Structural implications of BK polyomavirus sequence variations in the major viral capsid protein Vp1 and large T-antigen: a computational study

BK polyomavirus (BKPyV) is a double-stranded DNA virus causing nephropathy, hemorrhagic cystitis, and urothelial cancer in transplant patients. The BKPyV-encoded capsid protein Vp1 and large T-antigen (LTag) are key targets of neutralizing antibodies and cytotoxic T-cells, respectively. Our single-center data suggested that variability in Vp1 and LTag may contribute to failing BKPyV-specific immune control and impact vaccine design. We, therefore, analyzed all available entries in GenBank (1516 VP1; 742 LTAG) and explored potential structural effects using computational approaches. BKPyV-genotype (gt)1 was found in 71.18% of entries, followed by BKPyV-gt4 (19.26%), BKPyV-gt2 (8.11%), and BKPyV-gt3 (1.45%), but rates differed according to country and specimen type. Vp1-mutations matched a serotype different than the assigned one or were serotype-independent in 43%, 18% affected more than one amino acid. Notable Vp1-mutations altered antibody-binding domains, interactions with sialic acid receptors, or were predicted to change conformation. LTag-sequences were more conserved, with only 16 mutations detectable in more than one entry and without significant effects on LTag-structure or interaction domains. However, LTag changes were predicted to affect HLA-class I presentation of immunodominant 9mers to cytotoxic T-cells. These global data strengthen single center observations and specifically our earlier findings revealing mutant 9mer epitopes conferring immune escape from HLA-I cytotoxic T cells. We conclude that variability of BKPyV-Vp1 and LTag may have important implications for diagnostic assays assessing BKPyV-specific immune control and for vaccine design.

IMPORTANCE

Type and rate of amino acid variations in BKPyV may provide important insights into BKPyV diversity in human populations and an important step toward defining determinants of BKPyV-specific immunity needed to protect vulnerable patients from BKPyV diseases. Our analysis of BKPyV sequences obtained from human specimens reveals an unexpectedly high genetic variability for this double-stranded DNA virus that strongly relies on host cell DNA replication machinery with its proof reading and error correction mechanisms. BKPyV variability and immune escape should be taken into account when designing further approaches to antivirals, monoclonal antibodies, and vaccines for patients at risk of BKPyV diseases.

Visual, rapid, and cost-effective BK virus detection system for renal transplanted patients using gold nanoparticle coupled loop-mediated isothermal amplification (nanoLAMP)

A substantial percentage of kidney transplant recipients show transplant failure due to BK virus-induced nephropathy. This can be clinically controlled by the rapid and timely detection of BK virus infection in immune-compromised patients. We report a rapid (two hours from sample collection, processing, and detection), cost-effective (< 2$), highly sensitive and BKV-specific nanoLAMP (loop-mediated isothermal amplification) diagnostic methodology using novel primers and gold nanoparticles complex-based visual detection. The standardized nanoLAMP showed an analytical sensitivity of 25 copies/µl and did not cross-react with closely related JC and SV40 viruses. This nanoLAMP showed diagnostic sensitivity and specificity as 91% and 96%, respectively, taking 50 BK virus-negative (confirmed by qPCR from the plasma of healthy donors) and 57 positive BKV patient samples (confirmed by clinical parameters and qPCR assay). This simple two-step, low-cost, and quick (1-2 h/test) detection would be advantageous over the currently used diagnostic methodology. It may change the paradigm for polyomavirus infection-based failure of renal transplant.

Fatal outcome of BK virus encephalitis in an allogeneic stem cell transplantation recipient

BK virus (BKV) encephalitis is a rare complication after hematopoietic stem cell transplantation (HSCT). A 43-year-old woman with recurrent follicular lymphoma after autologous HSCT received allogeneic bone marrow transplantation from a human leukocyte antigen-matched related donor. Neutrophil engraftment was achieved on post-transplant day 13. Memory loss and noncooperative attitude toward the medical staff were observed on day 16, and her mental status worsened progressively. Magnetic resonance imaging (MRI) showed nonspecific findings on day 19; however, cerebrospinal fluid (CSF) analysis including real-time polymerase chain reaction on day 20 revealed elevated levels of BKV 4.67 × 104 copy/mL. BKV encephalitis was diagnosed based on CSF findings, intravenous administration of immunoglobulin and cidofovir was started, and the immunosuppressive agent dose was reduced. Diffusion-weighted MRI on day 28 showed signal abnormalities in the bilateral periventricular white matter. Although the follow-up CSF analysis on day 35 was negative for BKV, her mental status and MRI findings did not improve, and she died on day 55 because of respiratory failure. This case emphasizes the importance of considering BKV encephalitis as a differential diagnosis of post-transplant encephalitis, considering the central nervous system-associated immune reconstitution inflammatory syndrome in patients with worsening central nervous system findings after eradication of BKV in the CSF.

Accuracy of quantitative viral secondary standards: a re-examination

Interlaboratory agreement of viral load assays depends on the accuracy and uniformity of quantitative calibrators. Previous work demonstrated poor agreement of secondary cytomegalovirus (CMV) standards with nominal values. This study re-evaluated this issue among commercially produced secondary standards for both BK virus (BKV) and CMV, using digital polymerase chain reaction (dPCR) to compare the materials from three different manufacturers. Overall, standards showed an improved agreement compared to prior work, against nominal values in both log10 copies/mL and log10 international unit (IU)/mL, with bias from manufacturer-assigned nominal values of 0.0-0.9 log10 units (either copies or IU)/mL. Standards normalized to IU and those values assigned by dPCR rather than by real-time PCR (qPCR) showed better agreement with nominal values. The latter reinforces prior conclusions regarding the utility of using such methods for quantitative value assignment in reference materials. Quantitative standards have improved over the last several years, and the remaining bias from nominal values might be further reduced by universal implementation of dPCR methods for value assignment, normalized to IU.

IMPORTANCE

Interlaboratory agreement of viral load assays depends on accuracy and uniformity of quantitative calibrators. Previous work, published in JCM several years ago, demonstrated poor agreement of secondary cytomegalovirus (CMV) standards with nominal values. This study re-evaluated this issue among commercially produced secondary standards for both BK virus (BKV) and CMV, using digital polymerase chain reaction (dPCR) to compare the materials from three different manufacturers. Overall, standards showed an improved agreement compared to prior work, against nominal values, indicating a substantial improvement in the production of accurate secondary viral standards, while supporting the need for further work in this area and for the broad adaption of international unit (IU) as a reporting standard for quantitative viral load results.

Cidofovir for Viral Infections in Immunocompromised Children: Guidance on Dosing, Safety, Efficacy, and a Review of the Literature

OBJECTIVE

To describe the use of cidofovir (CDV) for viral infections in immunocompromised children (IC) and provide guidance on dosing and supportive care.

DATA SOURCES

A PubMed search was conducted for literature published between 1997 and January 2022 using the following terms: cidofovir, plus children or pediatrics.

STUDY SELECTION AND DATA EXTRACTION

Limits were set to include human subjects less than 24 years of age receiving intravenous (IV) or intrabladder CDV for treatment of infections due to adenovirus, polyomavirus-BK (BKV), herpesviruses, or cytomegalovirus.

DATA SYNTHESIS

Data were heterogeneous, with largely uncontrolled studies. Conventional dosing (CDV 5 mg/kg/dose weekly) was commonly used in 60% (31/52) of studies and modified dosing (CDV 1 mg/kg/dose 3 times/week) was used in 17% (9/52) of studies, despite being off-label. Nephrotoxicity reported across studies totaled 16% (65/403 patients), which was higher for conventional dosing 29 of 196 patients (15%) than modified dosing 1 of 27 patients (4%). Saline hyperhydration and concomitant probenecid remain the cornerstones of supportive care, while some regimens omitting probenecid are emerging to target BKV.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

To our knowledge, this is the first comprehensive review of CDV use (indications, dosing, supportive care, response, and nephrotoxicity) in pediatric IC.

CONCLUSIONS

Effective utilization of CDV in IC remains challenging. Further prospective studies are needed to determine the optimal CDV dosing; however, less aggressive dosing regimens such as modified thrice weekly dosing or low dosing once weekly omitting probenecid to enhance urinary penetration may be reasonable alternatives to conventional dosing in some IC.

