Expression of a new woodchuck IFN-alpha gene by a helper-dependent adenoviral vector in woodchuck hepatitis virus-infected primary hepatocytes.

Recombinant interferon-alpha (rIFN-alpha) is currently used in the treatment of viral hepatitis either alone or in combination with small molecules. However, this treatment is not very efficacious, and more effective protocols are needed. To this end, we have explored the woodchuck hepatitis system, validated as an infection model for vaccination and antiviral studies against human hepatitis B virus (HBV) infection. The lack of a woodchuck IFN-alpha (WoIFN-alpha) homolog has prevented study of viral inhibition, which may be instrumental in understanding the IFN-alpha-induced antiviral pathways responsible for HBV clearance in humans. We have, therefore, cloned two WoIFN-alpha homologs from the woodchuck genome, which showed high similarity to the human IFN-alpha (HuIFN-alpha) gene at both nucleotide and amino acid levels. WoIFN-alpha showed a species-specific activity without any efficacy on human or mouse cells. In agreement with this antiviral activity, induction of Mx protein was observed in woodchuck cells only on WoIFN-alpha treatment. The antiviral efficacy of a WoIFN-alpha gene transfer was explored using a helper-dependent adenoviral (Ad) vector (HD-WoIFN) as a delivery vehicle. This treatment resulted in the reduction of woodchuck hepatitis viral proteins in primary hepatocytes from chronically woodchuck hepatitis virus (WHV)-infected woodchucks.