797. Long-Term Inhibition of Hepatitis B Virus in Transgenic Mice by Adeno-Associated Virus- Delivered Short Hairpin RNA
Authors: Chun-Chi Chen, Tai-Ming Ko, Hsin-I Ma, Hui-Lin Wu, Xiao Xiao, Mi-Hua Tao
Journal: Molecular Therapy (2006)

RNA interference (RNAi) was reported to block viral infections in animal models when treatment began before or shortly after viral challenge. However, it remains unknown whether RNAi can eliminate more established infections, such as chronic hepatitis B virus (HBV) infection, which presumably requires more extensive and uniform transduction of the whole infected hepatocytes. To increase the in vivo transfection efficiency in liver, we used a double-stranded adeno- associated virus 8-pseudotyped vector (dsAAV2/8) to deliver small hairpin RNA (shRNA). HBV transgenic mice, which produced large amounts of HBV in liver and maintained a high viral load in circulation, were used an animal model to evaluate the inhibition effect of the RNAi-based gene therapy. A single administration of dsAAV2/8 vector, carrying HBV-specific shRNA, effectively suppressed the steady level of HBV protein, mRNA and replicative DNA in liver of HBV transgenic mice, leading to up to 2–3 log10 decrease in HBV load in the circulation. Significant HBV suppression was still observed 120 days after administration of the vector. The therapeutic effect of shRNA was target sequence dependent and did not involve activation of interferon. In conclusion, by combining the high liver transduction efficiency of the dsAAV2/8 vector and the power of RNAi silencing, a rapid, profound, and durable HBV inhibition could be achieved in animal models with a heavily ongoing HBV replication. These results support that dsAAV2/8 vector may be applicable to design an effective RANi-based therapy to treat chronic HBV infection as well as other persistent liver infections. RNA interference (RNAi) was reported to block viral infections in animal models when treatment began before or shortly after viral challenge. However, it remains unknown whether RNAi can eliminate more established infections, such as chronic hepatitis B virus (HBV) infection, which presumably requires more extensive and uniform transduction of the whole infected hepatocytes. To increase the in vivo transfection efficiency in liver, we used a double-stranded adeno- associated virus 8-pseudotyped vector (dsAAV2/8) to deliver small hairpin RNA (shRNA). HBV transgenic mice, which produced large amounts of HBV in liver and maintained a high viral load in circulation, were used an animal model to evaluate the inhibition effect of the RNAi-based gene therapy. A single administration of dsAAV2/8 vector, carrying HBV-specific shRNA, effectively suppressed the steady level of HBV protein, mRNA and replicative DNA in liver of HBV transgenic mice, leading to up to 2–3 log10 decrease in HBV load in the circulation. Significant HBV suppression was still observed 120 days after administration of the vector. The therapeutic effect of shRNA was target sequence dependent and did not involve activation of interferon. In conclusion, by combining the high liver transduction efficiency of the dsAAV2/8 vector and the power of RNAi silencing, a rapid, profound, and durable HBV inhibition could be achieved in animal models with a heavily ongoing HBV replication. These results support that dsAAV2/8 vector may be applicable to design an effective RANi-based therapy to treat chronic HBV infection as well as other persistent liver infections.