Targeting functional RNA structures in CHIKV and ZIKV

Emerging arboviruses such as Zika virus (ZIKV) and Chikungunya virus (CHIKV) represent a significant threat to human health and have a high potential to cause outbreaks in the near future. At present, there are no specific antivirals available for either of these important pathogens, despite the wide global prevalence of their vector, Aedes spp. mosquitos.

The positive-strand genomes of ZIKV and CHIKV, members of the flavivirus and alphavirus genera respectively, contain functional, structured cis-acting RNA elements which are essential for virus replication. By specifically targeting such RNA elements using antisense locked nucleic acid oligonucleotides (antisense-LNA), we aim to disrupt their function, and analyse the effect this has on virus replication at different life cycle stages.

Obtaining high quality, single-nucleotide-resolution structural data is essential prior to targeting RNA structures. Consequently, we mapped RNA structural elements within the ZIKV 5’ genome region using a combination of biochemical SHAPE probing, thermodynamic models and phylogenetic analysis. We are currently validating our structural data by analysis of mutant phenotypes in a reverse genetic system.

We demonstrate that functional RNA elements in CHIKV can be specifically targeted - inhibiting replication in both sub-genomic replicon and infectious virus systems. Surface plasmon resonance confirmed that an antisense-LNA binds to a specific stem-loop target with a Kd of 310nM and has an IC50 of 35nM in a sub-genomic replicon system. In future work, we aim to investigate selection of RNA-aptamers against CHIKV and target ZIKV genomic stem-loops using antisense-LNAs.