FIGURE 3. Induction of high-titre neutralizing antibodies against clade B viruses through the highly heterologous DNA-prime protein-boost regime.

Data are shown for individual animals from groups 1 and 2 combined (n=24) (A–H). Lines represent median. Sera were collected before immunization (wk 0), 4 weeks after last DNA immunization (DNA), 4 weeks after first SIV_mac239gp140 boost (DNA/gp140) and 2 weeks after the second SIV_mac239gp140 boost (DNA/gp140/gp140). Three months later sera were analyzed for the longevity of responses (3 mo after last boost). High ID₅₀ neutralizing titres were detected in a TZM-bl assay against tier 1 isolates from clade B SF162.LS (A) and MN.3 (B). Purified IgGs were tested in a TZM-bl assay against HIV-1 clade B SF162 and BX08 (C and D). Percent neutralization is shown using 130 μg/ml IgG final concentration approximately corresponding to a 1/80 serum dilution and dotted line indicates ID₅₀. Neutralizing titres in sera were detected in a TZM-bl assay against tier 1 isolates from clade C (MW965.26, E) and CRF01 AE (TH023.6, F). An arbitrary color code indicate the animals with the highest titres against SF162.LS in red (n=8), lowest in blue (n=8) and those in between in yellow (n=8). These colors are kept throughout the figure to be able to track the animals and their respective response to other viruses. ID₅₀ titres in sera from groups 1 and 2 were tested in the A3R5.7 assay against clade B viruses RHPA.LucR (G) and SC22.3C2.LucR (H). Neutralization titres obtained in the TZM-bl assay for the control groups that received control DNA and albumin (Gr.3, displayed in green) or only SIV_mac239 protein without a DNA prime (Gr.4, displayed in blue) are shown for neutralization of HIV-1 MN.3 (I) and the lab-adapted sensitive TCLA-SIV_mac251 isolate (J). Significant values are indicated by *** p<0.001, **p<0.01 and *p<0.05 using One-Way ANOVA with Multiple Comparison Test.