Clinical Utility of Urinary Cytology to Detect BK Viral Nephropathy.

BACKGROUND: Reactivation of BK polyoma virus can result in destructive viral allograft nephropathy (BKVAN) with limited treatment options. Screening programs using surrogate markers of viral replication are important preventive strategies, guiding immunosuppression reduction. METHODS: We prospectively evaluated the diagnostic test performance of urinary decoy cells and urinary SV40T immunochemistry of exfoliated cells, to screen for BKVAN, (defined by reference histology with SV40 immunohistochemistry, n = 704 samples), compared with quantitative viremia, from 211 kidney and 141 kidney-pancreas transplant recipients. RESULTS: The disease prevalence of BKVAN was 2.6%. Decoy cells occurred in 95 of 704 (13.5%) samples, with a sensitivity of 66.7%, specificity of 88.6%, positive predictive value (PPV) of 11.7%, and negative predictive value of 98.5% to predict histologically proven BKVAN. Quantification of decoy cells improved the PPV to 32.1% (10 ≥ cells threshold). Immunohistochemical staining of urinary exfoliated cells for SV40T improved sensitivity to 85.7%, detecting atypical or degenerate infected cells (specificity of 92.3% and PPV of 33.3%), but was hampered by technical failures. Viremia occurred in 90 of 704 (12.8%) with sensitivity of 96.3%, specificity of 90.3%, PPV of 31.5%, and negative predictive value of 99.8%. The receiver-operator curve performance of quantitative viremia surpassed decoy cells (area under the curve of 0.95 and 0.79, respectively, P = 0.0018 for differences). Combining decoy cell and BK viremia in a diagnostic matrix improved prediction of BKVAN and diagnostic risk stratification, especially for high-level positive results. CONCLUSIONS: Although quantified decoy cells are acceptable surrogate markers of BK viral replication with unexceptional test performances, quantitative viremia displayed superior test characteristics and is suggested as the screening test of choice.

Human polyoma virus in kidney transplants: SV40 T-antigen demonstration in the urine.

We wanted to develop an immunostaining method of urine cytopreparations to detect polyoma virus infection by using fresh urine samples and staining with the monoclonal SV40 antibody and to compare the findings to the demonstration of decoy cells in the urine or to kidney histology. Routine urine samples from pediatric kidney transplant patients were collected either early after transplantation or later, cytocentrifuged, and immunostained with SV40-T-antibody. The number of SV40-T-antigen-positive epithelial cells was counted in the cytopreparations and compared to the findings in routine urine cytology and transplant histology. Immunostaining of urine cytology with SV40-T-ab demonstrated clearly that the infected epithelial cells and the rate of infection could be estimated by semiquantitative counting. There was strong correlation between the findings in the urine and in the biopsies, but in the urine preparations the number of infected cells was much higher than in the biopsies. The high number of SV40-positive cells in the urine also correlated to the severity of clinical infection and to the state of transplant. Immunostaining of urine cytology with SV40-T-antibody seems to be useful in the diagnosis and follow-up of polyoma virus reactivation disease in transplant patients, especially in children with renal transplants.

Identification of SV40 in brain, kidney and urine of healthy and SIV-infected rhesus monkeys.

Recent reports of simian virus 40 (SV40) sequences in human tumors have prompted investigations into the poorly understood association of this polyomavirus with its primate host, the rhesus monkey (Macaca mulatta). In the present study we have used PCR to analyze tissues from 20 monkeys for the presence of SV40. Five of the animals, which were infected with simian immunodeficiency virus (SIV), were found to exhibit SV40-induced lesions and to have SV40 sequences present in their kidney and brain. Lesions associated with SV40 were not observed in 15 SIV monkeys, and SV40 DNA was detected in kidney and urine of only one of these animals. Three regions of SV40 DNA were examined in each tissue: the non-coding transcriptional control region (TCR), the sequences encoding the host range domain (HRD) within the carboxy-terminus of T antigen (TAg), and a portion of the VP1 gene. Each region contained nucleotide alterations compared to the SV40 reference strain 776. In all six animals, the TCR had an archetype structure containing a single 72 bp enhancer element. In addition, the TCR amplified from two animals lacked one of three copies of a GC-rich 21 bp repeat which is part of the promoter in strain 776. Multiple clones of unique HRD sequences were derived from different animals, and in some instances from the same animal. No correlation was found between a particular HRD sequence and its presence in a specific tissue type. Nucleotide changes identified within the VP1 gene indicate that this region, as with the closely-related human polyomavirus JCV, may permit the typing of the virus into individual strains. This study is the first to characterize SV40 sequences present in both healthy and SIV-infected animals and supports the suggestion that strain 776 is not the predominant type of SV40 circulating in its natural host.