N362 is associated with enhanced fusogenicity and reduced sensitivity to T-20. For each of the Envs cloned from the cross sectional panel of primary R5 HIV-1 viruses, the maximal levels of fusion (determined at 12 h post-fusion) (A), cell surface Env expression on 293T effector cells (B), and IC50 (C) and IC80 (D) values for sensitivity to inhibition by T-20, were stratified based on the presence or absence of N362. Box plots were constructed from mean values of duplicate experiments with each Env using Prism version 4.0c (GraphPad Software). Boxes represent upper and lower quartiles and median scores, and whiskers represent minimum and maximum values. The data shown are representative of 3 independent experiments.