BK virus infection: an update on diagnosis and treatment

Prevalence of hypogammaglobulinemia and its management with subcutaneous immunoglobulin supplementation in patients after allogeneic hematopoietic stem cell transplantation-a single-center analysis

Secondary immunodeficiencies are frequently observed after allo-HSCT. The efficacy of subcutaneous IgG preparations in this population is unknown. A retrospective single-institution study involved 126 adult patients transplanted in 2012–2019 for hematological malignancies. Patients were tested every 2–3 weeks for plasma IgG concentration during the 1st year after transplantation and supplemented with facilitated subcutaneous immunoglobulin when they either had IgG concentration < 500 mg/dl or between 500 and 700 mg/dl and recurrent infection. The IgG concentration < 500 mg/dL was diagnosed in 41 patients, while 500–700 mg/dL in 25 and altogether 53 patients received IgG supplementation. The median number of IgG administrations was 2. The median time to the first IgG administration after allo-HSCT was 4.1 months, while to the next administration (if more than one was required) 53 days (prophylactic group) and 32 days (group with infections). We did not observe any significant toxicity. Two situations were associated with increased probability of meeting criteria for IgG supplementation: diagnosis of either acute lymphoblastic leukemia (ALL) or chronic lymphocytic leukemia (CLL) (83.8% versus 39.3% for other diagnosis, p = 0.000) and the systemic use of corticosteroids (64.2% versus 31.5% for patients without systemic corticosteroids, p = 0.005). Over 40% of the adult recipients may require at least incidental immunoglobulin supplementation during the first year after allo-HSCT. Low IgG concentrations are associated with inferior outcomes. The subcutaneous route of IgG administration appeared to be safe and may allow for long persistence.

Incidence and risk factors of kidney allograft loss due to BK nephropathy in the pediatric population: A retrospective analysis of the UNOS/OPTN database

BACKGROUND

BK virus infection can lead to graft dysfunction and loss in kidney transplant recipients. Risk factors for BKV and BKVN have been inadequately studied in children. Here, we evaluate the incidence and risk factors of allograft loss due to BKVN in the pediatric population of the UNOS data set.

METHODS

We conducted a retrospective cohort analysis of the UNOS database and identified all pediatric recipients of kidney transplantation between 2000 and 2018. We compared donor and recipient characteristics, including cause of ESRD, among patients who lost their graft due to BKVN or other causes, and those with functioning allograft. Kaplan-Meier curve and Cox regression analysis were performed to evaluate the risk factors.

RESULTS

A total of 66 patients (0.47%) suffered graft failure from BKVN. Older age, male gender, HLA mismatch, and rejection at 1 year were significantly associated with BKVN graft failure, compared to recipients with functioning allograft. In comparison with graft loss due to other causes, male gender, higher HLA mismatch, rejection in 1st year and tacrolimus use at discharge were significantly associated with BKVN graft loss. Recipients who received mycophenolate at time of discharge were at reduced risk for BKVN graft failure. Compared to graft failure from other causes, BKVN graft failure had shorter death censored graft survival [P = .001]. ESRD due to urologic causes and Alport syndrome had higher rate of BKVN graft failure.

CONCLUSION

Incidence of graft loss from BKVN in the pediatric population was 10.2 per 10 000 patient-years in this study. BKVN is associated with early allograft failure in the pediatric population, compared to other causes of graft loss. Male gender, HLA mismatch, rejection in 1st year, and urological cause of ESRD are risk factors for graft failure from BKVN in children.

BK Polyomavirus-Biology, Genomic Variation and Diagnosis

The BK polyomavirus (BKPyV), a representative of the family Polyomaviridae, is widespread in the human population. While the virus does not cause significant clinical symptoms in immunocompetent individuals, it is activated in cases of immune deficiency, both pharmacological and pathological. Infection with the BKPyV is of particular importance in recipients of kidney transplants or HSC transplantation, in which it can lead to the loss of the transplanted kidney or to haemorrhagic cystitis, respectively. Four main genotypes of the virus are distinguished on the basis of molecular differentiation. The most common genotype worldwide is genotype I, with a frequency of about 80%, followed by genotype IV (about 15%), while genotypes II and III are isolated only sporadically. The distribution of the molecular variants of the virus is associated with the region of origin. BKPyV subtype Ia is most common in Africa, Ib-1 in Southeast Asia, and Ib-2 in Europe, while Ic is the most common variant in Northeast Asia. The development of molecular methods has enabled significant improvement not only in BKPyV diagnostics, but in monitoring the effectiveness of treatment as well. Amplification of viral DNA from urine by PCR (Polymerase Chain Reaction) and qPCR Quantitative Polymerase Chain Reaction) is a non-invasive method that can be used to confirm the presence of the genetic material of the virus and to determine the viral load. Sequencing techniques together with bioinformatics tools and databases can be used to determine variants of the virus, analyse their circulation in populations, identify relationships between them, and investigate the directions of evolution of the virus.

Clinicopathologic Characteristics of JC Virus Nephropathy in Kidney Transplant Recipients

BACKGROUND

The vast majority of polyomavirus nephropathy (PVN) is due to BK virus, but rare cases result from JC virus reactivation. To date, only a handful of biopsy-proven JC-PVN cases have been reported. Here, we describe the clinical and pathologic findings in 7 patients with biopsy-proven JC-PVN.

METHODS

Search of the pathology archives at 2 institutions found 7 cases of JC-PVN. Clinical data were extracted from the electronic medical records, and the biopsies were reviewed.

RESULTS

Four cases were diagnosed at 6 y posttransplant or later. The remaining 3 cases presented within approximately 2 y posttransplant, of which 2 showed subclinical JC-PVN on surveillance biopsy. Two early presenting patients were treated for acute rejection just before acquiring JC-PVN. Late presenting patients had higher chronicity, which correlated to worse outcome. All but 1 biopsy showed nonspecific inflammation within areas of interstitial fibrosis without significant inflammation in unscarred cortex. The earliest presenting patient was the exception and showed active inflammation with tubulitis. Viral cytopathic changes were detected in all cases with moderate or high-histologic viral load (pvl), showing preference for the distal tubules and medulla. The 2 cases with low pvl did not demonstrate cytopathic changes but were SV40 positive.

CONCLUSIONS

JC-PVN can be insidious in presentation, which may cause delayed or missed diagnosis. Unlike BK-PVN, which typically occurs early in the posttransplant period, JC-PVN can occur both early and late following transplant. Overreliance on negative plasma and urine BK viral loads to exclude PVN can be a pitfall.