Proteome Analysis for Inflammation Related to Acute and Convalescent Infection

Infectious diseases are a significant burden in global healthcare. Pathogens engage with different host defense mechanisms. However, it is currently unknown if there are disease-specific immune signatures and/or if different pathogens elicit common immune-associated molecular entities to common therapeutic interventions. We studied patients enrolled through the Human Immunology Project Consortium (HIPC), which focuses on immune responses to various infections. Blood samples were collected and analyzed from patients during infection and follow-up time points at the convalescent stage. The study included samples from patients with Lyme disease (LD), tuberculosis (TB), malaria (MLA), dengue virus (DENV), and West Nile virus (WNV), as well as kidney transplant patients with cytomegalovirus (CMV) and polyomavirus (BKV) infections. Using an antibody-based assay, we quantified ~ 350 cell surface markers, cytokines, and chemokines involved in inflammation and immunity. Unique protein signatures were identified specific to the acute phase of infection irrespective of the pathogen type, with significant changes during convalescence. In addition, tumor necrosis factor receptor superfamily member 6 (TNR6), C-C Motif Chemokine Receptor 7 (CCR7), and C-C motif chemokine ligand-1 (CCL1) were increased in the acute and convalescent phases across all viral, bacterial, and protozoan compared to blood from healthy donors. Furthermore, despite the differences between pathogens, proteins were enriched in common biological pathways such as cell surface receptor signaling pathway and response to external stimulus. In conclusion, we demonstrated that irrespective of the pathogen type, there are common immunoregulatory and proinflammatory signals.

Management of severe BK viremia in a patient receiving a kidney transplant from a hepatitis C virus-positive donor: A case report

PURPOSE

A case of BK nephropathy in a kidney transplant recipient who received an organ from a hepatitis C virus (HCV)-positive donor is reported.

SUMMARY

A 66-year-old male negative for HCV with chronic kidney disease secondary to diabetic glomerulosclerosis received a kidney transplant from an HCV-viremic donor. His initial postoperative course was uncomplicated, and HCV treatment with glecaprevir/pibrentasvir was initiated after discharge. On postoperative day (POD) 60, the patient developed BK viremia and his mycophenolate mofetil dose was decreased. Over the next few months, the BK viral load increased, with mycophenolate mofetil stopped and the tacrolimus goal lowered in response. On POD 130, the patient was admitted for a hypertensive crisis and found to have decreased renal function. During this hospitalization, the patient received a course of intravenous immune globulin (IVIG). Despite an initial response to the modification of immunosuppression therapy and several courses of IVIG over the following months, the patient's renal function continued to decline. At 18 months after transplantation, the patient was restarted on dialysis and taken off all immunosuppression.

CONCLUSION

Utilization of organs from HCV-positive donors in HCV-negative recipients allows for expansion of the donor pool and facilitates shorter times on the waitlist. Although initial data in HCV-discordant transplantation did not find an increased risk for opportunistic infections, more recent studies have shown that such risk may be present. This case report describes a patient who developed BK viremia and eventual allograft failure after an HCV-discordant transplantation.

The molecular footprints of BK virus in the product of conception over the second and third gestational trimesters

OBJECTIVE

Prior studies have shown controversial results on the vertical transmission of BK virus (BKV). The present study aimed to assess the possibility of BKV vertical transmission from mother to fetus in the product of conception (embryo, fetuses, and/or placentas) over the three stages of pregnancy.

RESULTS

Of the 26 placental studied tissues, 6 were in the first trimester, and none of which were positive. Only one out of the 13 (7.7%) placental materials in the second trimester was positive. Only one out of 7 (14%) placental materials of the third trimester was positive. There were cases that no virus was detected in their placental but BKV was detected in their other tissues. Among 26 conceptuses, 17 (65%) were negative for BKV and 9 (34.6%) were positive, 7/13 (54%) were positive in the second, and 2/7 (29%) were positive in the third trimester fetuses. BKV was most frequently detected in the liver (eight cases), heart (three cases), and placenta (2 cases). There were cases that no virus was detected in their placental but BKV was detected in their other tissues.

An Unusual Presentation of Metastatic BK Virus-Associated Urothelial Carcinoma Arising in the Allograft, Persisting After Transplant Nephrectomy

We report a 32-year-old male 14 years post-living-related kidney transplant presenting with new-onset hematuria and BK viremia. He was found to have BK virus-associated urothelial carcinoma originating in the renal allograft with locally advanced disease and metastases to multiple sites. He also developed acute T-cell-mediated rejection in the setting of immunosuppression reduction for BK viremia prior to undergoing transplant nephrectomy. Eight months following transplant nephrectomy and immunosuppression cessation, distant metastases persisted with partial response to chemotherapy and immunotherapy. Here, we discuss this unique presentation and compare it with other BK virus-associated allograft carcinomas reported in the literature, in addition to discussing evidence for the role of BK virus in oncogenesis.

High grade urothelial carcinoma in kidney transplant patients with a history of BK viremia - Just a coincidence?

INTRODUCTION

Kidney transplant recipients (KTR) have a three-to-four-fold increased risk of developing urothelial carcinoma (UC) compared to the general population. BK polyoma virus (BKV) infection is known to affect approximately 15% of KTR. In vitro models support a potential pathogenic role for BKV in the development of UC. We describe a series of UC in kidney transplant recipients.

METHODS

Electronic patient records were searched to identify KTR with UC who had undergone kidney only or simultaneous kidney and pancreas transplantation in a single UK center between 2009 and 2015. Where available, stored pathological samples were retrieved, re-examined and stained for SV40 as a marker of BKV using standard staining protocols for kidney biopsy samples.

RESULTS

Fourteen KTR had developed UC post-transplant. Of these, 10 KTR had a history of BKV infection post-transplant. Six of these 10 KTR developed a rare micropapillary tumor subtype of UC which is typically only found in <1% of UC cases. All six micropapillary tumor samples stained positive for SV40, including samples from metastases. Three tumor samples were available from the four KTR with no history of BKV infection and were not micropapillary subtype and were negative for SV40. Three micropapillary tumors from immunocompetent patients were examined as controls and were negative for SV40.

CONCLUSIONS

These findings would support a pathogenic role for BK virus in the development of rare micropapillary subtype urothelial tumors in the kidney transplant population.

BK polyomavirus DNAemia in pancreas transplant recipients compared to pancreas-kidney recipients

BACKGROUND

BK polyomavirus (BKV) infection is a common complication of kidney transplantation. While BKV has been described in non-kidney transplant recipients, data are limited regarding its epidemiology and outcomes in pancreas transplant recipients.

METHODS

We conducted a retrospective cohort study of adults who underwent pancreas transplantation from 2010-2020. The primary outcome was BKV DNAemia. Secondary outcomes were estimated glomerular filtration rate (eGFR) reduction by 30%, eGFR < 30 mL/min/1.73 m2 , endstage kidney disease, and pancreas allograft failure. Cox regression with time-dependent variables was utilized.

RESULTS

Four hundred and sixty-six patients were analyzed, including 74, 46, and 346 with pancreas transplant alone (PTA), pancreas-after-kidney, or simultaneous pancreas-kidney transplants, respectively. PTA recipients experienced a lower incidence of BKV DNAemia (8.8% vs. 32.9%; p < .001) and shorter duration of DNAemia (median 28.0 vs. 84.5 days). No PTA recipients with BKV DNAemia underwent kidney biopsy or developed endstage kidney disease. Lymphopenia, non-PTA transplantation, and older age were associated with BKV DNAemia, which itself was associated with pancreas allograft failure (adjusted hazard ratio 2.14, 95% confidence interval 1.27-3.60; p = .004). Among PTA recipients, BKV DNAemia was not associated with eGFR reduction or eGFR < 30 mL/min/1.73 m2 .

CONCLUSIONS

BKV DNAemia was common among PTA recipients, though lower than a comparable group of pancreas-kidney recipients. However, BKV DNAemia was not associated with adverse native kidney outcomes and no PTA recipients developed endstage kidney disease. Conversely, BKV DNAemia was associated with pancreas allograft failure. Further studies are needed to estimate the rate of BKV nephropathy in this population, and further evaluate long-term kidney outcomes.

Does PTCY increase the risk of infections?

