Please note that the serial serum dilutions shown are five-fold. Thus, the 50% neutralization endpoints calculated by linear regression analyses were 5.0 and 121.7-fold greater for the SF162 wild type and SF162-N332A variant, respectively, than for the SF162-K160N variant. These results demonstrate that the neutralization of strain SF162 was not mediated by antibodies with specificities like PG9/16 or PGT121/126. If antibodies dependent upon these glycans are involved in neutralization of other strains, they do not cross-react with SF162. Recent evidence indicates a correlation between vaccine efficacy in the Thai HIV vaccine efficacy trial and levels of antibody Gambogic-acid binding to various V1/V2 5,5-Dimethyloxazolidine-2,4-dione peptides. The prototype assay for this activity involved binding to the scaffold fusion protein, gp70-V1/V2, developed by Pinter et al. We evaluated the induction of antibodies targeting the V1/V2 region in ELISA assay using that scaffold fusion protein, as shown in Figure 4D. Each of the three immunized rabbits developed substantial antibody responses binding the V1/V2 fusion peptide. These assays were performed using ELISpot and flow cytometry techniques. In each case we used R2gp140-GCN4-L as antigen for detection of antibody producing cells in tissues of rabbits harvested 10 days after dose 7. To address possible concern that immunizations might have induced significant antibody responses against the GCN4 or linker domains of the fusion protein, we first tested the post 7 dose rabbit sera for binding to proteins with or without these domains in ELISA, as shown in Figure 5A. The two upper panels show relative binding to Hendra virus soluble G protein with or without GCN4 fusion domains. In neither case was there greater binding of the HeV-sG by immune than control sera, nor was there greater binding by immune sera of HeV-sGGCN4 than HeV-sG. The lower panel in Figure 5A shows comparative binding of R2gp140-GCN4 and R2gp140GCN4-L by the immune rabbit sera. There was slightly greater binding of the gp140-GCN4-L protein than the other. However, the difference was not significant, when the results obtained at log10 =3.4 were compared by paired student T test.