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 vir us envelope glycoprotein truncated of 102 amino acids (aa) at its C-te rminus (D2E Delta 102). The production, processing and transportation of the recombinant protein in baculovirus-infected Spodoptera frugiper da (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 transp orted through the Golgi complex and their N-oligosaccharides of the hi gh man-nose type were processed to the complex mannose type. D2E Delta 102 transited to the plasma membrane and was secreted whereas D2E Del ta 71 presumably remained associated with the plasma membrane. The rea ctivities of the recombinant proteins with neutralizing monoclonal ant ibodies were similar. Both intracellular and extracellular D2E Delta 1 02 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) w as lower than that induced with D2E Delta 71 (90%, P < 0.001). Sixty-e ight percent (P < 0.001) of mice vaccinated with 5 mu g of extracellul ar D2EL Delta 102 protein were protected against lethal challenge.