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 e to inhibit reverse transcription (RT) and to compare their efficacy with phosphorothioate oligodeoxynucleotides (S-ODNs). Methods The effect of two partly overlapping PNAs targeting e 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 IC 50 of 10nM, whereas up to 600-fold higher concentration of S-ODNs was required for similar inhibition. The PNA targeting the bulge and upper stem of e 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 Arg 7 cationic delivery peptide decreased DHBV replication. Conclusions We provide the first evidence that PNAs targeting the bulge and upper stem of e can efficiently and in a sequence-specific manner inhibit DHBV RT.