J Reyes

Epstein–Barr virus load monitoring: its role in the prevention and management of post-transplant lymphoproliferative disease

Abstract: The Epstein–Barr virus load in the peripheral blood at the time of diagnosis of post‐transplant lymphoproliferative disease (PTLD) is elevated 1000‐ to 10,000‐fold compared to the level detected in normal latency. With the use of quantitative polymerase chain reaction (PCR), changes in the viral load over time can be measured with a two‐ to fourfold accuracy. This has allowed early detection of first‐time infections and reactivations that may lead to PTLD and has provided an opportunity to intervene before symptomatic disease has occured. Viral load monitoring has also been used to follow patients with PTLD and, along with other parameters, provided an assessment of the effectiveness of therapeutic protocols. Viral load monitoring has led to the discovery that at least two‐thirds of transplant recipients become persistent viral load carriers. While the persistent load appears to be largely carried in latently infected memory B cells, more work is needed to clearly define this type of persistent infection and determine the risks associated with it. New diagnostic tests need to be developed to distinguish the persistent latent viral loads from viral loads that are likely to become symptomatic PTLD.

Pediatric Solid-Organ Transplant Recipients Carry Chronic Loads of Epstein-Barr Virus Exclusively in the Immunoglobulin D-Negative B-Cell Compartment

ABSTRACT Solid-organ transplant recipients are at risk for development of lymphoproliferative diseases. The purpose of this study was to examine the distribution of Epstein-Barr virus (EBV) load in the peripheral blood of pediatric transplant recipients who had become chronic viral load carriers (>8 copies/105 lymphocytes for >2 months). A total of 19 patients with viral loads ranging from 20 to 5,000 viral genome copies/105 lymphocytes were studied. Ten patients had no previous diagnosis of posttransplant lymphoproliferative disease (PT-LPD), while nine had recovered from a diagnosed case of PT-LPD. No portion of the peripheral blood viral load was detected in the cell-free plasma fraction. Viral DNA was found in a population of cells characterized as CD19hi and immunoglobulin D negative, a phenotype that is consistent with the virus being carried exclusively in the memory B-cell compartment of the peripheral blood. There was no difference in the compartmentalization based upon either the level of the viral load or the past diagnosis of an episode of PT-LPD. These results have implications for the design of tests to detect EBV infection and for the interpretation and use of positive EBV PCR assays in the management of transplant recipients.

Detection of Epstein-Barr Virus Genomes in Peripheral Blood B Cells from Solid-Organ Transplant Recipients by Fluorescence In Situ Hybridization

ABSTRACT Resolution of Epstein-Barr Virus (EBV) infection in pediatric solid-organ transplant recipients often leads to an asymptomatic carrier state characterized by a persistently elevated circulating EBV load that is 2 to 4 orders of magnitude greater than the load typical of healthy latently infected individuals. Elevated EBV loads in immunosuppressed individuals are associated with an increased risk for development of posttransplant lymphoproliferative disease. We have performed fluorescence in situ hybridization (FISH) studies with peripheral blood B cells from carriers of persistent EBV loads in order to directly quantitate the number of EBV genomes per infected cell. Patients were assigned to two groups on the basis of the level of the persistent load (low-load carriers, 8 to 200 genomes/105 peripheral blood lymphocytes; high-load carriers, >200 genomes/105 peripheral blood lymphocytes). FISH analysis revealed that the low-load carriers predominantly had circulating virus-infected cells harboring one or two genome copies/cell. High-load carriers also had cells harboring one or two genome copies/cell; in addition, however, they carried a distinct population of cells with high numbers of viral genome copies. The increased viral loads correlated with an increase in the frequency of cells containing high numbers of viral genomes. We conclude that low-load carriers possess EBV-infected cells that are in a state similar to normal latency, whereas high-load carriers possess two populations of virus-positive B cells, one of which carries an increased number of viral genomes per cell and is not typical of normal latency.