Novel Flavivirus Antiviral That Targets the Host Nuclear Transport Importin α/β1 Heterodimer.

Dengue virus (DENV) threatens almost 70% of the world's population, with no effective vaccine or therapeutic currently available. A key contributor to infection is nuclear localisation in the infected cell of DENV nonstructural protein 5 (NS5) through the action of the host importin (IMP) alpha/beta 1 proteins. Here, we used a range of microscopic, virological and biochemical/biophysical approaches to show for the first time that the small molecule GW5074 has anti-DENV action through its novel ability to inhibit NS5-IMP alpha/beta 1 interaction in vitro as well as NS5 nuclear localisation in infected cells. Strikingly, GW5074 not only inhibits IMP alpha binding to IMP beta 1, but can dissociate preformed IMP alpha/beta 1 heterodimer, through targeting the IMP alpha armadillo (ARM) repeat domain to impact IMP alpha thermal stability and alpha-helicity, as shown using analytical ultracentrifugation, thermostability analysis and circular dichroism measurements. Importantly, GW5074 has strong antiviral activity at low mu M concentrations against not only DENV-2, but also zika virus and West Nile virus. This work highlights DENV NS5 nuclear targeting as a viable target for anti-flaviviral therapeutics.