title: Structural characterization of plant-derived hepatitis B surface antigen employed in oral immunization studies.
abstract: Several subunit vaccine antigens have been successfully expressed in plants and recently the hepatitis B surface antigen (HBsAg), expressed in potatoes, was shown to be orally immunogenic in animal studies. However, to date, a detailed analysis of the plant-derived antigen is lacking. Herein, we comprehensively characterize the structure and post-translational processing of HBsAg from potato tuber and two plant cell suspension cultures. The HBsAg was found to accumulate intracellularly as tubular structures, with a complex size distribution, differing substantially from the virus-like particle (VLP) preparations of the current commercial vaccines. Extensive disulfide-bond cross-linking, which is important for immunogenicity, was evident and 21-37% of total HBsAg protein displayed epitopes which correlate with vaccine potency. The significance of these results with regard to the production of cost-effective orally delivered vaccines is discussed.
authors.affiliation: Department of Chemical Engineering, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Mark L
authors.initials: ML
authors.lastname: Smith
authors.forename: Lizabeth
authors.initials: L
authors.lastname: Richter
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Arntzen
authors.forename: Michael L
authors.initials: ML
authors.lastname: Shuler
authors.forename: Hugh S
authors.initials: HS
authors.lastname: Mason
mesh_terms: D000284:Administration, Oral; D015153:Blotting, Western; D002499:Centrifugation, Density Gradient; D004220:Disulfides / Q000737:chemistry; D000939:Epitopes / Q000276:immunology; D006514:Hepatitis B Surface Antigens / Q000096:biosynthesis* / Q000276:immunology*; D017325:Hepatitis B Vaccines / Q000276:immunology*; D008854:Microscopy, Electron; D016253:Microscopy, Immunoelectron; D059828:Plant Cells; D010936:Plant Extracts / Q000737:chemistry; D010944:Plants / Q000276:immunology* / Q000378:metabolism*; D011198:Solanum tuberosum / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D013025:Glycine max / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D013395:Sucrose; D014026:Nicotiana / Q000166:cytology / Q000276:immunology / Q000378:metabolism
chemical_list: D004220:Disulfides; D000939:Epitopes; D006514:Hepatitis B Surface Antigens; D017325:Hepatitis B Vaccines; D010936:Plant Extracts; D013395:Sucrose