FIG. 4.

Neutralization of primary isolates by anti-V3 MAbs derived from individuals infected with non-B- and B-subtype viruses. Neutralization of primary isolates was performed in the GHOST cell neutralization assay, with MAbs at a final concentration of 25 μg/ml. The cutoff value of 29% is based on the 95% confidence level obtained with 60 experiments using the nonneutralizing human anti-C2 MAb 847. The percentages represent the means from three separate experiments. Light gray cells indicate neutralization in excess of the cutoff value; dark gray cells indicate virus/MAb combinations giving >50% neutralization. nt, not tested.