Large-Scale Isolation of Dane Particles from Plasma Containing Hepatitis B Antigen and Demonstration of a Circular Double-Stranded DNA Molecule Extruding Directly from Their Cores

A method was developed to isolate, on a large scale, Dane particles from five liters of pooled plasma of asymptomatic carriers of hepatitis B antigen. It involved three successive ultracentrifugation procedures; the final preparation was more than 98% pure in Dane particles. Purified Dane particles had the density of 1.23 to 1.24 g/cm3. The concentration of nucleic acids in the preparation containing purified Dane particles was too low to be detected either by chemical or by spectrophotometric method. However, a circular double-stranded DNA molecule extruding directly from the core of Dane particles was clearly demonstrated by elelctron microscopic observations. The cores of Dane particles (hepatitis B core antigen; HBcAg) were prepared by treating the Dane particle preparation with mercaptoethanol and Nonidet P-40. They were sufficient both in purity and amounts to allow the determination of antibody to HBcAg by an immune adherence hemagglutination method.