IMMUNIZATION OF MONKEYS WITH BACULOVIRUS-DENGUE TYPE-4 RECOMBINANTS CONTAINING ENVELOPE AND NONSTRUCTURAL PROTEINS - EVIDENCE OF PRIMING AND PARTIAL PROTECTION

Groups of rhesus monkeys were immunized with baculovirus-dengue type-4 (DEN-4) recombinant-infected cell extracts. One recombinant contained all of the DEN-4 structural proteins and two nonstructural (NS) prote ins (C-M-E-NS1-NS2a), while the other was a fusion protein containing a portion of the respiratory syncytial virus G glycoprotein and DEN-4 envelope glycoprotein (RSVG-E). Both preparations were immunogenic; al l monkeys receiving either immunogen responded with the production of antivirion antibodies in enzyme immunoassays. All except one monkey re ceiving the recombinant b(C-M-E-NS1-NS2a) made antibodies to NS1. One monkey that received b(RSVG-E) showed the production of low levels of neutralizing antibodies. Following challenge with unmodified DEN-4 vir us, seven of nine monkeys in the immunized group became infected and w ere viremic for a mean of 4.1 days. The control, sham-inoculated monke ys were also viremic; the mean number of days of viremia in this group was 4.7 days. The remaining monkeys in the immunized group (n = 7), a lthough not protected, had evidence of priming. Hemagglutination inhib ition antibody responses following challenge indicated an anamnestic r esponse in this group of animals. Based on these results, it was concl uded that future immunization schedules should be altered to optimize immune responses and that immunization with more potent and purified i mmunogens would probably result in higher seroconversion rates and ant ibody levels in monkeys.