Abstract: Objective To investigate the inhibitory effects of hepatitis B virus(HBV) S gene-specific antisense locked nucleic acid(LNA) on HBV replication and expression in HepG22.2.15 cells ,and screen the effective short sequence of LNA. Methods Four different lengths of short sequence of antisense locked nucleic acid which were complementary to the initiator of HBV S gene were designed, synthesized and transfected by cationic liposomes into HepG22.2.15 cells. The HBsAg and HBV DNA of supernatant was tested by enzyme linked immunoadsorbent assay(ELISA) and real-time fluorescent quantitative PCR(FQ-PCR) at 24 ,48 and 72th hour after treatment respectively. LNA's toxicity on cell was evaluated by MTT method. Results Four different lengths of short sequence of LNA could inhibit the expression of HBsAg and the replication of HBV DNA with the inhibition rates of 46.58%,54.38%,72.43%,69.92% and 27.09%,28.77%,34.71%,32.68% respectively after 72 hours. There's no obvious toxicity on cell. Conclusion Antisense LNA that targeted at HBV S gene has strong inhibition on HBV in vitro, and the optimal length of LNA sequence might be in the range of 15 basic group to 25 basic group.It has a therapeutic potential in the treatment of patients infected with HBV.

Key words: hepatitis B virus, locked nucleic acid, 2.2.15 cell, gene therapy, cationic liposomes