Testing for polyomavirus type BK DNA in plasma to identify renal-allograft recipients with viral nephropathy

Serum and urine nucleic acid screening tests for BK polyomavirus-associated nephropathy in kidney and kidney-pancreas transplant recipients

BACKGROUND

BK polyomavirus-associated nephropathy (BKPyVAN) occurs when BK polyomavirus (BKPyV) affects a transplanted kidney, leading to an initial injury characterised by cytopathic damage, inflammation, and fibrosis. BKPyVAN may cause permanent loss of graft function and premature graft loss. Early detection gives clinicians an opportunity to intervene by timely reduction in immunosuppression to reduce adverse graft outcomes. Quantitative nucleic acid testing (QNAT) for detection of BKPyV DNA in blood and urine is increasingly used as a screening test as diagnosis of BKPyVAN by kidney biopsy is invasive and associated with procedural risks. In this review, we assessed the sensitivity and specificity of QNAT tests in patients with BKPyVAN.

OBJECTIVES

We assessed the diagnostic test accuracy of blood/plasma/serum BKPyV QNAT and urine BKPyV QNAT for the diagnosis of BKPyVAN after transplantation. We also investigated the following sources of heterogeneity: types and quality of studies, era of publication, various thresholds of BKPyV-DNAemia/BKPyV viruria and variability between assays as secondary objectives.

SEARCH METHODS

We searched MEDLINE (OvidSP), EMBASE (OvidSP), and BIOSIS, and requested a search of the Cochrane Register of diagnostic test accuracy studies from inception to 13 June 2023. We also searched ClinicalTrials.com and the WHO International Clinical Trials Registry Platform for ongoing trials.

SELECTION CRITERIA

We included cross-sectional or cohort studies assessing the diagnostic accuracy of two index tests (blood/plasma/serum BKPyV QNAT or urine BKPyV QNAT) for the diagnosis of BKPyVAN, as verified by the reference standard (histopathology). Both retrospective and prospective cohort studies were included. We did not include case reports and case control studies.

DATA COLLECTION AND ANALYSIS

Two authors independently carried out data extraction from each study. We assessed the methodological quality of the included studies by using Quality Assessment of Diagnostic-Accuracy Studies (QUADAS-2) assessment criteria. We used the bivariate random-effects model to obtain summary estimates of sensitivity and specificity for the QNAT test with one positivity threshold. In cases where meta-analyses were not possible due to the small number of studies available, we detailed the descriptive evidence and used a summative approach. We explored possible sources of heterogeneity by adding covariates to meta-regression models.

MAIN RESULTS

We included 31 relevant studies with a total of 6559 participants in this review. Twenty-six studies included kidney transplant recipients, four studies included kidney and kidney-pancreas transplant recipients, and one study included kidney, kidney-pancreas and kidney-liver transplant recipients. Studies were carried out in South Asia and the Asia-Pacific region (12 studies), North America (9 studies), Europe (8 studies), and South America (2 studies).

INDEX TEST

blood/serum/plasma BKPyV QNAT The diagnostic performance of blood BKPyV QNAT using a common viral load threshold of 10,000 copies/mL was reported in 18 studies (3434 participants). Summary estimates at 10,000 copies/mL as a cut-off indicated that the pooled sensitivity was 0.86 (95% confidence interval (CI) 0.78 to 0.93) while the pooled specificity was 0.95 (95% CI 0.91 to 0.97). A limited number of studies were available to analyse the summary estimates for individual viral load thresholds other than 10,000 copies/mL. Indirect comparison of thresholds of the three different cut-off values of 1000 copies/mL (9 studies), 5000 copies/mL (6 studies), and 10,000 copies/mL (18 studies), the higher cut-off value at 10,000 copies/mL corresponded to higher specificity with lower sensitivity. The summary estimates of indirect comparison of thresholds above 10,000 copies/mL were uncertain, primarily due to a limited number of studies with wide CIs contributed to the analysis. Nonetheless, these indirect comparisons should be interpreted cautiously since differences in study design, patient populations, and methodological variations among the included studies can introduce biases. Analysis of all blood BKPyV QNAT studies, including various blood viral load thresholds (30 studies, 5658 participants, 7 thresholds), indicated that test performance remains robust, pooled sensitivity 0.90 (95% CI 0.85 to 0.94) and specificity 0.93 (95% CI 0.91 to 0.95). In the multiple cut-off model, including the various thresholds generating a single curve, the optimal cut-off was around 2000 copies/mL, sensitivity of 0.89 (95% CI 0.66 to 0.97) and specificity of 0.88 (95% CI 0.80 to 0.93). However, as most of the included studies were retrospective, and not all participants underwent the reference standard tests, this may result in a high risk of selection and verification bias.

INDEX TEST

urine BKPyV QNAT There was insufficient data to thoroughly investigate both accuracy and thresholds of urine BKPyV QNAT resulting in an imprecise estimation of its accuracy based on the available evidence.

AUTHORS' CONCLUSIONS

There is insufficient evidence to suggest the use of urine BKPyV QNAT as the primary screening tool for BKPyVAN. The summary estimates of the test sensitivity and specificity of blood/serum/plasma BKPyV QNAT test at a threshold of 10,000 copies/mL for BKPyVAN were 0.86 (95% CI 0.78 to 0.93) and 0.95 (95% CI 0.91 to 0.97), respectively. The multiple cut-off model showed that the optimal cut-off was around 2000 copies/mL, with test sensitivity of 0.89 (95% CI 0.66 to 0.97) and specificity of 0.88 (95% CI 0.80 to 0.93). While 10,000 copies/mL is the most commonly used cut-off, with good test performance characteristics and supports the current recommendations, it is important to interpret the results with caution because of low-certainty evidence.

