Inhibition of hepatitis C virus (HCV)‐RNA–dependent translation and replication of a chimeric HCV poliovirus using synthetic stabilized ribozymes

Ribozymes are catalytic RNA molecules that can be designed to cleave specific RNA sequences. To investigate the potential use of synthetic stabilized ribozymes for the treatment of chronic hepatitis C virus (HCV) infection, we designed and synthesized hammerhead ribozymes targeting 15 conserved sites in the 5′ untranslated region (UTR) of HCV RNA. This region forms an internal ribosome entry site that allows for efficient translation of the HCV polyprotein. The 15 synthetic ribozymes contained modified nucleotides and linkages that stabilize the molecules against nuclease degradation. All 15 ribozymes were tested for their ability to reduce expression in an HCV 5′ UTR/luciferase reporter system and for their ability to inhibit replication of an HCV‐poliovirus (HCV‐PV) chimera. Treatment with several ribozymes resulted in significant down‐regulation of HCV 5′ UTR/luciferase reporter expression (range 40% to 80% inhibition, P < .05). Moreover, several ribozymes showed significant inhibition (>90%, P < .001) of chimeric HCV‐PV replication. We further show that the inhibitory activity of ribozymes targeting site 195 of HCV RNA exhibits a sequence‐specific dose response, requires an active catalytic ribozyme core, and is dependent on the presence of the HCV 5′ UTR. Treatment with synthetic stabilized anti‐HCV ribozymes has the potential to aid patients who are infected with HCV by reducing the viral burden through specific targeting and cleavage of the viral genome.