Sequence-specific inhibition of duck hepatitis B virus reverse transcription by peptide nucleic acids (PNA)

Background/Aims Peptide nucleic acids (PNAs) appear as promising new antisense agents, that have not yet been examined as hepatitis B virus (HBV) inhibitors. Our aim was to study the ability of PNAs targeting the duck HBV (DHBV) encapsidation signal ε to inhibit reverse transcription (RT) and to compare their efficacy with phosphorothioate oligodeoxynucleotides (S-ODNs). Methods The effect of two partly overlapping PNAs targeting ε and of analogous S-ODNs was tested in cell-free transcription and translation system for DHBV RT expression. In addition their antiviral effect was investigated in primary duck hepatocytes (PDH). Results Both PNAs reproducibly inhibited DHBV RT in a dose-dependent manner with IC50 of 10 nM, whereas up to 600-fold higher concentration of S-ODNs was required for similar inhibition. The PNA targeting the bulge and upper stem of ε appeared as more efficient RT inhibitor than the PNA targeting only the bulge. Importantly, the inhibition was highly sequence-specific since double-mismatched PNA had no effect on the RT reaction. Moreover, in PDH the PNA coupled to Arg7 cationic delivery peptide decreased DHBV replication. Conclusions We provide the first evidence that PNAs targeting the bulge and upper stem of ε can efficiently and in a sequence-specific manner inhibit DHBV RT.