Quantification of DENV RNA copy number by RT-qPCR - Viral RNA was extracted from culture supernatants using the QIAamp Viral RNA Mini Kit (Qiagen, Hilden, Germany), according to the manufacturer’s instructions. The viral copy number was determined by RT-qPCR using the following DENV-specific primers against the conserved sequences in the core gene of DENV RNA: forward: 5′ CAA TAT GCT GAA ACG CGA GAG AAA 3′, and reverse: 5′ CCC CAT CTA TTC AGA ATC CCT GCT 3′ (Castillo et al. 2016). Calculation of the genomic RNA copy number was performed based on a standard curve, as previously described (Sachs et al. 2011). All experiments were performed in triplicate.