A Multicenter Application of the 2018 Banff Classification for BK Polyomavirus-associated Nephropathy in Renal Transplantation

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.

Polyomavirus nephropathy: diagnosis, histologic features, and differentiation from acute rejection

Polyomaviruses, particularly BK virus, are ubiquitous latent infections that may reactivate with immunosuppression during kidney transplantation, resulting in polyomavirus nephropathy (PVN). The levels of viruria and viremia serve as tools for screening and making a presumptive diagnosis of PVN, respectively, while a definitive diagnosis requires a kidney biopsy. There are histologic classifications of PVN based on the extent of tubular cell viral infection, interstitial fibrosis, and interstitial inflammation. These classifications correlate to some degree with graft function and loss, aiding in determining treatment efficacy and prognostication. PVN has histologic overlap with acute cell-mediated rejection, making the differential diagnosis challenging, although there are suggestive features for these different causes of graft dysfunction. This article reviews the diagnosis, histologic findings, and classifications of PVN, and discusses how to differentiate viral nephropathy from acute rejection.

Clinicopathological Correlation of Polyomavirus Nephropathy in Renal Allograft Recipients According to the Banff 2018 Classification

BACKGROUND

Polyomavirus nephropathy (PVN) is a rare kidney disease caused by the BK virus, a strain of polyomavirus. The disease primarily affects transplant recipients, which is related to intensive immunosuppression protocol and can lead to kidney allograft failure.

OBJECTIVES

The objective of this study is to analyze histopathological features of PVN using the Banff 2018 PVN classification and to determine clinical features and outcomes of patients with PVN in each histologic class.

MATERIALS AND METHODS

The study included 44 patients who had been diagnosed with PVN by renal allograft biopsy in a large tertiary care hospital in Thailand from January 2011 to January 2020. The kidney biopsy slides were reviewed for Banff 2018 PVN classification and other histologic features. Patient demographic information, clinical data, and laboratory results were retrospectively collected.

RESULTS

Nine (20.45%), 27 (61.36%), and eight (18.18%) cases of PVN were Class I, Class II, and Class III, respectively. The time from transplant to PVN diagnosis for Classes I, II, and III was four, 19, and 33.5 months, respectively. Class III had the worst clinical outcomes in terms of deterioration of allograft function, the lowest rate of resolution, and the highest rate of graft failure.

CONCLUSIONS

PVN classification provides prognostic information in renal allograft biopsy. Our study confirmed the validity of the three-tier histologic PVN classification put forward by the Banff Working Group in 2018.

Application of Real-Time Sound Touch Elastography for Evaluating Chronic Kidney Disease of Transplanted Kidneys

BACKGROUND

If chronic allograft nephropathy can be detected early and treated, the long-term survival rate of the transplanted kidney may be effectively improved.

PURPOSE

To compare the application value of real-time sound touch elastography (STE), strain elastography, and color Doppler flow imaging in evaluating chronic kidney disease of transplanted kidneys.

MATERIALS AND METHODS

A total of 101 patients with renal transplantation were divided into a normal group (serum creatinine <134 mol/L, 58 patients) and a chronic allograft nephropathy group after renal transplantation over 6 months (serum creatinine >134 mol/L, 43 patients). The maximum elastic modulus (Emax) was determined, and receiver operator characteristics were used to compare the diagnostic efficacy of STE ultrasound.

RESULTS

Emean, Emax, B/A (the strain rate of the internal oblique muscle tissue/ the strain rate of the central renal cortex) of cortical standard strain ratio in strain elastography, and resistance index (RI) between normal and chronic allograft nephropathy groups have statistical significance (P < .05). Emax is superior to B/A and arcuate artery RI in the chronic cortex in the diagnosis of renal dysfunction, and the area under the receiver operator characteristics curve is 0.88. The estimated glomerular filtration rate was negatively correlated with renal cortex Emax, B/A, and arcuate artery RI, among which Emax was the strongest (r = - 0.713, P < .001). The renal cortical Emax cut-off was 30.95 kPa, the sensitivity was 92%, the specificity was 88%, and the accuracy was 88%.