PTCY has been mainly used in haploidentical transplant (haploHSCT), but its use in matched donors allowed better evaluation of infectious risk conferred separately by PTCY or donor type. PTCY increased the risk of bacterial infections, both in haploidentical and matched donors, mainly pre-engraftment bacteremias. Bacterial infections, particularly due to multidrug-resistant Gram-negatives, were main causes of infection-related deaths. Higher rates of CMV and other viral infections were reported, mainly in haploHSCT. The role of donor might be more important than the role of PTCY. PTCY increased the risk of BK virus associated hemorrhagic cystitis, and seemed associated with higher risk of respiratory viral infections. Fungal infections were frequent in haploHSCT PCTY cohorts without mold active prophylaxis, but the exact role of PTCY needs to be established. Infections appear to be increased in patients receiving PTCY, although the exact role of GvHD prophylaxis and donor type can only be assessed in prospective trials.

Human polyomavirus 9 as a potential threat in kidney transplant recipients; lessons from BKPyV

As a therapeutic method, kidney transplantation significantly improved the life quality and prognosis of patients with the end-stage renal disease. Since a key element in stable kidney transplantation is continuous therapy with immunosuppressive agents, an inhibited immune response makes patients vulnerable to opportunistic viral and bacterial infections. Polyomavirus (PyV), from the Polyomaviridae family, includes a well-known BK virus (BKPyV) and less publicized human polyomavirus 9 (HPyV9). Both these viruses may inflict significant damage to kidney transplants because of their high prevalence and pathogenesis. While a great body of knowledge was accumulated about the BKPyV-caused nephropathy, much less information is about the potential threat from the HPyV9-caused damage to kidney transplants. The current review provides a glimpse of general information about the PyV-associated nephropathy with a special focus on the role of the HPyV9 in pathogenesis of nephropathy in kidney transplants.

Evaluating the Efficiency of the Cobas 6800 System for BK Virus Detection in Plasma and Urine Samples

We evaluated the overall performance of the Cobas 6800 BKV test in detecting BK virus (BKV). We examined the imprecision of the Cobas 6800 BKV test and compared the qualitative and quantitative results obtained from the Cobas 6800 BKV test and the Real-Q BKV quantification assay. We assessed 88 plasma and 26 urine samples collected between September and November 2022 from patients with BKV infection using the Real-Q BKV quantitative assay. The lognormal coefficient of variation indicated that the inter-assay precision of the Cobas 6800 BKV test ranged from 13.86 to 33.83%. A strong correlation was observed between the quantitative results obtained using the Cobas 6800 BKV test and the Real-Q BKV quantification assay for plasma samples. The Spearman's rank correlation coefficients (ρ) for plasma, polymerase chain reaction (PCR) media-stabilized urine, and raw urine samples were 0.939, 0.874, and 0.888, respectively. Our analyses suggest that the Cobas 6800 BKV test is suitable for clinical applications owing to the strong correlation between the results obtained using this test and the Real-Q BKV quantification assay in plasma and urine samples. Furthermore, utilizing fresh raw urine samples can be a viable approach for the Cobas 6800 BKV test as it is less labor- and time-intensive.

Role of human papillomavirus and associated viruses in bladder cancer: An updated review

Bladder cancer (BC) is a complex disease affecting the urinary system and is regulated by several carcinogenic factors. Viral infection is one such factor that has attracted extensive attention in BC. Human papillomavirus (HPV) is the most common sexually transmitted infection, and although multiple researchers have explored the role of HPV in BC, a consensus has not yet been reached. In addition, HPV-associated viruses (e.g., human immunodeficiency virus, herpes simplex virus, BK virus, and JC virus) appear to be responsible for the occurrence and progression of BC. This study systematically reviews the relationship between HPV-associated viruses and BC to elucidate the role of these viruses in the onset and progression of BC. In addition, the study aims to provide a greater insight into the biology of HPV-associated viruses, and assess potential strategies for treating virus-induced BC. The study additionally focuses on the rapid development of oncolytic viruses that provide a potentially novel option for the treatment of BC.

Recurrent C3 Glomerulonephritis along with BK-Virus-Associated Nephropathy after Kidney Transplantation: A Case Report

C3 glomerulonephritis (C3GN) is a rare cause of end-stage kidney disease and frequently recurrent in allografts following kidney transplantation (KT). Herein, we describe the case of a kidney transplant recipient who developed recurrent C3GN along with BK-virus-associated nephropathy (BKVAN) following KT. A 33-year-old man diagnosed with membranoproliferative glomerulonephritis 17 years ago underwent preemptive KT with a donor kidney from his aunt. Proteinuria gradually increased after 3 months following KT, and graft biopsy was performed 30 months after KT. Histopathological examination revealed recurrent C3GN. The dosages of triple immunosuppressive maintenance therapy agents were increased. Subsequently, serum C3 levels recovered to normal levels. However, at 33 months following KT, the BK viral load increased and graft function gradually deteriorated; a second graft biopsy was performed at 46 months following KT, which revealed BKVAN and decreased C3GN activity. The dosages of immunosuppressive agents were decreased; subsequently, BKVAN improved and graft function was maintained with normal serum C3 levels at 49 months following KT. This case indicates that C3GN is highly prone to recurrence following KT and that immunosuppressive therapy for C3GN increases the risk of BKVAN.

Pathological Approach to Kidney Allograft Infection

Infectious agents can pose a significant challenge in kidney transplantation, as they have the potential to cause direct infections in the transplanted kidney. These infections can lead to a decline in kidney function and reduce the longevity of the transplanted kidney. Common post-transplant allograft infections include bacterial pyelonephritis and the BK virus infection, while adenovirus, JC virus, and cytomegalovirus are less frequent but can also lead to significant allograft dysfunctions. The histopathological features of these infections are characterized by the infiltration of inflammatory cells in the kidney interstitial area and the presence of viral nuclear inclusions or cytopathic changes in the renal tubular epithelial cells. The confirmation of causative organisms can be achieved by immunohistochemical staining or the visualization of viral particles using electron microscopic examination. However, these methods typically require a longer turnaround time and are not readily available in developing countries, unlike standard hematoxylin-eosin staining. Notably, the differential diagnosis of interstitial inflammation in kidney allografts almost always includes T cell-mediated rejection, which has a different treatment approach than allograft infections. The aim of this review was to prompt clinicians to identify diverse pathological alterations as observed in kidney allograft biopsies, thereby facilitating further investigations and the management of suspected kidney allograft infections.

Decreased lymphocyte count before conditioning is associated with BK virus-associated hemorrhagic cystitis after allogeneic hematopoietic stem cell transplantation

BACKGROUND

BK virus-associated hemorrhagic cystitis (BKV-HC) is a serious complication after allogeneic hematopoietic stem cell transplantation (allo-HSCT). It can cause morbidity and may increase treatment-related mortality. Previous studies showed that the occurrence of BKV-HC was related to various factors. However, there are still many controversial factors. It is not clear whether BKV-HC will affect the long-term prognosis of patients.

OBJECTIVE

We aimed to identify risk factors for BKV-HC after allo-HSCT and evaluate the effect of BKV-HC on overall survival (OS) and progression- free survival (PFS) of patients.

STUDY DESIGN

We retrospectively analyzed the clinical data of 93 patients who underwent allo-HSCT. Univariate and multivariate analysis were used to identify risk factors for BKV-HC. The Kaplan-Meier method was used to estimate OS and PFS. A difference was considered statistically significant if P < 0.05.

RESULTS

A total of 24 patients developed BKV-HC. The median occurrence time of BKV-HC was 30 (range:8-89) days after transplantation, and the median duration was 25.5 (range:6-50) days. Multivariate logistic regression analysis indicated that peripheral blood lymphocyte count <1 × 10⁹/L before conditioning (OR = 4.705, P = 0.007) and haploidentical transplantation (OR = 13.161, P = 0.018) were independent risk factors for BKV-HC. The 3-year OS rate was 85.9% (95%CI:62.1%-95.2%) in the BKV-HC group and 73.1% (95%CI: 58.2%-88.0%) in the non-BKV-HC group. There was no significant difference between the two groups (P = 0.516). The 3-year PFS rate was 76.3% (95%CI: 57.9%-94.7%) in the BKV-HC group and 58.1% (95%CI: 39.5%-76.7%) in the non-BKV-HC group. There was no significant difference in the two groups (P = 0.459). The severity of BKV-HC was not related to the OS and PFS of the patients (P value was 0.816 and 0.501, respectively).

