during BKPyV DNAemia in 19 KTRs of our cohort who suffered from histologically verified PVAN (p = 0.005). In one individual with PVAN, continuous long-term shedding of MCPyV in urine was observed. ConclusionIn our cohort the recently discovered HPyVs HPyV9, TSPyV and MCPyV emerged in blood from KTRs with variable kinetics, while detection of MCPyV DNAuria occurred more frequently during BKPyV DNAemia in patients with PVAN.

Outcomes and complications following ABO-incompatible kidney transplantation performed after desensitization by semi-selective immunoadsorption - a retrospective study.

Because of the current organ shortage, ABO-incompatible (ABOi) transplantations have been increasingly performed in recent years. The results seem comparable to those of compatible transplantations, but there have also been reports of increased side effects possibly because of the desensitization therapy. To address an increase in severe infectious complications, we compared the outcomes of 48 ABOi transplant recipients to outcomes of 96 matched ABO-compatible (ABOc) controls transplanted at Heidelberg University Hospital from August 2005 to April 2018. Over a follow-up period of 8years, ABOi transplant recipients had comparable graft and patient survival as well as graft function compared with ABOc patients. T-cell-mediated and antibody-mediated rejections were not different between groups. In ABOi transplant recipients, urosepsis (22.9% vs. 8.5%; P=0.019) and pneumonia with opportunistic pathogens (8.3% vs. 1.0%, P=0.025) appeared more frequently. As a consequence, a significantly higher number of deaths from infection have been observed after ABOi transplantations (6.3% vs. 0%, P=0.010). High-titer recipients (isoagglutinin titer of ≥1:256) showed a higher incidence of BK virus replication and postoperative bleeding complications. ABO-incompatible transplantations can be performed with results that are not different from results after ABOc transplantations. However, an increased rate of serious infectious complications must be taken into account.

BK Virus Replication in the Glomerular Vascular Unit: Implications for BK Virus Associated Nephropathy.

Background: BK polyomavirus (BKV) reactivates from latency after immunosuppression in renal transplant patients, resulting in BKV-associated nephropathy (BKVAN). BKVAN has emerged as an important cause of graft dysfunction and graft loss among transplant patients. BKV infection in kidney transplant patients has increased over recent decades which correlates with the use of more potent immunosuppressive therapies. BKV infection of the Glomerular Vascular Unit (GVU) consisting of podocytes, mesangial cells, and glomerular endothelial cells could lead to glomerular inflammation and contribute to renal fibrosis. The effects of BKV on GVU infectivity have not been reported. methods: We infected GVU cells with the Dunlop strain of BKV. Viral infectivity was analyzed by microscopy, immunofluorescence, Western blot analysis, and quantitative RT-PCR (qRT-PCR). The expression of specific proinflammatory cytokines induced by BKV was analyzed by qRT-PCR. Results: BKV infection of podocytes, mesangial cells, and glomerular endothelial cells was confirmed by qRT-PCR and positive staining with antibodies to the BKV VP1 major capsid protein, or the SV40 Large T-Antigen. The increased transcriptional expression of interferon gamma-induced protein 10 (CXCL10/IP-10) and interferon beta (IFNβ) was detected in podocytes and mesangial cells at 96 h post-infection. conclusions: All cellular components of the GVU are permissive for BKV replication. Cytopathic effects induced by BKV in podocytes and glomerular endothelial cells and the expression of CXCL10 and IFNβ genes by podocytes and mesangial cells may together contribute to glomerular inflammation and cytopathology in BKVAN.

No correlation between Torque Teno virus viral load and BK virus replication after kidney transplantation

BackgroundAssessment of the intensity of immunosuppression in transplant recipients to estimate the risk of rejection and infection is not entirely satisfactory at the present time. Determination of Torque teno virus (TTV) viral load appears to be a promising tool in this setting. ObjectivesWe evaluated the level of replication and kinetics of TTV during the first three months after kidney transplantation compared to BK virus replication. ResultsIn a retrospective cohort of 116 renal transplant recipients, TTV viral load gradually increased during the first three months post-transplantation with no significant difference or discriminatory threshold between patients with and without BK virus replication. However, the level of TTV replication appeared to be indirectly related to the risk of BK virus replication, particularly according to the induction treatment used (antithymocyte globulin: ATG or basiliximab). Among patients receiving ATG, those receiving cyclosporine had significantly lower TTV viral loads (p < 0.01) with threefold lower reactivation of BKPyV (13 vs 37%) 3 months post-transplantation. Similarly, among the women in our cohort, TTV viral load was significantly higher in women receiving ATG (6.58 ± 1.57 versus 4.62 ± 2.0 log10 copies/mL for basiliximab: p < 0.01), also with threefold higher BKPyV reactivation frequencies (40 vs 13,3%). ConclusionThe multiparametric variation of TTV viral load does not appear to be individually appropriate for the early detection or monitoring of possible post-transplant BKPyV virus reactivation in renal transplant recipients.