Icon Genetics AG announces the publication in the Proceedings of the National Academy of Sciences of USA (S. Marillonnet et al., PNAS, 101, 6852-6857, May 4, 2004 ) of a first of a series of research papers describing a new generation expression technology for plants developed by Icon Genetics researchers.

The technology. The paper summarizes a novel efficient and user-friendly technology that is based on the use of proviral RNA vectors to quickly reprogram plant biosynthesis in favour of expression of the recombinant protein of interest. The vectors are delivered to leaf cells as DNA precursors by Agrobacterium-mediated transfection, 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.

Very fast R&D process. Starting with the DNA construct of the protein of interest, milligram and gram quantities are available in 3-4 weeks, and thus, the platform provides the highest possible speed and throughput of R&D in plant biotechnology. It is also often even faster than microbial genetic engineering thanks to the use of prefabricated expression modules in Agrobacterium, which allow building the amplicon and the gene 'on a fly' by mixing bacterial strains containing various viral blocks. Those include up- and downstream regulatory elements, targeting of the transgene-derived protein to various plant cell compartments including apoplast or chloroplast, as well as adding purification tags or cleavage sequences. Construct optimization for yield improvement and design of post-translational modification is therefore performed in weeks rather than in months or years.

Very high expression levels. magnICON® provides up to 5 milligram recombinant (enzyme) protein per gram of fresh leaf biomass with the yield of recombinant protein reaching up to 80 % of total soluble protein. The yield per biomass is 10-1000 fold higher than with other existing plant-based systems, and relative yields are 10-100 fold higher. Because of speed and expression levels, magnICON® is ideally suited for generating within weeks grams of purified protein necessary for pre-clinical or clinical studies.

Scale up. In the forthcoming publications, we shall describe our industrial versions of magnICON® that utilize the same principle, but require different amplicon formation and release mechanism.

Biosafety issues. magnICON® vectors are based on a 'deconstructed virus' strategy - they lack essential viral functions, and thus no wild type virus can be generated as a result of uncontrolled recombination events. The yields achieved allow production of hundreds of kilograms of protein per hectare annually in fully contained greenhouses, thus avoiding altogether any release in the environment. In addition, the use of tobacco, a non-food, non-feed plant, further mitigates the biosafety risk.

ICON Genetics is an integrated platform technology provider developing proprietary technologies and production hosts with application to a broad range of agricultural and pharmaceutical biotechnology products. ICON's new generation technologies of plant engineering (Transgene Operating Systems®) provide higher expression levels/yield, better expression control and higher biosafety. Corporate offices are headquartered in Munich, Germany and the Company's Research divisions are located in Halle and Freising, Germany.