Nephrotoxicity of calcineurin inhibitors as a risk factor for BK polyomavirus replication after kidney transplantation

BK polyomavirus-associated nephropathy (PyVAN) is responsible for a significant percentage of transplanted kidneys prematurely terminating their function. Its occurrence is closely related to the intensity of immunosuppressive therapy. In a group of 161 newly transplanted patients, we prospectively evaluated 457 protocol renal biopsies performed within the first year after transplantation. Using the calcineurin inhibitors (CI) nephrotoxicity score, the incidence of nephrotoxicity was monitored as a manifestation of excessive immunosuppression. Findings were correlated with clinical evidence of active BK polyomavirus (BKPyV) replication and PyVAN. Compared to the normal histology, nephrotoxicity was associated with more frequent BKPyV viremia and viruria (p = .01 and p < .01, respectively) and more common occurrence of PyVAN. The persistence of toxicity in the subsequent biopsy proved to be a negative risk factor of viremia and viruria (p = .03 and p < .01, respectively), independently of the initial BKPyV status. Toxicity could also be used as a predictor of viremia and viruria (p = .04 and p < .01, respectively) even in the absence of viral replication at the time of initial biopsy. The early histological manifestation of CI nephrotoxicity was associated with significant BKPyV reactivation in the risky first posttransplant year.

Post-allogeneic hematopoietic stem cell transplantation viral reactivations and viremias: a focused review on human herpesvirus-6, BK virus and adenovirus

Human cytomegalovirus and Epstein-Barr virus have been recognized as potential drivers of morbidity and mortality of patients undergoing allogeneic stem cell transplantation for years. Specific protocols for monitoring, prophylaxis and pre-emptive therapy are in place in many transplant settings. In this review, we focus on the next three most frequent viruses, human herpesvirus-6, BK virus and adenovirus, causing reactivation and/or viremia after allogeneic transplant, which are increasingly detected in patients in the post-transplant period owing to emerging techniques of molecular biology, recipients' characteristics, treatment modalities used for conditioning and factors related donors or stem cell source. Given the less frequent detection of an illness related to these viruses, there are often no specific protocols in place for the management of affected patients. While some patients develop significant morbidity (generally older), others may not need therapy at all (generally younger or children). Furthermore, some of the antiviral therapies used are potentially toxic. With the addition of increased risk of secondary infections, risk of graft failure or increased risk of graft-versus-host disease as well as the relationship with other post-transplant complications, the outcomes of patients with these viremias remain unsatisfactory and even long-term survivors experience increased morbidity.

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.

BK Polyomavirus Nephropathy in Kidney Transplantation: Balancing Rejection and Infection

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

BK virus nephropathy in non-renal solid organ transplant recipients: Are we looking hard enough?

We retrospectively examined the clinical characteristics, pathological features, and outcomes of BK viremia and nephropathy in a population of non-renal solid organ transplant patients (NRSOT) referred for outpatient nephrology consultation over a period of 5 years. In the entire cohort of liver, heart, and lung transplant recipients referred to this clinic, 14% percent were found to have BK viremia with a median peak serum BK viral load of 35 500 copies/ml (range 250 to 21 100 000 copies/ml). BK viremia resolved in six of the seventeen patients (35%). Four out of five patients biopsied showed BK virus (BKV) nephropathy. Eleven out of seventeen patients with BK viremia developed advanced (stage 4 or 5) chronic kidney disease. Four patients developed rejection of their solid organ transplant within the first year post detection of BK viremia after immunosuppression reduction. We conclude that a multi-center study is required to evaluate whether implementation of a systematic BK screening program would be effective in early detection and management of this problem in the NRSOT population.

Clinical evaluation of a laboratory-developed quantitative BK virus-PCR assay using the cobas® omni Utility Channel

BACKGROUND

In immunocompromised patients, BK Virus (BKV) reactivation may cause serious disease with high morbidity. Particularly for patient management after solid organ transplantation, monitoring of viral load in different clinical specimens is crucial to ensure early diagnosis and response to reactivation. In this study, we evaluated the clinical performance of a custom designed primer /probe set for detection of BKV on the cobas® 6800, a high-throughput platform, employing the open channel of the system for integration of a lab-developed test (LDT).

MATERIALS/METHODS

A primer/probe set was optimized for the use on a high-throughput platform. Clinical performance was assessed in EDTA-plasma, serum and urine samples. Limit-of-detection (LOD) was determined by using a dilution series of BKV WHO standard. A CE-labeled PCR test (Altona Diagnostics) was used as a comparison to the assay.

RESULTS

The LOD for the LDT BKV assay was 6.7 IU/mL. Inter-and intra-run variability (at 5 x LOD) was low (<1.5 Ct in all specimens). All quality control panel specimens (Instand Germany n = 19) were correctly identified. Of 290 clinical samples tested, results were concordant for 280 samples. Sensitivity and specificity of the assay were 96 % and 98 % respectively. The quantitative analysis revealed a strong correlation (linear regression) between the CE-labelled comparator assay and the new BKV LDT assay with r² = 0.96 for n = 123 urine samples and r² = 0.98 for n = 167 plasma/serum samples.

CONCLUSION

Compared to a CE-IVD assay, the adapted LDT showed good analytical and clinical sensitivity and specificity for the detection and quantification of BKV in different clinical specimens. It represents a convenient solution to automate the LDT workflow with low hands-on time and thus facilitates high-throughput screening for BKV reactivation in immunocompromised patients.

BK virus nephropathy in a heart transplant recipient

BK virus nephropathy in kidney transplantation is widely recognized as an important cause of graft dysfunction and loss. In the case of transplants of organs other than kidney, BK virus nephropathy in native kidneys has been recognized as a cause of chronic kidney disease, which is related with immunosuppression; however, the diagnosis is usually late because the renal dysfunction is attributed to other causes, such as toxicity by anticalcineurinic drugs, interstitial nephritis due to medications, hemodynamic changes, diabetes, hypertension, etc. We report a case of BK virus nephropathy in a patient who underwent heart transplantation due to peripartum cardiomyopathy. The kidney biopsy reported active chronic tubulointerstitial nephritis associated with late stage polyomavirus nephritis and the blood viral load for BK virus was positive (logarithm 4.5). The immunosuppressive treatment was reduced, and after two years of follow-up, the patient had stable renal function with a serum creatinine of 2.5 mg/dL (GFR of 23.4 mL/min/1.73m2). We recommend that the BK virus be considered as a cause of renal dysfunction in heart transplant recipients, with the aim of detecting its replication in time to reduce immunosuppressive therapy before irreversible compromise of renal function may manifest.

Survey of BK Virus in Renal Transplant Recipients in Iran: A Systematic Review and Meta-Analysis

INTRODUCTION

BK virus (BKV) infection in renal transplant (RT) recipients can cause hemorrhagic cystitis, transient renal dysfunction, and BKV nephropathy (BKVN). The prevalence and significance of BKV in RT recipients remain to be clarified in the Iranian population. The purpose of this review is to summarize the overall prevalence of BKV infection in RT recipients from previously published studies in Iran.

METHODS

We systematically reviewed articles through a comprehensive search of the main electronic and Persian national databases up to November 2019.