Mapping of Human Polyomavirus in Renal Cell Carcinoma Tissues

Worldwide, the incidence of renal cell carcinoma (RCC) is rising, accounting for approximately 2% of all cancer diagnoses and deaths. The etiology of RCC is still obscure. Here, we assessed the presence of HPyVs in paraffin-embedded tissue (FFPE) resected tissue from patients with RCC by using different molecular techniques. Fifty-five FFPE tissues from 11 RCC patients were included in this study. Consensus and HPyV-specific primers were used to screen for HPyVs. Both PCR approaches revealed that HPyV is frequently detected in the tissues of RCC kidney resections. A total of 78% (43/55) of the tissues tested were positive for at least one HPyV (i.e., MCPyV, HPyV6, HPyV7, BKPyV, JCPyV, or WUyV). Additionally, 25 tissues (45%) were positive for only one HPyV, 14 (25%) for two HPyVs, 3 (5%) for three HPyVs, and 1 one (1%) tissue specimen was positive for four HPyVs. Eleven (20%) RCC specimens were completely devoid of HPyV sequences. MCPyV was found in 24/55 RCC tissues, HPyV7 in 19, and HPyV6 in 8. The presence of MCPyV and HPyV6 was confirmed by specific FISH or RNA-ISH. In addition, we aimed to confirm HPyV gene expression by IHC. Our results strongly indicate that these HPyVs infect RCC and nontumor tissues, possibly indicating that kidney tissues serve as a reservoir for HPyV latency. Whether HPyVs possibly contribute to the etiopathogenesis of RCC remains to be elucidated.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

The value and complexity of studying cellular immunity against BK Polyomavirus in kidney transplant recipients

BK Polyomavirus is of particular concern for kidney transplant recipients, due to their immunosuppression. This problem is exacerbated by the high effectiveness of antirejection therapies, which also compromise the organism's ability to fight viral infections. The long-term risk is loss of graft function through BKPyV-associated nephropathy (BKPyVAN). The assessment of host immunity and its link to the control of viral infections is a major challenge. In terms of humoral immunity, researchers have highlighted the prognostic value of the pre-transplantation anti-BKPyV immunoglobulin G titer. However, humoral immunity alone does not guarantee viral clearance, and the correlation between the humoral response and the time course of the infection remains weak. In contrast, cellular immunity variables appear to be more closely associated with viral clearance, given that the cellular immune response to the kidney transplant is the main target of immunosuppressive treatments in recipients. However, the assessment of the cellular immune response to BK Polyomavirus is complex, and many details still need to be characterized. Here, we review the current state of knowledge about BKPyV cellular immunity, as well as the difficulties that may be encountered in studying it in kidney transplant recipient. This is an essential area of research for optimizing the management of transplant recipients and minimizing the risks associated with insidious BKPyV disease.

BK polyomavirus infection: more than 50 years and still a threat to kidney transplant recipients

BK polyomavirus (BKPyV) is a ubiquitous human polyomavirus and a major infection after kidney transplantation, primarily due to immunosuppression. BKPyV reactivation can manifest as viruria in 30%-40%, viremia in 10%-20%, and BK polyomavirus-associated nephropathy (BKPyVAN) in 1%-10% of recipients. BKPyVAN is an important cause of kidney graft failure. Although the first case of BKPyV was identified in 1971, progress in its management has been limited. Specifically, there is no safe and effective antiviral agent or vaccine to treat or prevent the infection. Even in the current era, the mainstay approach to BKPyV is a reduction in immunosuppression, which is also limited by safety (risk of de novo donor specific antibody and rejection) and efficacy (graft failure). However, recently BKPyV has been getting more attention in the field, and some new treatment strategies including the utilization of viral-specific T-cell therapy are emerging. Given all these challenges, the primary focus of this article is complications associated with BKPyV, as well as strategies to mitigate negative outcomes.

Human polyomaviruses JCPyV and MCPyV in urothelial cell carcinoma: a single institution experience

Objective

Urothelial cell carcinoma (UCC) is the most common type of urinary bladder. JCPyV and BKPyV have been detected in the urine and tissue of urothelial cell carcinomas (UCC) in immunocompetent patients. Here, we investigated the presence of several HPyVs in UCC samples using diverse molecular techniques to study the prevalence of HPyVs in UCC.

Methods

A large single-institution database of urine cytology specimens (UCS; n = 22.867 UCS) has previously been searched for decoy cells (n = 30), suggesting polyomavirus infection. The available urine sediments and formalin-fixed paraffin-embedded (FFPE) tissue samples of UCC patients were tested for the presence of JCPyV-LTAg expression by immunohistochemistry (IHC) labeled with SV40-LTAg antibody (clone: PAb416) and subsequent PCR followed by sequencing. In addition, the presence of the oncogenic Merkel cell polyomavirus (MCPyV) and the presence of human polyomavirus 6 (HPyV6) and 7 (HPyV7) DNA were tested with DNA PCR or IHC.

