Fig. 1

Construction of recombinant baculoviruses, and E2 protein expression and display. a Schematic representation of the constructed Bac-CMV-E2-gp64. P_PH, polyhedrin promoter of baculovirus; pCMV, cytomegalovirus immediate early promoter/enhancer; gp64 SP, gp64 signal peptide; His6 tag, a stretch of six histidine residues; E2 ectodomain, HCV E2 ectodomain gene; gp64 TM, gp64 transmembrane; gp64 CTD, gp64 cytoplasmic domain; SV40PA, Simian virus 40 Poly A. b Expression of E2 protein in SF9 cells. The cells were infected with recombinant Bac-CMV-E2-gp64 or wild type baculovirus (Bac-WT) as a negative control. Three days post infection, the infected cells supernatants were separated on 10% SDS-PAGE gel, and subjected to western blot analysis using anti-His MAb and goat anti-mouse IgG antibodies. E2 protein is visible in a 64 kDa band, while no band was observed for Bac-WT. c Immunofluorescence microscopy of SF9 cells infected with recombinant baculovirus Bac-CMV-E2-gp64. The E2 protein was observed to be located on plasma membrane of cells infected by Bac-CMV-E2-gp64 (left) while no signal was detected in uninfected cells (right). d Display of the recombinant E2 protein on the baculoviral envelope. Immunogold electron micrograph of the purified baculoviruses Bac-CMV-E2-gp64 and Bac-WT was performed using mouse anti-His MAb as the primary antibody and anti-mouse IgG conjugated with 10 nm gold particles as the secondary antibody. Gold particles on the envelope of baculovirus Bac-CMV-E2-gp64 were detected (left) whereas no gold particles were observed on envelope of Bac-WT (right)