RESULTS

The overall pooled prevalence of BKV infection among the Iranian population was 23% (95% CI; 15-33%). Comparing these studies revealed that the prevalence of BKV in plasma samples ranges from 3 to 40%, in renal biopsies 1-13%, and in urine samples 10-49%. Due to substantial heterogeneity among reported studies (I2 = 93%, p < 0.01), random-effect meta-analysis was performed. BKV infection rate was slightly higher in women than men (16%, p = 0.04 vs. 14%, p < 0.01, respectively). The majority of the studies employed real-time PCR (24%, I2 = 93, p < 0.01) and analyzed plasma samples alone or in combination with other types of specimens. BKV prevalence from 5 cities among the Iranian population showed a higher prevalence rate in Guilan.

CONCLUSION

Our analysis provides a preliminary estimate of the epidemiology of BKV infection in RT recipients in Iran. These results arouse a need for more epidemiological studies of BKV infection in different unanalyzed regions in Iran. Early detection of BKV in RT recipients helps timely nephropathy diagnosis and prevents graft loss.

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

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

A pilot study of immunosuppression resumption following BK viremia resolution

BACKGROUND

Immunosuppression reduction for BK viremia is associated with de novo humoral responses, which are a risk factor for rejection and graft loss. In this pilot project, we tested a protocol of immunosuppression resumption to standard dose after viral clearance for optimal protection against humoral immunity in patients undergoing treatment for BK viremia.

METHODS

Thirty-six consecutive kidney transplant recipients who developed BK viremia from 7/1/2014 to 11/18/2016 underwent immunosuppression reduction. After 4 weeks of absent viremia, mycophenolate mofetil (MMF) was increased by 500mg/day every 2 weeks up to standard dosage, followed by increase of tacrolimus trough levels to 5-7 ng/mL. If viremia recurred during the increase, immunosuppression was reduced in this same stepwise fashion, with stepwise increase again after 2 months of negative viremia.

RESULTS

Mean tacrolimus trough level (ng/mL) was 8.3 ± 2.7 at viremia onset, 5.3 ± 3.6 at resolution, and 5.6 ± 2.0 at study end date. Mean daily dose (mg) of MMF was 1574 ± 355 at onset, 910 ± 230 at resolution, and 1377 ± 451 at study end date. Only one patient developed low level viremia recurrence (peak 2875 copies/mL) during the period of immunosuppression resumption that ultimately resolved.

CONCLUSIONS

The results of our pilot project indicate that following BK viremia resolution, resumption of standard immunosuppression can be achieved safely without BK viremia recurrence. Larger trials with long-term follow up are required to determine whether such an approach improves long-term graft survival.

Advances in BK Virus Complications in Organ Transplantation and Beyond

Reactivation of BK virus (BKV) remains a dreaded complication in immunosuppressed states. Conventionally, BKV is known as a cause for BKV-associated nephropathy and allograft dysfunction in kidney transplant recipients. However, emerging studies have shown its negative impact on native kidney function and patient survival in other transplants and its potential role in diseases such as cancer. Because BKV-associated nephropathy is driven by immunosuppression, reduction in the latter is a convenient standard of care. However, this strategy is risk prone due to the development of donor-specific antibodies affecting long-term allograft survival. Despite its pathogenic role, there is a distinct lack of effective anti-BKV therapeutics. This limitation combined with increased morbidity and health care cost of BKV-associated diseases add to the complexity of BKV management. While summarizing recent advances in the pathogenesis of BKV-associated nephropathy and its reactivation in other organ transplants, this review illustrates the limitations of current and emerging therapeutic options and provides a compelling argument for an effective targeted anti-BKV drug.

Detection of Proximal Tubule Involvement by BK Polyomavirus in Kidney Transplant Recipients With Urinary Sediment Double-Immunostaining

Background

The extent and depth of BK polyomavirus (BKPyV) infection in renal allograft correlate with prognosis. This study was designed to evaluate the value of urinary sediment double-immunostaining for predicting BKPyV infection in proximal tubular epithelium.

Materials and methods

A total of 76 urine sediment cell blocks, as well as the corresponding transplanted kidney tissues with BK polyomavirus associated-nephropathy (BKPyVAN), were evaluated by automatic double-immunostaining with anti-58-kDa Golgi protein (58K, a proximal renal tubular marker) + anti-SV40-T and anti-homogentisate 1, 2-dioxygenase (HGD, a renal tubular marker) + anti-SV40-T.

Results

Immunohistochemical staining demonstrated that 58K was expressed in proximal tubular epithelium but not in distal tubular epithelium or transitional epithelium. Of the 76 patients, 28 (36.8%) had urinary 58K(+)/SV40-T(+) cells and HGD(+)/SV40-T(+) cells, 41 (53.9%) had only HGD(+)/SV40-T(+) cells, one (1.3%) had only 58K(+)/SV40-T(+) cells, and six (7.9%) had only 58K(−)/HGD(−)/SV40-T(+) cells. The presence of urinary 58K(+)/SV40-T(+) cells was correlated with BKPyV infection in proximal tubular epithelium (P < 0.001, r = 0.806). The mean extent of SV40-T staining was significantly more extensive in patients with urinary 58K(+)/SV40-T(+) cells than those without urinary 58K(+)/SV40-T(+) cells (21.4 vs. 12.0%, P < 0.001). The positive predictive value, negative predictive value, sensitivity, and specificity of urinary 58K(+)/SV40-T(+) cells for predicting BKPyV infection in proximal tubular epithelium were 89.7% (95% CI: 71.5–97.3%), 91.5% (95% CI: 78.7–97.2%), 86.7% (95% CI: 68.4–95.6%), and 93.5% (95% CI: 81.1–98.3%), respectively.

Conclusion

Urinary sediment double-immunostaining with anti-58K and anti-SV40-T is valuable for predicting the extent and depth of BKPyV infection in renal allograft.

Resurgence of BK virus following Covid-19 in kidney transplant recipients

Kidney transplant recipients have been supposed vulnerable to severe Covid-19 infection, due to their comorbidities and immunosuppressive therapies. Mild-term complications of Covid-19 are currently unknown, especially in this population. Herein, we report two cases of BKV replication after non-severe SARS-CoV-2 infection. The first case was a 59-year-old man, transplanted 3 months ago, with recent history of slight BKV viremia (3.3 log₁₀ DNA copies/ml). Despite strong reduction of maintenance immunosuppression (interruption of mycophenolic acid and important decrease of calcineurin inhibitors), BKV replication largely increased after Covid-19 and viremia persisted at 4.5 log copy/ml few months later. The second case was a 53-year-old woman, transplanted 15 years ago. She had a recent history of BKV cystitis, which resolved with a decrease of MPA dosage. Few weeks after SARS-CoV-2 infection, she presented recurrence of lower urinary tract symptoms. Our reports highlight that SARS-CoV-2 infection, even without severity, could disrupt immune system and particularly lymphocytes, thus leading to viral replication. Monitoring of viral replications after Covid-19 in kidney transplant recipients could permit to confirm these preliminary observations.

Urine Donor-Derived Cell-Free DNA Helps Discriminate BK Polyomavirus-Associated Nephropathy in Kidney Transplant Recipients With BK Polyomavirus Infection

Background: Studies have shown that plasma donor–derived cell-free DNA (dd-cfDNA) can predict renal allograft antibody-mediated rejection. This study was performed to evaluate the value of urine dd-cfDNA concentration and dd-cfDNA fraction (%) for discriminating BK polyomavirus-associated nephropathy (BKPyVAN) in kidney transplant recipients with urinary BK polyomavirus (BKPyV) infection.