Results

Of the 30 patients harboring decoy cells, 14 were diagnosed with UCC of the urinary bladder (14/30; 46.6%) before presenting with decoy cells in the urine. The SV40-LTAg IHC was positive in all 14 UCC urine sediments and negative in the FFPE tissues. JCPyV-DNA was identified in all five available UCS and in three FFPE samples of UCC (three of 14; 21.4%). Two UCC cases were positive for MCPyV-DNA (two of 14; 14.3%), and one of them showed protein expression by IHC (one of 14; 7.1%). All specimens were HPyV6 and HPyV7 negative.

Conclusion

Our findings show the presence of JCPyV in the urine and UCC of immunocompetent patients. Moreover, MCPyV was detected in two UCC cases. In total, five UCC cases showed the presence of either JCPyV or MCPyV. The evidence here supports the hypothesis that these viruses might sporadically be associated with UCC. Further studies are needed to confirm the relevance of JCPyV or MCPyV as a possible risk factor for UCC development.

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.

A cluster of broadly neutralizing IgG against BK polyomavirus in a repertoire dominated by IgM

The BK polyomavirus (BKPyV) is an opportunistic pathogen, which is only pathogenic in immunosuppressed individuals, such as kidney transplant recipients, in whom BKPyV can cause significant morbidity. To identify broadly neutralizing antibodies against this virus, we used fluorescence-labeled BKPyV virus-like particles to sort BKPyV-specific B cells from the PBMC of KTx recipients, then single-cell RNAseq to obtain paired heavy- and light-chain antibody sequences from 2,106 sorted B cells. The BKPyV-specific repertoire was highly diverse in terms of both V-gene usage and clonotype diversity and included most of the IgM B cells, including many with extensive somatic hypermutation. In two patients where sufficient data were available, IgM B cells in the BKPyV-specific dataset had significant differences in V-gene usage compared with IgG B cells from the same patient. CDR3 sequence-based clustering allowed us to identify and characterize three broadly neutralizing "41F17-like" clonotypes that were predominantly IgG, suggesting that some specific BKPyV capsid epitopes are preferentially targeted by IgG.

Transcriptomic analysis of human cytomegalovirus to survey the indirect effects on renal transplant recipients

Post-transplant human cytomegalovirus (HCMV) viremia has been linked to adverse "indirect effects" among transplant patients. HCMV-created immunomodulatory mechanisms could be associated with the indirect effects.

OBJECTIVE

In the present study, the RNA-Seq whole transcriptome of renal transplant (RT) patients was analyzed to seek the underlying pathobiologic pathways associated with the long-term indirect effects of HCMV.

METHODS

To investigate the activated biological pathways in HCMV infection, total RNA was extracted from PBMCs of 2 RT patients with active HCMV and 2 RT patients without infection and then were sequenced using RNA-Seq. The resulted raw data were analyzed by conventional RNA-Seq software to determine the Differentially Expressed Genes (DEGs). Afterward, Gene Ontology (GO) and pathway enrichment analyses were conducted to determine the enriched pathways and biological processes by DEGs. Eventually, the relative expressions of some significant genes were validated in the twenty external RT patients.

RESULT

The analysis of RNA-Seq data related to RT patients with HCMV active viremia led to the identification of 140 up-regulated and 100 down-regulated DEGs. KEGG pathway analysis revealed the enrichment of DEGs in IL18 signaling, AGE-RAGE signaling pathway in diabetic complications, signaling by GPCR, Platelet activation, signaling and aggregation, Estrogen signaling pathway and signaling by Wnt due to HCMV infection. The expression levels of six genes involved in enriched pathways including F3, PTX3, ADRA2B, GNG11, GP9, HBEGF were then verified using RT-qPCR. The results were in consistent with RNA-Seq resultsoutcomes.

CONCLUSION

This study specifies some pathobiological pathways which are activated in HCMV active infection and could be linked to the adverse indirect effects caused by HCMV infection in transplant patients.

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.

BK DNAemia and native kidney polyomavirus nephropathy following lung transplantation

BK virus DNAemia (BKPyV) and nephropathy are common after kidney transplant; however, there are limited data on BK infections in nonrenal solid organ transplant recipients. We examined the frequency, clinical and pathologic features, and kidney and lung outcomes of BKPyV and BK virus native kidney nephropathy (BKVN) in lung transplant recipients at our center. Among 878 recipients transplanted from 2003 to 2019, 56 (6%) developed BKPyV at a median of 30.1 months after transplant (range, 0.6-213) and 11 (1.3%) developed BKVN at a median of 46 months after transplant (range, 9-213). The incidence of end-stage kidney disease was significantly higher in patients with peak viral load ≥10 000 copies/mL (39% vs 8%, P < .001). All cases of BKVN were in patients with peak viral load of ≥10 000 copies/mL, and 55% of these patients developed end-stage kidney disease. Despite the reduction of immunosuppression to treat BKVN, only 1 patient developed acute rejection, and lung function was stable >1 year. BKPyV and nephropathy are more common after lung transplantation than previously reported. Routine screening for BKPyV should be considered in all lung transplant recipients.

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.

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.

