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

Abstract

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.

Synthetic gene design—The rationale for codon optimization and implications for molecular pharming in plants

“…Commercial algorithms used for codon optimization for different species are never disclosed and the relative benefits are often inconsistent. Indeed, genes that were codon optimized for another host have been reported to express better than the same gene that was codon optimized for the intended host (Lanza et al 2014;Maclean et al 2007;Rybicki et al 2014). …”

Human Papillomavirus and Related Diseases - From Bench to Bedside - A Clinical Perspective

“…5). Sucrose sedimentation analysis also showed that there is a large amount of not, or only partially assembled molecules, presumably capsomeres (fractions [18][19][20][21][22][23][24], as well as other larger aggregates (fractions 1-8) when compared to the insect cell-produced protein (Maclean et al, 2007). L1VLPs can be produced either in transgenic plants stably transformed with an expression cassette or transiently using one of several available plant-virus derived expression systems.…”

Plant Production of Vaccine Against HPV: A New Perspectives

“…5). Sucrose sedimentation analysis also showed that there is a large amount of not, or only partially assembled molecules, presumably capsomeres (fractions 18-24), as well as other larger aggregates (fractions 1-8) when compared to the insect cell-produced protein (Maclean et al, 2007). L1VLPs can be produced either in transgenic plants stably transformed with an expression cassette or transiently using one of several available plant-virus derived expression systems.…”

“…Plant crude extracts and their components were tested for their adjuvant capacity. The extract from leaves of Nicotiana bethamiana co-administrated subcutaneously with HPV16E7 (Franconi et al, 2002) or HPV16L1 VLP´s (Maclean et. al, 2007;Šmídková et al, 2010) enhanced specific humoral and cellular immune response in tested mice.…”