Fig. 1.

Differences between latent and lytic EBV infection. A. Latent EBV infection. In the latent forms of EBV infection, the virus persists as an episome in the nucleus and is replicated once per cell cycle by the cellular DNA polymerase and the viral protein, EBNA-1, using an origin of replication called oriP. The host cell is not killed by latent EBV infection. EBV proteins expressed during some forms of latent viral infection (especially LMP-1) have transforming functions. Drugs that inhibit the latent form of EBV replication are not currently available. Viral proteins expressed during type III latent infection are shown. B. Lytic EBV infection. Expression of the two viral immediate-early proteins, BZLF1 (Z) and BRLF1 (R), results in activation of the lytic form of viral replication. The virus is replicated by the virally-encoded DNA polymerase, using the oriLyt origin of replication. Infectious virion particles are released and the host cell is generally killed. Acyclovir and ganciclovir inhibit this form of viral replication.