CONCLUSION

Haploidentical transplantation and decreased peripheral blood lymphocyte count before conditioning increased the risk of BKV-HC after allo-HSCT. The occurrence of BKV-HC after allo-HSCT and the severity of which did not affect OS and PFS of the patients.

Detection of JCV or BKV viruria and viremia after kidney transplantation is not associated with unfavorable outcomes

Studies analyzing the relationship between BK polyomavirus (BKV) or JC polyomavirus (JCV) infection and kidney transplant (KT) long term clinical outcomes are scarce. Therefore, we evaluated this relationship in a single-center retrospective cohort of 288 KT patients followed for 45.4(27.5; 62.5) months. Detection of BKV viremia in two consecutive analyses led to discontinuation of antimetabolite and initiation of mammalian target of rapamycin inhibitor. Outcome data included de novo BKV and/or JCV viremia and/or viruria after KT, death-censored graft survival and patient survival. BKV viruria and viremia were detected in 42.4% and 22.2% of KT recipients, respectively. BKV viremic patients had higher urinary BKV viral loads at the onset of viruria, when compared to nonviremic patients (7 log₁₀ vs. 4.9 log₁₀  cp/mL, p < 0.001). JCV viruria was identified in 38.5% of KT patients; the 5.9% of KT recipients who developed JCV viremia had higher JCV urinary viral loads at the onset of viruria, when compared to non-viremic patients (5.3 vs. 3.7 log₁₀ cp/mL, p = 0.034). No differences were found in estimated glomerular filtration rate at the end of follow up, when comparing BKV or JCV viruric or viremic patients with nonviremic patients. No association was found between JCV or BKV viruria or viremia and death/graft failure. Therefore, higher BKV urinary viral loads at the onset could serve as an early maker of over immunosuppression. JCV and BKV replication was not associated with inferior clinical outcomes in KT patients with the above-mentioned immunosuppression strategy.

Long-Term Follow-Up after Adoptive Transfer of BK-Virus-Specific T Cells in Hematopoietic Stem Cell Transplant Recipients

The BK virus (BKV) causes severe hemorrhagic cystitis in hematopoietic stem cell transplant (HSCT) recipients. To eliminate reactivated BKV, symptomatic patients can be treated with a reduction of the immunosuppressive therapy, with the antiviral drug cidofovir, or with virus-specific T cells (VSTs). In the current study, we compared the effect of VSTs to other treatment options, following up specific T cells using interferon-gamma ELISpot assay. We observed BKV large T-specific cellular responses in 12 out of 17 HSCT recipients with BKV-related cystitis (71%). In recipients treated with VSTs, 6 out of 7 showed specific T-cell responses, and that number in those without VSTs was 6 out of 10. In comparison, 27 out of 50 healthy controls (54%) responded. In HSCT recipients treated for BKV-related cystitis, absolute CD4+ T-cell numbers and renal function correlated with BKV-specific cellular responses (p = 0.03 and 0.01, respectively). In one patient, BKV-specific cellular immunity could already be detected at baseline, on day 35 after HSCT and prior to VSTs, and remained increased until day 226 after VSTs (78 vs. 7 spots increment). In conclusion, the ELISpot appears to be suitable to sensitively monitor BKV-specific cellular immunity in HSCT recipients, even early after transplantation or in the long term after VSTs.

Regulation of Virus Replication by BK Polyomavirus Small T Antigen

Polyomavirus small T antigen (tAg) plays important roles in regulating viral replication, the innate immune response, apoptosis, and transformation for SV40, Merkel cell polyomavirus (MCPyV), murine polyomavirus (MuPyV), and JC polyomavirus (JCPyV). However, the function of BK polyomavirus (BKPyV) tAg has been much less studied. Here, we constructed mutant viruses that do not express tAg, and we showed that, in contrast with other polyomaviruses, BKPyV tAg inhibits large T antigen (TAg) gene expression and viral DNA replication. However, this occurs only in an archetype viral background. We also observed that the transduction of cells with a lentivirus-expressing BKPyV tAg kills the cells. We further discovered that BKPyV tAg interacts not only with PP2A A and C subunits, as has been demonstrated for other polyomavirus tAg proteins, but also with PP2A B''' subunit members. Knocking down either of two B''' subunits, namely STRN or STRN3, mimics the phenotype of the tAg mutant virus. However, a virus containing a point mutation in the PP2A binding domain of tAg only partially affected virus TAg expression and DNA replication. These results indicate that BKPyV tAg downregulates viral gene expression and DNA replication and that this occurs in part through interactions with PP2A. IMPORTANCE BK polyomavirus is a virus that establishes a lifelong infection of the majority of people. The infection usually does not cause any clinical symptoms, but, in transplant recipients whose immune systems have been suppressed, unchecked virus replication can cause severe disease. In this study, we show that a viral protein called small T antigen is one of the ways that the virus can persist without high levels of replication. Understanding which factors control viral replication enhances our knowledge of the virus life cycle and could lead to potential interventions for these patients.

BK Viremia and Changes in Estimated Glomerular Filtration Rate in Children and Young Adults after Hematopoietic Cell Transplantation

Kidney disease in allogeneic hematopoietic cell transplantation (HCT) recipients is associated with increased mortality rates. BK virus (BKV) viremia has been associated with kidney dysfunction in pediatric HCT recipients; however, few studies have investigated longer-term kidney outcomes in association with BKV in this population. Here we assessed the relationship between BK viremia and changes in estimated glomerular filtration rate (eGFR) in children in the first year post-HCT. We selected 136 patients age ≤26 years who underwent HCT in 2007 to 2018 at a single center and had plasma BK viral load data available at 2 time points, weeks 4 to 7 post-HCT and weeks 10 to 13 post-HCT from prospectively collected stored plasma samples. A total of 272 samples were analyzed for BKV using quantitative PCR. We used multivariate linear models to determine the association of BK viremia and change in eGFR by 1 year post-HCT. Forty percent of the patients (54 of 136) had BKV detection in weeks 4 to 7, 13% of whom (7 of 54) had a BK viral load of ≥10,000 copies/mL, and 46% (62 of 136) had BKV detected in weeks 10 to 13, 34% (21 of 62) of whom had a BK viral load of ≥10,000 copies/mL. The mean decline in eGFR was 25.73 mL/min/1.73 m² by 1 year post-HCT. In multivariate models, a BK viral load of ≥10,000 copies/mL during weeks 4 to 7 was associated with a mean decline in eGFR of 30.6 mL/min/1.73 m² (95% confidence interval, -55.94 to -5.17; P = .019) compared with a BK viral load <10,000 copies/mL. In adjusted analyses, a high BK viral load in the blood (≥10,000 copies/mL) was associated with a significant decline in eGFR by 1 year post-HCT.

BK virus genotypes and humoral response in kidney transplant recipients with BKV associated nephropathy

BACKGROUND

Among kidney transplant recipients (KTR) with BK virus associated nephropathy (BKVN), BKV genotypes' evolution and anti-BKV humoral response are not well established. We aim to analyze BKV replication and genetic evolution following transplantation, and characterize concomitant anti-BKV-VP1 humoral response.

METHODS

We retrospectively analyzed 32 cases of biopsy-proven BKVN. Stored plasma and kidney biopsies were tested for BKV viral load, and VP1 sequencing performed on positive samples. BKV-VP1 genotype-specific neutralizing antibodies (NAbs) titers were determined at transplantation and BKVN.

RESULTS

At the time of BKVN diagnosis, BKV viral load was 8.2 log₁₀ IU/10⁶ cells and 5.4 log₁₀ IU/mL in kidney and plasma, respectively. VP1 sequencing identified the same BKV-subtype in both compartments in 31/32 cases. At the time of transplantation, 8/20 (40%) of biopsies tested positive for BKV detection, whereas concomitant BKV viremia was negative. VP1 sequencing identified a different subtype compared to BKVN in 5/6 of these samples. This was confirmed following transplantation: 8 patients had a BKV+ biopsy before BKV viremia, and VP1 sequencing identified a different subtype compared to BKVN in all of them. After the onset of BKV viremia and prior to BKVN diagnosis, the BKV subtype in BKV+ plasma and kidney biopsy was the same as the one isolated at BKVN. BKV-VP1 NAbs titers were significantly higher at the time of BKVN compared to transplantation (p = .0031), with similar titers across genotypes.

