Development of an animal model of hepatitis C

The human hepatitis C virus (HCV) is an important cause of liver-related morbidity and mortality worldwide. A major impediment to developing antiviral therapies for HCV is the lack of an economical small animal model that supports viral replication. Our goal was to develop such a model, with the hypothesis that normal human hepatocytes transplanted into a suitable murine liver would be capable of supporting the replication of HCV. Using purified collagenase blends and a small volume perfusion circuit, viable human hepatocytes were reliably isolated from surgically obtained liver biopsies in high yield (9.7 ± 2.1 × 106 viable cell/gram tissue). Hepatocytes transplanted intrasplenically into the immunodeficient murine strain C.b17-SCID-beige translocated to and engrafted within the recipient liver, but revealed progressive loss of graft function over time (median survival 3 weeks). Addition of a 50% partial hepatectomy concurrent with transplantation extended graft function to a median of 6 weeks, confirming the capacity of human hepatocytes to respond in part to murine growth signals. Administration of human hepatocyte growth factor via implantable osmotic pumps extended graft function to a median of 8.2 weeks, showing species-specific growth factors can significantly enhance overall graft survival. Despite these improvements in graft survival, however, recipient mice were incapable of supporting detectable replication of the human hepatitis B virus, suggesting this system would be inadequate for supporting HCV replication. A novel strain of transgenic mouse was then developed, termed Alb-uPA/SCID-beige, which was shown through detection of human protein production and by immunohistochemical demonstration of human cell surface markers to have the capacity to stimulate rapid proliferation of human hepatocytes after transplantation, producing chimeric human-mouse livers which in some cases sustain hepatocyte function for prolonged (>30 weeks) periods of time. These chimeric animals were susceptible to infection both human hepatitis B and hepatitis C virus, and were capable of supporting replication for extended periods (>18 weeks) at levels equivalent to those seen in humans. This represents the first robust, reproducible small animal model of human hepatitis C virus infection and replication, and with should significantly impact upon the ability to develop antiviral strategies against the hepatitis C virus.