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Dengue is a disease caused by dengue virus and represents the most important arthropod-borne viral disease in humans. Dengue virus enters host cells via binding of envelope glycoprotein (E) to a receptor. In this study, plant expression vectors containing native and synthetic glycoprotein E genes (sE) modified based on plant-optimized codon usage and fused with an ER retention signal were constructed under control of the rice amylase 3D promoter expression system. Plant expression vectors were introduced into rice callus (Oryza sativa L. cv. Dongin) via particle bombardment-mediated transformation. The integration and expression of target genes were confirmed in the transgenic callus by genomic DNA PCR and Northern blot analyses, respectively. The plant-codon optimized sE gene with an ER retention signal showed high protein production levels based on Western blot analysis of approximately 18.5 ug/g dried calli weight by immunoblot-based densitometric analysis. These results suggest that the plant-codon optimized sE gene with an ER retention signal was highly produced in the transgenic rice callus.

The spread of dengue (DEN) virus is becoming a major concern due to the possibility of primary infection with one of the four dengue serotypes (DEN 1-4) and secondary infection with other heterotypes, which can further aggravate clinical manifestations. A gene encoding consensus envelope protein domain III (cEDIII) of dengue virus with neutralizing activity against four dengue virus serotypes was fused to M cell-targeting peptide ligand (Co1) to increase its mucosal immunogenicity and was introduced into rice calli under the control of the inducible rice amylase 3D promoter expression system. The integration and expression of scEDIII-Co1 fusion gene in transgenic rice calli were confirmed by genomic DNA PCR amplification, Northern and Western blot analyses, respectively. The deliveries of cEDIII-Co1 fusion proteins into mucosal immune inductive site (including M cells) were confirmed by in vitro and in vivo antigen uptake assays. These results showed that plant-produced M cell-targeting peptide ligand, Co1, fusion antigen proteins have the potential to be targeted to the mucosal immune system for improvement of immune responses.