Methods: In this retrospective single-center observational study, we enrolled kidney transplant recipients who were diagnosed with urine BKPyV infection between August 2018 and May 2019 at the First Affiliated Hospital of Sun Yat-sen University. Urine dd-cfDNA was measured by using a novel target region capture sequencing methodology. The pathological diagnosis of BKPyVAN was confirmed by anti-SV40-T immunohistochemical staining and classified using the American Society for Transplantation schema. Receiver operating characteristic curve analysis was used to investigate the relations of urine dd-cfDNA and dd-cfDNA% to intrarenal allograft BKPyV infection states.

Results: In total, 93 patients were enrolled, including 40 cases of proven BKPyVAN, seven cases of probable BKPyVAN, 23 cases of possible BKPyVAN, and 23 cases of resolving BKPyVAN. Urine dd-cfDNA level in proven BKPyVAN (22.09 ± 21.27 ng/ml) was comparable to that in probable BKPyVAN (15.64 ± 6.73 ng/ml, P = 0.434) but was significantly higher than that in possible BKPyVAN (5.60 ± 3.53 ng/ml) and resolving BKPyVAN (5.30 ± 3.34 ng/ml) (both Ps < 0.05). Urine dd-cfDNA% of proven BKPyVAN (0.71 ± 0.21) was lower than that of probable BKPyVAN (0.91 ± 0.04, P < 0.001), but was significantly higher than that of possible BKPyVAN (0.56 ± 0.30) and resolving BKPyVAN (0.46 ± 0.28) (both Ps < 0.05). For distinguishing biopsy-proven BKPyVAN from biopsy-excluded BKPyVAN, the discrimination capacity of urine dd-cfDNA (AUC: 0.842, 95% CI: 0.735, 0.918) was superior to that of plasma BKPyV DNA load (AUC: 0.660, 95% CI: 0.537, 0.769) with 0.181 (95% CI: 0.043, 0.319) difference between areas under ROC curves (P = 0.010).

Conclusion: The elevated urine dd-cfDNA level may help discriminate BKPyVAN in kidney transplant recipients with BKPyV viruria.

Association of Pretransplant BK Polyomavirus Antibody Status with BK Polyomavirus Infection After Kidney Transplantation: A Prospective Cohort Pilot Study of 47 Transplant Recipients

BACKGROUND

Prevention and early detection of BK polyomavirus (BKV) infection is important for long-term kidney graft survival; hence, pretransplant screening methods are essential to identify recipients at high risk for BKV infection. This study investigated the association of pretransplant donor and recipient BKV antibody status with the occurrence of post-transplant BKV infection.

METHODS

We prospectively enrolled 47 adult living donor kidney transplant pairs from December 2014 to January 2016. Recipient and donor pretransplant BKV antibody titer was measured by hemagglutination inhibition (HI) test. Donor and recipient median HI titer of 1:20 was used as a cutoff to define seropositivity. Recipients were divided into 2 groups (BKV antibody donor-seropositive/recipient-seronegative (D+/R-) and non-D+/R-). Urinary cytology was used to screen for BKV infection. Plasma polymerase chain reaction testing for BKV DNA was used when decoy cells in urine were persistently detected.

RESULTS

Nine (19.2%) of 47 patients belonged to the D+/R- group. Decoy cells were observed in 32 recipients (68.1%) during follow-up. BK viremia occurred in 3 (6.4%) cases. The maximum decoy cell count was significantly higher in the D+/R- group than in the non-D+/R- group (P = .0002). Decoy-cell-free survival was significantly shorter in the D+/R- group (P = .0220). Multivariate analysis identified only BKV antibody serostatus as an independent risk factor for decoy cell appearance (P = .0491).

CONCLUSIONS

Pretransplant donor and recipient BKV antibody status was associated with higher maximum decoy cell count and shorter decoy-cell-free survival after kidney transplantation.

Development of a Nucleic Acid Lateral Flow Immunoassay for the Detection of Human Polyomavirus BK

The BK virus (BKV) is an emerging pathogen in immunocompromised individuals and widespread in the human population. Polymerase chain reaction is a simple and highly sensitive method for detecting BKV, but it is time consuming and requires expensive instruments and expert judgment. The lateral flow assay, a rapid, low-cost, minimal-labor, and easy-to-use diagnostic method, was successfully applied for pathogen detection. In this study, we used oligonucleotide probes to develop a simple and rapid sandwich-type lateral flow immunoassay for detecting BKV DNA within 45 minutes. The detection limit for the synthetic single-stranded DNA was 5 nM. The specificity study showed no cross-reactivity with other polyomaviruses, such as JC virus and simian virus 40. For the Escherichia coli containing BKV plasmid cultured samples, the sensitivity was determined to be 107 copies/mL. The approach offers great potential for BKV detection of various target analytes in point-of-care settings.

Everolimus for BKV nephropathy in kidney transplant recipients: a prospective, controlled study

There is no specific therapy for polyoma BK virus nephropathy (BKVN) in kidney transplant recipients, a condition associated with poor outcomes. Everolimus showed promising antiviral effects, but data from prospective studies are limited. Therefore, we converted ten consecutive kidney transplant recipients with biopsy-proven BKVN from standard exposure Calcineurin inhibitors and Mycophenolate to Everolimus and reduced exposure Calcineurin inhibitors. Ten patients not administered Everolimus, on reduced exposure Calcineurin inhibitor and halved MPA doses served as controls. All kidney transplant recipients continued steroid therapy. Each patient underwent kidney graft biopsy, BKV replication by PCR, and de novo DSA determination. During a 3-year follow-up no graft loss occurred in kidney transplant recipients on Everolimus but it was observed in 5/10 controls (P = 0.032). eGFR improved on Everolimus and worsened in controls (between group difference + 25.6 ml/min/1.73 m², 95% CI 10.5-40.7, P = 0.002). BKV replication declined in the Everolimus group alone (from 6.4 ± 0.8 to 3.6 ± 1.6 Log 10 genomic copies, P = 0.0001), and we found a significant inverse relationship between eGFR and BKV genomic copy changes (P = 0.022). Average Calcineurin inhibitors trough levels did not differ between the two study groups during follow-up. By multivariable Cox regression analysis, Everolimus treatment resulted the only significant predictor of survival free of a combined endpoint of graft loss and 57% eGFR reduction (P = 0.02). Kidney transplant recipients on Everolimus had a higher survival free of adverse graft outcome (log-rank test, P = 0.009). In conclusion an Everolimus-based immunosuppressive protocol with minimization of Calcineurin inhibitors and antimetabolite discontinuation effectively treated BKVN in kidney transplant recipients.

