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.