CONCLUSION

The STE technique to evaluate chronic renal dysfunction after renal transplantation is more sensitive than traditional strain-type elastography and hemodynamic parameters, with renal function decline, renal cortex Emax, renal cortical B/A, and arcuate artery RI gradually increased, and renal cortex Emax was particularly obvious.

An observational cohort study of histological screening for BK polyomavirus nephropathy following viral replication in plasma

Systematic screening for BKPyV-DNAemia has been advocated to aid prevention and treatment of polyomavirus associated nephropathy (PyVAN), an important cause of kidney graft failure. The added value of performing a biopsy at time of BKPyV-DNAemia, to distinguish presumptive PyVAN (negative SV40 immunohistochemistry) and proven PyVAN (positive SV40) has not been established. Therefore, we studied an unselected cohort of 950 transplantations, performed between 2008-2017. BKPyV-DNAemia was detected in 250 (26.3%) transplant recipients, and positive SV40 in 91 cases (9.6%). Among 209 patients with a concurrent biopsy at time of first BKPyV-DNAemia, 60 (28.7%) biopsies were SV40 positive. Plasma viral load showed high diagnostic value for concurrent SV40 positivity (ROC-AUC 0.950, 95% confidence interval 0.916-0.978) and the semiquantitatively scored percentage of tubules with evidence of polyomavirus replication (pvl score) (0.979, 0.968-0.988). SV40 positivity was highly unlikely when plasma viral load is below 4 log10 copies/ml (negative predictive value 0.989, 0.979-0.994). In SV40 positive patients, higher plasma BKPyV-DNA load and higher pvl scores were associated with slower viral clearance from the blood (hazard ratio 0.712, 95% confidence interval 0.604-0.839, and 0.327, 0.161-0.668, respectively), whereas the dichotomy positivity/negativity of SV40 immunohistochemistry did not predict viral clearance. Although the pvl score offers some prognostic value for viral clearance on top of plasma viral load, the latter provided good guidance for when a biopsy was unnecessary to exclude PyVAN. Thus, the distinction between presumptive and proven PyVAN, based on SV40 immunohistochemistry, has limited clinical value. Hence, management of BKPyV-DNAemia and immunosuppression reduction should be weighed against the risk of occurrence of rejection, or exacerbation of rejection observed concomitantly.

Importance of Follow-Up Biopsies in the Prediction of Renal Allograft Survival Following Polyomavirus-Associated Nephropathy

OBJECTIVES

Allograft biopsy is the gold standard for diagnosing polyomavirus-associated nephropathy. We aimed to establish the effects of histopathologic findings proposed by the Banff Polyomavirus Working Group on graft outcome. We also aimed to understand the clinical importance of follow-up biopsies for patients with polyomavirus-associated nephropathy.

MATERIALS AND METHODS

Our study included 22 patients with polyomavirus-associated nephropathy. All biopsies were classified according to the latest Banff Polyomavirus Working Group classification. Follow-up biopsies of all patients were evaluated in detail.

RESULTS

The mean interval between polyomavirus-associated nephropathy and transplant was 10 ± 1.6 months. Of 22 patients, biopsy revealed stage 1 in 3 (13.6%), stage 2 in 17 (77.3%), and stage 3 in 2 patients (9.1%). Fourteen patients (63.6%) had polyomavirus viral load 3, 5 (22.7%) had polyomavirus viral load 2, and 3 had polyomavirus viral load 1. Among patients included in analyses, 18.2% had antibody-mediated rejection and 27.2% had T-cell-mediated rejection simultaneously with polyomavirus-associated nephropathy. Graft loss increased with increasing polyomavirus-associated nephropathy class and polyomavirus viral load (P = .015 and P = .002, respectively). The mean time of graft survival decreased with increasing degree of tubulitis, interstitial inflammation, plasma infiltration, and neutrophil infiltration. Patients with interstitial fibrosis, glomerular polyoma, and cortical plus medullar involvement showed earlier graft loss. Follow-up biopsies showed that diffuse interstitial fibrosis or persistent inflam-mation negatively influenced graft loss.

