Introduction

anpic2Prof. Ann Depicker coordinates the Plant-made Antibodies and Immunogens group. Plant-based systems provide an attractive alternative for the production of valuable recombinant proteins as compared to mammalian and bacterial production platforms. Besides applying the eukaryotic processing machinery, they offer several advantages, including low production costs, the lack of mammalian pathogen contaminants, and the ease of agricultural scale-up. Different plant tissues can be used for the production of recombinant proteins, of which leaves and seeds are very promising bioreactors. Seeds allow recombinant proteins to stably accumulate at a relatively high concentration and they can be stored at room temperature for long periods of time. Both these factors further enable convenient downstream processing. Besides, antibodies and immunogens in the seed matrix can be used for oral delivery.

Our research group successfully established a system for high-level production of recombinant antibodies in Arabidopsis thaliana seeds (De Jaeger et al., 2002; Van Droogenbroeck et al., 2009; De Buck et al., 2013). Which has been successfully used to produce diagnostic and therapeutic antibodies and vaccines. To obtain full advantage of the seed production system, it is essential to constantly evaluate its limitations and develop novel technologies to overcome the remaining obstacles. Hence we also focus on optimizing this technology, for example, the best strategy to produce the complex secretory-IgA is currently being worked out and also a generic protocol for purification of IgG and IgA antibodies.

For screening of new immunoglobulin variants and fusions, we are using the Nicotiana benthamiana transient expression system because it is very flexible and up to milligram amounts can be obtained within one week. To obtain recombinant protein for proof of concept studies, we are employing Arabidopsis thaliana seeds as experimental recombinant protein production system because of its ease, low workload and speed to go from DNA construct to 100 mg of recombinant protein in about one year. For cost-effective production of bulk amounts of complex recombinant proteins as is for instance needed for passive immunization we are exploring the use of larger protein-rich seed crops such as soybean and pea.

The capacity to conveniently produce milligram to gram amounts of novel therapeutic proteins provides a unique platform for addressing question of animal and public health importance, right from fundamental to applied level. We focus on therapeutic antibodies, specific vaccines and biotechnological tools. Towards a valorization objective, we are exploring the passive immunization approach in weaned piglets against the enterotoxigenic Escherichia coli together with the Cox lab (Laboratory of Immunology, Ghent University); together with Sam Millet (ILVO) we are analyzing how colostrum and milk protects the suckling piglets and how mucosal immunity develops in weaned piglets. At fundamental level, together with the Saelens lab and Schepens (Unit of Molecular Virology, VIB-Ghent University we are evaluating the effectiveness of different immunoglobulin fusions in protecting against the human respiratory syncytial virus (HRSV) in animal models. In another project aimed at studying mucosal immunity, we are investigating the various enterocyte receptor mediated transcytosis processes with receptor targeting antigen fusions together with Cox lab and Devriendt. Our group is also developing biotechnological tools based on known antibody sequences for improved diagnostic tests and immunoprecipitation.