CONCLUSION

Altogether, our data suggest that among some KTR with BKVN, the BKV genotype from the donor may not be responsible for BKVN pathogenesis.

Characteristics, risk factors and outcome of BKV nephropathy in kidney transplant recipients: a case-control study

BACKGROUND

Following kidney transplantation, BK virus associated nephropathy (BKVN) occurs in 1 to 10% of kidney transplant recipients (KTR) and represents a major cause of graft loss. We aim at identifying factors associated with biopsy proven BKVN among KTR.

METHODS

We conducted a retrospective case-control study including all KTR with a biopsy-proven diagnosis of BKVN between 2005 and 2019. Clinical characteristics and outcome were described. For each case, one control KTR without BKV infection was identified and matched by age, transplant date, and donor status. Factors associated with BKVN diagnosis were identified using exact conditional logistic regression. Comparative survival was described using Kaplan-Meier estimator.

RESULTS

Sixty-four cases of BKVN were identified among 1737 new kidney transplantation (3.7% prevalence). Clinical characteristics did not differ between groups, except for a higher c-PRA among cases. BKVN occurred in a median time of 11 (5-14.5) months after KT, and was associated with a significantly impaired graft function at diagnosis. Following BKVN, 61 (95%) of the patients had immunosuppression reduction, which led to BKV DNAemia resolution in 49% of cases. In multivariate analysis, factors associated with BKVN diagnosis were lymphopenia < 500/mm³ and a prednisone dose > 7.5 mg/day. Median duration of follow-up was 40 months for both groups. BKVN was associated with a significantly increased risk of graft rejection (P = 0.02) and return to dialysis (P = 0.01).

CONCLUSIONS

BKVN remains a severe complication in KTR and is associated with an increased risk for acute rejection and return to dialysis. Lymphopenia below 500/mm³ and corticosteroid maintenance therapy are significantly associated with biopsy-proven BKVN diagnosis.

Screening for polyomavirus nephropathy and viremia in children with renal transplantation

BACKGROUND

Polyomavirus, known as BK virus, is an important cause of allograft dysfunction in renal transplant patients, leading to BK virus nephropathy. The main study objectives were to assess the disease incidence and disease course in pediatric patients, and assess the diagnostic accuracy of BK screening for asymptomatic patients.

METHODS

This is a single-center observational study, which included 81 pediatric renal allograft recipients that were transplanted and/or followed at King Fahad Specialist Hospital-Dammam, Saudi Arabia. Screening for BK virus was performed prospectively according to a predetermined hospital protocol. Our BK screening protocol consisted of periodic quantitative real time polymerase chain reaction test in the plasma. In patients with deranged graft function, graft biopsies were evaluated for the presence of BK nephropathy.

RESULTS

Our study detected BK viremia in 14 patients (17.3%), while BK nephropathy occurred in seven patients (8.6%). The onset of BK viremia had bimodal distribution, 78 percent occurring within first year post-transplantation, while 21.4% occurred late. Patients who developed BK nephropathy had a higher BK level than BK viremia patients, for both mean and peak values (p = .02, p = .02). A BK cutoff level of 40 000 copies/mL showed sensitivity and specificity of 85.7%, 85.7%, respectively, in predicting the conversion of BK viremia to BK nephropathy.

CONCLUSIONS

BK viremia and BK nephropathy occur in pediatric patients with similar incidence rates compared to adult patients. Protocolized screening led to early detection of viremia, and could predict the conversion of BK viremia to BK nephropathy and allow for early immunosuppression modulation.

[Haemorrhagic cystitis following hematopoietic stem cell transplantation: Prophylaxis, diagnosis, and treatment. Guidelines from the SFGM-TC]

Hemorrhagic cystitis (HC) is a common complication after allogeneic hematopoietic cell transplantation (allo-HCT). Its manifestations range from microscopic hematuria without urinary symptoms to extensive and prolonged macroscopic hemorrhage requiring invasive interventions that can often prolong the duration of hospitalization and result in significant morbidity. The early onset of HC is related to allo-HCT conditioning regimen, whereas the late onset form is secondary to viral infection, most commonly due to BK virus. In the framework of the Francophone Society of Bone Marrow Transplantation and Cellular Therapy (SFGM-TC) practice harmonization workshops held in Lille in September 2021, the prophylaxis, the diagnostic approach and the treatments of HC following allografting were reviewed after analysis of published studies.

Development of de novo donor-specific antibodies in renal transplant recipients with BK viremia managed with immunosuppression reduction

BACKGROUND

Reduction of immunosuppression (IS) upon detection of Polyomavirus (BK) viremia is widely used to prevent BK virus nephropathy. This retrospective case-control study assesses the frequency of de novo donor-specific antibodies (dnDSA) in renal transplant recipients with IS modulation due to BK viremia and the associated risk of antibody mediated rejection.

METHODS

Our cohort included recipients of kidney transplantation between 2007 and 2017 with clinical, HLA antibody, and biopsy data. BK positivity was defined as viremia >10 000 c/ml or biopsy proven BK nephropathy. A total of 190 BK cases matched our inclusion criteria, each case was matched with two controls based on gender, donor type, and transplant within 1 year (N = 396).

RESULTS

Despite lower number of HLA antigen mismatches (mean = 3.5 vs. 4.4, p < .001), dnDSA rates were higher in BK cases than in control group (22.1% vs. 13.9%, p = .02), with the majority detected following IS reduction for BK infection, and arising earlier posttransplant compared with no BK infection (294d vs. 434d, p < .001). Antibody mediated rejection rates were similar between cases and controls (8.9% and 8.3%, respectively), but rejection was more likely to occur earlier posttransplant in the BK cases (354d vs. 602d, p = .03).

CONCLUSION

Our data suggest a link between IS reduction and the generation of dnDSA and/or rejection, supporting close monitoring for DSA in patients with reduced IS due to BK infection given their increased risk to develop dnDSA.

Undetectable JC virus CSF PCR in patients with JC virus-induced progressive multifocal leukoencephalopathy

The diagnosis of progressive multifocal leukoencephalopathy (PML) is based on a combination of clinical, radiographic, and laboratory findings. However, negative JC polyomavirus (JCPyV) PCR in CSF does not always rule out JCPyV-related PML. In this narrative review, we sought to examine the characteristic of biopsy-proven PML in patients with undetectable JCPyV CSF PCR and provide alternative approaches in this scenario.

Rapid point-of-care detection of BK virus in urine by an HFman probe-based loop-mediated isothermal amplification assay and a finger-driven microfluidic chip

Background

BK virus (BKV)-associated nephropathy (BKVN) is one of the leading causes of renal dysfunction and graft loss in renal transplant recipients. Early monitoring of BKV in urine is crucial to minimize the deleterious effects caused by this virus on preservation of graft function.

Methods

We report a simple, rapid, sensitive loop-mediated isothermal amplification (LAMP) assay using an HFman probe for detecting BKV in urine. To evaluate the performance of the assay, a comparison of the HFman probe-based LAMP (HF-LAMP) assay with two qPCR assays was performed using urine samples from 132 HIV-1 infected individuals. We further evaluated the performance of HF-LAMP directly using the urine samples from these HIV-1 infected individuals and 30 kidney transplant recipients without DNA extraction. Furthermore, we combined the HF-LAMP assay with a portable finger-driven microfluidic chip for point-of-care testing (POCT).

Results

The assay has high specificity and sensitivity with a limit of detection (LOD) of 12 copies/reaction and can be completed within 30 min. When the DNA was extracted, the HF-LAMP assay showed an equivalent and potentially even higher sensitivity (93.5%) than the qPCR assays (74.2-87.1%) for 132 urine samples from HIV-1 infected individuals. The HF-LAMP assay can be applied in an extraction-free format and can be completed within 45 min using a simple heat block. Although some decreased performance was seen on urine samples from HIV-1 infected individuals, the sensitivity, specificity, and accuracy of the extraction-free BKV HF-LAMP assay were 95%, 100%, and 96.7% for 30 clinical urine samples from kidney transplant recipients, respectively.

Conclusion

The assay has high specificity and sensitivity. Combined with a portable finger-driven microfluidic chip for easy detection, this method shows great potential for POCT detection of BKV.

