*2.5. Quantification of Viral Stocks*

Zika virus samples were analysed by titration on Vero cells while genomic viral RNA was quantified by RT-qPCR, as previously described [23]. Briefly, viral RNA was extracted from virus particles using QIAmp Kit (Qiagen, Hilden, Germany). PCR standard curve used for quantification of ZIKV copy numbers was obtained with a pUC57/ZIKV-E amplicon plasmid containing a synthetic

cDNA encompassing nucleotides 961 to 1301 of genomic RNA (MR766). The pair of ZIKV E primers was used to equally amplify pUC57/ZIKV-E amplicon and cDNA encompassing nucleotides 1046 to 1213 from genomic RNA of ZIKV molecular clones used in this study.