Polyoma BK Virus in Kidney Transplant Recipients: Screening, Monitoring, and Management

Polyomavirus BK virus (BKPyV) infection is an important complication of kidney transplantation and allograft failure. The prevalence of viremia is 10%-15%, compared with BK-associated nephropathy (BKPyVAN) at 3%-5%. Given that there are no effective antiviral prophylaxis or treatment strategies for BKPyVAN, active screening to detect BKPyV viremia is recommended, particularly during the early posttransplant period. Immunosuppression reduction to allow viral clearance may avoid progression to severe and irreversible allograft damage. The frequency and duration of screening are highly variable between transplant centers because the evidence is reliant largely on observational data. While the primary treatment goals center on achieving viral clearance through immunosuppression reduction, prevention of subsequent acute rejection, premature graft loss, and return to dialysis remain as major challenges. Treatment strategies for BKPyV infection should be individualized to the recipient's underlying immunological risk and severity of the allograft infection. Efficacy data for adjuvant therapies including intravenous immunoglobulin and cidofovir are sparse. Future well-powered and high-quality randomized controlled trials are needed to inform evidence-based clinical practice for the management of BKPy infection.

Assessment of the Banff Working Group classification of definitive BK polyomavirus nephropathy

Polyomavirus associated nephropathy (PyVAN) continues to be a burden in renal transplantation leading to allograft insufficiency or graft failure. A presumptive diagnosis of PyVAN is made based on the presence of BK polyomavirus in patients' plasma; however, kidney biopsy remains the gold standard to establish a definitive diagnosis. The Banff Working Group on PyVAN proposed a novel classification of definitive PyVAN based on polyomavirus replication/load level and the extent of interstitial fibrosis. The aim of our study was to test the newly defined classes of PyVAN using independent cohorts of 124 kidney transplant patients with PyVAN with respect to the initial presentation and outcome, and to compare our analysis to that previously reported. Detailed analysis of our cohort revealed that the proposed classification of PyVAN did not stratify or identify patients at increased risk of allograft failure. Specifically, while class 3 was associated with the worst prognosis, there was no significant difference between the outcomes in classes 1 and 2. We also found that the timing post-transplantation and inflammation in areas of interstitial fibrosis and tubular atrophy might be additional factors contributing to an unfavorable allograft outcome in patients with PyVAN.

Chk1 and the Host Cell DNA Damage Response as a Potential Antiviral Target in BK Polyomavirus Infection

The human BK polyomavirus (BKPyV) is latent in the kidneys of most adults, but can be reactivated in immunosuppressed states, such as following renal transplantation. If left unchecked, BK polyomavirus nephropathy (PyVAN) and possible graft loss may result from viral destruction of tubular epithelial cells and interstitial fibrosis. When coupled with regular post-transplant screening, immunosuppression reduction has been effective in limiting BKPyV viremia and the development of PyVAN. Antiviral drugs that are safe and effective in combating BKPyV have not been identified but would be a benefit in complementing or replacing immunosuppression reduction. The present study explores inhibition of the host DNA damage response (DDR) as an antiviral strategy. Immunohistochemical and immunofluorescent analyses of PyVAN biopsies provide evidence for stimulation of a DDR in vivo. DDR pathways were also stimulated in vitro following BKPyV infection of low-passage human renal proximal tubule epithelial cells. The role of Chk1, a protein kinase known to be involved in the replication stress-induced DDR, was examined by inhibition with the small molecule LY2603618 and by siRNA-mediated knockdown. Inhibition of Chk1 resulted in decreased replication of BKPyV DNA and viral spread. Activation of mitotic pathways was associated with the reduction in BKPyV replication. Chk1 inhibitors that are found to be safe and effective in clinical trials for cancer should also be evaluated for antiviral activity against BKPyV.

Prospective analysis of BKV hemorrhagic cystitis in children and adolescents undergoing hematopoietic cell transplantation

BK virus is one of the most common causes of hemorrhagic cystitis (HC) in children undergoing hematopoietic cell transplantation (HCT). Viruses can be found in urine and serum samples of immunocompromised patients. Malignant diseases, age, cell source, day of granulocyte reconstitution, conditioning regimen, or use of total body irradiation may play an important role in BKV epidemiology, development of hemorrhagic cystitis course, and outcome. The aim of this study was to evaluate the incidence, clinical course, and risk factors for BKV-HC in children undergoing HCT. A total number of 133 patients who were prospectively tested for BKV colonization/infection were enrolled into this multicenter analysis. Episodes of BKV-HC occurred in 36/133 (27%) enrolled subjects. In a univariate analysis for BKV-HC incidence, the following factors were significant: age >5 years, peripheral blood transplantation, matched unrelated donor (MUD) transplantation, busulfan-cyclophosphamide-melphalan conditioning regimen, and acute myeloblastic leukemia (AML) diagnosis. Presence of acute graft-versus-host disease (aGVHD) in liver and gut GVHD was a significant risk factor of BKV-HC. No BKV-attributed deaths were reported. In multivariate analysis, the incidence of HC was significantly higher in patients with AML, age >5 years, MUD transplants, and children with GVHD. HC is a frequent complication after HCT among children causes prolonged hospitalization but rarely contributes to death. We identified risk factors of BKV-HC development in children, with focus on aGVHD: we concluded that excessive immune reaction connected with GVHD and immunosuppression drugs might play a pivotal role in the development of BKV-HC.

BK Polyomavirus-specific T Cells as a Diagnostic and Prognostic Marker for BK Polyomavirus Infections After Pediatric Kidney Transplantation

BACKGROUND

After kidney transplantation, uncontrolled BK polyomavirus (BKPyV) replication causes kidney graft failure through BKPyV-associated nephropathy (BKPyVAN), but markers predicting outcome are missing. BKPyV-specific T cells may serve as a predictive marker to identify patients at risk of persistent DNAemia and BKPyVAN.