In silico design and evaluation of a novel mRNA vaccine against BK virus: a reverse vaccinology approach

Human polyomavirus type 1, or BK virus (BKV), is a ubiquitous pathogen belonging to the polyomaviridae family mostly known for causing BKV-associated nephropathy (BKVN) and allograft rejection in kidney transplant recipients (KTRs) following the immunosuppression regimens recommended in these patients. Reduction of the immunosuppression level and anti-viral agents are the usual approaches for BKV clearance, which have not met a desired outcome yet. There are also debating matters such as the effect of this pathogen on emerging various comorbidities and the related malignancies in the human population. In this study, a reverse vaccinology approach was implemented to design a mRNA vaccine against BKV by identifying the most antigenic proteins of this pathogen. Potential immunogenic T and B lymphocyte epitopes were predicted through various immunoinformatic tools. The final epitopes were selected according to antigenicity, toxicity, allergenicity, and cytokine inducibility scores. According to the obtained results, the designed vaccine was antigenic, neutral at the physiological pH, non-toxic, and non-allergenic with a world population coverage of 93.77%. Since the mRNA codon optimization ensures the efficient expression of the vaccine in a host cell, evaluation of different parameters showed our designed mRNA vaccine has a stable structure. Moreover, it had strong interactions with toll-like receptor 4 (TLR4) according to the molecular dynamic simulation studies. The in silico immune simulation analyses revealed an overall increase in the immune responses following repeated exposure to the designed vaccine. Based on our findings, the vaccine candidate is ready to be tested as a promising novel mRNA therapeutic vaccine against BKV.

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

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

Cidofovir-induced anterior uveitis in an allogeneic stem cell transplant recipient

Anterior uveitis is a reported complication of intravenous cidofovir, almost exclusively described in human immunodeficiency virus (HIV) infected patients treated for cytomegalovirus retinitis. In this study, we report the case of an allogeneic stem cell transplant recipient with significant visual impairment and hypotony following administration of high-dose intravenous cidofovir for hemorrhagic cystitis due to BK virus.

Incidence, risk factors, outcomes, and clinical management of BK viremia in the modern era of kidney transplantation

BK viremia is endemic among kidney transplant recipients (KTRs). Incidence, risk factors, outcomes, and clinical management of detectable versus high BK viremia have not been considered previously in KTR in the modern era. This observational study examined KTR transplanted between January 1, 2009 and December 31, 2016. Any BK viral load in the serum constituted detectable BK viremia and ≥10³ copies/ml constituted high viremia. Among 1193 KTRs, the cumulative probability of developing detectable and high BK viremia within 2 years posttransplant were 27.8% and 19.6%, respectively. Significant risk factors for detectable BK viremia included recipient age (HR 1.02 [95% CI: 1.01, 1.03]) and donor age (HR 1.01 [95% CI: 1.00, 1.02]). Recipient age also predicted high BK viremia (HR 1.02 [95% CI: 1.01, 1.03]), whereas White race (HR 0.70 [95% CI: 0.52, 0.95]), nondepleting induction therapy (HR 0.61 [95% CI: 0.42, 0.89]), and delayed graft function (HR 0.61 [95% CI: 0.42, 0.88]) were protective. Mean estimated glomerular filtration rates were 4.28 ml/min/1.72 m² (95% CI: 2.71, 5.84) lower with detectable BK viremia. Although low viral load was usually not acted upon at first presentation, antiproliferative dose reductions were the most common initial management. BK viremia remains a common early complication in a modern cohort of KTRs. These findings highlight the benefit of early BKV monitoring in addition to intensive clinical management. Clinical responses beyond first positive BK viremia tests, and their implications for graft outcomes, merit further investigation.

Proteomic analysis of urinary extracellular vesicles of kidney transplant recipients with BKV viruria and viremia: A pilot study

INTRODUCTION

To better define the biological machinery associated with BK virus (BKV) infection, in kidney transplantation, we performed a proteomics analysis of urinary extracellular vesicles (EVs).

METHODS

Twenty-nine adult kidney transplant recipients (KTRs) with normal allograft function affected by BKV infection (15 with only viremia, 14 with viruria and viremia) and 15 controls (CTR, KTRs without BKV infection) were enrolled and randomly divided in a training cohort (12 BKV and 6 CTR) used for the mass spectrometry analysis of the EVs (microvesicles and exosomes) protein content and a testing cohort (17 BKV and 9 CTR) used for the biological validation of the proteomic results by ELISA. Bioinformatics and functional analysis revealed that several biological processes were enriched in BKV (including immunity, complement activation, renal fibrosis) and were able to discriminate BKV vs. CTR. Kinase was the only gene ontology annotation term including proteins less abundant in BKV (with SLK being the most significantly down-regulated protein). Non-linear support vector machine (SVM) learning and partial least squares discriminant analysis (PLS-DA) identified 36 proteins (including DNASE2, F12, AGT, CTSH, C4A, C7, FABP4, and BPNT1) able to discriminate the two study groups. The proteomic profile of KTRs with BKV viruria alone vs. viremia and viruria was quite similar. Enzyme-linked immunosorbent assay (ELISA) for SLK, BPNT1 and DNASE2, performed on testing cohort, validated proteomics results.

DISCUSSIONS

Our pilot study demonstrated, for the first time, that BKV infection, also in the viruric state, can have a negative impact on the allograft and it suggested that, whether possible, an early preventive therapeutic strategy should be undertaken also in KTRs with viruria only. Our results, then, revealed new mechanistic insights into BKV infection and they selected potential biomarkers that should be tested in future studies with larger patients' cohorts.

A rare case of BK virus non-hemorrhagic cystitis following lung transplant

BK virus cystitis is known to occur following hematopoietic stem cell transplant (HSCT), but few cases exist in the literature following lung transplant. Because of the rarity of this presentation, patients may have missed diagnoses and prescribed ineffective treatments. We present our case of an atypical presentation of BK virus cystitis appearing as bladder carcinoma in situ in a lung transplant patient.

Daily low dose intravesical cidofovir for the treatment of BK virus associated hemorrhagic cystitis after allogeneic stem cell transplantation

INTRODUCTION

BK virus associated hemorrhagic cystitis(BKV-AHC) is a serious complication observed after allogeneic stem cell transplantation and the current therapeutic options are scarce with substantial renal side effects. Although the guidelines recommend intravenous cidofovir application with caution to nephrotoxicity, there are few studies which investigated intravesical administration and reported similar therapeutic results with less renal side effects.

METHODS

We administered low dose, daily and consecutive (75 mg/day, for 5 days) intravesical cidofovir to 25 patients with BKV-AHC that developed after (ASCT).

RESULTS

The response rate in our cohort was 92% and relapse was not encountered in 84% of the patient population during one year of follow-up. The median BK urine viral load significantly decreased from 260,000,000 IU/mL to 53,000,000 IU/mL after a week of treatment (p = 0.0001). Rise in serum creatinine was observed in 5 patients during treatment and post-treatment nephrotoxicity was seen in only 1 patient.

CONCLUSIONS

Daily low dose intravesical cidofovir might be an effective treatment option for BKV-AHC after ASCT with favorable less systemic side effects.

Matrix Matters: Assessment of Commutability among BK Virus Assays and Standards

Quantitative testing of BK virus (BKPyV) nucleic acid has become the standard of care in transplant patients. While the relationship between interassay harmonization and commutability has been well characterized for other transplant-related viruses, it has been less well studied for BKPyV, particularly regarding differences in commutability between matrices. Here, interassay agreement was evaluated among six real-time nucleic acid amplification tests (NAATs) and one digital PCR (dPCR) BKPyV assay. Differences in the commutability of three quantitative standards was examined across all assays using a variety of statistical approaches. Panels, including 40 samples each of plasma and urine samples previously positive for BKPyV, together with one previously negative plasma sample and four previously negative urine samples, were tested using all assays, with each real-time NAAT utilizing its usual quantitative calibrators. Serial dilutions of WHO, National Institute for Standards and Technology (NIST), and commercially produced (Exact/Bio-Rad) reference materials were also run by each assay as unknowns. The agreement of the clinical sample values was assessed as a group and in a pairwise manner. The commutability was estimated using both relativistic and quantitative means. The quantitative agreement across assays in the urine samples was within a single log10 unit across all assays, while the results from the plasma samples varied by 2 to 3 log10 IU/mL. The commutability showed a similar disparity between the matrices. Recalibration using international standards diminished the resulting discrepancies in some but not all cases. Differences in the sample matrix can affect the commutability and interassay agreement of quantitative BKPyV assays. Differences in commutability between matrices may largely be due to factors other than those such as amplicon size, previously described as important in the case of cytomegalovirus. Continued efforts to standardize viral load measurements must address multiple sources of variability and account for differences in assay systems, quantitative standards, and sample matrices.

