Search

Cyclic citrullinated peptide (CCP) antibody has been shown recently to be a promising marker for early detection and diagnosis of rheumatoid arthritis (RA). In order to exploit newly developed therapies for RA, early intervention is crucial in preventing irreversible joint damage. Here, we describe use of a plant expression system to produce a CCP antibody that could be used in the early diagnosis of RA. Heavy and light chain gene sequences of a CCP monoclonal antibody (CCP mAb) were cloned from the hybridoma cell (12G1) and introduced into two separate plant expression vectors under the control of the rice α-amylase 3D (RAmy3D) promoter system. The vectors were introduced into rice calli (Oryza sativa L. cv. Dongjin) using Agrobacterium tumefaciens mediated transformation. Integration of the CCP mAb genes into rice chromosomes was confirmed by a genomic DNA polymerase chain reaction and expression was verified by northern blot analysis of mRNA. The in vivo assembly and secretion of CCP mAb occurred in transgenic rice cell suspension culture under the RAmy3D expression system; accumulated CCP mAbs in the medium were purified by protein G affinity chromatography. Immunoblot assays and ELISA showed these plant-produced CCP mAbs successfully bound to a synthetic CCP antigen. Taken together, our results suggest that CCP mAb produced in a transgenic rice suspension culture were easily purified and biologically active against their antigen in the RA, and thus may be used a specific serological marker, which is present very early in the RA.

Lysosomal storage diseases are a group of inherited metabolic disorders. Patients are treated with enzyme replacement therapy (ERT), in which the replacement enzymes are required to carry terminal mannose or mannose 6-phosphate residues to allow efficient uptake into target cells and tissues. N-acetylglucosaminyltransferase-I (GnTI) mediates N-glycosylation in the cis cisternae of the Golgi apparatus by adding N-acetylglucosamine to the exposed terminal mannose residue of core N-glycan structures for further processing. Mutant rice lacking GnTI produces only high mannosylated glycoproteins. In this study, we introduced a gene encoding recombinant human acid α-glucosidase (rhGAA), which is used in ERT for Pompe disease, into gnt1 rice callus by particle bombardment. Integration of the target gene into the genome of the gnt1 rice line and its mRNA expression were confirmed by PCR and Northern blot, respectively. Western blot analysis was performed to confirm secretion of the target proteins into the culture media. Using an indirect enzyme linked immunosorbent assay, we determined the maximum expression of rhGAA to be approximately 45mg/L, 13days after induction. To assay the enzymatic activity and determine the N-glycan profile of rhGAA, we purified the protein using a 6×histidine tag. The in vitro α-glucosidase activity of rhGAA from gnt1 rice callus (gnt1-GAA) was 3.092U/mg, similar to the activity of the Chinese hamster ovary cell-derived GAA (3.154U/mg). N-glycan analysis revealed the presence of high-mannose N-glycans on gnt1-GAA. In addition, the production of high-mannose GAA using gnt1 rice calli as an expression host was characterized, which may aid the future development of therapeutic enzymes for the treatment of Pompe disease.

Vascular endothelial growth factors (VEGFs) are secreted by tumor cells and other cells exposed to hypoxia, and play a critical role in the development and differentiation of the vascular system. In this study, we investigated the production of functional recombinant human VEGF165 (rhVEGF165) in transgenic rice cell suspension culture. Complementary DNA was synthesized from human leukemia HL60 cells and cloned into expression vectors under the control of the rice α-amylase 3D (RAmy3D) promoter. The rice seed (Oryza sativa L. cv. Dongjin) was transformed with this recombinant vector by the Agrobacterium mediated method and the integration of the target gene into the plant genome was confirmed by genomic PCR. The expression of rhVEGF165 in the rice cells was determined by Northern blot and Western blot analyses. The accumulated rhVEGF165 protein in the culture medium was 19 mg/L after 18 days of culturing in a sugar-free medium. The rhVEGF165 was purified using a heparin HP column and its biological activity was tested on human umbilical vein endothelial cells (HUVECs). The purified rhVEGF165 significantly increased the proliferative activity of the HUVECs. Therefore, it was demonstrated that functional rhVEGF165 could be produced using transgenic rice suspension culture vector under the control of the RAmy3D promoter.