Longitudinal analysis of Epstein-Barr viral load in plasma and peripheral blood mononuclear cells of transplanted patients by real-time polymerase chain reaction

Background. Posttransplant lymphoproliferative disease (PTLD) is a significant cause of morbidity and mortality in transplant recipients and is caused by iatrogenic suppression of T cell function. Elevations in the Epstein-Barr viral (EBV) load in plasma (>1000 EBV copies/100 muL plasma) or peripheral blood mononuclear cells (PBMC) (>5000 EBV copies/mug PBMC DNA) as determined by real-time quantitative polymerase chain reaction (RQ-PCR) have been shown to be sensitive indicators for the development of PTLD in patients. Methods. The diagnostic value of frequent monitoring of EB viral load in peripheral blood from 46 patients after heart transplantation was investigated compared with 21 healthy controls in a prospective longitudinal study. EB viral load was detected in PBMC and plasma using real-time quantitative (RQ)-polymerase chain reaction (PCR)-based assays and compared with serological parameters of EBV infection or with the occurrence of CMV reactivations. Results. EB viral load was significantly increased in PBMC and in plasma from transplanted patients compared with healthy controls. Regarding levels and fluctuations of EB viral load in PBMC, patients were grouped in three distinct categories with high, intermediate, or low EB viral load. Although in one patient without PTLD, the EB viral load exceeded the threshold value for PTLD of 5000 EBV copies/mug PBMC DNA, all patients had an EB viral load in plasma of less than 1000 EBV copies/100 muL plasma. No correlation was found between the level of EB viral load and serological parameters of EBV reactivations in patients or in healthy control individuals. EBV and cytomegalovirus reactivations occurred independently in the majority of patients. Conclusions. EB viral load measurements in plasma and PBMC of patients using RQ-PCR are superior to serology and are a powerful tool for monitoring transplanted patients.