FIG. 1.

Sensitivities for sCD4-, IgG1b12-, 2F5-, 2G12-, and 4E10-mediated neutralization of coexisting R5 and (R5)X4 HIV-1 obtained early or late after X4 emergence. Neutralization was determined by a 7-day culture of clonal virus isolates on PBMC in the presence or absence of serial dilutions of neutralizing agent, followed by analysis of p24 production by ELISA. Distribution of IC₅₀s for individual virus clones as determined by linear regression is shown. Bottom, middle, and top horizontal lines represent the 25th, 50th, and 75th percentiles, respectively. Per time point, IC₅₀s of R5 and (R5)X4 viruses were evaluated using the Mann-Whitney U test. Data shown are from one representative experiment out of two to three performed.