The company claims that its system can dramatically speed up the time it takes to engineer plant cells to produce a target protein. Not only is it the fastest way to achieve this objective in plants, but it also outperforms various bacteria-based expression systems, according to Icon.
"Starting with the DNA construct of the protein of interest, milligram and gram quantities are available in just 3-4 weeks," according to Icon, which has published the research in the Proceedings of the National Academy of Sciences (4 May issue).
Icon researchers use proviral RNA vectors to reprogram plant biosynthesis in favour of expression of the recombinant protein of interest. The vectors are delivered to leaf cells as DNA precursors using bacteria that infect plant cells and rapidly spread throughout the entire plant by cell-to-cell or systemic movement. This process is essentially the backbone of Icon's R&D platform.
The rapidity of the process is thanks to the use of prefabricated expression modules in the bacterial vectors. These include up- and downstream regulatory elements that targeting of the protein sequence to the plant components involved in protein synthesis, as well as purification tags or cleavage sequences to improve yields.
"Construct optimisation for yield improvement and design of post-translational modification is therefore performed in weeks rather than in months or years," claims Icon.
One key feature of the technology - known as magnICON - is the high expression levels it can achieve. Up to 5 milligrammes of recombinant protein can be produced per gramme of fresh leaf biomass with the yield of recombinant protein reaching up to 80 per cent of total soluble protein. This yield per biomass is 10-1000 fold higher than with other existing plant-based systems, and relative yields are 10-100 fold higher.
Icon aid that this combination of speed and expression levels makes magnICON ideal for generating the gramme quantities of purified protein necessary for preclinical or clinical studies.
Although the PNAS article only covers the use of magnICON for research-scale production, ICON has developed a scale-up capability suitable for commercial production.
The yields achieved allow production of hundreds of kilograms of protein per hectare annually in fully contained greenhouses that avoid any release into the environment. And as the company uses tobacco as a production vehicle - a non-food, non-feed plant - this mitigates the biosafety risk.