METHODS

Out of a total of 114 pediatric kidney recipients transplanted between 2008 and 2018, 36 children with posttransplant BKPyV-DNAemia were identified. In a prospective noninterventional study, BKPyV-specific CD4 and CD8 T cells were measured in 32 of 36 viremic pediatric kidney recipients using intracellular cytokine staining and flow cytometry. The course of the BKPyV replication was monitored with regard to duration of BKPyV-DNAemia and need of therapeutic intervention and diagnosis of proven BKPyVAN.

RESULTS

Levels of BKPyV-specific T cells negatively correlated with subsequent duration of BKPyV-DNAemia. Patients with BKPyV-specific CD4 T cells ≥0.5 cells/µL and/or BKPyV-specific CD8 T cells ≥0.1 cells/µL had transient, self-limiting DNAemia (PPV 1.0, NPV 0.86). BKPyV-specific CD4 and CD8 T cells below these thresholds were found in children with persistent BKPyV-DNAemia and biopsy-proven BKPyVAN with need for therapeutic intervention. After reducing immunosuppressive therapy, levels of BKPyV-specific CD4 T cells increased while plasma BKPyV-DNAemia declined.

CONCLUSIONS

This study found that BKPyV-specific T cell levels may help to distinguish patients with transient, self-limiting BKPyV-DNAemia from those with persisting BKPyV-DNAemia and biopsy-proven BKPyVAN, who would benefit from individualized therapeutic interventions such as reduced immunosuppression. Thereby the risk for rejection because of unnecessary reduction of immunosuppression in case of self-limiting BKPyV-DNAemia can be minimized.

BK virus infection and outcome following kidney transplantation in childhood

BK virus associated nephropathy (BKN) is an important cause of kidney allograft failure. In a cohort of paediatric kidney transplant recipients, we aimed to understand the incidence and clinical outcome associated with BKN, as well as identify risk factors for BKN and BK viraemia development. We retrospectively analysed all patients who received a kidney transplant and received follow up care in our centre between 2009-2019. Among 106 patients included in the study (mean follow up 4.5 years), 32/106 (30.2%) patients experienced BK viraemia. The incidence of BKN was 7/106 (6.6%). The median time of BK viraemia development post-transplant was 279.5 days compared to 90.0 days for BKN. Development of BKN was associated with younger age at transplantation (p = 0.013). Development of BK viraemia was associated with negative recipient serology for cytomegalovirus (CMV) at time of transplantation (p = 0.012) and a higher net level of immunosuppression (p = 0.039). There was no difference in graft function at latest follow up between those who experienced BKN and those without BKN. This study demonstrates that BK virus infection is associated with younger age at transplantation, CMV negative recipient serostatus and higher levels of immunosuppression. Judicious monitoring of BK viraemia in paediatric transplant recipients, coupled with timely clinical intervention can result in similar long-term outcomes for BKN patients compared to controls.

The Urinary Polyomavirus-Haufen Test: A Highly Predictive Non-Invasive Biomarker to Distinguish "Presumptive" from "Definitive" Polyomavirus Nephropathy: How to Use It-When to Use It-How Does It Compare to PCR Based Assays?

"Definitive" biopsy proven polyomavirus nephropathy (PyVN), usually caused by BK polyomavirus (BKPyV), remains a significant infection of kidney transplants. Diagnosis depends upon an allograft biopsy and outcome depends upon early intervention. Here, we report data on a non-invasive biomarker for PyVN, the urinary PyV-Haufen test. Test results were compared to those of conventional laboratory assays targeting PyV replication, i.e., BKPy-viremia, -viruria and urinary decoy cell shedding. Of 809 kidney transplant recipients, 228 (28%) showed PyV replication with decoy cell shedding and/or BKPy-viremia by quantitative PCR; only a subset of 81/228 (36%) showed "definitive" PyVN. Sensitivity and specificity for identifying patients with PyVN was: 100% and 98%, respectively, urinary PyV-Haufen test; 50% and 54%, respectively, urinary decoy cell shedding; 97% and 32%, respectively, BKPy-viremia with cut-off of ≥250 viral copies/mL; 66% and 80%, respectively, for BKPy-viremia ≥104 viral copies/mL. The PyV-Haufen test showed a very strong correlation with the severity of PyVN (Spearman's ρ = 0.84) and the Banff PyVN disease classes (p < 0.001). In comparison, BKPy-viremia and -viruria levels by PCR displayed modest correlations with PyVN severity (Spearman's ρ = 0.35 and 0.36, respectively) and were not significantly associated with disease classes. No association was found between decoy cell shedding and PyVN severity or disease classes. Pilot data demonstrated that PyVN resolution with decreasing Banff pvl-scores was reflected by a gradual decrease in PyV-Haufen shedding; such a tight association was not noted for BKPy-viremia. In conclusion, urinary PyV-Haufen testing is a highly specific, non-invasive method to accurately diagnose patients with "definitive" PyVN and to optimize patient management. Assay specifics are discussed.

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.

