FIGURE 2. Schematic representation of the immunization regimes and binding antibodies elicited.

A) Schematic immunization schedules of two independent studies (n= 48) and a comparative group 5 (n=4) with arrows depicting immunizations. Sera were collected before immunization (wk 0). Animals (New Zealand white rabbits) received a mix of three clade B env-DNA plasmids at weeks 0 (twice first week), 4, 8 and 12 (200 μg DNA by i.d. electroporation). Sera were collected 4 weeks after last DNA immunization (wk 16). Animals then received a heterologous protein SIV_mac239 gp140 by i.d. injection and sera were collected 4 weeks after first protein boost (50 μg)(wk 20). Animals received a second protein boost with SIV_mac239 gp140 4 weeks after the first protein immunization and sera were collected 2 weeks after second protein boost (50 μg) (wk 22). Three months later sera were analyzed for memory responses (wk 34). In the first study, twelve animals were included in Gr. 1 and the second study entailed six animals in this group. In the first study, Gr. 2 (n=12) received AAC adjuvant during the DNA priming phase and in the second study Gr. 2 (n=6) received a TLR5 agonist pFliC. Gr. 3 (n=6) received control DNA and albumin protein and Gr. 4 received three immunizations with SIV_mac239 gp140 protein by i.d. injection (n=6). Gr.5 received the mix of three clade B env DNA immunizations followed by one i.d. injection with HIV-1_{ITM-1_4} gp140 (n=4). (B) Endpoint titres (log10) of IgG binding to SIV_mac239 gp140 (white bars) or heterologous HIV-1_UG37 gp140 (black bars) as measured by ELISA analyzing sera obtained before immunizations (wk 0) and after immunizations at wk 22 from the first study. Data are depicted as median and range. (C) Endpoint IgG titres from the second study are shown for binding to heterologous HIV-1_UG37 gp140 and SIV_mac239 gp140, as marked, in sera obtained at wk 0 (black bars), after the DNA priming (grey bars), and after the first gp140 boost (white bars) from the second study. Statistically significant lower endpoint IgG titres against SIV_mac239 were found in Gr. 3 and against HIV-1_UG37 in Groups 3 and 4 when compared with Groups 1 and 2 (One-way ANOVA using Bonferroni’s Multiple Comparison Test p<0.05).