Correlation between CYP3A5 gene polymorphism and BK virus infection in kidney transplant recipients

BACKGROUND

Cytochrome P450 3A5 (CYP3A5) includes two active genotypes, namely CYP3A5*1/*1 or *1/*3 with the fast metabolic activity and CYP3A5*3/*3 with slow metabolic. We retrospectively analyzed the correlation between CYP3A5 gene polymorphism and the susceptibility to the BK virus (BKV) infection in renal transplant recipients.

METHODS

According to the inclusion/ exclusion criteria, we selected 134 recipients who received kidney transplantation at the Renmin Hospital of Wuhan University from January 2019 to December 2019. Based on the pre-operative CYP3A5 sequencing results, 134 recipients were divided into two groups: those expressing the fast metabolic CYP3A5*1/*1 or *1/*3 genotype; and, those expressing slow metabolic CYP3A5*3/*3 genotype. These two recipient groups were then analyzed for the BKV infection rate with different metabolic types to establish the potential relationship between CYP3A5 gene polymorphism and BKV infection.

RESULTS

The overall incidence of BKV viruria was 37.3%, whereas BKV viremia was 4.5% among all 134 recipients. The fast metabolism group had 9.1% incidence of BKV viremia and 49.1% incidence of BKV viruria. In contrast, the slow metabolism group had only 1.3%incidence of BKV viremia (P = 0.031) with only 29.1% BKV viruria (P = 0.011). The incidence of low levels of urinary BKV in the fast metabolism group was higher than that in the slow metabolism group (P = 0.005), while no significant statistical difference in the incidence of high levels of urinary BKV and high and low levels of blood BKV.

CONCLUSION

After kidney transplantation, CYP3A5 gene polymorphism of recipients present a certain relationship with the occurrence of BKV infection, which may be of value for the prediction and prevention of BKV infection.

Molecular characterization of BK virus detected in renal transplant patients in Sri Lanka: a preliminary study

Background & objectives

BK virus (BKV) is a polyomavirus and cause of a common infection after renal transplantation which could be preceded to BKV-associated nephropathy. It has four main subtypes (I-IV). BKV subtypes II and III are rare, whereas subtype I shows a ubiquitous distribution. The objective of the present study was to investigate the prevailing BKV subtypes and subgroups in renal transplant patients in Sri Lanka.

Methods

The presence of BKV in urine was tested through virus load quantification by real-time PCR from 227 renal transplant patients who were suspected to have BKV infection. Of these patients only 41 were found to be BKV infected (>10³ copies/ml) and those were subjected to conventional PCR amplification of VP1 gene followed by BKV genotyping via phylogenetic analysis based on DNA sequencing data.

Results

Persistent BK viral loads varied from 1×10³ to 3×10⁸ copies/ml. Of the 41 patient samples, 25 gave positive results for PCR amplification of subtyping region of VP1 gene of BKV. BKV genotyping resulted in detecting subtype I in 18 (72%) and subtype II in seven (28%) patients. BKV subgroups of Ia, Ib-1 and Ib-11, and Ic were identified with frequencies of 6/18 (33.3%), 6/18 (33.3%), 5/18 (27.8%), and 1/18 (5.6%), respectively.

Interpretation & conclusions

Findings from this preliminary study showed a high occurrence of subtype I, while the presence of subtype II, which is rare and less prevalent, was a novel finding for this Asian region. This emphasizes the need for further molecular and serological studies to determine the prevalence of different BKV subtypes in Sri Lanka.

BK Virus Nephropathy in Kidney Transplantation: A State-of-the-Art Review

BK virus maintains a latent infection that is ubiquitous in humans. It has a propensity for reactivation in the setting of a dysfunctional cellular immune response and is frequently encountered in kidney transplant recipients. Screening for the virus has been effective in preventing progression to nephropathy and graft loss. However, it can be a diagnostic and therapeutic challenge. In this in-depth state-of-the-art review, we will discuss the history of the virus, virology, epidemiology, cellular response, pathogenesis, methods of screening and diagnosis, evidence-based treatment strategies, and upcoming therapeutics, along with the issue of re-transplantation in patients.

Kidney transplant from hepatitis C viremic donors into aviremic recipients and risk for post-transplant BK and CMV infection

BACKGROUND

kidney transplantation from HCV-viremic donors to uninfected recipients is associated with excellent short-term outcomes. However, HCV viremia might be associated with an increased risk for post-transplant viral complications.

METHODS

We designed a retrospective study of HCV-negative kidney-only transplant recipients between 2018 and 2020. Recipients were grouped into group 1; HCV-negative donors, and group 2; HCV-viremic donors. Patients were matched 1:1 using propensity score. Primary objectives were to compare the incidence of CMV viremia ≥ 200 ml/IU, and BK viremia ≥1000 copies/ml between the groups. Secondary outcomes included group comparison of CMV disease, BK viremia ≥10,000 copies/ml, and one year patient and allograft survival.

RESULTS

The study included 634 patients in group 1, and 71 patients in group 2. 65 pairs of patients were matched. Incidence of CMV viremia (33.3% vs 40.0%, p = 0.4675), and BK viremia (15.9% vs 27.7%, P = 0.1353) did not differ significantly between groups in the matched cohort. Incidence of CMV disease (81.0% Vs 76.9%; p = 1.000), and BK viremia ≥10,000 copies/ml (9.5% vs 16.9%, p = 0.2987) were comparable between groups. There was no difference in the one-year patient or allograft survival between groups.

CONCLUSION

kidney transplant from HCV-viremic donors is not associated with increased risk for BK or CMV viremia. This article is protected by copyright. All rights reserved.

In Vitro Generation of BK polyomavirus-specific T cells for adoptive cell therapy in refractory cystitis hemorrhagic patients after hematopoietic stem cell transplantation

Introduction

BKPyV associated hemorrhagic cystitis (BKPyV-HC) is a major and prevalent outcome of hematopoietic stem cell transplantation (HSCT) with no standard treatment option. Adoptive T cell therapy (ACT) against transplant-associated viruses has shown promising potential. We sought to produce virus-specific T cells (VSTs) against BKPyV with the aim of treating refractory HSCT-associated HC.

Methods

Peripheral blood mononuclear cells (PBMC) from healthy donors were isolated by Ficoll-Hypaque density gradient centrifugation. BKPyV-pulsed, monocyte-derived dendritic cells (mo-DCs) and T cells were co-cultured and expanded over 2–3 weeks with the addition of IL-2. The T cells were examined for various functional assays.

Results

Comparison analysis of Carboxyfluorescein diacetate succinimidyl ester (CFSE) indicated that the percentage of proliferated cells were significantly higher in donors (49.62 ± 7.09%) than controls (7.96 ± 4.55%). Furthermore, expanded T cells exhibited specificity to BKPyV antigens by IFN-γ ELISPOT assay. The expanded cells showed cytotoxic function versus human lymphoblastoid cell line (LCL). Final VST products mainly comprised of CD8/CD69 double-positive T cells, which were significantly higher in donors (46.8 ± 7.1%) than controls (16.91 ± 3.40%).

Conclusion

In this study we demonstrated the feasibility of producing functional BKPyV-specific T cells in healthy donors using BKPyV PepMixes. These functional cells were able to proliferate and produce IFN-γ cytokine in response to BKPyV PepMixes. In addition, these T cells had cytotoxic ability against BKPyV antigen-expressing target cells.

The diagnostic and therapeutic dilemma of the co-existence of BK virus nephropathy with acute rejection - an experience from a single Centre and review of the literature

INTRODUCTION

BKV nephropathy (BKVN) is one of the major causes of graft loss with the advent of potent immunosuppressive drugs. The literature on the co-existence of acute rejection (AR) and BKVN is scarce.

MATERIALS AND METHODS

This is a single-center retrospective analysis, where the allograft biopsies of patients transplanted between 2011 and 2021 were reviewed. The biopsies, which showed evidence of coexistent AR and BKVN, were included. In addition, demographic profiles, clinical presentation, treatment details, response to therapy, and follow-up were analyzed.

