Distribution of cell-free and cell-associated Epstein-Barr virus (EBV) DNA in the blood of patients with nasopharyngeal carcinoma and EBV-associated lymphoma.

Abstract

Monitoring of Epstein–Barr virus (EBV) DNA load in the circulation is clinically valuable for the management of EBV-associated diseases, including nasopharyngeal carcinoma (NPC) and certain lymphomas (1)(2). Many studies have used lymphocytes or peripheral blood mononuclear cells as materials for EBV DNA detection in such patients (3)(4)(5)(6). However, cell-free EBV DNA has also been reported in the plasma and serum of patients with NPC and certain lymphoid malignancies (1)(7). These reports raise fundamental questions on whether EBV DNA exists predominantly in a cellular or cell-free form in the peripheral blood of such patients and whether the relative distribution of these forms of EBV DNA differs in different types of EBV-associated disorders. To study these issues, it is important to ensure that the EBV DNA present in the plasma is truly acellular and that the isolated cellular EBV DNA is free from contamination from the cell-free form that may be present in the plasma. Previous reports on cell-associated EBV DNA have not addressed the impact of the thoroughness of the washing of the isolated circulating cells during sample processing. The first objective of the current study was to investigate the efficiencies of different peripheral blood cell (PBC) clean-up procedures in producing data that would truly reflect the concentration of the cell-associated form of EBV DNA. We then studied the relative distribution profiles of cell-free and cell-associated EBV DNA in blood samples from patients with NPC and lymphoid malignancies. For this study, we recruited 49 patients with NPC and 14 patients with Hodgkin disease, natural killer (NK)/T-cell lymphoma, or Burkitt lymphoma managed at the Department of Clinical Oncology at the Prince of Wales Hospital, Hong Kong. Patients gave informed consent, and ethics approval was received from the Institutional Review Board. EDTA blood …