A long-term hepatitis B viremia model generated by transplanting nontumorigenic immortalized human hepatocytes in Rag-2-deficient mice

Development of new therapies for human hepatitis B virus infection (HBV) wo uld be greatly facilitated by the availability of a suitable small-animal m odel for HBV virus production in vivo. To develop a murine model for HBV pr oduction, we established an immortalized, cloned liver cell line by transfe rring the Simian Virus 40 Large T-Antigen into primary human hepatocytes. T hese cells were stably transfected with a full-length HBV genome to generat e a clone that expresses HBV genes and replicates HBV. The HBV-producing ce lls were transplanted into the livers of mice with combined immunodeficienc y (Rag-2 deficient) by intrasplenic injection. Survival of the engrafted hu man hepatocytes was shown in several ways: fluorescent in situ hybridizatio n (PISH) with a human-chromosome-specific DNA probe (human alpha satellite) , dot-blot hybridization of the genomic DNA extracted from liver biopsy spe cimens with a human-specific Alu repetitive DNA probe, Blur-8, as well as w ith an HBV DNA probe, and secretion of human proteins into plasma. Histolog ical examination of mouse liver up to 8 months following human cell transpl ant shows completely normal architecture. Determination of plasma HBV DNA l evels indicated that engrafted cells secreted 3x10(7) to 3x10(8) virions pe r mt into the blood, and HBsAg was detected in plasma. This new murine mode l of HBV viremia should be useful for in vivo HBV studies.