Flow cytometry analysis of gamma-radiation-induced Epstein-Barr virus reactivation in lymphocytes.

Epstein-Barr virus (EBV), a member of the gamma-herpesvirus family, is involved in the development of several diseases, and the infection is believed to persist for life in latent form. Ionizing radiation at clinically relevant doses may increase the amount of virus reactivation in B cells, and the combination of radiation with stress could amplify EBV reactivation. In vitro experiments were performed on several cell lines, including EBV-positive Burkitt lymphoma cells. The presence of the immediate-early protein ZEBRA, which is a hallmark of EBV reactivation, was evaluated using flow cytometry, which enabled us to measure the percentage of ZEBRA-positive cells. The process was studied previously in the EBV-positive Burkitt lymphoma cell line B95-8. Forty-eight hours after irradiation alone, 13.6 and 19.9% ZEBRA-positive cells were observed at 2 and 4 Gy, respectively, compared to the basal level of 1.85%. Thus irradiation induces EBV reactivation. The addition of a glucocorticoid (the final effector of the stress response) had no effect on EBV reactivation in our model. However, the combination of radiation and treatment with a glucocorticoid (dexamethasone) increased the expression of ZEBRA in B95-8 cells (15.8 and 28.75% of the cells was positive at 24 and 48 h after gamma irradiation, respectively). Thus the combination of gamma radiation and a glucocorticoid may play an important role in EBV reactivation.