Potent vaccine sera target epitopes that overlap the CD4 binding site.

Selected vaccine sera (1:10 dilution) were competed against various biotinylated monoclonal bnAbs for binding to SOS E168K trimer VLPs by ELISA. E168K+N189A mutant trimer VLPs were used for assays involving biotinylated V2 quaternary mAbs to ensure a full epitope knock in [56]. Three previously mapped HIV-1-infected plasmas were included for reference purposes [54]. These are (epitopes in parentheses) 1702 (some MPER and unmapped nAb), 1686 (predominantly CD4bs nAb) and BB34 (predominantly MPER nAb). Numbers are expressed as the residual % binding titer of biotinylated mAb in the presence of competitor compared to its titer in the presence of a control rabbit prebleed or HIV-1 seronegative human plasma (from donor 210). Each assay was performed at least in duplicate. Standard errors are shown in S8 Fig.