Construction and expression of the prM-E-△-PA3 fusion protein
Based on the baculovirus expression system, we constructed several prM-E-△ -PA3 fragments fusing the ZIKV prM-E-△ gene (ST-TM region deletion) and the gene for the carrier protein PA3, as shown in Fig. 1A. In the construction strategies, signal peptides from different sources, such as JEV and gp67 (a surface glycoprotein of baculovirus), were considered. Three kinds of recombinant baculoviruses (ZI-△-PA vir, ZI-JE-△-PA vir and ZI-GP-△-PA vir) were constructed and were seeded in Sf9 cells for ZIKV-E protein detection. IFA of the ZIKV-E protein showed positive results, with bright green fluorescence (Fig. 1B), and the cell control showed red due to Evans blue. To determine the localization of the target protein, the supernatants and sonicated supernatants of cell cultures were subjected to WB analysis. The results showed that ZI-△-PA, ZI-JE-△-PA and ZI-GP-△-PA protein were secreted into the supernatant (Fig. 1C). The IFA and WB results implied that the prM-E-△ -PA3 (ZI-△-PA, ZI-JE-△-PA and ZI-GP-△-PA) protein reacted with an anti-flavivirus mAb with good antigenicity. When ST-TM was not included, the target protein was secreted.