Human hepatocytes transplanted into genetically immunocompetent rats are susceptible to infection by hepatitis B virus in situ.

Immune tolerance of human cells without generalized immunosuppression was created in groups of normal fetal rats at 17 days of gestation by inoculation ip with primary human hepatocytes in utero. One day after birth, suspensions of human hepatocytes were transplanted via intrasplenic injection and one week later groups of rats were inoculated with hepatitis B virus (HBV). Tolerized rats that were transplanted with human hepatocytes and subsequently infected with HBV produced hepatitis B surface antigen (HBsAg) in serum beginning on day 3. Levels rose fivefold and remained stable at 0.75 pg/ml through at least 60 days. Of cells that stained positive for human serum albumin, approximately 30% were found to be also positive for HBsAg by immunohistochemistry. Serum HBV DNA was detectable from 1 to 15 weeks postinfection. Finally, covalently closed circular DNA, reflecting HBV replication, was found in liver and serum. Controls that were tolerized and not transplanted, but inoculated with HBV, as well as untreated controls, had no evidence of HBV gene expression or replication under identical conditions. The data support the conclusion that primary human hepatocytes transplanted into genetically immunocompetent rodent hosts, survive and maintain sufficient differentiation to produce human serum albumin and be infected by HBV.