BACKGROUND/AIMS: Hepatitis C virus infection is a major worldwide health 
problem, causing chronic hepatitis, cirrhosis and primary liver cancer. In 
addition to its role in the viral polyprotein-processing, the viral NS3 serine 
protease has been implicated in interactions with various cell constituents 
resulting in phenotypic changes including malignant transformation. NS3 is 
currently regarded a prime target for anti-viral drugs thus specific inhibitors 
of its activities should be important. With the aim of inhibiting NS3 protease 
activity as a means to inhibit HCV replication we used a novel bacterial genetic 
screen to isolate NS3-inhibiting peptide aptamers.
METHODS: We have isolated and characterized seven NS3-inhibiting peptide 
aptamers. We investigated the phenotypic changes that SEAP-secreting subgenomic 
RNA replicons undergo upon intracellular expression of these peptide aptamers, 
assayed by real-time RT-PCR and inhibition of SEAP secretion by transfected 
replicon cells.
RESULTS AND CONCLUSIONS: The peptide aptamers inhibited NS3 protease activity in 
vitro with an IC50 in the low micromolar range. Upon transfection, aptamers 
inhibited the replication of SEAP-secreting genotype 1b subgenomic RNA 
replicons. Aptamer-based intracellular immunization may emerge as a promising 
antiviral approach to interfere with the life cycle and pathogenicity of HCV.