S-43. Antiviral agents against hepatitis C virus: newer approaches and novel strategies

Research on HCV antiviral has been primarily restricted to molecules targeting HCV replication (inhibiting NS5B), post translational modification (inhibiting NS3 protease) and viral RNA translation (targeting IRES element). IRES mediated translation of viral RNA is an attractive target for designing antiviral because of its fundamental difference from cap-dependent translation of cellular mRNAs. Antisense RNAs, Ribozymes, DNAzymes have been studied as potential inhibitors of HCV translation. Recently, with the discovery of RNAi technology and also availability of HCV cell culture system, research on HCV-antiviral is extended to small RNA molecules (si, sh RNAs). In an alternative approach we have targeted a host factor (human La protein) important for the HCV RNA translation. A synthetic peptide LaR2C (24 residue), derived from La protein, has been shown to act as dominant negative. The peptide interferes with the ribosome assembly during internal initiation of HCV RNA. Using NMR spectroscopy of the RNA bound peptide we have mapped the residues important for RNA recognition to a unique beta-turn. A smaller 7-residue peptide comprising of this turn was found to retain the translation inhibitory activity. More importantly, addition of hexa-arginine tag enabled the 7-mer peptide to enter Huh7 cells and inhibit HCV translation and replication. Elucidation of the structural determinant of the peptide provides basis for developing small peptidomimetic as potent anti-HCV therapeutics. Taken together, it appears that use of cocktail of antiviral agents (nucleic acids and peptides) with multiple targets using different approaches could be more effective in therapeutic intervention against hepatitis C virus infection.