Purification of recombinant HBc antigen expressed in Escherichia coli and Pichia pastoris: comparison of size-exclusion chromatography and ultracentrifugation

Hepatitis B virus core protein (HBc) is an important serology marker of hep atitis B infection and patient follow-up. It is an M-r 21 000 protein, whic h has the intrinsic capacity to self-assemble as a capsid-like particle. Th e hepatitis B core protein has been expressed in Escherichia coli and Pichi a pastoris (three different constructions) in order to select a HBc recombi nant antigen suitable for serodiagnosis requirements with a cost effective downstream strategy. The expression and purification of the different forms of recombinant HBc have been described. For the last step, ultracentrifuga tion and size-exclusion chromatography were compared. The morphology of the se capsids was observed using an electron microscope. Our data shows that H Bc antigen is produced in large quantities in E. coli but some contaminants remained which were associated with the E. coli HBc protein after ultracen trifugation or size-exclusion chromatography; The ultracentrifugation enabl es a higher purity of HBc antigen to be obtained than size-exclusion chroma tography but the latter enables a higher recovery rate. P. pastoris enables the expression and extraction of a highly purified HBc antigen suitable fo r diagnostic purposes. (C) 2001 Elsevier Science B.V. All rights reserved.