Induction of lytic Epstein-Barr virus (EBV) infection in EBV-associated malignancies using adenovirus vectors in vitro and in vivo

The consistent presence of EBV genomes in certain tumor types tin particula r, AIDS-related central nervous system lymphomas and nasopharyngeal carcino mas) may allow novel, EBV-based targeting strategies. Tumors contain the la tent (transforming) form of EBV infection. However, expression of either of the EBV immediate-early proteins, BZLF1 and BRLF1, is sufficient to induce lytic EBV infection, resulting in death of the host cell. We have construc ted replication-deficient adenovirus vectors expressing the BZLF1 or BRLF1 immediate-early genes and examined their utility for killing latently infec ted lymphoma cells in vitro and in vivo. We show that both the BZLF1 and BR LF1 vectors efficiently induce lytic EBV infection in Jijoye cells tan EBV- positive Burkitt lymphoma cell line). Furthermore, lytic EBV infection conv erts the antiviral drug, ganciclovir (GCV), into a toxic (phosphorylated) f orm, which inhibits cellular as well as viral DNA polymerase. When Jijoye c ells are infected with the BZLF1 or BRLF1 adenovirus vectors in the presenc e of GCV, viral reactivation is induced, but virus replication is inhibited (thus preventing the release of infectious EBV particles); yet cells are s till efficiently killed, Finally, we demonstrate that the BZLF1 and BRLF1 a denovirus vectors induce lytic EBV infection when they are directly inocula ted into Jijoye cell tumors grown in severe combined immunodeficiency mice. These results suggest that induction of lytic EBV infection in tumors, in combination with GCV, may be an effective strategy for treating EBV-associa ted malignancies.