Extended Data Fig. 7: Antibodies isolated from cows immunized using BG505 sgp140 SOSIP.664 immunogens exhibit a preference for state 2.

a, FRET histogram of HIV-1_BG505(T332N). b, Neutralization curves of HIV-1_BG505 by NC-Cow1, NC-Cow8, NC-Cow9 and NC-Cow10 antibodies. Data are presented as mean ± s.d. determined from three independent experiments in triplicate. c–e, FRET histograms of native HIV-1_BG505 in the presence of 10 μg ml⁻¹ NC-Cow1 (c), NC-Cow8 (d) and NC-Cow10 (e). f, The FRET histogram of HIV-1_BG505 that carries the T332N substitution in Env is overlaid with that of wild-type HIV-1_BG505. The T332N substitution in HIV-1_BG505 Env does not detectably change the conformation of the Env. g, h, Cow antibodies (NC-Cow1, NC-Cow8, NC-Cow9 and NC-Cow10) shift the conformational landscape of native Env on the virus from state 1 towards that of BG505 sgp140 SOSIP.664 (state 2). FRET population histograms (a, c–e) represent mean ± s.e.m., from three independent populations of smFRET traces. i, j, Ligand preferences for states 1 and 2 probed by antibody staining of cell-expressed HIV-1_JR-FL Env(ΔCT). Increasing amounts of the first ligand were pre-bound to cells for 1 h. The cells were washed, incubated with the second dye-labelled probe for 30 min, and the binding was quantified by flow cytometry. The ratio of measured mean fluorescence intensity (MFI) was normalized to that seen in the absence of pre-bound ligand (Methods). Matched combinations (state 1 and state 1 or state 2 and state 2) and non-matched combinations (state 1 and state 2 or state 2 and state 1) at the highest concentration of pre-bound first ligand were compared, and statistical significance was evaluated using a paired Student’s two-sided t-test. *P < 0.05. Note that the strong interference between 3BNC117 and PGT151 is due to a steric clash between the two antibodies, and was included as a control.