Association of DNA Amplification With Progress of BK Polyomavirus Infection and Nephropathy in Renal Transplant Recipients

The Second International Consensus Guidelines on the Management of BK Polyomavirus in Kidney Transplantation

BK polyomavirus (BKPyV) remains a significant challenge after kidney transplantation. International experts reviewed current evidence and updated recommendations according to Grading of Recommendations, Assessment, Development, and Evaluations (GRADE). Risk factors for BKPyV-DNAemia and biopsy-proven BKPyV-nephropathy include recipient older age, male sex, donor BKPyV-viruria, BKPyV-seropositive donor/-seronegative recipient, tacrolimus, acute rejection, and higher steroid exposure. To facilitate early intervention with limited allograft damage, all kidney transplant recipients should be screened monthly for plasma BKPyV-DNAemia loads until month 9, then every 3 mo until 2 y posttransplant (3 y for children). In resource-limited settings, urine cytology screening at similar time points can exclude BKPyV-nephropathy, and testing for plasma BKPyV-DNAemia when decoy cells are detectable. For patients with BKPyV-DNAemia loads persisting >1000 copies/mL, or exceeding 10 000 copies/mL (or equivalent), or with biopsy-proven BKPyV-nephropathy, immunosuppression should be reduced according to predefined steps targeting antiproliferative drugs, calcineurin inhibitors, or both. In adults without graft dysfunction, kidney allograft biopsy is not required unless the immunological risk is high. For children with persisting BKPyV-DNAemia, allograft biopsy may be considered even without graft dysfunction. Allograft biopsies should be interpreted in the context of all clinical and laboratory findings, including plasma BKPyV-DNAemia. Immunohistochemistry is preferred for diagnosing biopsy-proven BKPyV-nephropathy. Routine screening using the proposed strategies is cost-effective, improves clinical outcomes and quality of life. Kidney retransplantation subsequent to BKPyV-nephropathy is feasible in otherwise eligible recipients if BKPyV-DNAemia is undetectable; routine graft nephrectomy is not recommended. Current studies do not support the usage of leflunomide, cidofovir, quinolones, or IVIGs. Patients considered for experimental treatments (antivirals, vaccines, neutralizing antibodies, and adoptive T cells) should be enrolled in clinical trials.

Risk factors for BK virus infection in DCD donor kidney transplant recipients

Background

BK virus infection after kidney transplantation can negatively impact the prognosis of patients. However, current risk factor analyses primarily focus on BK virus nephropathy, while BK viruria and BK viruria progressing to BK viremia receive less attention. This study aims to analyze the risk factors associated with BK viruria and BK viruria progressing to BK viremia in recipients of donation after cardiac death (DCD), with the goal of facilitating early intervention.

Methods

Donor characteristics and clinical data of recipients before and after transplantation were evaluated, and logistic univariate and multivariate analyses were performed to determine the risk factors associated with BK viruria and the progression of BK viruria to BK viremia. Additionally, machine learning techniques were employed to identify the top five features associated with BK viruria evolving into BK viremia.

Results

During a median follow-up time of 1,072 days (range 739-1,418), 69 transplant recipients (15.6% incidence rate) developed BK viruria after transplantation, with 49.3% of cases occurring within 6 months post-transplantation. Moreover, 19 patients progressed to BK viremia. Donor age [OR: 1.022 (1.000, 1.045), p = 0.047] and donor procalcitonin (PCT) levels [0.5-10 ng/ml; OR: 0.482 (0.280, 0.828), p = 0.008] were identified as independent risk factors for BK viruria. High BK viruria [OR: 11.641 (1.745, 77.678), p = 0.011], recipient age [OR: 1.106 (1.017, 1.202), p = 0.018], and immunoinduction regimen [ATG; OR: 0.063 (0.006, 0.683), p = 0.023] were independent risk factors for BK viruria progressing to BK viremia. Machine learning analysis confirmed the importance of high BK viruria, recipient age, and immunoinduction regimen (ATG) in predicting the progression of BK viruria to BK viremia.

Conclusion

The development and progression of BK virus in DCD kidney transplant recipients is influenced by multiple factors. Early intervention and treatment could potentially extend the lifespan of the transplanted organ.

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.

Usefulness of BK virus-specific interferon-γ enzyme-linked immunospot assay for predicting the outcome of BK virus infection in kidney transplant recipients

BACKGROUND/AIMS

To investigate if BK virus (BKV)-specific T cell immunity measured by an interferon-γ enzyme-linked immunospot (ELISPOT) assay can predict the outcome of BK virus infection in kidney transplant recipients (KTRs).

