Screening for polyomavirus associated nephropathy in renal transplantation with blood viral load measurement

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.

Effect of polyoma viremia on 3-year allograft kidney function

BACKGROUND

Polyoma viremia is associated with damage to renal tubular and urothelial cells. This may imply that a certain level of viremia, even cleared thereafter, could be associated with long-term renal dysfunction.

METHODS

We, retrospectively, analyzed 390 first renal transplants adult recipients (≥18 years) who were monitored for BK viremia in the first 12 months and evaluated estimated GFR (MDRD-4 equation) at 1 month and at the last follow-up (959 ± 392 days).

RESULTS

One hundred and ninety-nine patients (51%) developed at least one positive viremia: 105 (53%) low viremia (<10⁴  copies/mL), 36 (18%) high viremia (4 × 10⁴  > viremia ≥ 10⁴  copies/mL) and 58 (15%) viremia (≥4 × 10⁴  copies/mL) consistent with polyoma virus associated nephropathy (PyVAN). Out of these 58 patients, 24 (6%) developed bx-proven (SV40+) PyVAN and 34(8.7%) presumptive PyVAN (SV40-). Baseline characteristics, immunosuppression, KDRI, rejection episodes, etc., did not differ among groups but there were more deceased donors and ATG induction therapy in the high viremia group. At last follow-up, all patients in the low, high viremia and presumptive PyVAN (except 2) had cleared BK viremia. Bx-proven PyVAN led to 14 graft losses, 10 due to PyVAN. In the presumptive PyVAN there was only one graft loss registered as due to PyVAN. eGFR, at 1 month after KTx, did not differ among groups (51 ± 22 vs 48 ± 24 vs 45 ± 27 vs 43 ± 18 vs 46 ± 22 mL/min/1.73 m² ), for no, low and high viremia as well for presumptive PyVAN and bx-proven PyVAN groups, respectively. At the last follow-up, eGFR did not differ between the no, low, and high viremia compared to baseline and to each other but was statistically lower in the presumptive and bx-proven PyVAN (38 ± 15 and 17 ± 7 mL/min/1.73 m² ) either compared to baseline or to the other groups.

CONCLUSIONS

This study shows that low and high levels of BK viremia do not lead to GFR changes although very high viremia levels, compatible with presumptive or bx-proven PyVAN, even if cleared thereafter, lead to allograft damage and decreased GFR.

IL28B rs12979860 genotype as a predictor marker of progression to BKVirus Associated nephropathy, after kidney transplantation

BK virus (BKV) associated nephropathy (BKVAN) is still an important cause of allograft dysfunction after kidney transplantation (KT). Recent data have shown that the new interferon (IFN)-λ family has been ascribed antiviral properties similar to IFNα, and that the response to IFNλ in kidney is restricted to epithelial cells, suggesting that the IFNλ system evolves as specific protection of the epithelia. We aimed to test the hypothesis of correlation between a single nucleotide polymorphism (C/T dimorphism rs12979860) in the genomic region of IL28B and BKVAN, in patients after KT. Fifty kidney-transplanted patients were included as follow: Group 1 (BKV+/BKVAN+): 11 patients with active BKV- replication and biopsy-proven BKVAN; Group 2 (BKV+/BKVAN-): 22 patients with active BKV- replication but without evidence of BKVAN; Group 3 (BKV-/BKVAN-): 17 patients without evidence of BKV- replication (control group). Here we show that the C/C genotype was statistically higher in group 2 than in group 1 and BKVAN was detected significantly more frequently in patients with C/T and T/T genotypes than in patients with C/C genotype. We therefore propose IL28B polymorphism (rs12979860), as a predictor-marker to differentiate between patients with self-limited, even if persistent, BKV- reactivation and patients with a high risk of progression towards BKVAN, and to modulate the clinical management of these patients accordingly.

A rolling circle amplification screen for polyomaviruses other than BKPyV in renal transplant recipients confirms high prevalence of urinary JCPyV shedding

OBJECTIVES

Multiple novel human polyomaviruses (HPyVs) have been discovered in the last few years. These or other, unknown, nephrotropic HPyVs may potentially be shed in urine.

METHODS

To search for known and unknown HPyVs we investigated BKPyV-negative urine samples from 105 renal transplant recipients (RTR) by rolling circle amplification (RCA) analysis and quantitative JCPyV PCR. Clinical data was analysed to identify risk factors for urinary polyomavirus shedding.

RESULTS

In 10% (11/105) of the urine samples RCA with subsequent sequencing revealed JCPyV, but no other HPyV sequences. Using quantitative JCPyV PCR, 24% (25/105) of the samples tested positive. Overall sensitivities of RCA of 44% (11/25) in detecting JCPyV in JCPyV DNA-positive urine and 67% (10/15) for samples with JCPyV loads >10,000 copies/ml can be assumed. Despite frequent detectable urinary shedding of JCPyV in our cohort, this could not be correlated with clinical risk factors.