Renal Allograft Biopsies with Polyomavirus BK Nephropathy: Turin Transplant Center, 2015-19

Background: In kidney transplant patients, polyomavirus-associated nephropathy (PVAN) represents a serious complication; the key factor for the development of PVAN is immunosuppression level and modulation of anti-rejection treatment represents the first line of intervention. Allograft biopsy and histology remain the criterion standard for diagnosing PVAN. Methods: All consecutive renal biopsies with the diagnosis of PVAN carried out at the University Hospital City of Health and Science of Turin over a five-years period were studied. Renal allograft biopsy was performed due to renal function alterations associated to medium-high polyomavirus BK (BKV)-DNA levels on plasma specimen. Results: A total of 21 patients underwent a first biopsy to diagnose a possible BKV nephropathy, in 18, a second biopsy was made, in eight, a third biopsy, and finally, three underwent the fourth renal biopsy; following the results of each biopsies, immunosuppressant agents dosages were modified in order to reduce the effect of PVAN. Conclusions: In this study, the clinical and histological features of 21 kidney transplant recipients with BKV reactivation and development of PVAN are described. To date, the only treatment for PVAN consists in the reduction of immunosuppressive agents, constantly monitoring viral load.

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

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

Persistent BK Polyomavirus Viruria is Associated with Accumulation of VP1 Mutations and Neutralization Escape

To investigate the relationship between neutralization escape and persistent high-level BK polyomavirus replication after kidney transplant (KTx), VP1 sequences were determined by Sanger and next-generation sequencing in longitudinal samples from KTx recipients with persistent high-level viruria (non-controllers) compared to patients who suppressed viruria (controllers). The infectivity and neutralization resistance of representative VP1 mutants were investigated using pseudotype viruses. In all patients, the virus population was initially dominated by wild-type VP1 sequences, then non-synonymous VP1 mutations accumulated over time in non-controllers. BC-loop mutations resulted in reduced infectivity in 293TT cells and conferred neutralization escape from cognate serum in five out of six non-controller patients studied. When taken as a group, non-controller sera were not more susceptible to neutralization escape than controller sera, so serological profiling cannot predict subsequent control of virus replication. However, at an individual level, in three non-controller patients the VP1 variants that emerged exploited specific “holes” in the patient’s humoral response. Persistent high-level BK polyomavirus replication in KTx recipients is therefore associated with the accumulation of VP1 mutations that can confer resistance to neutralization, implying that future BKPyV therapies involving IVIG or monoclonal antibodies may be more effective when used as preventive or pre-emptive, rather than curative, strategies.

BK virus infection in allogeneic hematopoietic cell transplantation: An update on pathogenesis, immune responses, diagnosis and treatments

In hematopoietic cell transplantation (HCT) patients, BK polyomavirus (BKPyV) infection results in significant morbidity mainly due to hemorrhagic cystitis (HC). Despite increased knowledge acquired over recent decades, no treatment has shown effectiveness in the management of organ damage in HCT allografts. This review summarizes the current knowledge on BKPyV, from the virus constitution to the pathophysiology and immune-related mechanisms. We next focus on BKPyV-induced HC in HCT to discuss the benefit of monitoring BKPyV viruria and viremia in the management of patients. At last, we review currently used therapeutics, along with future promising therapies to propose clinical and practical guidelines and further interesting research areas.

Immunosuppression, BK polyomavirus infections, and BK polyomavirus-specific T cells after pediatric kidney transplantation

BACKGROUND

After kidney transplantation, immunosuppressive therapy increases risk of BK polyomavirus-associated nephropathy (BKPyVAN). Outcomes of BKPyV viremia are various and prognostic markers are missing. The impact of different immunosuppressive regimens on BKPyV infections is currently under discussion.

METHODS

We analyzed immunosuppressive therapy and BKPyV-specific cellular immunity to distinguish patients at risk of BKPyVAN from those with self-limiting viremia for purposes of risk-stratified BKPyV management. In a retrospective analysis, 46 pediatric kidney recipients with BKPyV viremia were analyzed with regard to duration of BKPyV viremia and immunosuppressive therapy; in addition, in 37/46 patients, BKPyV-specific CD4 and CD8 T cells were measured.

RESULTS

Nine patients showed persistent BKPyV viremia and BKPyVAN, and required therapeutic intervention, while 37 patients had asymptomatic, self-limiting viremia. At onset of viremia, 78% of patients with persistent viremia and BKPyVAN were treated with tacrolimus, whereas tacrolimus therapy was significantly less frequent in patients with self-limiting viremia (14%). The majority of patients with transient, self-limiting viremia received cyclosporine A (81%) and/or mTOR inhibitors (81%). Patients with persistent BKPyV viremia and BKPyVAN showed lack of BKPyV-specific CD4 and CD8 T cells (6/6), whereas the majority of patients with self-limiting viremia (27/31) had detectable BKPyV-specific CD4 and/or CD8 T cells ≥ 0.5 cells/μl (p < 0.001).

CONCLUSIONS

These results indicate that tacrolimus enhances risk of BKPyVAN with need of therapeutic intervention, whereas under cyclosporine A and mTOR inhibitors, the majority of pediatric kidney recipients showed self-limiting viremia. In patients at risk of BKPyV infections, combination of cyclosporine A and mTOR inhibitor may be advantageous.

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.

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.

