In Vitro And Vivo Anti-hepatitis B Virus Activities Of A Niobium-substituted-heteropolytungstate

Objective: To synthesize and characterize the novel polyoxometalateCs₂K₄Na[SiW₉Nb₃O₄₀]] H₂O for its anti-hepatitis B virus (HBV) properties by usingthe HepG2.2.15cell and HBV transgenic mice.Methods: The methylthiazol tetrazolium assay was used to evaluate the growthinhibitory effect of Cs₂K₄Na[SiW₉Nb₃O₄₀]] H₂O on HepG2.2.15cell. By usingELISA and real-time PCR, respectively, the presence of extracellular hepatitis Bsurface antigen (HBsAg), e antigen (HBeAg), and HBV DNA were measured. Thelevels of intracellular HBV DNA and mRNA were determined by using Southern blotor reverse-transcription-PCR, respectively. Intracellular distribution of antigen weremeasured by Western blot.HBV transgenic mice were treated with Cs₂K₄Na[SiW₉Nb₃O₄₀]] H₂O byintragastric administration. Adefovir and distilled water were administered as controls.Serum HBV DNA was measured by quantitative real time PCR. Serumaminotransferase and HBsAg levels were measured by automatic biochemicalanalyzer or ELISA. The hepatitis B virus surface antigen (HBsAg) in liver cells wasdetected by immunohistochemistry (IHC). Pathological changes in the liver tissueswere also observed by light and electron microscopy.Results: A1995μmol/L concentration of the commercially-available hepatitis Bdrug, adefovir dipivoxil (ADV), was required to achieve50%cytotoxicity againstcultured cells (CC50) by day nine; in contrast, only1747μmol/L ofCs₂K₄Na[SiW₉Nb₃O₄₀]] H₂O was required for the same result. Treatment ofHepG2.2.15cells with Cs₂K₄Na[SiW₉Nb₃O₄₀]] H₂O effectively suppress thesecretion of HBV antigens and HBV DNA in a dose-dependent and time-dependentmanner. IC50values were determined to be80μmol/L for HBsAg,75μmol/L forHBeAg and3.72μmol/L for supernatant HBV DNA at day nine post-exposure, asopposed to266,296,30.09μmol/L, respectively, for ADV. Intracellular HBV DNA,mRNA and antigen were also found to be decreased by Cs₂K₄Na[SiW₉Nb₃O₄₀]] H₂O.The same dose of ADV yielded a significantly less robust inhibitory effect. Cs₂K₄Na[SiW₉Nb₃O₄₀]] H₂O significantly decreased serum aminotransferase,HBsAg, and HBV DNA levels. Cs₂K₄Na[SiW₉Nb₃O₄₀]] H₂O resulted in a98%decrease in HBV DNA at day28, from4.3log10copies/mL at baseline to2.5log10copies/mL after treatment, and the inhibition rate of HBV DNA was higher than ADVat the same dose. Significant differences were observed7d after withdrawal of theagent. The HBV replication levels in each group slightly increased at7d afterwithdrawal, but rebounded slightly more in the Cs₂K₄Na[SiW₉Nb₃O₄₀]] H₂Otreatment group compared to the H₂O control group (P<0.0⁵). No significantdifferences were observed in the pathology, but there were decreased HBsAg levels inthe Cs₂K₄Na[SiW₉Nb₃O₄₀]] H₂O-treated group compared to the control group.Conclusion: Cs₂K₄Na[SiW₉Nb₃O₄₀]] H₂O can clear HBV from hepatic cells andHBV transgenic mice.It may represent a therapeutic agent to treat HBV infection.