Abstract
The monitoring of Epstein-Barr virus (EBV) DNA loads is important for the detection and prevention of EBV-related disorders. EBV loads have been evaluated by quantitative real-time PCR analysis requiring the preparation of standards. The standard materials for the quantification of EBV loads vary among clinical laboratories. Therefore, it is difficult to obtain comparable EBV DNA quantitative values among laboratories. In this study, the copy number of plasmids containing a fragment corresponding to the EBV BNRF1 gene was calibrated with the 1st WHO International Standard for EBV quantification tests, and then the calibrated plasmids were used as secondary standards to quantitate the EBV DNA loads of subsequent samples from patients. Additionally, the theoretical conversion factor was calculated to convert the EBV DNA loads obtained using noncalibrated standards into those obtained using the present secondary standards. The EBV DNA loads in hematopoietic-stem-cell-transplanted patients suspected of having post-transplant lymphoproliferative disorder (PTLD) and patients with EBV-related hemophagocytic lymphohistiocytosis (EBV-HLH) were 8.74 × 102−1.51 × 104 and 1.58 × 104−1.33 × 106 IU/μg DNA, respectively, as determined by these methods. The utilization of secondary unified standards for the quantification of EBV DNA loads available for many clinical laboratories would contribute to the establishment of a diagnostic reference and therapeutic intervention criteria based on the quantitative values of EBV DNA, not only in PTLD patients but also in those with various disorders related to EBV infection.
