Optimization of human papillomavirus type 16 (HPV-16) L1 expression in plants: comparison of the suitability of different HPV-16 L1 gene variants and different cell-compartment localization.
Virus-like particle-based vaccines for high-risk human papillomaviruses (HPVs) appear to have great promise; however, cell culture-derived vaccines will probably be very expensive. The optimization of expression of different codon-optimized versions of the HPV-16 L1 capsid protein gene in plants has been explored by means of transient expression from a novel suite of Agrobacterium tumefaciens binary expression vectors, which allow targeting of recombinant protein to the cytoplasm, endoplasmic reticulum (ER) or chloroplasts. A gene resynthesized to reflect human codon usage expresses better than the native gene, which expresses better than a plant-optimized gene. Moreover, chloroplast localization allows significantly higher levels of accumulation of L1 protein than does cytoplasmic localization, whilst ER retention was least successful. High levels of L1 (>17% total soluble protein) could be produced via transient expression: the protein assembled into higher-order structures visible by electron microscopy, and a concentrated extract was highly immunogenic in mice after subcutaneous injection and elicited high-titre neutralizing antibodies. Transgenic tobacco plants expressing a human codon-optimized gene linked to a chloroplast-targeting signal expressed L1 at levels up to 11% of the total soluble protein. These are the highest levels of HPV L1 expression reported for plants: these results, and the excellent immunogenicity of the product, significantly improve the prospects of making a conventional HPV vaccine by this means.
Maclean
J
J
Department of Molecular and Cell Biology, University of Cape Town, Cape Town, South Africa.|Institute of Infectious Disease and Molecular Medicine, Faculty of Health Science, University of Cape Town, Cape Town, South Africa.
Koekemoer
M
M
Department of Molecular and Cell Biology, University of Cape Town, Cape Town, South Africa.
Olivier
A J
AJ
Biovac Institute, Pinelands, Cape Town, South Africa.
Stewart
D
D
Institute of Infectious Disease and Molecular Medicine, Faculty of Health Science, University of Cape Town, Cape Town, South Africa.
Hitzeroth
I I
II
Institute of Infectious Disease and Molecular Medicine, Faculty of Health Science, University of Cape Town, Cape Town, South Africa.
Rademacher
T
T
Fraunhofer Institute, Aachen, Germany.
Fischer
R
R
Fraunhofer Institute, Aachen, Germany.
Williamson
A-L
AL
Institute of Infectious Disease and Molecular Medicine, Faculty of Health Science, University of Cape Town, Cape Town, South Africa.
Rybicki
E P
EP
Department of Molecular and Cell Biology, University of Cape Town, Cape Town, South Africa.|Institute of Infectious Disease and Molecular Medicine, Faculty of Health Science, University of Cape Town, Cape Town, South Africa.
D000818:Animals; D017931:DNA Primers; D004279:DNA, Viral / Q000235:genetics; D015967:Gene Expression Regulation, Viral; D014644:Genetic Variation; D005822:Genetic Vectors; D052162:Human papillomavirus 16 / Q000235:genetics*; D006801:Humans; D051379:Mice; D018515:Plant Leaves / Q000382:microbiology / Q000821:virology; D010944:Plants / Q000821:virology*; D030821:Plants, Genetically Modified; D010957:Plasmids; D015183:Restriction Mapping; D012231:Rhizobium / Q000235:genetics; D014026:Nicotiana / Q000382:microbiology / Q000821:virology; D014765:Viral Vaccines
D017931:DNA Primers; D004279:DNA, Viral; D014765:Viral Vaccines