Imaging of Renal Transplant Complications throughout the Life of the Allograft: Comprehensive Multimodality Review

The kidney is the most commonly transplanted solid organ. Advances in surgical techniques, immunosuppression regimens, surveillance imaging, and histopathologic diagnosis of rejection have allowed prolonged graft survival times. However, the demand for kidneys continues to outgrow the available supply, and there are efforts to increase use of donor kidneys with moderate- or high-risk profiles. This highlights the importance of evaluating the renal transplant patient in the context of both donor and recipient risk factors. Radiologists play an integral role within the multidisciplinary team in care of the transplant patient at every stage of the transplant process. In the immediate postoperative period, duplex US is the modality of choice for evaluating the renal allograft. It is useful for establishing a baseline examination for comparison at future surveillance imaging. In the setting of allograft dysfunction, advanced imaging techniques including MRI or contrast-enhanced US may be useful for providing a more specific diagnosis and excluding nonrejection causes of renal dysfunction. When a pathologic diagnosis is deemed necessary to guide therapy, US-guided biopsy is a relatively low-risk, safe procedure. The range of complications of renal transplantation can be organized temporally in relation to the time since surgery and/or according to disease categories, including immunologic (rejection), surgical or iatrogenic, vascular, urinary, infectious, and neoplastic complications. The unique heterotopic location of the renal allograft in the iliac fossa predisposes it to a specific set of complications. As imaging features of infection or malignancy may be nonspecific, awareness of the patient's risk profile and time since transplantation can be used to assign the probability of a certain diagnosis and thus guide more specific diagnostic workup. It is critical to understand variations in vascular anatomy, surgical technique, and independent donor and recipient risk factors to make an accurate diagnosis and initiate appropriate treatment.^©RSNA, 2019.

Outcome Comparison between Low-Dose Rabbit Anti-Thymocyte Globulin and Basiliximab in Low-Risk Living Donor Kidney Transplantation

The objective of this study was to compare outcomes between basiliximab and low-dose r-ATG in living donor kidney transplantation recipients with low immunological risk. Patients in the low-dose r-ATG group received 1.5 mg/kg of r-ATG for 3 days (total 4.5 mg/kg). Graft survival, patient survival, acute rejection, de novo donor specific antibody (DSA), estimated glomerular filtration rate (e-GFR) changes, and infection status were compared. Among 268 patients, 37 received r-ATG, and 231 received basiliximab. There was no noticeable difference in the graft failure rate (r-ATG vs. basiliximab: 2.7% vs. 4.8%) or rejection (51.4% vs. 45.9%). de novo DSA was more frequent in the r-ATG group (11.4% vs. 2.4%, p = 0.017). e-GFR changes did not differ noticeably between groups. Although most infections showed no noticeable differences between groups, more patients in the r-ATG group had cytomegalovirus (CMV) antigenemia and serum polyomavirus (BK virus) (73.0% vs. 51.9%, p = 0.032 in CMV; 37.8% vs. 15.6%, p = 0.002 in BK), which did not aggravate graft failure. Living donor kidney transplantation patients who received low-dose r-ATG and patients who received basiliximab showed comparable outcomes in terms of graft survival, function, and overall infections. Although CMV antigenemia, BK viremia were more frequent in the r-ATG group, those factors didn’t change the graft outcomes.

Outcomes of kidney retransplantation after graft loss as a result of BK virus nephropathy in the era of newer immunosuppressant agents

We conducted this study using the updated 2005-2016 Organ Procurement and Transplantation Network database to assess clinical outcomes of retransplant after allograft loss as a result of BK virus-associated nephropathy (BKVAN). Three hundred forty-one patients had first graft failure as a result of BKVAN, whereas 13 260 had first graft failure as a result of other causes. At median follow-up time of 4.70 years after the second kidney transplant, death-censored graft survival at 5 years for the second renal allograft was 90.6% for the BK group and 83.9% for the non-BK group. In adjusted analysis, there was no difference in death-censored graft survival (P = .11), acute rejection (P = .49), and patient survival (P = .13) between the 2 groups. When we further compared death-censored graft survival among the specific causes for first graft failure, the BK group had better graft survival than patients who had prior allograft failure as a result of acute rejection (P < .001) or disease recurrence (P = .003), but survival was similar to those with chronic allograft nephropathy (P = .06) and other causes (P = .05). The better allograft survival in the BK group over acute rejection and disease recurrence remained after adjusting for potential confounders. History of allograft loss as a result of BKVAN should not be a contraindication to retransplant among candidates who are otherwise acceptable.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Non-invasive urinary sediment double-immunostaining predicts BK polyomavirus associated-nephropathy in kidney transplant recipients

Background

The positive predictive value (PPV) of urinary decoy cells for diagnosing BK polyomavirus associated-nephropathy (BKPyVAN) is low. This study was designed to increase the PPV of urinary decoy cells for diagnosing BKPyVAN in kidney transplant recipients.

Methods

A total of 105 urine sediment samples from 105 patients with positive BK viruria and decoy cells were evaluated by automatic double-immunostaining with anti-HGD (a renal tubular marker) antibody + anti-SV40-T antibody or anti-S100P (an urothelial marker) antibody + anti-SV40-T antibody.

Results

Of the 105 patients, 76 (72.4%) had both HGD(+)/SV40-T(+) cells and S100P(+)/SV40-T(+) cells (group A), 24 (22.9%) had only S100P(+)/SV40-T(+) cells (group B), and 5 (4.6%) had only S100P(-)/HGD(-)/SV40-T(+) cells (group C). Seventy patients in group A (92.1%), 3 patients in group B (12.5%), and no patients in group C were diagnosed with BKPyVAN. The area under the ROC curve of predicting BKPyVAN by decoy cells was 0.531 (0.431-0.630), with an optimal cut-off value of 29 (per 10 high power field), a sensitivity of 45.8% (95% CI: 34.0-58.0%), and a specificity of 68.8% (95% CI: 50.0-83.9%). Besides, the area under the ROC curve of predicting BKPyVAN by plasma BKPyV load was 0.735 (95% CI: 0.632-0.822), with an optimal cut-off value of 1,000 copies/mL, a sensitivity of 61.1% (95% CI: 48.9-72.4%) and a specificity of 84.2% (95% CI: 60.4-96.6%). In contrast, the PPV, negative predictive value, sensitivity, and specificity of HGD(+)/SV40-T(+) cells for diagnosing BKPyVAN were 92.1% [95% confidence interval (CI): 83.0-96.7%], 89.7% (95% CI: 71.5-97.3%), 95.9% (95% CI: 87.7-98.9%), and 81.3% (95% CI: 63.0-92.1%) respectively.

Conclusions

Double-immunostaining with anti-HGD or anti-S100P and anti-SV40-T antibodies helps to identify the origin of decoy cells and diagnose BKPyVAN.

Pathogenicity of BK virus on the urinary system

Introduction

The polyomaviruses are omnipresent in nature. The major sites of BK virus appearance are the kidney tubular epithelial cells and urinary bladder surface transitional cells.

