Expression of Recombinant Antibodies

Frenzel, André; Hust, Michael; Schirrmann, Thomas

The generation of genetically modified dicotyledonous plants is mainly done by the transfer of the expression cassette of the transgene with the help of Agrobacterium tumefaciens. In principle, the gene of interest is cloned into the T-DNA of a binary plasmid (186, 187) which is flanked by two 25 bp imperfect repeats. In most cases, the expression of the transgene is under the control of one or two (188) copies of the constitutive cauliflower mosaic virus (CaMV). In addition, a selection marker is located on the T-DNA and transferred into the host genome for effective screening of successfully transformed plants. After integration of the T-DNA into the host genome by non-homologous recombination complete plants can be regenerated from transformed pieces of the plant [RB (189) ]. As this procedure requires several months of transformation and special regeneration protocols, transient expression systems have been developed which allow time saving production of recombinant proteins: McCormick and colleagues designed a tobacco mosaic virus (TMV) based vector for the secretory expression of different scFvs for the treatment of non-Hodgkin's lymphoma (190) . Expression yields in Nicotiana benthamiana were up to 100-800 µg/mL in the crude secretory extract. Same technique has been applied for the expression of idiotype-scFvs for personalized vaccination of follicular B-cell lymphoma patients in a phase I clinical study (191) . In this study, nearly half of the treated patients developed an antigen specific immune response despite differences in glycosylation pattern.