Estudo prospectivo da infecção pelo citomegalovírus humano e poliomavírus BKV em pacientes com transplante renal: desenvolvimento de testes moleculares para detecção e quantificação viral e análise de associação de desfechos clínicos com a infecção viral ativa

Abstract

Active infection by cytomegalovirus (CMV) and polyomavirus (BKV) is common in patients with kidney transplantation and can be associated with disease, worsening renal function and risk of graft loss. Periodically monitoring patients for CMV and BKV, especially in the first year after transplant, is important to minimize the risk of morbidity from these infections. This study aimed to validate real-time PCR assays for the detection and quantification of CMV and BKV and, applying these tests, to evaluate the impact of infection by these viruses on patients with kidney transplantation at the Nephrology Center of Santa Casa de Belo Horizonte. Two real-time PCR tests were developed and validated for the detection and quantification of CMV and BKV from the extraction of viral DNA in blood and urine samples. The analytical sensitivity (minimum detection limit) was 10 viral copies (equivalent genome) for the two PCRs. Using international standards (NIBSC), the clinical sensitivities for CMV and BKV PCRs were 5,000 IU/mL and 15,800 IU/mL, respectively. For the analysis of the impact of viral infections, a prospective study was carried out, consisting of 64 patients with kidney transplantation, who were followed up for a period of up to 13 months after transplantation. A total of 352 plasma samples and 346 urine samples were tested, evidenced high rates of BKV DNAuria (87.5%), followed by BKV DNAemia (59.4%) and CMV DNAemia (32.8%). Despite these high rates of CMV and BKV infection, most samples had low viral load. BKV viral load levels were significantly higher in urine than in plasma, and also higher than CMV load levels. There was a significant association between detection of DNAemia and DNAuria of BKV, and patients with BKV detected in plasma had a significantly higher viral load of the virus in urine than those patients without detection of BKV in plasma. The mean post-transplant time for the first detectable BKV viremia was 62 days in urine, 186 days in plasma and for CMV it could not be defined. Histological findings in renal biopsies were mainly related to graft rejection. The prevalence of BKV nephropathy (BKVN) was 4.7%, and occurred in three patients with detection of BKV DNAemia and DNAuria. CMV disease was not diagnosed during follow-up. Taken together, the results showed that the high rate of BKV DNAuria and DNaemia in patients with kidney transplantation shows that these patients are at constant risk of developing BKVN. However, unlike CMV, whose infection is monitored by the antigenemia test, no test has been applied at the Nefrology Center of Santa Casa de Belo Horizonte to monitor BKV infection, and the implementation of the real-time PCR test for BKV can assist in monitoring patients with kidney transplantation. The use of sensitive and non-invasive molecular diagnostic methods, such as those developed in this study, should be adopted as an auxiliary tool for the correct diagnosis of viral infections in patients with kidney transplantation.