The Epstein-Barr virus DNA load in the peripheral blood of transplant recipients does not accurately reflect the burden of infected cells.

Transplant recipients frequently exhibit an increased Epstein-Barr virus (EBV) load in the peripheral blood. Here we quantitated the EBV-infected cells in the peripheral blood of these patients and defined the mode of viral infection, latent or lytic. These data indicated that there is no strong correlation between the number of infected cells and the EBV load. This can be explained by a highly variable number of EBV copies per infected cell and by lytic replication in some cells. The plasma of these patients did not contain any free infectious viruses, but contained nevertheless EBV DNA, sometimes in large amounts, that probably originates from cell debris and contributed to the total EBV load. Some of the investigated samples carried a highly variable number of infected cells in active latency, characterized by an expression of the EBNA2 protein. However, a third of the samples expressed neither EBNA2 nor lytic proteins. Patients with an increased EBV load represent a heterogeneous group of patients whose infection cannot be characterized by this method alone. Precise characterization of the origin of an increased EBV load, in particular in terms of the number of EBV-infected cells, requires additional investigations including the number of EBER RNA-positive cells. This article is protected by copyright. All rights reserved.