['Chronic HBV infection is a significant public health problem and one major cause of liver cirrhosis and hepatocellular carcinoma (HCC). HBV impairs the host immune system and results in immunotolerance, which is a major obstacle to HBV therapy. CpG oligodeoxynucleotide (ODN) is a strong immunostimulant which activates the innate immune response rapidly and has been shown to be an efficient therapy agent in viral infection treatment. Here, we report the anti-HBV activity of CpG-1826 in a hydrodynamic injection murine model.', 'CpG-1826 was administrated intraperitoneally every other day in HBV carrier mice established by tail vein hydrodynamic injection of HBV plasmids. The serum concentrations of HBV surface antigen (HBsAg), HBV e antigen (HBeAg), HBV surface antibody (HBsAb), HBV core antibody (HBcAb), interferon-α (IFN-α) and interferon-γ (IFN-γ) were measured by enzyme-linked immunosorbent assay (ELISA). The activities of alanine aminotransferase (ALT) were determined by ALT kit using a Spectramax Plus spectrophotometer. Hepatic HBV DNA was quantified by quantitative real-time PCR. The expression of HBV core antigen (HBcAg) in liver was detected by immunohistochemistry. Drug toxicity of CpG-1826 was evaluated by body weighting and liver histopathology confirmation.', 'CpG-1826 administration inhibited HBV replication efficiently with significant reduction of serum HBsAg and HBeAg, hepatic HBcAg and HBV DNA levels. The serum levels of IFN-α, IFN-γ and HBsAb increased but the HBcAb level declined in the CpG-1826 group compared to CpG-1982 and PBS control groups. Results of ALT activity indicated no significant difference among CpG-1826 group, CpG-1982 and PBS control groups. Body weighting and histopathology examination showed no obvious toxicity.'] Does cpG oligodeoxynucleotide inhibit HBV replication in a hydrodynamic injection murine model?