SCREENING OF HIV-1 ENV GLYCOPROTEINS FOR THE ABILITY TO RAISE NEUTRALIZING ANTIBODY USING DNA IMMUNIZATION AND RECOMBINANT VACCINIA VIRUS BOOSTING

HIV-1 envelopes from two series of primary isolates (from Swedish pati ents 5 and 6), from JR-FL and Bat (prototypic monocyte/macropbage trop ic viruses) and from HXB-2 (a prototypic T-cell-line-adapted virus), h ave been screened for their ability to elicit neutralizing antibody to HIV-1. Rabbits were primed by gene gun inoculation with plasmids expr essing secreted monomeric (gp120) and oligomeric (gp140) forms of each Env. After four to six DNA immunizations administered over a 1-year p eriod, rabbits were boosted with 10(8) plaque-forming units of a mixtu re of seven recombinant vaccinia viruses which express chimeric gp140 Envs (primary clade B sequences in a IIIb-related BH10 backbone). Neut ralizing antibodies were assayed against two T-cell-line-adapted virus es (MN and IIIb), two non-syncytium-inducing (NSI) and two syncytium-i nducing (SI) primary isolates, and two HIV-1 -NL4-3-recombinants with patient 5 or 6 Envs (NL4-3/5A, NL4-3/6C). The DNA priming and recombin ant vaccinia virus boosting raised low titers of neutralizing antibody in 10 of 19 rabbits. The highest titers of neutralizing activity (sim ilar to 1:150 for MN) were raised in rabbits DNA primed with Envs from Swedish patient 5. These sera cross-neutralized IIIb and MN but did n ot neutralize the primary isolates or the NL4-3 recombinant with the h omologous 5A Env. Sera from rabbits primed with the HXB-2 Env DNA were , for the most part, type-specific for neutralization of IIIb. In one of three assays, sera from rabbits primed with plasmids expressing the JR-FL and Bat Envs had possible low titer neutralizing activity for t wo NSI, but not two SI, primary isolates. Our results highlight the lo w immunogenic potential of the HIV-1 Env and demonstrate that differen t Envs have different potentials to raise low titer neutralizing antib ody. (C) 1997 Academic Press.