HBV-targeted ribonuclease (TR) is a fusion of HBV core protein (HBVc) and human eosinophil-derived neurotoxin (hEDN). Introduction of TR by transfection or transduction into HepG2.2.15 cells (a cell model of HBV infection) revealed that it significantly reduces serological markers of HBV replication (including HBsAg, HBeAg and HBV DNA) in cell supernatants, suggesting that the targeted ribonuclease inhibits HBV replication. To further our understanding of the molecular mechanism of the anti-HBV effect of TR, we expressed TR in E. coli and found that purified TR possesses RNase activity and targeting activity. Furthermore, the antiviral effect of TR depends both on an enzymatically active hEDN and on the core domain. In or out of HepG2.2.15 cells, TR coassembles with the wild-type capsid protein into particles with internal hEDN domains. Our data suggest an intracellular ribonuclease activation mechanism that, owing to the characteristics of HBV morphogenesis, is highly virus specific. HBV may therefore be particularly vulnerable to the capsid-targeted viral inactivation approach.

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