Uncovering the conformational dynamics of dengue virus and its virus-like particles as novel vaccine candidates.

Abstract

Dengue virus (DENV) is an enveloped virus that infects millions of people worldwide. The only commercially available vaccine has low efficacy and safety issues. DENV is ∼50 nm in diameter, and contains 90 envelope (E) and membrane (M) protein dimers embedded within a lipid envelope, encapsulating an RNA genome. There are four closely related DENV serotypes, which hamper broad neutralization by host antibodies and can result in antibody dependent enhancement worsening the clinical symptoms of dengue infections. During its life cycle, DENV adopts numerous conformations in response to environmental factors such as pH and temperature changes, which result in varying degrees of exposure of its accessible epitopes. These factors make vaccine development challenging both from the immunological and structural points of view. Virus-like particles (VLPs) represent promising platforms as novel vaccine alternatives because they are non-infectious and highly immunogenic. DENV VLPs are ∼30 nm in diameter, containing 30 E/M protein dimers on their surface, likely leading to significant differences in their conformational dynamics compared to the virus itself. Notably, these VLPs exhibit a significant “groove” at the E protein dimeric interface, yielding more exposed epitopes than those present on the typical DENV particle. This factor is likely to be critical to the efficacy of resultant vaccines. Here, we employed an integrative modeling and multiscale simulation approach supported by various experimental measurements to understand the differences in conformational dynamics between both mature and immature DENV and its VLPs, to assess epitope exposure and particle stability. Similar tools were also used to guide several site-directed mutations that may guide the improvement of such VLPs, and hence represents a platform for novel vaccine development strategies.