ANALYSIS OF C-TERMINALLY TRUNCATED DENGUE-2 AND DENGUE-3 VIRUS ENVELOPE GLYCOPROTEINS - PROCESSING IN INSECT CELLS AND IMMUNOGENIC PROPERTIES IN MICE

We constructed two recombinant Autographa californica nuclear polyhedr osis baculoviruses. Spodoptera frugiperda (Sf9) cells containing these constructs produce carboxy-terminally truncated envelope E proteins r epresenting dengue (DEN) virus serotypes 2 and 3. The two recombinant proteins contained their homologous signal sequences at the N terminus and were truncated by 71 and 74 amino acids at the C terminus, respec tively, This allowed the translocation of the recombinant proteins to the endoplasmic reticulum followed by glycosylation processing and sec retion into the extracellular medium. An additional unglycosylated for m which was not secreted was detected inside the infected Sf9 cells. S era from Swiss mice immunized with the infected Sf9 cell lysates gave a DEN cross-reactive response in ELISA and substantial amounts of neut ralizing antibodies to the homologous virus. Similar antibody titres w ere obtained when the two recombinant proteins were inoculated concomi tantly. BALB/c mice were vaccinated with three doses of the recombinan t E proteins, taken as monovalent or bivalent immunogens, and challeng ed with mouse-adapted DEN-2 virus. DEN-2 E protein induced a good prot ection (90%) against lethal encephalitis and recombinant DEN-3 E prote in gave a substantial cross-protection (54%). Eighty-two percent of th e mice immunized with a mixture of both recombinant E proteins survive d the DEN-2 virus challenge.