Induction of linear and conformational V2-specific antibodies using HIV-1 gp145 clade B envelope protein as the immunogen (P4505)

Abstract

Abstract TThe potential importance of binding antibodies (Abs) in preventing HIV-1 acquisition was recently demonstrated by the case control analysis of the RV144 phase III HIV-1 vaccine trial, which showed that binding Abs to a gp70 scaffolded V1V2 loop of gp120 correlated inversely with infection. We examined if immunization with a HIV-1 env trimer in the absence of any priming vector could induce functional V2-specific Abs. The clade B HIV-1 gp145 env protein consisting of gp120, gp41 ectodomain, and MPER, trimerized with foldon was expressed in 293F cells and purified. The protein adjuvanted with liposomes containing lipid A was used to immunize New Zealand white rabbits. Strong Ab binding titers (50,000-400,000) were induced to env epitopes including V2 and V3 peptides (linear) and MuLV gp70-scaffolded V1V2 protein (conformational) as measured by ELISA and Biacore. The sera neutralized infectious molecular clones and pseudoviruses in PBMC, monocyte-derived macrophage, and TZM-bl assays. Purified IgG neutralized primary US-1 in a dose-dependent manner in the macrophage assay. Depletion of linear V2 or V3 epitope-specific Abs retained the conformation-specific gp70 V1V2 binding Abs and did not completely abolish neutralization. Further depletion of gp70 V1V2-specific Abs significantly reduced neutralization. These data indicate that gp145 trimers induce linear as well as conformational V2-specific antibodies and might be a good candidate for designing a preventative HIV-1 vaccine.