FIG 7.

Measurement of Env incorporation. Viral preparations of WT and V1/V2 mutants were lysed, and 100 ng of p24^Gag from the viral lysate was analyzed by Western blotting. The b13 antibody was used to measure the incorporation of Env into virions, while the p24^Gag antibody was used to control for the virion input. (A) Viral incorporation for the set of WT and V1 mutant Envs corresponding to pair 109. The ratio between the intensities of the Env and p24^Gag bands was first calculated for all the genotypes. Then, the fold change in Env incorporation between the mutant and its corresponding WT was calculated by dividing the ratio of Env/p24 obtained for the mutant by the one obtained for the corresponding WT. These fold changes are given for each mutant of transmission pair 109. (B) Relationship between changes in Env incorporation and V1/V2 length. The Mut/WT fold change in Env incorporation was then graphed against the changes in Env length measured by subtracting the number of amino acids of the WT sequence from the number of amino acids of the mutant (WT − Mut).