METHODS

We included 68 KTRs with different viremia status (no viremia [n = 17], BK viremia [n = 27], and cleared viremia [n = 24]) and 44 healthy controls (HCs). The BK viremia group was divided into controller (< 3 months) and noncontroller (> 3 months) according to sustained duration of BKV infection. We compared BKV-ELISPOT results against five BKV peptides (large tumor antigen [LT], St, VP1-3).

RESULTS

BKV-ELISPOT results were higher in three KTRs groups with different BKV infection status than the HCs group (p < 0.05). In KTR groups, they were higher in cleared viremia group than no viremia or BK viremia group. Within the BK viremia group, controller group had higher LT-ELISPOT results compared to noncontroller group (p = 0.032). Also, KTRs without BK virus-associated nephropathy (BKVN) had higher LT, St, VP1, and VP2-ELISPOT results than those with BKVN (p < 0.05).

CONCLUSION

BKV-ELISPOT assay may be effective in predicting clinical outcomes of BKV infection in terms of clearance of BK virus and development of BKVN.

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

Background and Aims:

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

Methods:

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

Results:

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

Conclusion:

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

[Characteristics of BK polymavirus infection in kidney transplant recipients]

OBJECTIVE

To analyze the characteristics of BK polymavirus (BKV) infection and the optimal time window for intervention in kidney transplant recipients (KTRs).

METHODS

We retrospectively analyzed the clinical data and treatment regimens in 226 KTRs in our center between January, 2013 and January, 2018. Among the recipients, 157 had a urine BKV load ≥1.0×104 copy/mL after transplantation, and 69 had a urine BKV load below 1.0×104 copy/mL (control group).

RESULTS

Among the 157 KTRs, 60 (38.2%) recipients were positive for urine BKV, 66 (42.0%) had BKV viruria, and 31(19.7%) had BKV viremia. The incidence of positive urine occult blood was significantly higher in BKV-positive recipients than in the control group (P < 0.05). The change of urine BKV load was linearly related to that of Tacrolimus trough blood level (r2=0.351, P < 0.05). In urine BKV positive group, the average estimated glomerular filtration rate (eGFR) was below the baseline level (60 mL·min-1·1.73 m-2) upon diagnosis of BKV infection reactivation, and recovered the normal level after intervention. In patients with BKV viruria and viremia, the average eGFR failed to return to the baseline level in spite of improvement of the renal function after intervention.

CONCLUSIONS

Positive urine occult blood after transplantation may be associated with BKV infection reactivation in some of the KTRs. BKV infection is sensitive to changes of plasma concentration of immunosuppressive agents. Early intervention of BKV replication in KTRs with appropriate dose reduction for immunosuppression can help to control virus replication and stabilize the allograft function.

Risk factors for BK virus viremia and nephropathy after kidney transplantation: A systematic review

In the last 20 years, the management of BK polyomavirus (BKPyV) reactivation in kidney transplant patients has become a true challenge for the transplant community. The only treatment option is based on the early identification of at-risk patients. The number of reported risk factors for BKPyV reactivation has increased markedly in the literature last years, although they are sometimes in an unclear or contradictory manner. Our purpose is to provide a systematic review and meta-analysis of risk factors for BKPyV viremia and nephropathy described in multivariate analyses. The PubMed database was searched for prospective or prospectively-based observational studies on risk factors for BKPyV viremia and/or nephropathy. Our qualitative assessment of risk factors was based on the odds ratios and hazard ratios calculated in multivariate regression analyses. Of the 241 publications screened, 34 were included in the qualitative analysis. In all, 144 and 19 distinct factors were analyzed for BKPyV viremia and for BKPyV nephropathy, respectively. Our evaluation highlighted eight risk factors for BKPyV viremia: a tacrolimus regimen, a deceased donor, a male recipient, a history of previous transplant, age at transplantation, ureteral stent use, delayed graft function, and acute rejection episodes increased the risk of BKV viremia to varying extents. Tacrolimus and acute rejection episodes were also associated with a higher incidence of BKPyV nephropathy. BKPyV reactivation is a serious complication after renal transplantation. With a view to combating this problem, existing data should be published in full, and new prospective international multicenter studies should be performed.

