The clade B and C HIV-1 Reference Panels of Env clones [44, 45] and the SF162 clone were obtained through the NIH-ARRRP. Other non-clade B isolates were provided by the Comprehensive Antibody Vaccine Immune Monitoring Consortium (CA-VIMC). HIV-1 subtype B clone JRFL was provided by Dennis Burton (Scripps Institute, La Jolla, US). Pseudoviruses were produced by co-transfecting HEK293T/17 cells with the envexpressing plasmids and the complementing viral-genome reporter gene vector, pNL4-3.Luc + .E 2 R + (kindly provided by John R. Mascola, VRC, NIAID, NIH, US).