Fig 6.

VRC06 and related MAbs recognized quaternary epitopes on Env functional trimer. (A) Binding of VRC03, VRC06, and VRC06b to JR-FL gp160ΔCT-transfected 293T cell surface by FACS assay, represented by MFI (mean of fluorescence intensity). JR-FL gp160ΔCT is the cleaved trimer; JR-FL gp160ΔCT cleavage-defective is the uncleaved trimer, which contains two mutations that render it cleavage defective (29). (B) VRC06 neutralization potency against JR-FL gp160ΔCT virus was affected by Env mutations leading to an alteration of neutralization sensitivity. Top graphs, Env mutants Δ301 and T569A/I675V display enhanced neutralization sensitivity to CD4bs MAb F105 but substantially decreased neutralization sensitivity to VRC06; the bar graphs on the bottom depict the effects of the Env mutations Δ301 and T569A/I675V on the HIV sensitivity (IC₅₀ values) to VRC06 and other CD4bs ligands.