Production of transgenic plant-derived vaccines via plastid transformation technology
Abstract of thesis entitled
PRODUCTION OF TRANSGENIC PLANT-DERIVED VACCINES VIA PLASTID TRANSFORMATION TECHNOLOGY
Lee Yuk Ting
for the degree of Master of Philosophy
at The University of Hong Kong
in July 2004
With the advent of genetic engineering in higher plants, the need for very large quantities of therapeutic protein at low cost, and the desire to have heat-stable edible vaccines directed at human and animal diseases, transgenic plant-derived vaccines offer a new strategy for the development of safe, inexpensive vaccines against infectious diseases. The first success of plastid transformation in tobacco in 1990 has opened up the opportunities for genetically modifying plastids in higher plants for high level expression of biopharmaceuticals, such as antibodies and vaccines for oral administration. Since each plant cell contains up to 10,000 copies of identical plastid genome, plastid engineering should result in very high levels of transgene expression. In addition, due to the prokaryotic feature of the plastids, engineering the plastid genome bears the advantages of expressing multiple genes as operons without the problem of positional and epigenetic effects affecting transgene activity. Therefore, plastid transformation technology is a promising alternative to the conventional nuclear transformation.
The objectives of this research are: 1) to examine if plastids can be used to produce edible vaccines suitable for uses against Epstein-Barr (EBV) and Hepatitis
B Virus (HBV), and 2) if such a production can be regulated through a chemically inducible gene expression system.
The genes encoding the early antigen of the Epstein-Barr virus and the Hepatitis B surface antigen (HBsAg) are introduced into tobacco plastids via biolistic bombardment techniques. Simultaneously, an alcohol-inducible alc gene expression system is established and integrated into the tobacco nuclear genome for controlling plastid expression of antigen genes. It was found that chloroplast-derived antigen against EBV could be successfully produced in transplastomic tobacco using a constitutive plastid-derived promoter. However, constitutive expression of Hepatitis B surface antigen (HBsAg) apparently results in growth retardation and lethality of the plants. By adapting the ethanol inducible (alc) gene expression system to control engineered plastid operons, it is possible to regulate a marker gene (uidA) expression and the production of antigen (HBsAg) in plastids upon ethanol administration. The technology developed here could contribute to a much more cost-effective system for vaccine production system in the future.
School:The University of Hong Kong
School Location:China - Hong Kong SAR
Source Type:Master's Thesis
Keywords:plastids transgenic plants vaccines viral antigens
Date of Publication:01/01/2004