A Viperin Mutant Bearing the K358R Substitution Lost its Anti-ZIKA Virus Activity

Interferon-induced viperin (VP) was identified as playing an important role in the innate immune response against Zika virus (ZIKV). The 361 amino acid long human VP protein comprises of a highly conserved C-terminal region, which has been associated with VP antiviral properties against ZIKV. In the present study, we sought to determine whether the very last C-terminal amino-acid residues of VP might play a role in VP-mediated ZIKV inhibition. To address this issue, a recombinant human viperin (rVP^wt) was overexpressed by transfection in human epithelial A549 cells. We confirmed that transient overexpression of rVP^wt prior to ZIKV infection dramatically reduced viral replication in A549 cells. Deletion of the last 17 C-terminal amino acids of VP resulted in a higher expression level of mutant protein compared to wild-type VP. Mutational analysis revealed that residue substitution at positions 356 to 360 with five alanine led to the same phenotype. The charged residues Asp356, Lys358, and Asp360 were then identified to play a role in the weak level of VP^wt protein in A549 cells. Mutant VP bearing the D360A substitution partially rescued ZIKV growth in A549 cells. Remarkably, a single Lys-to-Arg substitution at position 358 was sufficient to abrogate VP antiviral activity against ZIKV. In conclusion, our study showed that Asp356, Lys358, and Asp360 may have an influence on biochemical properties of VP. Our major finding was that Lys358 was a key amino-acid in VP antiviral properties against ZIKV.