Hepatitis B surface antigen (HBsAg) expression in plant cell culture: Kinetics of antigen accumulation in batch culture and its intracellular form
Article first published online: 23 OCT 2002
Copyright © 2002 Wiley Periodicals, Inc.
Biotechnology and Bioengineering
Volume 80, Issue 7, pages 812–822, 30 December 2002
How to Cite
Smith, M. L., Mason, H. S. and Shuler, M. L. (2002), Hepatitis B surface antigen (HBsAg) expression in plant cell culture: Kinetics of antigen accumulation in batch culture and its intracellular form. Biotechnol. Bioeng., 80: 812–822. doi: 10.1002/bit.10444
- Issue published online: 23 OCT 2002
- Article first published online: 23 OCT 2002
- Manuscript Accepted: 5 JUN 2002
- Manuscript Received: 3 DEC 2001
- NSF/Whitaker Foundation Program for Cost-Reducing Health Care; NSF. Grant Numbers: BES97-08250, BES-0109936
- plant cell culture;
- hepatitis B vaccine
The production of edible vaccines in transgenic plants and plant cell culture may be improved through a better understanding of antigen processing and assembly. The hepatitis B surface antigen (HBsAg) was chosen for study because it undergoes substantial and complex post-translational modifications, which are necessary for its immunogenicity. This antigen was expressed in soybean (Glycine max L. Merr. cv Williams 82) and tobacco NT1 (Nicotiana tabacum L.) cell suspension cultures, and HBsAg production in batch culture was characterized. The plant-derived antigen consisted predominantly of disulfide cross-linked HBsAg protein (p24s) dimers, which were all membrane associated. Similar to yeast, the plant-expressed HBsAg was retained intracellularly. The maximal HBsAg titers were obtained with soybean suspension cultures (20–22 mg/L) with titers in tobacco cultures being approximately 10-fold lower. For soybean cells, electron microscopy and immunolocalization demonstrated that all the HBsAg was localized to the endoplasmic reticulum (ER) and provoked dilation and proliferation of the ER network. Sucrose gradient analysis of crude extracts showed that HBsAg had a complex size distribution uncharacteristic of the antigen's normal structure of uniform 22-nm virus-like particles. The extent of authentic epitope formation was assessed by comparing total p24s synthesized to that reactive by polyclonal and monoclonal immunoassays. Depending on culture age, between 40% and 100% of total p24s was polyclonal antibody reactive whereas between 6% and 37% was recognized by a commercial monoclonal antibody assay. Possible strategies to increase HBsAg production and improve post-translational processing are discussed. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 80:812–822, 2002.