Figure 7. Both immunization regimens elicited antibody responses capable of neutralizing lab-adapted, but not primary isolates of SIV.

Binding antibody responses were measured for Group A (A) and Group B (B) animals at a 1/20 dilution of plasma on ELISA plates coated with whole-virus lysate. The mean and standard deviation (error bars) of the antibody responses in each group are plotted in gray. Arrows indicate the time points of each inoculation, and the dashed line indicates the mean level of non-specific binding for pre-immune plasma at the time of the first inoculation. (C) SIV-specific neutralizing antibody titers at the time of challenge. Serial two-fold dilutions of plasma were tested for the ability to inhibit infection of target cells harboring a Tat-inducible SEAP reporter gene by lab-adapted SIV_mac251 (SIV_mac251_LA), SIV_mac316, SIV_mac155T3, and SIV_mac239. The dashed line in each plot indicates 50% neutralization of virus infectivity.