Abstract
BackgroundDengue is a rapidly spreading mosquito borne tropical viral disease affecting hundreds of millions of people across the globe annually. The dengue virus (DENV) includes four genetically distinct serotypes that cause serious life-threatening infections, including dengue hemorrhagic fever/dengue shock syndrome. Dengue vaccine development is complicated by the possibility of vaccine-enhanced severe dengue disease due to antibody-dependent enhancement by pre-existing cross-reactivity, as well as homotypic antibodies. Thus, the development of an efficacious dengue vaccine conferring simultaneous and durable immunity to each of the four DENV serotypes has not yet been developed despite years of research. For mass immunization in deeply affected resource-limited countries, oral vaccination is considered more beneficial than conventional approaches. Therefore, in a continuing effort towards designing economical and potent vaccine candidates, the current study applied yeast surface display technology to develop an oral dengue vaccine candidate using whole recombinant yeast cells displaying the recombinant fusion protein of M cell targeting ligand Co1 fused to the synthetic consensus dengue envelope domain III (scEDIII). Female Balb/c mice were orally fed with recombinant yeast cells and immunogenicity in terms of systemic and mucosal immune responses was monitored.ResultsImmunofluorescence microscopy with dengue specific antibody and fluorescein isothiocyanate-conjugated anti-mouse IgG antibody clearly showed that recombinant protein Co1-scEDIII-AGA was localized on the cell surface of the respective clones in comparison with scEDIII-Co1 and Mock cells with no fluorescence. Oral dosage applications of surface displayed Co1-scEDIII-AGA stimulated a systemic humoral immune response in the form of dengue-specific serum IgG, as well as a mucosal immune response in the form of secretory immunoglobulin A (sIgA). Antigen-specific B cell responses in isolated lymphoid cells from the spleen and Peyer’s patches further supported an elevated mucosal immune response. In addition, surface displayed Co1-scEDIII-AGA feeding elicited strong immune responses in comparison with scEDIII-Co1 and Mock following intraperitoneal booster with purified scEDIII antigen.ConclusionsSurface displayed preparations of Co1-scEDIII-AGA induced strong immunogenicity compared with non-displayed scEDIII-Co1. Prior studies have supported the neutralization potential of scEDIII constructs against all four serotypes. Thus, the oral administration of genetically engineered yeast whole cells displaying biologically active Co1-scEDIII fusion protein without any further processing shows prospective as a potent oral vaccine candidate against dengue viral infection.
Highlights
Dengue is a rapidly spreading mosquito borne tropical viral disease affecting hundreds of millions of people across the globe annually
Taking into consideration the immunogenic efficacy of synthetic consensus dengue envelope domain III (scEDIII), the efficient mucosal targeting, elicitation of immune responses by Co1, and advantages of the surface display technology of S. cerevisiae, we evaluated the immunogenicity of the fused recombinant antigen surface displayed preparations of S. cerevisiae as an oral dengue vaccine candidate in a female BALB/c mouse model
Following transformation of the above plasmid into S. cerevisiae strain 2805, more than 20 transformants were randomly selected on ura− medium and were further examined using colony polymerase chain reaction (PCR) and E. coli back transformation to confirm the presence of the corresponding recombinant plasmid
Summary
Dengue is a rapidly spreading mosquito borne tropical viral disease affecting hundreds of millions of people across the globe annually. The development of an effica‐ cious dengue vaccine conferring simultaneous and durable immunity to each of the four DENV serotypes has not yet been developed despite years of research. Various factors, including the epidemiology of the four DENV serotypes and the complexity of immunoprotective and immunopathogenic responses following natural infection or vaccination, have created obstacles in the path of dengue vaccine development, despite 70 years of research [4]. The first licensed dengue vaccine CYD-TDV [5] has recently been approved, it was associated with an elevated risk of hospitalization for dengue among children younger than 9 years of age [6], and exhibited limited overall vaccine efficacy of 54% and reduced efficacy of 34% against DENV2, which is known to cause severe dengue infection and dengue outbreaks [7]. Further studies on the development of potent and effective vaccines are required
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