Viperin is an anti-viral protein from host that is primarily interferon stimulated gene (ISG). This protein is up-regulated in a number of viral infections via IFN dependent or IFN independent mechanisms. It is reported that viperin inhibits HIV egress, influenza virus release and protein production in HCMV infection.
Researchers in this study have shown that dengue virus type-2 (DENV-2) infection causes induction of viperin. The mechanism for such process involves retinoic acid-inducible gene I (RIG-I) and along with viperin causes production of viral RNA also. Viperin expressing cells show inhibition of virus release and DENV-2 RNA.
The anti DENV effect of viperin protein is mediated by C-terminal, not N-terminal; although N-terminal includes motifs or structural amphiphatic helical domains that are known to be involved in membrane association, e.g., helix domain, leucine zipper and S-adenosylmethionine. The C-terminal is unstructured but highly conserved and with unknown functions.
Viperin colocalised and interacted with lipid droplet markers (dengue capsid protein) and DENV-2 capsid (CA), NS3 protein and viral RNA respectively. Such interaction ability is associated with anti-viral activity of viperin, which is in contrast with lipid droplet markers.
So overall this manuscript suggests that infection of DENV2 causes viperin induction. Since C-terminal of viperin has anti-viral properties associated with it, hence restrict early DENV-RNA accumulation.
Reference: Helbig KJ, Carr JM, Calvert JK, Wati S, Clarke JN, et al. (2013) Viperin Is Induced following Dengue Virus Type-2 (DENV-2) Infection and Has Anti-viral Actions Requiring the C-terminal End of Viperin. PLoS Negl Trop Dis 7(4): e2178. doi:10.1371/journal.pntd.0002178.