Evaluation of a Tetravalent DNA Vaccine against Dengue: Integrating Biochemical Studies on Dengue Virus Envelope Protein to a Domain-Based Antigen Design.
Dengue virus (DENV) is among the most important mosquito-borne human pathogens worldwide. Concerns regarding the effectiveness of Dengue vaccines together with emergence of Zika virus (ZIKV) have reignited the interest for new vaccines using alternative approaches. Given that the envelope glycoprotein (E) is the main target of neutralizing antibodies, it has been used as the antigen of choice for vaccine development efforts.
Here we present a detailed analysis of factors involved in the expression, secretion and folding of the E ectodomain from all four DENV serotypes and ZIKV in mammalian cells. Our data demonstrate that E domains II and III (DII and DIII) are important for proper E folding and stabilization of soluble dimers, respectively. In addition, we show that successful covalent stabilisation of E dimers, and E folding in general is strongly dependent on temperature but not on PrM co-expression, and that DENV and ZIKV E proteins can form heterodimers and assemble into mosaic viral particles.
Our findings also show that antigen secretion determines the efficiency of DNA vaccines. Based on this, we developed a novel DNA gene-gun immunisation strategy using an engineered version of DIII fused to the CH3 domain of the IgG H chain, which is efficiently secreted from transfected cells and induced strong antibody responses that neutralise all DENV serotypes. The antibody responses were stable over long periods of time and different tetravalent formulations of the vaccine showed induction of neutralising antibodies against all four dengue serotypes as well.
Finally, our results also indicate that the polyclonal antibody responses against DI/DII are highly cross-reactive, poorly neutralising and promote ADE towards all DENV serotypes, ZIKV, WNV and YFV. Conversely, anti-DIII antibodies are type-specific, with no ADE towards related flaviviruses, and with strong neutralisation activity restricted only to DENV
