Generation of pGUD plasmid constructs - pGUD plasmids containing the 3′ UTRs of DENV-1, -2, or -4 downstream of green fluorescent protein (GFP) in the pEGFP-C1 (Clontech, CA, USA) construct were previously described (Castillo et al. 2016). Briefly, the 3′ UTRs of the three DENV serotypes were amplified by polymerase chain reaction (PCR) from viral RNA obtained from infected cell culture supernatants using specific primers (forward: 5′ GAATTCGTAGGTGCGGCTCATTGATTGGGCTAAC 3′ and reverse: 5′ GTCGACGAACCTGTTGATTCAACAGCACC 3′). A stop codon (indicated in bold in the 5′ end of the forward primer), and a restriction site for EcoRI and SalI (underlined) at the 5′ end of the forward and reverse primers respectively, were incorporated during amplification. The PCR products were purified and cloned into the pEGFP-C1 construct, using the EcoRI and SalI enzymes (Thermo Scientific, NH, USA). The constructs generated were designated pGUD1, pGUD2, and pGUD4 for the DENV-1, DENV-2, and DENV-4 3′ UTR respectively. We were unable to amplify the 3′ UTR of DENV-3 RNA from the available DENV-3 isolates.