Targeted inhibition of HBV gene expression by single-chain antibody mediated small interfering RNA delivery

RNA interference is highly effective at inhibiting HBV gene expression and replication. However, before small interfering RNA (siRNA) coin be used in the clinic, it is essential to develop a system to target their delivery. Antibody-mediated delivery is a novel approach for targeting siRNA to appropriate cells. In this report, we asked whether this siRNA delivery strategy would be effective against HBV. Of 5 candidates, a specific siRNA that effectively inhibited HBV gene expression and replication was determined. Two fusion proteins, s-tP and sC kappa-tP, were constructed to contain a single chain of the human variable fragment, scFv, against hepatitis B surface antigen (HBsAg), a truncated protamine (tP), and in the case of sC kappa-tP, a constant region of the K chain (C kappa). S-tP and SC kappa-tP were developed to provide targeted delivery of the siRNA, siRNA expressing cassettes (SEC), and siRNA-producing plasmids. Fluorescein isothiocyanate-siRNA, fluorescein isothiocyanate-SEC, and plasmid DNA were specifically delivered into HBsAg-positive cells using the SC kappa-tP fusion protein, and effectively inhibited HBV gene expression and replication. HBV gene expression was also inhibited by siRNA or siRNA-producing plasmids in HBV transgenic mice. Conclusion: Our results describe a potential method for the targeted delivery of siRNA or siRNA-producing plasmids against HBV, using anti-HBsAg fusion proteins.