Simultaneous immunostaining with anti-S100P and anti-SV40 antibodies revealed the origin of BK virus-infected decoy cells in voided urine samples

Presence of decoy cells for 6 months on urine cytology efficiently predicts BK virus nephropathy in renal transplant recipients

OBJECTIVES

To investigate the association between duration of consecutive presence of decoy cells on urine cytology and BK virus nephropathy after kidney transplantation.

METHODS

In total, 121 kidney transplant recipients were retrospectively evaluated. The best duration of consecutive presence of decoy cells that could be used to predict BK virus nephropathy was analyzed using the area under the curve for each duration, and recipients were divided into two groups based on the best predictive performance. The effectiveness of SV40 immunostaining on urinary cytology was also analyzed.

RESULTS

In total, 2534 urine specimens as well as SV40 immunostaining in 2241 urine specimens were analyzed. Six consecutive months of decoy cell positivity had the best predictive performance for BK virus nephropathy (area under the curve = 0.832). The incidence of BK virus nephropathy in recipients with positive decoy cells for 6 months or more consecutive months (5/44) was significantly higher than in those who had positive decoy cells for less than 6 months (0/77; P = 0.005). Decoy cell positivity had a sensitivity, specificity, positive predictive value, and negative predictive value for BK virus nephropathy of 100%, 66%, 11%, and 100% respectively. SV40 immunostaining provided slightly better specificity (68%) and positive predictive value (12%).

CONCLUSIONS

The detection of decoy cells at 6 months or more on urine cytology had high predictive value for BK virus nephropathy in kidney transplant recipients. SV40 immunostaining on urine cytology added minimal diagnostic accuracy.

BK Virus-Associated Nephropathy after Renal Transplantation

Recent advances in immunosuppressive therapy have reduced the incidence of acute rejection and improved renal transplantation outcomes. Meanwhile, nephropathy caused by BK virus has become an important cause of acute or chronic graft dysfunction. The usual progression of infection begins with BK viruria and progresses to BK viremia, leading to BK virus associated nephropathy. To detect early signs of BK virus proliferation before the development of nephropathy, several screening tests are used including urinary cytology and urinary and plasma PCR. A definitive diagnosis of BK virus associated nephropathy can be achieved only histologically, typically by detecting tubulointerstitial inflammation associated with basophilic intranuclear inclusions in tubular and/or Bowman’s epithelial cells, in addition to immunostaining with anti-Simian virus 40 large T-antigen. Several pathological classifications have been proposed to categorize the severity of the disease to allow treatment strategies to be determined and treatment success to be predicted. Since no specific drugs that directly suppress the proliferation of BKV are available, the main therapeutic approach is the reduction of immunosuppressive drugs. The diagnosis of subsequent acute rejection, the definition of remission, the protocol of resuming immunosuppression, and long-term follow-up remain controversial.

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.

Association Between the Polyomaviruses Titers and Decoy Cell Positivity Rates After Renal Transplantation

BACKGROUND

Urinary decoy cells develop after renal transplantation and their appearance is attributable primarily to the proliferation of polyomavirus types BK and JC. We measured the levels of these 2 viruses that cause decoy cells to appear in the urine.

PATIENTS AND METHODS

BK and JC virus levels were quantified in 1182 urine samples from 335 renal transplant patients using a multiplex Taqman real-time polymerase chain reaction assay. Forty-four samples were excluded from analyses because both viruses were present at ≥10(4) copies/mL. We analyzed the relationship between viral load and the presence of urinary decoy cells.

RESULTS

Decoy cells were observed in 237 of 1138 urine samples (21%) and the BK and JC viruses were positive in 205 (18%) and 455 (40%) samples, respectively. Decoy cells were observed in 0%, 21%, 67%, 87%, 100%, and 96% of urine samples when the BK viral load was <10(4), 10(4)-10(5), 10(5)-10(6), 10(6)-10(7), 10(7)-10(8), and ≥10(8) copies/mL, respectively; and in 1%, 13%, 41%, 59%, 87%, and 97% of urine samples when the JC viral load was <10(4), 10(4)-10(5), 10(5)-10(6), 10(6)-10(7), 10(7)-10(8), and ≥10(8) copies/mL, respectively.

CONCLUSIONS

BK virus more frequently triggered the appearance of decoy cells than did JC virus at equivalent viral titers.

Correlation between the presence of degenerated inclusion-bearing cells in voided urine samples and the occurrence of polyomavirus infection

OBJECTIVE

The purpose of the present, prospective, cohort study was to monitor urine cytology samples from recipients of renal transplants to search for the occurrence of decoy cells and degenerated inclusion-bearing cells with an aim to correlate the existence of these cells with molecular detection of polyomavirus BK (BKV) DNA in urine.

MATERIAL AND METHODS

This study included patients who underwent renal transplantation. Patients had their urine tested quarterly, during the first year post-transplantation, for the presence of decoy cells and degenerated cells, as well as by quantitative determination of BKV load in the urine and plasma.

RESULTS

Three hundred and sixty-one examinations were performed on 101 patients within 12 months of attendance. Urine cytology results were: 198 (54.9%) negative and 60 (16.6%) positive for the presence of viral cytopathic effects depending on the presence of BKV infection, 72 (19.9%) positive for the manifestation of degenerated cells and 31 (8.6%) unsatisfactory for analysis. There was a subtle tendency towards the presence of degenerated inclusion-bearing cells in cases in which the virus was detected in voided urine. However, the presence of degenerated cells exhibited a tendency to BKV positivity in months 3, 6 and 9 and, exclusively in month 12, this trend was statistically significant.

CONCLUSIONS

There were not enough strong morphological and staining elements to state the origin of the degenerated cells or to describe the nature of the infection (viral or bacterial), given that these cells were undergoing an apoptotic process in post renal transplant patients.