Vaccine 19 (2001) 2756–2761 Production of antibodies and antibody fragments in plants Koen Peeters, Chris De Wilde 1 , Geert De Jaeger, Geert Angenon, Ann Depicker * Vakgroep Moleculaire Genetica, Departement Plantengenetica, Vlaams Interuniersitair Instituut oor Biotechnologie, Uniersiteit Gent, K.L. Ledeganckstraat 35, B-9000 Gent, Belgium Abstract Our current knowledge allows the generation of transgenic plants that efficiently produce heterologous proteins from plant, bacterial, fungal or animal origin. Among all types of recombinant proteins, antibodies are particularly attractive because of their ability to specifically recognize and bind virtually any type of antigen. Plants show several advantages as a large-scale antibody production system: they can be grown easily and inexpensively in large quantities that can be harvested, stored and processed by using existing infrastructures. Isolation and purification of plant-made antibodies, if necessary, allow fundamental, industrial, and therapeutical applications. In the past, we and others have successfully generated antibody-producing plants. The maximal accumulation levels of antibodies and antibody fragments that we observed are 1 – 5% of the extracted proteins. Currently, several biotechnological companies grow field crops to produce antibodies for ex planta applications on an industrial scale. © 2001 Elsevier Science Ltd. All rights reserved. Keywords: Antibody production systems; Plant-derived antibodies; Transgenic plants www.elsevier.com/locate/vaccine 1. Introduction Plant biotechnology is a rapidly evolving technology that is extending the boundaries of crop improvement and offers new agricultural perspectives. Examples in this field are genetically engineered crops with better disease and pest resistance, herbicide and stress toler- ance, improved nutritional value or male sterility for hybrid seed production. In addition, transgenic plants have increasingly been considered as economic expression systems for ‘molecu- lar farming’, i.e. the bulk production of high-value molecules such as novel carbohydrates and lipids, bio- plastics, therapeutic proteins, enzymes and vaccines [1 – 5]. The appealing advantages of molecular farming are the low costs of crop production in the field, the ease of scaling up production to meet industrial demand, the absence of animal or human pathogens, the existing infrastructure for harvesting and processing plant derived products and the possibility to stably store molecules in storage organs such as seeds or tubers. Antibodies and antibody fragments may be one of the most interesting types of recombinant proteins to be produced in large quantities because of their high spe- cificity and affinity for a wide range of antigens. Mono- clonal antibodies have already proven to be of indispensable value for therapy, diagnostics and labora- tory or industrial applications. In this review we will focus on the current status and views concerning the production of antibodies and their derived fragments in plants. Antibody production in plants can also be used for the modification of biochemical pathways (im- munomodulation) or to obtain pathogen resistance (in- tracellular immunisation) [6]. 2. Expression of recombinant antibodies in plants Antibodies are glycoproteins that all have a common basic structure consisting of two identical heavy (H) chain polypeptides and two identical light (L) chain polypeptides held together by disulfide bridges and non-covalent bounds. Because of the domain structure of antibodies, many different types of antibody frag- ments can be engineered. Several of those have been functionally produced in plants, for example a single- domain antibody (dAb) [7], a Fab fragment [8] and single-chain variable fragments (scFvs) [9,10]. * Corresponding author. Tel.: +32-9-2645174; fax: +32-9- 2645349. E-mail address: anna.depicker@rug.ac.be (A. Depicker). 1 Crop Design, Technologiepark 3, B-9052 Zwijnaarde, Belgium. 0264-410X/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved. PII:S0264-410X(00)00514-4