Biological consequences of interactions between hepatitis B virus and human nonhepatic cellular genomes.

The incidence of free and integrated hepatitis B virus (HBV) in various human tissues is discussed. Although hepadnavirus replication is restricted to a more or less stringent host cell range, it is clear that viral integration is not restricted to any particular organ but occurs in many tissues, including the placenta, embryo, and spermatozoa. The evidence for mother-to-infant transmission of HBV is presented. Direct transfer of HBV through the germ line cells and its implication in the development of embryonal tumours are discussed. HBV may thus possess potential oncogenicity not only for those directly infected by the virus, but also for their offspring.