Some properties of hepatitis B core antigen isolated from serum of infected humans

The nucleocapsid of Dane particles (= hepatitis B core antigen; HBcAg) was isolated from human sera either positive or negative for e-antigen (HBeAg)--an apparent marker for the level of infectious hepatitis B virus in serum. HBcAg from the HBeAg-positive serum pool consisted of two distinct populations of particles, one with a buoyant density (d) of 1.358 g/ml and a sedimentation coefficient (S20, w) of approximately 110, and another with d = 1.25 to 1.30 g/ml and S20, w approximately 70. Only the latter type of particles was isolated from an HBeAg-negative serum pool. HBcAg was labelled with 125I-p-hydroxyphenylpropionic acid N-hydroxysuccinimide ester, dissociated and analysed by polyacrylamide gel electrophoresis. One major and one minor polypeptide with apparent mol. wt. of 16000 +/- 500 and 68000, respectively, were detected. Another component have the properties of a glycolipid with a mol. wt. in the order of 10(3) was observed. After isoelectric focusing, HBcAg was recovered in fractions with a pH between 4.0 and 5.8, suggesting heterogeneity in isoelectric points.