Effect of mutations in the MPER on Env antibody sensitivity. Antibody neutralization of pseudoviruses containing either the wild-type 92UG037.8 Env or one of the MPER mutants shown was determined for the ordinarily nonneutralizing antibodies, b6 (CD4 binding site; blue), 3791 (V3; cyan), and 17b (CD4-induced; purple) and for the trimer-specific bnAbs, PG9 (orange), PG16 (red), and PGT145 (magenta). The CD4 binding site bnAb VRC01 (green) was a control. The experiment was performed in duplicate.