FIG. 2.
Neutralization sensitivity of LW_H8res (open circles), LW_G9sens (solid circles), and IIIB (gray diamonds). We incubated 100 TCID50 of each virus inoculum with increasing concentrations of (a) sCD4, (b) MAb b12, (c) MAb gp13, (d) MAb gp68, (e) MAb F105, (f) MAb 902, (g) pooled polyclonal serum Amshps, and (h) pooled polyclonal serum HIVIg. MAbs b12, gp13, gp68, and F105 are directed to epitopes overlapping the CD4bs of gp120, whereas MAb 902 is directed to an epitope in the V3 loop of gp120. Incubation of virus with sCD4, MAbs, or sera was performed for 2 h at 37°C before PHA-stimulated PBMCs were added. The concentration of p24 in culture supernatants was measured, and the percent viral inhibition was calculated as the mean reduction in p24 level in triplicate cultures in the presence of the neutralizing ligand compared to that in cultures with virus only. IC50s were determined by linear regression when possible. Neutralization assays were performed at least twice.