Variability in assessing for BK viremia: whole blood is not reliable and plasma is not above reproach - a retrospective analysis

Polyomavirus nephropathy (PVN) is a major complication of kidney transplantation. Most reports describe polyomavirus viremia either precedes or is detectable at the time of diagnosis of PVN. This association is the basis of current screening recommendations. We retrospectively reviewed the PCR results of blood and urine samples from 29 kidney transplant recipients with biopsy-proven PVN. Biopsies were performed for a rise in serum creatinine or persistent high-level BK viruria. All biopsies showed polyoma virus large T-antigen expression in tubular epithelium using immunohistochemistry. All had viruria preceding or at the time of biopsy (range, 5.2 × 10⁴ to >25 × 10⁶ BKV DNA copies/ml). Twenty (69%) had viremia ranging from 2.5 × 10³ to 4.3 × 10⁶ copies/ml at the time of the biopsy. Via blood BK PCR assay, nine (31%) had no BK viremia detected either preceding or at the time of the biopsy. In five recipients where sufficient specimen permitted, additional plasma BK assessment revealed positive detection of viremia. A comparative analysis of assays from two centres was performed with spiked samples. BK DNA may not be detected in the blood of some kidney transplant recipients with histologically confirmed PVN. This may reflect limitation of whole blood as opposed to plasma-based BK DNA assessment.

Increased gene expression of TGF-β in peripheral blood mononuclear cells from renal transplant patients with polyomavirus BK viremia

We aimed to investigate the roles of cytokines during polyomavirus BK (BKV) reactivation in renal transplant patients. Forty-eight renal allograft recipients were enrolled, and their sera BKV viral load and mRNA expression levels of cytokines in peripheral blood mononuclear cells were measured by real-time polymerase chain reaction. Patient's age and gene expression levels of interleukin (IL)-2 (10.04 ± 2.63 vs. 8.70 ± 2.40, p = 0.049) and transforming growth factor (TGF)-β (12.58 ± 2.59 vs. 10.89 ± 1.91, p = 0.015) were significantly higher in BKV viremia (+) renal transplant patients. Multivariate logistic regression analysis revealed that age and mRNA expression levels of TGF-β, but not IL-2, significantly correlated with the presence of BKV viremia. Sera BKV viral loads showed a positive correlation with patient age and the levels of TGF-β and IL-6 mRNA. After adjusting for age and sex in the regression model, both age and TGF-β mRNA levels maintained a significant positive association with sera BKV viral loads. Serum TGF-β concentration tended to be higher in BKV viremia (+) patients (p = 0.079). In conclusion, expression levels of TGF-β were found to correlate with both BKV viremia positivity and sera BKV viral loads in renal transplant patients.

Association of BK Virus Titers With Lymphocyte Count in Renal Transplant Patients

OBJECTIVES

Regular screening for the BK virus (BKV) is recommended for early intervention in renal transplant patients. Identification of predictors for the development of BK viremia would improve their monitoring. We performed a retrospective study investigating whether the lymphocyte count may be a predictor of BKV development in renal transplant patients.

PATIENTS AND METHODS

We retrospectively analyzed 268 renal transplant patients who were followed in our clinic from January 2011 to August 2014. The viral loads of BKV in blood detected by quantitative real-time polymerase chain reaction test were performed according to relevant guidelines. We also retrospectively monitored lymphocyte count, creatinine, immunosuppressive drug doses, and tacrolimus/cyclosporine/mTor inhibitors levels during the same time as BKV screening. Demographic and other clinical data were extracted from patients' files. The calculation of correlation coefficients and receiver operating characteristics (ROC) curve analysis were performed.

RESULTS

Overall, 16 patients (5.9%) who experienced BKV-DNA positivity were included the study. Mean age of patients was 38.2 ± 12.8 years. All patients received steroid and calcineurin inhibitors (CNIs). Mycophenolate mofetil/mycophenolic acid (MMF/MPA) was administered to 14 patients. BKV-DNA was found in 64 of the 88 (72.7%) plasma samples. The lymphocyte count on the first day of positive BKV-DNA test was significantly lower than in those with negative BKV-DNA results (1700/μl vs 2400/μl, respectively; P = .009). Its AUC of the ROC curve was 0.77 (P = .012). The optimal cutoff point for lymphocyte count was 1900/μl, and sensitivity and specificity for predict BKV positivity were 75% and 78.57%, respectively. We also found that lymphocyte count negatively correlated with the first detectable BKV titers (r = -0.438; P = .015). However, there is no relation between CNI/mTOR inhibitor levels, MMF/MPA doses, lymphocyte count, and all BKV-titers.

CONCLUSIONS

Decreased lymphocyte count may be a predictor for preceding BKV viremia. Clinicians should be more careful in terms of the decreased lymphocyte count in case of BKV replication in renal transplant patients.