The ultrastructural morphology of native hepatitis B virus

Cell lines (2.2.15 cells) capable of supporting the replication of hepatitis B virus (HBV) DNA and intact viral particles have been established by HBV DNA transfection into HepG2 cells. The purpose of this study was to determine the ultrastructural morphology of native HBV particles without purification in the culture supernatants and in sera from patients. Electron microscopy (EM) and immunogold EM of the samples were carried out using polyclonal and monoclonal anti-hepatitis B surface antigen antibodies. HBV particles in the purified samples from the culture supernatants by density-gradient centrifugation were examined to compare the morphology with that of unpurified samples. EM and immunogold EM studies demonstrated the presence of Dane particles (41.8 nm in diameter), cobra-shaped (head diameter, 42.4 nm), and horn-shaped (head diameter, 43.5 nm) particles in the culture supernatants and in the sera from two patients. The tail of the cobra-like particles had a diameter of 21.0 nm and a length of 214 nm. The hornlike particles had a long branch 20.1 nm in diameter with a length of 189 nm, and a short branch 21.4 nm in diameter with a length of 112 nm. The ratio of Dane particles and cobra- and horn-shaped particles in the supernatants was 5 : 4 : 1. After ultracentrifugation, the cobra- and horn-shaped particles completely disappeared; there were only Dane particles together with spheres of 22 nm and filaments. In conclusion, this study showed for the first time that the native replicative form of HBV is cobra- and horn-shaped.