FIGURE 2.
ALVAC-SIV–primed FLSC boosted animals have increased recognition of gp120 peptides. (A) Binding Ab titers to monomeric gp120 proteins in ALVAC-SIV/gp120 and ALVAC-SIV/FLSC–vaccinated animals measured in serum 2 wk after the last vaccination. (B) Binding Ab titers to the FLSC immunogen in vaccinated animals measured in serum 2 wk after the last vaccination. Significantly higher binding was observed in the ALVAC-SIV/FLSC group compared with the ALVAC-SIV/gp120 group measured by the Mann–Whitney–Wilcoxon test with a p value <0.0001 for both proteins. (C) All data for the ALVAC-SIV/gp120 group have been previously reported (24). Ratio of Abs binding to the FLSC immunogen versus the monomeric gp120 immunogen (FLSC/gp120). This ratio demonstrates the abundance of FLSC-specific Abs. It was significantly higher in the ALVAC-SIV/FLSC group compared with the ALVAC-SIV/gp120 group evaluated by the Mann–Whitney–Wilcoxon test with p values <0.0001 for both proteins. (D) Peptide binding to 89 overlapping linear peptides that span SIVmac251 gp120. Shown is the average binding measured as absorbance to animals in the ALVAC-SIV/FLSC group on top and the ALVAC-SIV/gp120 group on the bottom. The constant regions of gp120 are shown in black and/or white bars, whereas the variable loops are in color (E). Comparative recognition of overlapping peptides presented as the difference between the median absorbance in the ALVAC-SIV/FLSC group, relative to the ALVAC-SIV/gp120 group, is shown in red on the right y-axis. The statistical significance of the differences is shown by the Z statistic of the Mann–Whitney–Wilcoxon test in black, on the left y-axis, with the dashed lines marking significance at the p < 0.056 level after a stringent correction for multiple comparisons by the Hochberg method. Increased recognition by the ALVAC-SIV/FLSC group is presented as positive (0–6) on the top half of the graph, whereas increased recognition in the ALVAC-SIV/gp120 group is presented as negative (−6 to 0) on the lower half of the graph.