Determinação do limite mínimo de detecção da técnica de Nested-PCR para os poliomavírus JC e BK / Assessment of minimum detection limit of Nested-PCR for JC and BK polyomaviruses

Introduction: Polyomaviruses (BKV and JCV) cause infection mainly in immunocompromised adults. A sensitive and specific diagnosis tool is fundamental to demonstrate the BKV and JCV infections. Nowadays many laboratories are using a PCR technique for detecting polyomaviruses genome in clinical samples. In this context, the purpose of this study is to determine the threshold of detection of the nested-PCR for polyomaviruses JC and BK. Methods: Serial dilutions of the samples of BKV and JCV of known concentration (100 copies/mL, 50 copies/mL, 25 copies/mL, 10 copies/mL, 5 copies/mL, and 1 copy/ml) were subjected to the technique of nested-PCR. All dilutions were tested 11 times to determine the minimum detection limit. Results: The minimum detection limit of the nested-PCR for JC and BK viruses was 25 copies/mL. This dilution (25 copies/mL) showed 100% PCR positive reaction. Furthermore, we found that weak positive results were obtained at dilutions of 1,5 and 10 copies/mL in some repetitions. Dilutions of 25, 50, and 100 copies/mL always had very positive results. Conclusions: These values are similar to those reported in other studies, contributing to the indication of this PCR for potential diagnostic purposes.

Introdução: Os poliomavírus (JCV e BKV) causam infecções principalmente em adultos imunocomprometidos. Um diagnóstico sensível e específico é de fundamental importância para os pacientes portadores de JCV e BKV. Atualmente alguns laboratórios têm utilizado a técnica de PCR para a detecção do material genético destes vírus em amostras clínicas. Assim, o objetivo deste estudo é determinar o limite mínimo de detecção da técnica de nested-PCR para os poliomavírus JC e BK. Métodos: Diluições seriadas (100 cópias/mL; 50 cópias/mL; 25 cópias/mL; 10 cópias/mL; 5 cópias/mL e 1 cópia/mL) de controles positivos comerciais de JCV e BKV com concentrações conhecidas foram submetidas à técnica de nested-PCR semi-duplex. Todas as diluições foram testadas 11 vezes para determinação do limite mínimo de detecção. Resultados: O limite mínimo de detecção da reação de nested-PCR para os vírus JC e BK foi de 25 cópias/mL para ambos, com 100% de positividade das diluições testadas na reação de PCR. Ainda, pudemos observar que resultados positivos fracos foram obtidos nas diluições de 1, 5 e 10 cópias/mL em algumas das repetições realizadas. As diluições de 25, 50 e 100 cópias/mL sempre obtiveram resultado rancamente positivo. Conclusões: Estes valores são semelhantes aos relatados em outros estudos, contribuindo para a indicação desta reação de PCR para potenciais fins diagnósticos.

JC polyomavirus infection in candidates for kidney transplantation living in the Brazilian Amazon Region

This study evaluated the relative occurrences of BK virus (BKV) and JC virus (JCV) infections in patients with chronic kidney disease (CKD). Urine samples were analysed from CKD patients and from 99 patients without CKD as a control. A total of 100 urine samples were analysed from the experimental (CKD patients) group and 99 from the control group. Following DNA extraction, polymerase chain reaction (PCR) was used to amplify a 173 bp region of the gene encoding the T antigen of the BKV and JCV. JCV and BKV infections were differentiated based on the enzymatic digestion of the amplified products using BamHI endonuclease. The results indicated that none of the patients in either group was infected with the BKV, whereas 11.1% (11/99) of the control group subjects and 4% (4/100) of the kidney patients were infected with the JCV. High levels of urea in the excreted urine, low urinary cellularity, reduced bladder washout and a delay in analysing the samples may have contributed to the low prevalence of infection. The results indicate that there is a need to increase the sensitivity of assays used to detect viruses in patients with CDK, especially given that polyomavirus infections, especially BKV, can lead to a loss of kidney function following transplantation.

Comparison of Detecting Methods of BK Virus Infection in Patients with Renal Allograft Recipients

BACKGROUND: BK virus nephropathy (BKVN) is an emerging problem as a consequence of the use of potent immunosuppressive agents. Because optimal detection methods for the diagnosis of BKVN are required clinically, we compared the results of renal allograft biopsy, urine cytology, and urine and blood viral loads. METHODS: Four hundred sixty two case notes from 2004 to 2009 at Seoul St. Mary's Hospital were reviewed. During that period, 286 cases of urine cytology for decoy cells, 938 cases of urine BKV reverse transcription-polymerase chain reaction (RT-PCR), and 1,029 cases of blood BKV RT-PCR were performed. All diagnostic methods were performed in 85 cases. RESULTS: A histological diagnosis of BKVN was made in 2.4% of cases (11/462). Urine cytology for decoy cells was positive in 26.2% (75/286). BKV RT-PCR revealed viruria in positivity of 22.1% (207/938) and viremia in 5.2% (54/1,029). In cases of BKVN, the sensitivities of urine and blood BKV RT-PCR were all 100% and the specificities were 69% and 94.5%, respectively. In cases with positive urine decoy cells, the sensitivities of urine and blood BKV RT-PCR were 50% and 27.7%, with specificities of 77.7% and 100%, respectively. CONCLUSIONS: BKV screening by RT-PCR assays may be a clinically useful noninvasive test to identify renal recipients with concurrent BKVN.

Polyomavirus (BK Virus) Nephropathy in Kidney Transplant Patients: A Pathologic Perspective

Reactivation of polyoma virus (BK virus) is a significant cause of morbidity in kidney transplant patients. This seemingly insignificant viral infection that affects the majority of population at a young age, once reactivated by immunosuppression, is a major factor contributing to graft loss. Screening techniques have been developed for early prediction of BK virus reactivation. These include plasma and urine assays for detection of BK virus DNA by PCR, urine cytology for detection of "decoy cells" and electron microscopy. Combining urine cytology and serology screening can be more effective for early detection of BK virus reactivation. Immunohistochemistry can be utilized as an additional tool to support the diagnosis. Once screening tests reveal a suspicious BK virus reactivation, tissue biopsy should be performed to confirm the diagnosis, rule out acute cellular rejection and plan treatment approaches. Treatment normally includes decreasing immunosuppression and the use of antiviral drug therapy. Unfortunately, disease outcome is often unfavorable and can culminate with eventual graft loss. Renal retransplantation has been performed with mixed results. As new data emerges, we will gain a better understanding of the disease caused by BK virus and respond with improved early diagnosis and treatment to preserve graft function.