Evaluation of the oral immunogenicity of M cell-targeted tetravalent EDIII antigen for development of plant-based edible vaccine against dengue infection

Abstract

Four serotypes of the dengue virus that can cause severe disease in humans greatly increases the complexity of vaccine development. In this study, we evaluated an ‘all-in-one’ tetravalent dengue vaccine candidate as an alternative to the classical four viruses ‘cocktail’ vaccination approach. A single polypeptide chain of the tetra-EDIII comprising all four serotypes fused to the M-cell target ligand peptide (tEDIII-Co1) was constructed and expressed using a rice expression system under the control of a strong inducible promoter (rice amylase 3D: Ramy3D) and rice 3′ untranslated region (UTR). The tEDIII-Co1 was constructed using wild type or plant codon optimized gene sequence to compare the expression levels. The codon optimized gene combined with ER-localization showed higher and more stable expression than codon-optimization alone or the wild type. To test the oral immunogenicity of this construct, the transgenic rice cells containing 100 µg of tEDIII-Co1 were fed to mice and the antigen specific IgG and IgA antibodies analysed in sera or fecal extracts. The tEDIII fused to Co1 induced strong antibody responses in the absence of any adjuvants. We observed the strongest antigen-specific B and T cell responses in animals immunized with tEDIII-Co1. Taken together, this simple tetravalent EDIII-based fusion protein with the M cell ligand could has potential as an alternative dengue vaccine strategy against all four serotypes.