Cell-to-cell fusion of HeLa cells expressing different patient-derived envelopes with changes at positions 38 and 140 in gp41. Cocultures of Env+ HeLa cells with TZM-bl cells were performed for 6 h, and fusion activity was determined by measuring the luciferase activity. The relative fusogenicity of each recombinant Env was calculated by normalization against the luminescence obtained using the recombinant Env of NL4-3 (100%) for each experiment. The boxes represent the median and interquartile range of the values. The median values obtained from the clones constructed from samples from each patient were compared in an inter-patient analysis, and those obtained from baseline (white boxes) and after treatment samples with the change V38A (gray boxes) clones were also compared in an intra-patient analysis using a nonparametric Mann Whitney test. * p < 0.05 *** p = 0.001 ns, non-significant differences.