Comparing Urine and Blood Screening Methods to Detect BK Virus After Renal Transplant

OBJECTIVES

BK polyomavirus can infect healthy individuals; however, in renal transplant recipients, it can cause nephropathy, which can lead to renal allograftfailure. There are currently no effective antiviral agents against BK polyomavirus. Surveillance after kidney transplant for BK polyomavirus is the only means to prevent allograft failure. Transplant centers routinely screen for BK polyomavirus in either urine or blood. If BK polyomavirus replication occurs, itis usually detected first in urine, which is followed by detection in blood in a subset of cases. Screening for BK polyomavirus in urine has the potential for earlier detection of viralreactivation.However, not all patients with BK polyomavirus in urine will progress to BK viremia. Therefore, adding urine screening could increase the cost oftests without a clear clinical benefit.

MATERIALS AND METHODS

We conducted an analysis of BK polyomavirus screening methods at 2 different centers and compared their clinical outcomes and efficiency of testing.

RESULTS

We analyzed 209 patientswith BK polyomavirus reactivation after kidney transplant at 2 different institutions from 2008 to 2018. BK polyomavirus reactivation in blood was detected earlierifthe patient was screened by urine screening protocol. However, measurable clinical outcomes were similarin all groups with different screening methods.

CONCLUSIONS

Although screening for BK polyomavirus in urine did detect viralreactivation earlier,there were no differences in graft or clinical outcomes when either the urine or blood screening method was used.

[Eulogy to Prof. Dr. Med. Michael J. Mihatsch : Presentation of the Rudolf Virchow Medal 2019 of the German Society of Pathology]

Michael Mihatsch, born in 1943 in Gleiwitz, studied medicine in Bonn and Freiburg, and then went to Basel to begin studying pathology. In 1978, he became Assistant Professor at the University of Basel, and led the Institute there from 1988 until 2007. Mihatsch made Basel a center for prospective renal pathologists.His most significant achievement is the description of the connection between phenacetin administration and nephropathy with renal atrophy and the concomitant occurrence of urothelial carcinoma. His campaign against phenacetin finally contributed to a ban on the medication.His textbook Renal Pathology in Biopsy is a classic of medical literature.As a leading nephropathologist worldwide, Prof. Dr. Med. Michael J. Mihatsch received the Rudolf Virchow Medal of the German Society of Pathologists in 2019.

The Very Low Frequency of Epstein-Barr JC and BK Viruses DNA in Colorectal Cancer Tissues in Shiraz, Southwest Iran

Viruses including Epstein-Barr virus (EBV), JCV and BKV have been reported to be associated with some cancers. The association of these viruses with colorectal cancers remains controversial. Our objective was to investigate their infections association with adenocarcinoma and adenomatous polyps of the colon. Totally, 210 paraffin-embedded tissue specimens encompassing 70 colorectal adenocarcinoma, 70 colorectal adenomatous and 70 colorectal normal tissues were included. The total DNA was extracted, then qualified samples introduced to polymerase chain reaction (PCR). The EBV, JCV and BKV genome sequences were detected using specific primers by 3 different in-house PCR assays. Out of 210 subjects, 98 cases were female and the rest were male. The mean age of the participants was 52 ± 1.64 years. EBV and JCV DNA was detected just in one (1.42%) out of seventy adenocarcinoma colorectal tissues. All adenomatous polyp and normal colorectal tissues were negative for EBV and JCV DNA sequences. Moreover, all the patients and healthy subjects were negative for BKV DNA sequences. The results suggested that EBV and JCV genomes were not detectable in the colorectal tissue of patients with colorectal cancer in our population. Hence, BKV might not be necessitated for the development of colorectal cancer. The findings merit more investigations.

Impact of human leukocyte antigen and calculated panel reactive antibody on BK viremia in kidney transplant recipients: A single-center experience and literature review

BACKGROUND

The aim of this retrospective analysis was to investigate the effect of human leukocyte antigen (HLA) and calculated panel reactive antibody (cPRA) on BK virus activation as evidenced by BK viremia (BKV).

PATIENTS AND METHODS

At our institution, 649 kidney transplant patients were screened for BKV from 2009 to 2017. Patients were considered to have BKV if they had >10 000 copies/mL of BK DNA in their blood. Donor and recipient HLA and cPRA, demographic, clinical and laboratory data, as well as immunosuppressive medications were collected.

RESULTS

We identified 122 BK positive and 527 BK negative patients. Only 25% of the patients had cPRA of 20% or more, and 64% had more than three HLA-A, -B, and -DR mismatches. In both univariate and multivariate analyses, male gender, age, and maintenance of steroid therapy significantly increased the risk of BKV (P = 0.005, 0.005 and <0.001, respectively). The degree of cPRA and the individual HLA allele and HLA allele matching did not significantly affect BKV.

CONCLUSION

Neither the degree of HLA mismatching nor cPRA appears to affect BKV. Moreover, no specific HLA allele, HLA allele matching, or cPRA were associated with BKV.

