We thank A. B. Ward, R. W. Sanders and P. J. Bjorkman for discussions, R. Blakemore for assistance with molecular modelling, D. Burton and M. Feinberg for reagents including PGT121, PGT122, PGT145, PGT151 and NC-Cow1, NC-Cow8, NC-Cow9 and NC-Cow10 antibodies, and the AIDS Research and the Reference Reagent Program (Division of AIDS, NIAID, NIH) for the antibodies 3BNC117, 10-1074, PG9 and PG16. This work was supported by NIH grants RO1 GM116654 and UM1 AI100645 to W.M., RO1 GM098859 to S.C.B., RO1 AI124982 and RO1 AI100645 to J.G.S., K22 AI116262 to J.B.M., CRC Tier 2 RCHS0235 and a CIHR foundation grant 352417 to A.F., PO1 GM056550 to W.M., J.G.S., S.C.B, A.B.S. and C.A., by a Brown Coxe Fellowship to M.L., a fellowship from the China Scholarship Council-Yale World Scholars to X.M., by the International AIDS Vaccine Initiative’s (IAVI’s) Neutralizing Antibody Consortium to P.D.K. and by the Intramural Research Program of the Vaccine Research Center (NIAID, NIH) to P.D.K. and A.B.M., and by the SFB1129 and the Emmy-Noether programme (project number 317530061) of the German Research Foundation to E.A.L. and I.N.-S., respectively.

Reviewer information

Nature thanks David Millar, Alexandra Trkola and the other anonymous reviewer(s) for their contribution to the peer review of this work.