Dengue virus (DENV) is a membrane-enveloped virus, and a member of the Flavivirus genus. It causes an estimated 400 million human infections worldwide, which can lead to dengue fever and in severe cases can be fatal. Currently, there are no approved antiviral drugs and limited vaccination options, emphasizing the need for further study. To infect a host cell, DENV is first internalized by endocytosis. Acidification of the endosome triggers membrane fusion with the endosomal membrane. This process is mediated by the viral envelope E protein which undergoes a series of conformational changes to catalyze membrane fusion. In this study, we use fluorescence microscopy to perform single particle hemi-fusion (lipid mixing) measurements of DENV virus-like particles and tethered lipid membranes. We measure both the rate and extent of hemi-fusion under a range of pH conditions. By computationally modeling the observed fusion kinetics, we determine that the kinetic model of DENV must contain a reversible off-pathway state, similar to what has been reported for Zika virus and West Nile virus. This suggests that an off pathway mechanism may be a general feature of Flavivirus fusion. We also present evidence that the presence of late endosomal anionic lipids does not appear to affect the rate-limiting step of hemi-fusion or the requirement for an off-pathway state in our computational models. Finally, we present data for investigating small molecule inhibitors which block DENV fusion and their effects on the resulting mechanism.
Walker et al. (Sun,) studied this question.