Fig. 1

Expression vector construct and expression analysis. a Schematic illustration of the expression plasmid pYEG-LTB-scEDIII. Western blot analysis of recombinant Escherichia coli heat-labile toxin protein B-subunit (LTB) fused to the consensus dengue envelope domain III (scEDIII) in cell-free extracts (CFEs) using b anti-LTB IgG and c anti-dengue IgG antibodies under non-denaturing (lanes 1–4) and denaturing conditions (lanes 5–8). Lanes 1 and 5 contain 1 µg of total soluble protein (TSP) extracted from E. coli-expressed scEDIII [14] and lanes 2 and 6 contain 1 µg of TSP from S. cerevisiae-expressed LTB [32] as positive controls. Lanes 3 and 7 contain 40 µg of TSP extracted from mock-transformed yeast as negative controls. Lanes 4 and 8 contain 40 µg of TSP extracted from recombinant LTB-scEDIII. SM represents protein size marker. Arrows indicate the recombinant LTB-scEDIII protein. The numbers in bold letters on the right indicate the estimated sizes in kDa