HUMAN HEPATITIS-B VIRUS AND HEPATOCELLULAR-CARCINOMA .1. EXPERIMENTAL-INFECTION OF TREE SHREWS WITH HEPATITIS-B VIRUS

Tree shrews (Tupaia belangeri chinenesis) can be experimentally infect ed with human hepatitis B virus (HBV) by inoculation with human serum positive for HBV, the experimental infection rate being 55.21%. Succes sive infections have been passed through five generations among the tr ee shrews inoculated with HBV-positive sera from the infected animals, the average infection rate being 94.0%. The experimental infection of tree shrews with HBV may be prevented by immunization with hepatitis B vaccine, the protection rate being 88.89%. Standard serum containing HBV at 10(8) CID (chimpanzee infection dose)/ml, was diluted 10(-6), 10(-7), 10(-8), 10(-9), and 10(-10) and produced infection rates of 80 .0%, 88.8%, 66.7%, 55.6% and 42.9% respectively. Thus the CID50 in tre e shrews may reach a dilution of 10(-9), which shows that tree shrews are sensitive to HBV infection. These results successfully establish t ree shrews as a reliable and useful animal model for research on HBV i nfection and its relation to hepatocarcinogenesis.