Incorporation of Env glycoproteins into virions. NL4-3 viruses containing the WT and mutant Env proteins were produced in 293T cells and pelleted through a 25% sucrose cushion. Resuspended viral pellets were then subjected to p24 ELISAs, gp120 ELISAs, and gp41 western blotting. Incorporation of Env into virions is calculated as the ratio of gp120/p24 (A) and gp41/p24 (B) and shown as the percentage of WT. The data represents results from three independent experiments conducted in triplicate. The error bars represent the standard deviation of the means.