BK virus-associated viruria and viremia in a patient with lymphangioleiomyomatosis after lung re-transplantation: A case report and review of the literature on BK virus infection post-lung transplantation

The BK virus (BKV) is a member of the polyomaviridae family of DNA viruses. BKV reactivates under a highly immunosuppressed state and causes renal dysfunction. In renal transplant patients, BKV infection leads to tubular impairment and loss of transplanted kidney grafts. However, few studies have reported on the relationship between BKV and lung transplantation. Adjustment of the dosage of immunosuppressants is needed in some cases, but the treatment method has not been established. Here, we report a case of BKV-associated viruria and viremia in a patient with lymphangioleiomyomatosis (LAM) after lung re-transplantation. A 44-year-old female refractory LAM patient who had undergone lung re-transplantation 3 months earlier was diagnosed with BKV-associated viruria and viremia. Urine cytology indicated decoy cells and the urine and serum polymerase chain reaction test was positive for BKV. As scheduled after re-transplantation surgery, immunosuppressive drugs were progressively reduced. This patient was considered to have experienced spontaneous BKV-associated viremia and viruria. Review of the literature suggested that 17%-42% of BKV-associated viruria cases have been reported after lung transplantation, but cases of BKV-associated nephropathy are rarely reported. Based on the present case, doctors involved in lung transplantation should monitor patients for BKV infection. Decoy cell monitoring by urine cytology is a useful screening method in the follow-up observation after lung transplantation. Early-stage interventions may prevent BKV-associated nephropathy even in patients who have developed BKV viremia, and sirolimus can be administered to patients with histories of BKV infection if they are carefully monitored.

Non-immunological complications following kidney transplantation

Kidney transplantation (KT) is the most effective way to decrease the high morbidity and mortality of patients with end-stage renal disease. However, KT does not completely reverse the damage done by years of decreased kidney function and dialysis. Furthermore, new offending agents (in particular, immunosuppression) added in the post-transplant period increase the risk of complications. Cardiovascular (CV) disease, the leading cause of death in KT recipients, warrants pre-transplant screening based on risk factors. Nevertheless, the screening methods currently used have many shortcomings and a perfect screening modality does not exist. Risk factor modification in the pre- and post-transplant periods is of paramount importance to decrease the rate of CV complications post-transplant, either by lifestyle modification (for example, diet, exercise, and smoking cessation) or by pharmacological means (for example, statins, anti-hyperglycemics, and so on). Post-transplantation diabetes mellitus (PTDM) is a major contributor to mortality in this patient population. Although tacrolimus is a major contributor to PTDM development, changes in immunosuppression are limited by the higher risk of rejection with other agents. Immunosuppression has also been implicated in higher risk of malignancy; therefore, proper cancer screening is needed. Cancer immunotherapy is drastically changing the way certain types of cancer are treated in the general population; however, its use post-transplant is limited by the risk of allograft rejection. As expected, higher risk of infections is also encountered in transplant recipients. When caring for KT recipients, special attention is needed in screening methods, preventive measures, and treatment of infection with BK virus and cytomegalovirus. Hepatitis C virus infection is common in transplant candidates and in the deceased donor pool; however, newly developed direct-acting antivirals have been proven safe and effective in the pre- and post-transplant periods. The most important and recent developments on complications following KT are reviewed in this article.

BK virus salivary shedding and viremia in renal transplant recipients

OBJECTIVES

This study aimed to verify the presence of polyomavirus BK (BKPyV) in the saliva of kidney transplant recipients and to correlate it with blood viremia.

MATERIAL AND METHODS

We have conducted a cross-sectional study with a sample involving 126 renal transplant recipients. 126 samples of saliva and 52 samples of blood were collected from these patients. Detection and quantification of BKPyV were performed using a real-time PCR. To compare the presence of BKPyV in blood and saliva, the binomial proportion test was used. To verify associations between salivary shedding BKPyV and post-transplant periods (in months), the Mann-Whitney test was used. Spearman's correlation was used to correlate the viral load in the saliva with blood of kidney transplant recipients.

RESULTS

The mean age of the study group was 51.11±12.45 years old, and 69 participants (54.8%) were female, with a mean post-transplantation time of 4.80±6.04 months. BKPyV was quantified in several samples of saliva and blood, with medians of 1,108 cp/mL and 1,255 cp/mL, respectively. Only 16/52 (30.8%) participants presented BKPyV in blood, and 59/126 (46.8%) excreted the virus in saliva (p=0.004). BKPyV shedding was found in patients at a shorter post-transplantation period (3.86±5.25, p=0.100). A weak correlation was observed between viral quantification in saliva and blood (Spearman's correlation coefficient=0.193).

CONCLUSION

The results of this study suggested that, although saliva excretes more BKPyV than blood, there is no reliable correlation between salivary shedding and blood viremia, showing two independent compartments of viral replication.

Management of BK Polyomavirus Infection in Kidney and Kidney-Pancreas Transplant Recipients: A Review Article

BK virus (BKV) can cause graft dysfunction or failure in kidney transplant recipients and hemorrhagic cystitis in allogeneic hematopoietic stem cell transplant patients. BKV-associated nephropathy (BKVAN) emerged as a common complication in the late 1990s, probably due to the introduction of potent immunosuppressive agents. BKVAN occurred in up to 5% of kidney transplant recipients, with graft failure in up to 70%. Since universal implementation of effective screening and treatment strategies, BKV is no longer a common cause of graft failure; reported graft loss is only 0% to 5%. This article briefly describes BK virology, epidemiology, diagnosis, and management.

Patient Selection for Kidney Transplant

The incidence of end-stage renal disease has continued to increase. Similarly, the number of patients living with a functioning renal allograft has also increased. Transplantation has improved with advances in surgical techniques, immunosuppression, and better control of comorbid conditions. Transplantation is transformative and offers the greatest potential for restoring a healthy, productive, and durable life to appropriately selected patients. This article describes factors to address in selection of renal transplant candidates and discusses commonly encountered perioperative events. Paramount to selecting appropriate candidates is the collaboration between a multidisciplinary team focused on a systematic process guided by protocols and common practices.