Analysis of viral counter regulation against host's defense mechanism for viral infection using HCV transgenic mouse model

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Missing of proper culture system and animal model has hampered fine analysis of viral life cycle and pathogenesis of HCV infection. We established HCV transgenic mouse model using Cre/loxP switching system. We put neomycin resistance gene as a stuffer flanked by loxP sequence at both 5' and 3' end between CAG promoter and core to NS2, HCV cDNA CN2. Spleens were harvested from CN2 transgenic mice. In 2 lineages out of 8, cultured spleen cell and fibroblast highly expressed core, E1 and E2 proteins by western blot and immunostaining after infection with recombinant adeno virus (AxCANCre) which express cre DNA recombinase in infected cell. To induce HCV expression in vivo and in the liver, we injected AxCANCre to CN2 transgenic mouse from tail vein and HCV protein expression was confirmed in its liver tissue. With the expression of HCV structural protein, acute liver injury which was similar to human acute viral hepatitis was occurred. It was accompanied with apoptotic liver cell death. Serum core protein was detected in transgenic mice 7 days after AxCANCre injection with evident serum ALT elevations, subsequently, anti-core antibody response was detected at 14 days after infection. Furthermore, CD4 and CD8 positive cell depletion assay normalized the serum ALT elevations of mice and pathological changes in the liver. These results suggest that HCV proteins are not direct cytopathic and the host immune response has a pivotal roles in HCV infection. This transgenic mouse model system allows us to analyze the functions of viral products and host immune system in HCV infection and hepatocellular carcinogenesis of HCV.