Epstein-Barr virus (EBV) has been causally implicated in the etiology of more than half of the AIDS-related non-Hodgkin's lymphomas (ARL). These EBV-associated ARL's are surprisingly heterogeneous with respect to histology, clonality, and latent viral gene expression. Nonetheless, all EBV-associated ARL's harbor EBV DNA and express EBNA-1, the latent viral protein required for viral DNA replication. Although it is likely that EBV plays a critical role in maintaining the transformed phenotype in some, if not all, EBV-associated ARL's, the precise biological function of the virus in the tumorigenesis remains unclear and may vary in different sub-types. The modulation of critical EBV latent proteins by antisense techniques is a theoretically sound and powerful strategy for elucidating the biological role of EBV and its latent proteins in the EBV-associated ARL's. Importantly, in addition to defining the biological role of EBV in lymphomagenesis, antisense strategies may have important therapeutic implications for the treatment of ARL as this technology moves from the laboratory to the clinic. We have undertaken important preliminary studies using antisense to EBNA-1 that demonstrate the potential usefulness of antisense techniques to suppress viral gene expression and elicit biological effects. We have shown that EBNA-1 antisense oligomers to codons 6-10 suppress EBNA-1 protein, inhibit proliferation, and decrease viral DNA content of EBV- immortalized lymphoblastoid cell lines (LCL's). The observed biological effects of EBNA-1 antisense are sequence-specific, EBV-specific, and temporally associated with EBNA-1 suppression. These initial studies suggest that the appropriate use of EBNA-1 antisense may impact on the critical function of EBNA-1 in replicating latent viral DNA, and as a result, may provide a tool for inducing loss of viral DNA from EBV- infected cells or defining additional functions of EBNA-1. These preliminary studies provide the basis for additional studies of the modulation of critical latent viral proteins by antisense to define the biology of EBV-associated transformation and explore the potential therapeutic efficacy of this strategy. Thus, we propose to perform additional in vitro studies of the biological effects of EBNA-1 suppression by antisense in LCL's, Burkitt lymphoma cells, and normal B- cells infected de novo with EBV. The studies in LCL's and Burkitt cells will include studies of the effects of EBNA-1 antisense on viral DNA content, apoptosis, and expression of key cellular genes. We will utilize antisense DNA oligomers as well as vector-generated RNA antisense delivered by the adenovirus-polylysine gene transfer technique for these studies. Given the anti-proliferative effects of EBNA-1 antisense, we will explore the anti-tumor efficacy of EBNA-1 antisense in vivo using a SCID mouse model of EBV-associated lymphoproliferative disease. Finally, we will utilize antisense strategies to explore the biological effects of suppression of other critical latent viral proteins such as EBNA-2 and LMP-1.