CONCLUSIONS

The Banff Polyomavirus Working Group's schema significantly correlated with graft outcome. Early detection of polyomavirus-associated nephro-pathy and subsequent detection of persistent inflammation and interstitial fibrosis and tubular atrophy in follow-up biopsies and modification of immunosuppressive therapy can successfully prevent graft loss.

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.

Routine immunohistochemistry study for polyomavirus BK nephropathy in transplanted kidney biopsies, is it recommended?

BACKGROUND

Early diagnosis and treatment of Polyomavirus BK Nephropathy (PVBKN) is a challenging issue in the management of patients with kidney transplantation. Currently, histopathologic diagnosis is the gold standard method for diagnosis of PVBKN. However, typical viral inclusions may not be found in early stages of the PVBKN and should, instead, be diagnosed using immunohistochemistry (IHC) study. There is no clear consensus about routine IHC tests in the pathologic evaluation of transplanted kidney biopsy samples.

MATERIAL AND METHODS

The current study was conducted on transplanted kidney biopsy samples, since 2016 to 2019. The patients who have presented with new onset of allograft dysfunction, at least 2 weeks after transplantation surgery, were included in our study. All these biopsy samples were evaluated with routine renal biopsy stains as well as IHC for SV40 (Simvian Virus 40) antigen. The identification of typical nuclear virus inclusion body and any nuclear positive staining on IHC (≥1+ positive result) were considered as definite evidence of PVBKN. Sensitivity, specificity, Positive Predictive and Negative Predictive Values (PPV and NPV) of histopathologic assessment without IHC study were evaluated.

RESULTS

Among 275 included cases, 18 (6.5%) patients with PVBKN were diagnosed. In patients with PVBKN, typical viral inclusions were detected in 14 samples (77.7%), on primary histopathological examination. However, virus-infected cells were identified just after IHC study in 4 (22.2%) of patients. Sensitivity, Specifity, PPV and NPV of morphologic histopathological assay without IHC for detection of PVBKN was 77.7, 100, 100 and 98.4% respectively.

CONCLUSION

Routine IHC study for SV40 in all transplanted kidney biopsy samples with new onset of allograft dysfunction, will enhance the diagnostic sensitivity of early stage disease detection.

An application of the 2018 Banff Classification for BK polyomavirus-associated nephropathy in renal transplantation

BACKGROUND

There is still a lack of a recognized morphological classification of BK viral nephropathy (BKVN) which can better reflect the clinical manifestations and prognosis.

METHODS

We retrospectively analyzed the data of 53 patients with BKVN in our center from January 2011 to December 2018 and evaluated the new Banff 2018 classifications' predictive value for the graft prognosis.

RESULTS

The period between transplantation and BKVN diagnosis lasted for 10.3 months (IQR, 5.3-21.9 months). The main reason (92.5%) for puncture was the increase of blood serum creatinine. Of the 53 patients diagnosed with BKVN, 100% were positive for urinary BK virus-DNA, and the viral load was 1.4 × 10⁸  copies/mL (IQR, 3.7 × 10⁴ -1.3 × 10¹¹  copies/mL); 75.5% were positive for blood BK virus-DNA, and the viral load was 3.3 × 10⁴  copies/mL (IQR, 0-2.8 × 10⁷  copies/mL). There were five cases in class 1, 31 cases in class 2, and 17 cases in class 3; the viral load of urine BK was 3.3 × 10⁸ , 1.4 × 10⁸ , and 6.3 × 10⁷  copies/mL (P > .05); the viral load of blood BK was 3.3 × 10⁴ , 3.3 × 10⁴ , and 3.3 × 10⁴  copies/mL (P > .05); the 1-year graft survival rates were 100%, 90.3%, and 52.9%, respectively (P < .05).

CONCLUSION

BKVN mostly occurs within 1 year after transplantation. There is no correlation between BK virus load in hematuria and pathological damage at the time of diagnosis. The 2018 Banff Classification for BKVN can better indicate the prognosis of graft.