title: Field production and functional evaluation of chloroplast-derived interferon-alpha2b.
abstract: Type I interferons (IFNs) inhibit viral replication and cell growth and enhance the immune response, and therefore have many clinical applications. IFN-alpha2b ranks third in world market use for a biopharmaceutical, behind only insulin and erythropoietin. The average annual cost of IFN-alpha2b for the treatment of hepatitis C infection is $26,000, and is therefore unavailable to the majority of patients in developing countries. Therefore, we expressed IFN-alpha2b in tobacco chloroplasts, and transgenic lines were grown in the field after obtaining United States Department of Agriculture Animal and Plant Health Inspection Service (USDA-APHIS) approval. Stable, site-specific integration of transgenes into chloroplast genomes and homoplasmy through several generations were confirmed. IFN-alpha2b levels reached up to 20% of total soluble protein, or 3 mg per gram of leaf (fresh weight). Transgenic IFN-alpha2b had similar in vitro biological activity to commercially produced PEG-Introntrade mark when tested for its ability to protect cells against cytopathic viral replication in the vesicular stomatitis virus cytopathic effect (VSV CPE) assay and to inhibit early-stage human immunodeficiency virus (HIV) infection. The antitumour and immunomodulating properties of IFN-alpha2b were also seen in vivo. Chloroplast-derived IFN-alpha2b increased the expression of major histocompatibility complex class I (MHC I) on splenocytes and the total number of natural killer (NK) cells. Finally, IFN-alpha2b purified from chloroplast transgenic lines (cpIFN-alpha2b) protected mice from a highly metastatic tumour line. This demonstration of high levels of expression of IFN-alpha2b, transgene containment and biological activity akin to that of commercial preparations of IFN-alpha2b facilitated the first field production of a plant-derived human blood protein, a critical step towards human clinical trials and commercialization.
authors.affiliation: Department of Molecular Biology and Microbiology, University of Central Florida, Biomolecular Science, Orlando, FL 32816-2364, USA.
authors.forename: Philip A
authors.initials: PA
authors.lastname: Arlen
authors.forename: Regina
authors.initials: R
authors.lastname: Falconer
authors.forename: Sri
authors.initials: S
authors.lastname: Cherukumilli
authors.forename: Amy
authors.initials: A
authors.lastname: Cole
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Cole
authors.forename: Karen K
authors.initials: KK
authors.lastname: Oishi
authors.forename: Henry
authors.initials: H
authors.lastname: Daniell
mesh_terms: D002736:Chloroplasts / Q000378:metabolism*; D000077190:Interferon alpha-2; D016898:Interferon-alpha / Q000096:biosynthesis* / Q000494:pharmacology; D030821:Plants, Genetically Modified / Q000378:metabolism; D011994:Recombinant Proteins; D014026:Nicotiana / Q000378:metabolism
chemical_list: D000077190:Interferon alpha-2; D016898:Interferon-alpha; D011994:Recombinant Proteins