CONCLUSION

Routine urinary JCPyV monitoring in BKPyV-negative RTR without suspected polyomavirus-associated nephropathy might be of limited diagnostic value. As RCA works in a sequence-independent manner, detection of novel and known polyomaviruses shed in sufficient quantities is feasible. High-level shedding of HPyVs other than BKPyV or JCPyV in the urine of RTR is unlikely to occur.

Correlation between urine and serum BK virus levels after renal transplantation

BACKGROUND

Quantification of the serum level of BK virus is used as a surrogate marker for the early onset of BK virus nephropathy. However, little is known about the diagnostic value of the urine level of BK virus for nephropathy or the relationship between the serum and urine viral load. We investigated the correlation between urine and serum BK virus levels after renal transplantation.

METHODS

From November 2008 to August 2013, a total of 270 renal transplant patients who were followed at our institution were included in this study. Urine and serum were collected simultaneously. BK virus levels were quantified in 894 urine and serum samples using a real-time polymerase chain reaction assay.

RESULTS

BK virus was detected in 178 urine samples and 36 serum samples. Among the BK virus-positive urine subjects, the positive predictive value for viral detection in the serum was 9% (13/147) when the urinary virus level was <10(7) copies/mL and 74% (23/31) when the urinary virus was ≥ 10(7) copies/mL. Serum BK viral levels were ∼2-3 log units lower than those in urine.

CONCLUSIONS

BK virus was detected more frequently in serum when present in urine at ≥ 10(7) copies/mL after renal transplantation.

Test performance characteristics of quantitative nucleic acid testing for polyomaviruses in kidney and kidney-pancreas transplant recipients

Screening for polyoma BK virus (BK) using nucleic testing (NAT) is recommended for kidney and kidney-pancreas transplant recipients, but the performance characteristics of quantitative BK NAT at different thresholds of plasma BK viral loads are unclear. We aim to evaluate the diagnostic accuracy of quantitative BK NAT as an add-on test to qualitative polyoma NAT for the diagnosis of BK virus-associated nephropathy (BKVAN) in kidney and kidney transplant recipients. We calculated the test sensitivity, specificity, and predictive values at the different thresholds of plasma BK viral load for BKVAN. At the recommended threshold of >1 × 10(3) serum BK copies/mL serum for test positivity, the sensitivity for BKVAN was 92.9% (95% confidence intervals [CI]: 66.1-99.8) and specificity 79.1% (95%: CI 67.4-88.1), with corresponding positive and negative predictive values of 42.0% (95% CI: 24.8-57.7%) and 98.6% (95% CI: 98.3-99.9%), respectively. The overall area under curve for the quantitative BK NAT was 0.92 (95% CI: 0.85-0.97). Quantitative BK NAT displays properties of high sensitivity and specificity that are fit for purpose as an add-on test to qualitative polyomavirus NAT for kidney and kidney-pancreas transplant recipients at risk of BKVAN.

Prospective monitoring of BK virus reactivation in renal transplant recipients in North India

BACKGROUND

BK nephropathy (BKN) is an important complication of renal transplantation with a reported incidence between 1% and 10% in different parts of the world. Early diagnosis is important to plan early therapeutic strategies. The epidemiology and evolution of BKN is relatively unknown in India and hence, the present study has been designed to prospectively monitor the activation of BK virus (BKV) in renal transplant recipients in India.

PATIENTS AND METHODS

In this study, 32 renal allograft recipients were prospectively monitored with protocol biopsies of allografts, BKV DNA load in plasma, and viral particles in urine by electron microscopy (EM) on day 1, and at 1, 3, and 6 months. Additionally, the baseline BKV DNA load in plasma was quantitated in 21 corresponding donors.

RESULTS

On follow-up in 32 recipients, 9.7%, 23.8%, 19.2%, and 13.3% of patients showed viral profiles by EM at day 1, 1 month, 3 months, and 6 months, respectively. BKV DNA positivity in plasma was 25.8%, 42.9%, 15.4%, and 20% at day 1, 1 month, 3 months, and 6 months, respectively, with mean BKV copy number/mL plasma of 1796, 1029, 2611, and 3318, respectively. A total of 15.7% (17/108) urine samples of 32 renal recipients were positive by urine EM. Out of 100 protocol biopsies, none developed histologically demonstrable cytopathic effects of BKN, although 8% biopsies were SV-40 large T antigen (SV-40 T Ag) positive. By quantitative real-time polymerase chain reaction assay, 27/108 (25%) of recipients' plasma samples were positive for BKV. Peak viremia and viruria occurred at 1-3 months post transplantation. The baseline viremia in donors was predictive of viremia positivity in the post-transplantation period at 1 month. Twenty-four episodes of graft dysfunction were attributed mainly to rejection.

CONCLUSION

The study shows a total of 15.7% and 25% urine and plasma samples were positive for BKV at any time during a 6-month follow-up. The highest incidence of BK viruria and viremia occurred at 1 month. In protocol biopsies, focal positivity of SV-40 T Ag was seen in 8% biopsies.