Material and methods

A literature search according to PRISMA guidelines within the Medline database was conducted in July 2019 for articles presenting data about BK virus in urologic aspect without setting time limits, using the terms ‘BK virus’ in conjunction with transplantation, nephropathy, stenosis, cancer, bladder, prostate, kidney.

Results

The BK virus usually stays latent, however, its replication may become active in various clinical situations of impaired immunocompetence such as solid organ transplantation, bone marrow transplantation, AIDS, pregnancy, multiple sclerosis, administration of chemotherapy or biologic therapy. BK virus is associated with two main complications after transplantation: polyomavirus-associated nephropathy in kidney transplant patients and polyomavirus-associated hemorrhagic cystitis in allogeneic hematopoietic stem cell transplant patients.

Conclusions

The aim of this article was to present available data on urologic aspects of BK virus infection, its detection methods and available treatment.

Longitudinal assessment of the CXCL10 blood and urine concentration in kidney transplant recipients with BK polyomavirus replication-a retrospective study

In kidney transplant recipients (KTRs), BK polyomavirus (BKPyV) replication may progress to polyomavirus‐associated nephropathy (PVAN). In this retrospective study, we assessed the chemokine CXCL10 in urine and blood samples consecutively acquired from 85 KTRs who displayed different stages of BKPyV replication and eventually developed PVAN. In parallel to progression toward PVAN, CXCL10 gradually increased in blood and urine, from baseline (prior to virus replication) to BKPyV DNAuria (median increase in blood: 42.15 pg/ml, P = 0.0156), from mere DNAuria to low‐ and high‐level BKPyV DNAemia (median increase: 52.60 and 87.26 pg/ml, P = 0.0010 and P = 0.0002, respectively) and peaked with histologically confirmed PVAN (median increase: 145.00 pg/ml, P < 0.0001). CXCL10 blood and urine levels significantly differed among KTRs with respect to simultaneous presence of human cytomegalovirus (P < 0.001) as well as in relation to the clinical severity of respective BKPyV DNAemia episodes (P = 0.0195). CXCL‐10 concentrations were particularly lower in KTRs in whom BKPyV DNAemia remained without clinical evidence for PVAN, as compared to individuals who displayed high decoy cell levels, decreased renal function and/or biopsy‐proven PVAN (median blood concentration: 266.97 vs. 426.42 pg/ml, P = 0.0282). In conclusion, in KTRs CXCL10 rises in parallel to BKPyV replication and correlates with the gradual development of PVAN.

Longitudinal study of BK Polyomavirus outcomes, risk factors, and kinetics in renal transplantation patients

BACKGROUND

In the immunocompromised conditions following renal transplantation, BK virus can reactivate and cause BK virus associated nephropathy (BKVN). Increased BK viral loads and extended duration of infection have been linked to development of BKVN. The aim of this study was to observe the incidence of BKV infection and BKVN, and kinetics of infection and disease in renal transplantation recipients.

METHODS

From 2014 to 2018, we conducted a longitudinal cohort observational study of 139 renal transplantation patients treated at a single clinic. Quantitative PCR assay was conducted to assess longitudinal BK viral loads. Analysis of patient clinical characteristics was performed to determine risk factors for BKV infection and associated disease.

RESULTS

Of our cohort, 29 (20.9%) patients developed high BK viremia, and 7 (5.0%) developed biopsy-confirmed BKVN. Clinical parameters associated with diabetes (FBS, HbA1c) and hyperlipidemia (TG, TC, LDL-C) were found to be correlated with development of high BK viremia or BKVN. In 3 of 4 patients receiving intravenous immunoglobulin (IVIG) treatment, BK viral loads were reduced by at least 1 log within 2-3 months of administration. Significant differences were measured in BK viral loads and kidney function between BK viremic patients and BKVN patients by 3-9 months post-transplantation.

CONCLUSIONS

We identified diabetes and hyperlipidemia as potential risk factors for development of high BK viremia and/or BKVN. IVIG was seen to be effective in reducing viral titers. The period 3-9 months post-transplantation was identified as important for development of BKVN from high BK viremia.

Transplant renal artery stenosis in a child with BK nephropathy

TRAS and BK nephropathy are known complications of RT, but the association between both has not been reported. A 2-year-old girl underwent a deceased donor renal transplant from a 20-year-old donor, along with bilateral native nephrectomies. She had a DGF due to a renal artery thrombus and required thrombectomy with re-anastomosis. Heparin and aspirin were used. Immunosuppressive agents included thymoglobulin, steroid, tacrolimus, and MMF. CMV and EBV DNA PCRs were negative, but she developed BK viremia at 2 months with stable allograft function. Immunosuppression was reduced, and leflunomide was initiated. Blood pressures were well controlled on low-dose amlodipine. Five months after RT, she presented with hypertensive emergency, following a respiratory infection, and required dialysis for oliguric acute kidney injury. Allograft biopsy showed evidence of BK nephropathy. Immunosuppression was further minimized. Doppler renal US and renal artery duplex studies were both suggestive of TRAS. Angiogram showed severe proximal anastomotic TRAS (>95% occlusion). PTA with stenting was done with immediate improvement in the blood flow and reduction in the pressure gradient. BPs and renal function normalized. Ten months post-RT, she remains normotensive with stable renal function and resolution of BK viremia. Although ureteral stenosis and nephropathy are known to occur with BK infection, TRAS is an interesting association and possibly suggest the tropism of BK virus to the vascular endothelial cells. Timely recognition and management of both is important to prevent uncontrolled hypertension and allograft dysfunction.

Combined detection of urine specific gravity and BK viruria on prediction of BK polyomavirus nephropathy in kidney transplant recipients

BACKGROUND

BK polyomavirus (BKPyV)-associated nephropathy (BKPyVAN) is an important cause of dysfunction and failure of renal transplants. This study aimed to assess the diagnostic performance of morning urine specific gravity (MUSG) in diagnosing BKPyVAN in kidney transplant recipients.

METHODS

A total of 87 patients, including 27 with BKPyVAN, 22 with isolated BKPyV viruria, 18 with T cell-mediated rejection (TCMR), and 20 with stable graft function, were enrolled in the First Affiliated Hospital of Sun Yat-Sen University from March 2015 to February 2017. MUSG at biopsy and during a follow-up period of 24 months after biopsy was collected and analyzed. Receiver operating characteristic (ROC) curve analysis was used to determine the ability of MUSG to discriminate BKPyVAN.

RESULTS

At biopsy, the MUSG of BKPyVAN group (1.008 ± 0.003) was significantly lower than that of isolated BK viruria group (1.013 ± 0.004, P < 0.001), TCMR group (1.011 ± 0.003, P = 0.027), and control group (1.014 ± 0.006, P < 0.001). There was no significant difference in MUSG among the isolated BK viruria group, TCMR group, and control group (P = 0.253). In BKPyVAN group, the timing and trend of MUSG elevate were consistent with the timing and trend of the decline of viral load in urine and plasma, reaching a statistical difference at 3 months after treatment (1.012 ± 0.003, P < 0.001) compared with values at diagnosis. ROC analysis indicated that the optimal cut-off value of MUSG for diagnosis of BKPyVAN was 1.009, with an area under the ROC curve (AUC) of 0.803 (95% confidence interval [CI]: 0.721-0.937). For differentiating BKPyVAN and TCMR, the optimal MUSG cut-off value was 1.010, with an AUC of 0.811 (95% CI: 0.687-0.934).

