Protective efficacy in mice of a secreted form of recombinant dengue-2 virus envelope protein produced in baculovirus infected insect cells.

We constructed a recombinant baculovirus encoding a dengue (DEN)-2 virus envelope glycoprotein truncated of 102 amino acids (aa) at its C-terminus (D2E delta 102). The production, processing and transportation of the recombinant protein in baculovirus-infected Spodoptera frugiperda (Sf9) cells and its immunogenic properties in mice were compared to those of a previously characterized recombinant DEN-2 E-protein with a 71aa C-terminal truncation (D2E delta 71). Both proteins were transported through the Golgi complex and their N-oligosaccharides of the high mannose type were processed to the complex mannose type. D2E delta 102 transited to the plasma membrane and was secreted whereas D2E delta 71 presumably remained associated with the plasma membrane. The reactivities of the recombinant proteins with neutralizing monoclonal antibodies were similar. Both intracellular and extracellular D2E delta 102 induced neutralizing antibodies in mice and were thus immunogenic. The level of protective immunity to DEN-2 virus encephalitis challenge in mice vaccinated with intracellular D2E delta 102 (80%, p < 0.01) was lower than that induced with D2E delta 71 (90%, P < 0.001). Sixty-eight percent (P < 0.001) of mice vaccinated with 5 micrograms of extracellular D2E delta 102 protein were protected against lethal challenge.