Neutralization of late-stage sera against Env escape variants. Serum samples from Rh805, Rh806, Rh807, and Rh808 at a late stage were tested against selected escape Env variants. ID50 titers were calculated and are shown. Viruses tested are identified in the legend by the rhesus ID, the plasma sample that was the source of the envelope clone, and a clone number (e.g., 805 24w-2).