CONCLUSION

Combined detection of MUSG and BKPyV viruria is valuable for predicting BKPyVAN and distinguishing BKPyVAN from TCMR in renal transplant recipients.

Decoy Cells versus Plasma Real-Time Polymerase Chain Reaction for the Detection of Polyomaviruses in Renal Transplant Patients: A Single Institutional Experience

Background and Aims:

Microscopic detection of decoy cells is routinely performed in urine samples from renal transplant patients for the evaluation of polyomaviruses. However, they are scanty papers evaluated the diagnostic accuracy of decoy cells in urine samples. The aim of this study is to evaluate the diagnostic accuracy of decoy cells in urine samples and compare with plasma real-time polymerase chain reaction (RT-PCR) as a gold standard method. In addition, to compare the findings of this study with other similar studies.

Methods:

A retrospective study over a period of four years from January 2014 to December 2017 was performed. A total of 89 urine samples from renal transplant patients were assessed for the presence of polyomaviruses and compared with plasma RT-PCR. The sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) were measured.

Results:

There were 29 males and 18 females. The mean patient age was 40.3 years. The sensitivity, specificity, accuracy, PPV and NPV were 86.6%, 67.5%, 70.7%, 35.1% and 96.1%, respectively. Other similar studies reported a sensitivity of 41.9-84.6%, specificity of 65.8-100% and accuracy of 69.9-82%.

Conclusion:

The findings of this study show that the detection of decoy cells in urine samples is a sensitive screening method for polyomaviruses. The findings of this study are compatible with other similar studies.

Thermally stable and uniform DNA amplification with picosecond laser ablated graphene rapid thermal cycling device

Rapid thermal cycling (RTC) in an on-chip device can perform DNA amplification in vitro through precise thermal control at each step of the polymerase chain reaction (PCR). This study reports a straightforward fabrication technique for patterning an on-chip graphene-based device with hole arrays, in which the mechanism of surface structures can achieve stable and uniform thermal control for the amplification of DNA fragments. A thin-film based PCR device was fabricated using picosecond laser (PS-laser) ablation of the multilayer graphene (MLG). Under the optimal fluence of 4.72 J/cm2 with a pulse overlap of 66%, the MLG can be patterned with arrays of 250 μm2 hole surface structures. A 354-bp DNA fragment of VP1, an effective marker for diagnosing the BK virus, was amplified on an on-chip device in less than 60 min. A thin-film electrode with the aforementioned MLG as the heater was demonstrated to significantly enhance temperature stability for each stage of the thermal cycle. The temperature control of the heater was performed by means of a developed programmable PCR apparatus. Our results demonstrated that the proposed integration of a graphene-based device and a laser-pulse ablation process to form a thin-film PCR device has cost benefits in a small-volume reagent and holds great promise for practical medical use of DNA amplification.

BK Polyomavirus-specific T cell immune responses in kidney transplant recipients diagnosed with BK Polyomavirus-associated nephropathy

BACKGROUND

Adjustment of immunosuppression is the main therapy for BK polyomavirus (BKPyV)-associated nephropathy (BKPyVAN) after kidney transplantation (KT). Studies of BKPyV-specific T cell immune response are scarce. Here, we investigated BKPyV-specific T cell immunity in KT recipients diagnosed with BKPyVAN.

METHODS

All adult KT recipients with BKPyVAN diagnosed at our institution from January 2017 to April 2018 were included. Laboratory-developed intracellular cytokine assays measuring the percentage of IFN-γ-producing CD4⁺ and CD8⁺ T cells, after stimulation with large-T antigen (LT) and viral capsid protein 1 (VP1), were performed both at the time of diagnosis and after adjustment of immunosuppression.

RESULTS

We included 12 KT recipients diagnosed with BKPyVAN (7 proven, 4 presumptive, and 1 possible). Those with presumptive BKPyVAN had a median plasma BKPyV DNA load of 5.9 log10 copies/ml (interquartile range [IQR]: 4.9-6.1). Adjusted dosing of mycophenolic acid and tacrolimus with (86%) or without (14%) adjunctive therapies were implemented after diagnosis. There was a significantly higher median percentage of IFN-γ-producing CD4⁺ T cells to LT at a median of 3 (IQR: 1-4) months after adjustment of immunosuppression compared with at the time of diagnosis (0.004 vs. 0.015; p = 0.047). However, the difference between the median percentage of IFN-γ-producing CD4⁺ T cells to VP1 and CD8⁺ T cells to LT and VP1 did not reach statistical significance. Four (33%) patients achieved plasma BKPyV DNA clearance, and the remaining eight (67%) patients had persistent BKPyV DNAemia. Although eight (67%) patients developed allograft dysfunction, none required hemodialysis.

CONCLUSIONS

We observed a marginal trend of BKPyV-specific CD4⁺ T cell recovery after adjustment of immunosuppression in KT recipients diagnosed with BKPyVAN. A further study would be benefited to confirm and better assess BKPyV-specific immune response after KT.

The immunophenotyping of different stages of BK virus allograft nephropathy

Objectives: To investigate the immunohistochemical features of different stages of BK virus allograft nephropathy (BKVN) and further elucidate the underlying immunological mechanism involved in the evolution of BKVN. Methods: Fifty-two renal transplant recipients with biopsy proven BKVN were retrospectively selected. According to the third edition of the American Society of Transplantation Infection guidelines, 10 patients were categorized as having mild BKVN (stage A), 25 were moderate (stage B) and 17 were severe (stage C). The differential infiltrations of CD3+ (T lymphocytes), CD4+ (helper T lymphocytes), CD8+ (cytotoxic T lymphocytes), CD20+ (B lymphocytes), CD68+ (macrophages) and CD138+ (plasma cells) cells and the expression of interleukin-2 receptor (IL-2R) and human leukocyte antigen DR (HLA-DR) were compared among the three groups. Results: CD3+, CD4+, CD8+, CD20+, CD138+ and CD68+ cells infiltrations, IL-2R and HLA-DR expression were positive in the BKVN patients. Moreover, with increasing stages of BKVN, the numbers of positively stained inflammatory cells and the expression of IL-2R were significantly increased in the severe group compared to the mild group, whereas no statistically significant differences were observed with regard to HLA-DR expression. Eosinophil and neutrophil infiltration could also be observed in moderate to advanced BKVN. Conclusion: Renal allograft damage caused by BKVN involved T lymphocyte-, B lymphocyte- and mononuclear macrophage-mediated immune responses. Inflammatory cell infiltrations in the renal allograft were probably the driving force for BKVN progression. Additionally, eosinophils and neutrophils may be involved in the pathophysiological mechanism of BKVN.

