Nuclear trafficking of Venezuelan Equine Encephalitis Virus capsid protein as an antiviral target

DR Thomas1, A DeBono2, L Lundberg3, C Pinkham3, S Shechter4, K Kehn-Hall3, J Baell2, KM Wagstaff1 and DA Jans1

  1. Department of Biochemistry and Molecular Biology, Monash University, Clayton, Vic, Australia
  2. Department of Medicinal Chemistry, Monash University, Parkville, Vic, Australia
  3. National Center for Biodefence and Infectious Diseases, School of Systems Biology, George Mason University, Manassas, VA, USA
  4. Shechter Solutions, Andover, MA, USA

Venezuelan Equine Encephalitis Virus (VEEV) is an Alphavirus that can be fatal to either humans or equines, but there is no widely available treatment, and the only available vaccine has significant side effects and limited efficacy. The VEEV capsid protein is critical to VEEV biology, both encasing the viral RNA, and acting to down-regulate host antiviral defenses by inhibiting nuclear transport in the infected host cell. Capsid contains targeting signals for both nuclear import and export, with viruses containing mutations in either of these signals strongly attenuated. Capsid is thought to inhibit host cell nuclear transport by binding to and sequestering 3 members of the importin (IMP) superfamily of nuclear transport proteins (IMPα, IMPβ1, Crm1) within the nuclear envelope that surrounds the nucleus. Using fluorescence recovery after photobleaching (FRAP) in cells transfected to express capsid, we have shown that even though capsid localizes strongly at the nuclear envelope, it is able to translocate readily into and out of the nucleus, and exhibits dynamic localization at the nuclear envelope itself, Using high throughput screening and in silico approaches, we have identified and begun to characterize compounds that inhibit the capsid:IMPαβ1 interaction. Preliminary results suggest that these compounds both reduce the rate of capsid nuclear import, and show antiviral activity against VEEV in a cell culture infectious model. These compounds are exciting prospects as VEEV antivirals to be developed through medicinal chemistry in the future.