Construction of recombinant viruses
Several gene fragments containing prM-E of ZIKV (accession: KX601168.1) were designed (strategies shown in Fig. 1A). The gene fragment “ZI-△-PA” was obtained by overlap PCR, in which the sequences from the N-terminus to the C-terminus were prM-E of ZIKV (with deletion of the stem-transmembrane (ST-TM) region), a linker and protein anchor 3 (PA3, containing three lysin motifs). In ZI-JE-△-PA, the signal peptide of ZI-△-PA was replaced with the signal peptide of Japanese encephalitis virus (JEV) [14]. In ZI-GP-△-PA, the signal peptide of ZI-△-PA was replaced with the gp67 signal peptide. Signal peptide replacement was performed by PCR. All of the sequences were optimized for insect cells and synthesized in pUC vector by Sangon Biotech (Shanghai, China).
The above-mentioned target genes were cloned into the baculovirus transfer vector pFastBac Dual under the pH (Not I + HindIII) and p10 (Sma I + Nhe I) promoters. Then, the vector was transformed into E. coli DH10 Bac/AcMNPV competent cells, and the recombinant baculovirus plasmid (bacmid) carrying two copies of the target genes was obtained. The bacmid was transfected into Sf9 cells to obtain recombinant baculovirus using Cellfectin II Reagent (Invitrogen Co., Carlsbad, CA, USA) according to the manufacturer’s instructions.