FIG 4 .

Analysis of HIV-1 Env fusogenic activity. (A) Analysis of the ability to induce cell-to-cell fusion of HIV-1 Env proteins obtained from cluster LTNP-EC (dark gray bars), progressor individuals (light gray bars), or reference HIV-1 viral strains (SF162, NL4.3, BaL.01, and 89ES_061 [black bars]). Data are from three independent experiments, comparing mean values between groups (nonparametric Mann-Whitney test). (B) Spearman’s nonparametric correlation between HIV-1 transfer activity after cell-to-cell contact (a surrogate marker of binding of the Env protein to the CD4 molecule) and the fusion capacity of the Envs obtained from the LTNP-EC cluster viruses are shown. Mean values of the three independent experiments for each Env were used for the correlation analysis. (C) A fusogenicity index (FI) was calculated for each Env clone as the ratio of fusion activity and relative fluorescence intensity. Values for LTNPs, progressors, and reference Env clones are shown: n = 8, 6, and 4, respectively. Boxes represent medians and interquartile ranges of values.