BK polyomavirus genotypes in renal transplant recipients in the United States: A meta-analysis

BACKGROUND

In the United States, increasing ethnic diversity has been apparent. However, the epidemiology and trends of BKV genotypes remain unclear. This meta-analysis was conducted with the aim to assess the prevalence of BKV genotypes among kidney transplant (KTx) recipients in the United States.

METHODS

A comprehensive literature review was conducted through October 2018 utilizing MEDLINE, Embase, and Cochrane Database to identify studies that reported the prevalence of BKV subtypes and/or subgroups in KTx recipients in the United States. Pooled prevalence rates were combined using random effects, generic inverse variance method. The protocol for this study is registered with PROSPERO (no. CRD42019134582).

RESULTS

A total of eight observational studies with a total of 193 samples (urine, blood, and kidney tissues) from 188 BKV-infected KTX recipients were enrolled. Overall, the pooled estimated prevalence rates of BKV subtypes were 72.2% (95% confidence of interval [CI]: 62.7-80.0%) for subtype I, 6.8% (95% CI: 2.5-16.9%) for subtype II, 8.3% (95% CI: 4.4-15.1%) for subtype III, and 16.1% (95% CI: 10.4-24.2%) for subtype IV, respectively. While metaregression analysis demonstrated a significant positive correlation between year of study and the prevalence of BKV subtype I (slopes = +0.1023, P = .01), there were no significant correlations between year of study and percentages of BKV subtype II-IV (P > .05). Among KTx recipients with BKV subtype I, the pooled estimated percentages of BKV subgroups were 22.4% (95% CI: 13.7-34.5%) for subgroup Ia, 30.6% (95% CI: 17.7-47.5%) for subgroup Ib1, 47.7% (95% CI: 35.8-59.9%) for subgroup Ib2, and 4.1% (95% CI:1.2-13.3%) for subgroup Ic, respectively.

CONCLUSION

BKV subtype I is the most prevalent subtype among KTx recipients in the United States and its prevalence seems to increasing overtime. Subgroup Ib2 is the most common subgroup among BKV subtype I.

Identification of BK Virus Genotypes in Recipients of Renal Transplant in Vietnam

OBJECTIVES

This study aims to investigate the prevalence and distribution of BK polyomavirus (BKV) genotypes in recipients of renal transplant in Vietnam.

METHODS

One hundred six patients who underwent renal transplantation were included in this study. These patients were from the Department of Nephrology, Military Hospital 103, Vietnam Military Medical University. Quantification and genotyping of the BK virus was performed using in-house molecular methods from urine and plasma samples.

RESULTS

BKV infection was detected in 82 patients (77.4%), including 58 patients who had the presence of both BK viremia and BK viruria, and 24 patients (22.60%) with BKV positive findings in the urine alone. Particularly, 16 patients (15.09%) had high BK viremia >10⁴ copies/mL and 20 patients (18.9%) had BK viruria >10⁷ copies/mL. BK virus nephropathy (BKVN) was confirmed in 6 patients (5.66%) by immunohistochemistry examination. Genotyping of BKV was performed successfully in 50 out of the 82 patients, with 36 out of 50 (72%) belonging to the BKV-I subtype and 14 out of 50 (28%) belonging to the BKV-IV subtype; no cases of genotypes II or III were observed. Using phylogenetic analysis of the subgroups, the BKV-I/b-1 subtype was found the predominant subgroup (100%), whereas BKV-IV included 21.43% of IV/a-1, 6.67% of IV/a-2, and 50% of IV/c-1, respectively. There remain 3 cases of BKV-IV (21.43%) that could not be categorized into any subgroups. In the 6 patients diagnosed BKVN, 5 of them were infected with subgroup I/b-1 (83.3%) and 1 patient was infected with subgroup IV/c-1 (16.7%). No significant difference between BKV genotypes was observed in relation to age, sex, HLA mismatch, viral load, BKVN, and immunosuppressive therapy.

CONCLUSIONS

This research indicated a high prevalence of BKV infection and BKV-I was predominant, followed by BKV-IV among recipients of renal transplant in Vietnam.

Clinical Significance of Mycophenolate Mofetil Withdrawal in Kidney Transplant Recipients

INTRODUCTION

The most effective immunosuppressant protocol in kidney transplantation (KT) is the combination of a calcineurin inhibitor, steroid, and mycophenolate mofetil (MMF) until now. However, MMF withdrawal (MW) is performed for many reasons, and the clinical course of the KT recipients after MW is not clearly known. The purpose of this study was to investigate the clinical outcomes of KT after MW.

MATERIALS AND METHODS

We retrospectively analyzed the medical records of 626 KT recipients between 2000 and 2016. We evaluated the incidence of biopsy-proven acute rejection (BPAR), graft and patient survival rates, and risk factors related with graft failure.

RESULTS

The proportion of MW was 33.2% (208 of 626 patients). The median time between KT and MW was 6.4 months (range, 3.2-32.1 months). The common causes of MW were infection (70.7%), hematologic abnormalities (9.1%), and gastrointestinal trouble (7.7%). The incidence of BPAR was significantly higher in the MW group compared with the MMF continuation group (27.4% vs 8.9%, respectively, P < .001). Death-censored graft survival and patient survival rates were significantly lower in the MW group compared with the MMF continuation group (P < .001; P < .001, respectively). In the multivariate analysis, BPAR after MW was an independent risk factor for graft failure (hazard ratio 6.058, 95% confidence interval, 3.172-11.569, P < .001).

CONCLUSIONS

The incidence of rejection, graft failure, and patient mortality in KT were high after MW. Therefore, MW should be considered carefully.

BK viremia and nephropathy in pediatric renal transplant recipients

The renal survival rate of pediatric renal transplant recipients (pRTR) has improved with the use of modern immunosuppressive agents; however, the incidence of post-transplantation viral infection has increased. This study investigated the incidence of BK viremia and BK viral-associated nephropathy (BKVAN) in pRTR. One-hundred-and-thirty-four pRTR were divided into two groups: group 1 (n = 20, 14.9%) comprised those who were prospectively followed with longitudinal analyses after renal transplantation in the time period from May 2007 to June 2008, while group 2 (n = 114, 85.1%) cross-sectional study of those who were transplanted from January 1994 to April 2007. The mean ages at transplantation in groups 1 and 2 were 10.6 ± 4.7 years and 7.8 ± 4.5 years, respectively. BK viremia was detected in four (20.0%) patients in group 1, and seven (6.1%) in group 2 (P = 0.04), with increased incidence associated with induction therapy. The median time to detection of BK viremia after transplantation was 44 days in group 1 and 142 days in group 2. BKVAN was diagnosed in three patients (two in group 1 and one in group 2). All three patients diagnosed with BKVAN were receiving tacrolimus, mycophenolate mofetil, and corticosteroids as maintenance immunosuppression. Reducing immunosuppression resulted in reduced BK viremia. Monitoring for BK viremia and BKVAN is important in pRTR being treated with the current immunosuppressive regimen. The first line of treatment for BK viremia remains careful reduction of immunosuppression and close monitoring of renal allograft function.