title: Plant-expressed Hepatitis B core antigen virus-like particles: Characterization and investigation of their stability in simulated and pig gastro-intestinal fluids.
abstract: Virus-like particles (VLPs) are potential oral vaccine candidates, as their highly compact structure may allow them to withstand the harsh conditions of the gastro-intestinal (GI) environment. Hepatitis B core antigen (HBcAg) is an immunogenic protein that assembles into 30 or 34nm diameter VLPs. Here, the stabilities of both the HBcAg polypeptide itself and the three-dimensional structure of the VLPs upon exposure to in vitro and ex vivo simulated gastric and intestinal fluids were investigated. Plant-expressed HBcAg VLPs were efficiently purified by sucrose density gradient and characterized. The purified VLPs did not show major chemical or physical instability upon exposure to the low pH conditions typically found in the stomach; however, they completely agglomerated upon acidification and subsequent pH neutralization. The HBcAg polypeptide was highly digested upon exposure to pepsin in simulated gastric fluids. HBcAg appeared more stable in both simulated and ex vivo intestinal fluids, where despite a partial digestion of the HBcAg polypeptide, the VLPs maintained their most immunogenic epitopes and their particulate conformation. These results suggest that HBcAg VLPs are likely to be unstable in gastric fluids, yet if the gastric instability could be bypassed, they could maintain their particulate structure and immunogenicity in intestinal fluids.
authors.affiliation: School of Pharmacy, University of East Anglia, Norwich Research Park, Norwich, UK; Department of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich, UK.
authors.forename: Alberto
authors.initials: A
authors.lastname: Berardi
authors.affiliation: Department of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich, UK.
authors.forename: George P
authors.initials: GP
authors.lastname: Lomonossoff
authors.affiliation: Department of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich, UK.
authors.forename: David J
authors.initials: DJ
authors.lastname: Evans
authors.affiliation: School of Pharmacy, University of East Anglia, Norwich Research Park, Norwich, UK. Electronic address: susan.anne.barker@ucl.ac.uk.
authors.forename: Susan A
authors.initials: SA
authors.lastname: Barker
mesh_terms: D000284:Administration, Oral; D000818:Animals; D001826:Body Fluids / Q000737:chemistry*; D004355:Drug Stability; D000939:Epitopes; D006514:Hepatitis B Surface Antigens / Q000737:chemistry*; D007422:Intestines / Q000737:chemistry; D010944:Plants / Q000737:chemistry / Q000378:metabolism*; D013270:Stomach / Q000737:chemistry; D034421:Sus scrofa; D013552:Swine; D014026:Nicotiana / Q000737:chemistry / Q000378:metabolism; D058425:Vaccines, Virus-Like Particle / Q000737:chemistry*
chemical_list: D000939:Epitopes; D006514:Hepatitis B Surface Antigens; D058425:Vaccines, Virus-Like Particle
keywords: Gastrointestinal fluids; Gastrointestinal stability; HBcAg; Oral delivery; Proteins; VLPs