Purification and partial characterization of hepatitis e antigen (HB(e)Ag)

Abstract

Purification of hepatitis e antigen (HBeAg) from 200 ml of chimpanzee plasma was accomplished by a combination of ion-exchange chromatography on diethylaminoethyl-cellulose followed by gel filtration. High-resolution sodium dodecyl sulfate-polyacrylamide gel electrophoresis of purified HBeAg demonstrated two major polypeptides with estimated molecular weights of 22,000 and 55,000. HBeAg labeled with 125I showed a high affinity for protein A-conjugated Sepharose CL-4B. The precipitation reaction between HBeAg and anti-HBe was inhibited by preincubating the purified antigen with rabbit anti-human immunoglobulin G (IgG). These data show that HBeAg is associated with a serum fraction with the biophysical and antigenic properties of an immunoglobulin of the IgG class. Sedimentation coefficient analysis of purified HBeAg resulted in an s20,w value of 11.6 and a molecular weight value of 324,000. These findings, supported by gel filtration and polyacrylamide gradient gel electrophoresis, revealed that HBeAg has properties analogous to those of a dimer of IgG.