Inhibition of the EBV Lytic Cycle by Sequence Specific Antisense Oligonucleotides
The capacity of EBV to encode a ribonucleotide reductase enzyme was revealed soon after the entire DNA sequence of the B95–8 strain of EBV had been determined (1). This association was based upon computer determined homology of the BAM HI 0/a rightward reading frame of EBV DNA with the region of HSV-1 DNA known to encode a ribonucleotide reductase. Ribonucleotide reductase is responsible for mediating the first unique step of DNA synthesis by reducing all four ribonucleotides to their corresponding deoxyribonucleotides (2). We have identified the major restricted early antigen (EA-R) of EBV to be the viral encoded ribonucleotide reductase (3,4). Unique properties of this virally encoded enzyme distinguish it from its cellular counterpart (5,4). These differences, along with the fact that the expression of EAR is essential during early phases of virus replication and does not occur during latency, make it an ideal target for antiviral therapy. We have, therefore, examined the possibility of inhibiting viral replication by synthetic antisense oligonucleotides directed to viral sequences encoding this protein. Using this approach on cells chemically stimulated to produce virus, we have been able to demonstrate a dramatic reduction of the corresponding 85kDa EA-R viral protein. This inhibition also resulted in a parallel decrease in the production of the 50-52kDa diffuse early antigen complex (EA-D) of EBV, suggesting that the expression of these two early antigen complexes is coupled. The down regulation of these antigens dramatically inhibited virus production as monitored by the expression of viral capsid proteins. We hope to use this information to help delineate the sequence of EBV antigen expression during induction of the lytic cycle, and to investigate the feasibility of employing antisense oligonucleotides in combating EBV associated diseases.
KeywordsAntisense Oligonucleotide Sodium Butyrate Ribonucleotide Reductase Lytic Cycle Viral Capsid Protein
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