Abstract
The recurring outbreak of Zika virus (ZIKV) worldwide makes an emergent demand for novel, safe and efficacious anti-ZIKV agents. ZIKV non-structural protein 5 (NS5) methyltransferase (MTase), which is essential for viral replication, is regarded as a potential drug target. In our study, a luminescence-based methyltransferase assay was used to establish the ZIKV NS5 MTase inhibitor screening model. Through screening a natural product library, we found theaflavin, a polyphenol derived from tea, could inhibit ZIKV NS5 MTase activity with a 50% inhibitory concentration (IC50) of 10.10 μM. Molecular docking and site-directed mutagenesis analyses identified D146 as the key amino acid in the interaction between ZIKV NS5 MTase and theaflavin. The SPR assay indicated that theaflavin had a stronger binding activity with ZIKV NS5 wild-type (WT)-MTase than it with D146A-MTase. Moreover, theaflavin exhibited a dose dependent inhibitory effect on ZIKV replication with a 50% effective concentration (EC50) of 8.19 μM. All these results indicate that theaflavin is likely to be a promising lead compound against ZIKV.
Highlights
Zika virus (ZIKV), emerging as a global healthcare threat, belongs to mosquito-transmitted Flavivirus in the Flaviviridae family, which includes Dengue (DENV), yellow fever (YFV), West Nile (WNV), Japanese encephalitis (JEV) and tick-borne encephalitis (TBEV) viruses (Miner and Diamond, 2017; Mittal et al, 2017)
The non-structural protein 5 (NS5) MTase recombinant protein was expressed in a soluble form and was purified using Ni2+ HisTrap chelating columns
CCK-8 assay indicated that CC50 (50% cytotoxic concentration) of theaflavin to Huh7 cells was higher than 128 mM, which is 10 times higher than its EC50 to ZIKV infected Huh-7 cells, indicating the inhibitory effect of theaflavin to Huh7 was not due to its cytotoxicity (Figure 5C). These results revealed that theaflavin could target D146 of ZIKV NS5 MTase to inhibit ZIKV infection
Summary
Zika virus (ZIKV), emerging as a global healthcare threat, belongs to mosquito-transmitted Flavivirus in the Flaviviridae family, which includes Dengue (DENV), yellow fever (YFV), West Nile (WNV), Japanese encephalitis (JEV) and tick-borne encephalitis (TBEV) viruses (Miner and Diamond, 2017; Mittal et al, 2017). All the flavivirus can bring global emergencies and cause great burdens to public health. Before the French Polynesian outbreak in 2013, ZIKV was considered a mild disease (Musso et al, 2015). Severe Guillain-Barre syndrome was found in this outbreak (Musso et al, 2014). In 2015, ZIKV was declared a global public health emergency by WHO due to its explosive spread through the Americas (Faria et al, 2016). As a result, developing anti-ZIKV agents becomes an emergency
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