RESULTS

Out of 1175 live transplants done between January 2011 and March 2021, 49 had BKVN representing 4.17%. Only seven patients (0.59%) had coexistent BKVN with AR. The mean serum creatinine at presentation was 2.3 mg/dl. The mean duration to diagnosis from transplant was seven months (range 3-22 months). All had significant viremia at presentation (17450-4,750,000 copies/ml). All biopsies showed type 1 inclusion bodies with SV40 positivity except one. Coexistent acute T cell-mediated rejection (TCMR) was found in five and acute ABMR in two patients. Three patients received pulse IV methylprednisolone, five received 2 g/kg IVIG, two received plasma exchange as upfront therapies. Maintenance immunosuppression reduction was made in all. Viremia clearance was noted at a mean duration of 3.5 months. However, three patients lost their grafts on follow-up. Four had stable graft function with a mean serum creatinine of 1.54 mg/dl.

CONCLUSION

Intensifying immunosuppression to treat AR followed by a reduction in maintenance immunosuppression and IVIG and antiviral therapies seems optimal strategy and showed good long-term graft survival in patients with coexistent BKVN and AR.

Research progress of BK virus and systemic lupus erythematosus

Background: Systemic lupus erythematosus (SLE) is an autoimmune disease in which patients are often infected by viruses due to deficient immunity or immunosuppressant use. BK virus (BKV)mainly affects the kidney and can also cause multiple organ involvement throughout the body, which is similar to SLE. BKV is mostly a latent infection in vivo. The incidence of virus reactivation is higher in SLE patients. Reactivation of BKV can induce the production of autoantibodies, thereby promoting the occurrence and development of SLE.Purpose: Aim of this article is to review the prevalence and pathegenesis of BKV infection in SLE patients.Method: The literature search was conducted using four different databases including PubMed, Cochrane Library, Scopus and Web of Science.Results: BK virus is higher infection and reactivation in SLE patients. The "hapten carrier" mechanism may lead to the production of autoantibodies. Some immunosuppressive drugs, like leflumide and hydroxychloroquine, may show a protective effect.Conclusions: BKV infection plays a role in the occurrence and development of SLE, and its significance deserves further exploration.

BKV Related Hemorrhagic Cystitis-An Insight into Risk Factors and Later Complications-An Analysis on Behalf of Polish Adult Leukemia Group

Simple Summary

Despite noticeable progress in allogeneic hematopoietic stem cell transplantation, potential viral reactivations are still one of the most challenging complications. The aim of our study was to identify predictive and risk factors associated with the occurrence of the BK virus related hemorrhagic cystitis following hematopoietic stem cell transplantation. Furthermore, we investigated the impact of various factors on the clinical course of patients after hematopoietic stem cell transplantation. We confirmed that >0.75 × 10³ BK virus copies/mL in serum at day +21 after allogeneic hematopoietic stem cell transplantation has a strong predictive ability for hemorrhagic cystitis. Thus, we believe that our findings could be helpful in establishing the predictive validity of the BK viral load measurement in polyomavirus BK-associated hemorrhagic cystitis and survival.

Abstract

BK virus reactivation increases the likelihood of hemorrhagic cystitis (HC) after allogeneic hematopoietic stem cell transplant (HCT). In this study, we aimed to identify predictive and risk factors associated with the increased occurrence of this condition following HCT. On a group of 124 patients aged ≤71 years old (median 40 years) who underwent HCT, we analyzed sex, age, time from diagnosis to transplantation, type of conditioning, donor’s relationship, age, and sex, the impact of immunosuppression with different drugs, and acute and chronic GVHD, BK viremia and viruria as potential factors increasing the risk of BK-related HC after HCT. HC occurred among 24 patients (24/124; 29.2%). A significant correlation was observed between HC incidences after HCT, BK viremia and viruria, and acute GVHD occurrence. Furthermore, the level of BKV DNA in serum at day +21 (>0.75 × 10³) significantly impacted the patients’ survival time. According to our results, the likelihood ratio of BKV-DNA on day +21 in serum is 6.25, indicating that this diagnostic test has the potential to be utilized in a clinical setting. These findings may be used as a voice in the discussion on implementing an optimal preemptive treatment in BKV reactivation after allogeneic HCT.

Concomitant BK virus infection and visceral Leishmaniasis in a pediatric liver transplant recipient

BACKGROUND

Solid organ transplant recipients are vulnerable to various unusual infections. Visceral Leishmaniasis (VL) is a protozoal opportunistic infection, which may affect the immune-suppressed hosts and solid organ transplant recipients. The BK virus infection is an evolving challenge in kidney transplant recipients. However, there are very few reports of BK virus (BKV) nephropathy involving the native kidney in liver transplant recipients. To the best of our knowledge, this is the first report of the simultaneous occurrence of these rare infections in a liver transplant recipient.

CASE REPORT

The patient was a 9-year-old girl, a case of liver transplantation who presented with the incidental finding of proteinuria, azotemia, and cytopenia. Investigations revealed that she had concomitant BKV nephropathy and visceral leishmaniasis. Both infections were successfully treated.

CONCLUSION

BK virus should be considered as a cause of nephropathy in liver transplant recipients. The presenting features of fever, cytopenia, and splenomegaly in a post-transplant patient should remind of unusual infections such as VL other than the common post-transplant conditions.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

DISCUSSION

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

Intravesical alprostadil as a promising agent in BK virus-associated hemorrhagic cystitis: A report of a refractory case

Allogeneic stem cell transplant recipients are at risk of BK virus-associated hemorrhagic cystitis. This condition causes a significant morbidity and worsens clinical outcomes. The standard cares for BK virus-associated hemorrhagic cystitis are saline irrigation and forced diuresis. Notably, several beneficial roles are proposed for antiviral and anti-inflammatory agents against BK virus-associated hemorrhagic cystitis. However, cases who are at risk of cystectomy remain refractory. Herein, we present a 13-year-old boy with severe hematuria by passing two months from his allogeneic stem cell transplantation. The laboratory work up showed high BK viremia >1.1 ×  10⁸ copies/ml in this case's urine sample. The patient was treated with antiviral agents in combination with supportive care. Moreover, intravesical alum was administered, but no clinical benefits were achieved. Finally, intravesical alprostadil was prepared under the supervision of a pediatric clinical pharmacist. In this regard, an alprostadil solution was prepared by constitution of 250 μg alprostadil in 50 mL saline. After administrating the first dose of intravesical alprostadil, an acceptable clinical response was observed, and hematuria stopped. Of note, alprostadil induces platelet aggregation and vasoconstriction. Thus, bleeding can be controlled after the administration of intravesical alprostadil. This strategy may be associated with several side effects including bladder spasm. This study is the first report describing the special role of intravesical alprostadil in refractory cases of BK virus-associated hemorrhagic cystitis. In such refractory cases, clinicians can use intravesical alprostadil rather than invasive therapies in the treatment of BK virus-hemorrhagic cystitis.

[BK virus encephalitis in children with hematopoietic stem cell transplantation]

目的

探讨异基因造血干细胞移植患儿中BK病毒（BKV）脑炎的发病率、病死率、中位发病时间、临床表现、诊治及转归等，以提高临床医师对本病的认识。

方法

回顾性分析2015年1月1日至2020年12月31日在北京大学人民医院接受单倍型造血干细胞移植治疗的709例儿童患者，其中14例诊断为BKV脑炎，分析其临床特征、治疗过程及转归。

结果

BKV脑炎发生率为1.97％（14例）。患儿多为男性（12例），中位年龄为11岁，中位发病时间为移植后第55天。最常见的临床表现为意识障碍、抽搐发作（7例）。14例患儿予阿昔洛韦、更昔洛韦单用，或联合丙种球蛋白治疗，9例患儿痊愈，1例患儿死于病毒性脑炎，4例患儿死于其他疾病，病死率为35.7％。

结论

BKV脑炎主要表现为脑炎或脑膜炎。虽然确诊BKV脑炎后积极予药物治疗，但许多患者仍死于多器官衰竭或其他并发症。当异基因造血干细胞移植患者出现神经系统症状、出血性膀胱炎时，必须高度警惕BKV脑炎，尽早施救，从而改善患者的生存率及生活质量。