Figure 3.

Induction and boosting of cross-neutralizing anti-V3 Abs in the absence of viremia. Plasma samples (weeks 0 and 7) were tested for neutralizing activity against the challenge virus, SHIV-1157ipEL-p (A) and the heterologous clade B SHIV_SF162P4 (B) by TZM-bl assay [20]. Neutralization titers are expressed as the reciprocal plasma dilution inhibiting 50% of virus infection (IC₅₀). Each bar represents the average titer of at least two independent assays using triplicates of each sample and error bars show the SEM. Plasma nAb titers were compared between weeks 0 (before live-virus challenges) and 7 (after 5x multiple low-dose challenges). Plasma samples were incubated with either medium (plasma only, white bars) or one of the two peptide sets (red bars, 1084i V3; blue bars, consensus clade C V3) and IC₅₀ values were calculated. In case of a decreased IC₅₀ (depletion of neutralizing activity), percentages illustrate the degree of inhibition reached with each peptide set. P-values are shown (significance after Bonferroni correction, P < 0.025). Gray box and asterisks indicate neoantigen reactivity.