FIG. 1.

Neutralization sensitivity as determined on human PHA-stimulated PBMC. (A) One hundred TCID₅₀ of the primary isolate HIV_Ams37/ml, before (●) and after (○) in vitro passage through chimpanzee PBMC (HIV_Ams37/ch-in vitro). Viruses were incubated with increasing concentrations of sCD4, IgG1b12, gp68, and gp13 or increasing dilutions of HIVIG and Ams^hps as indicated. P24 production was measured, and mean OD values were calculated from quadruplicate cultures from at least duplicate experiments. The percent neutralization was calculated by determining the reduction in supernatant p24 production in the presence of the neutralizing agents relative to control cultures lacking these agents. (B) Neutralization sensitivity of the primary isolates HAN2 (■) and HAN2 after one (HAN2/ch-in vitro-p1; □) or three (HAN2/ch-in vitro-p3; ▨) in vitro passages through chimpanzee PBMC.