Molecular heterogeneity of hepatitis B virus e antigen in liver and serum

Hepatitis B virus e antigen (HBeAg) derived from liver at autopsy or from the serum of asymptomatic carriers has been characterized. The liver-derived HBeAg consisted of two different molecules, one with a mol. wt. of 30 000 (monomer) and the other with a mol. wt. of 90 000 (trimer), in a ratio of 3:1. Both were free of IgG. The serum-derived HBeAgs were heterogeneous with mol. wt. of 30 000, 90 000, 240 000, 400 000 and 540 000. Among them, the so-called IgG-free HBeAgs consisted almost exclusively of the 30 000 and 90 000 molecular species, in a ratio of 1:9. The serum HBeAg of mol. wt. 90 000 was further differentiated into two molecular species, one trimer and the other associated with albumin. The large mol. wt. HBeAgs (240 000, 400 000 and 540 000) were associated with IgG in ratios of one molecule of HBeAg to one, two or three molecules of IgG respectively. The complete dissociation of the IgG molecule was not achieved by 5 M-urea treatment of such HBeAgs, suggesting that it was bound in an immune complex. A hypothetical model is proposed which describes the heterogeneity of the HBeAgs derived from both the liver and serum, and containing HBeAgs either in a free form or associated with serum IgG.