Ultrastructural study of hepatitis B virus in biliary epithelial cells of duck liver

Liver specimens from the Shanghai Ma ducks congenitally infected with duck hepatitis B virus (DHBV) were examined by immunohistochemical technique and electron microscopy. All the 12 serum DHBV positive ducks showed varying degrees of positive straining in hepatocytes. In 8 of the 12 ducks, DHBV antigen was discovered in the cytoplasm of biliary epithelial cells. Conventional electron microscopy revealed two kinds of virus particles in the biliary epithelial cells: 1. the incomplete virus, 40-50 nm in diameter and spherical in shape with an outer membrane, located mainly in the dilated cisternae of rough endoplasmic reticulum of the cells in large amounts; 2. the complete virions, 55-60 nm in diameter, were spherical with an outer membrane and located mainly in the cytoplasmic vesicles in small amount. We believe the particles found in the biliary epithelial cells in this study were DHBV particles. It is most likely that the infection and replication of DHBV not only take place in the liver cells but also in the biliary epithelial cells.