Distribution of the copy number of EBV genomes per infected cell in 4 healthy carriers and 3 patients with active PTLD.

Copy numbers per cell were measured by QC-PCR at dilutions of PBMCs that were estimated to have less than one EBV-infected cell. The dilutions of PBMCs were mixed with CA46 cells so as to achieve a total cell number of 1 × 10⁶ cells per sample. In a typical experiment on healthy carrier H3 (23 EBV-infected cells per 10⁶ PBMCs), a dilution of 30 000 PBMCs per sample was used. The PBMCs were mixed with 9.7 × 10⁵ CA46 cells before DNA isolation, and 17 DNA samples were measured by QC-PCR. EBV load was detected in 10 of the 17 samples, which was consistent with the percentage of PCR positivity obtained by BamH-W PCR (Figure 3). EBV genome copy numbers per cell are also shown Table 4.