Viral vectors, such as recombinant adenovirus, have been important tools to introduce gene expression in cell or animal to address biomedical questions. For example, we have used recombinant adenoviral vector to introduce a transient expression of Hepatitis C Virus RNA-dependent RNA polymerase (RdRp), NS5B, in mouse liver. We found that NS5B producted small RNA species that activate innate immune signaling via TBK1-IRF3 and NF-kB and induce cytokine production, including type I interferons (IFN) and IL-6. NS5B-expression also results in liver damage. The adenoviral vector can be used as a surrogate tool to examine gene function in vivo.