The neutralizing activity of the mAbs was initially measured using 20 pseudotyped HIV-1 primary isolate envs characterized by different sensitivity to neutralization [44, 45] . The mAbs were tested at a fixed concentration (100 mg/ml) in a luciferase-based neutralization assay using HOS-CD4.R5 as target cells. Out of the 46 mAbs tested against the whole virus panel, 37 showed neutralizing activity on at least one isolate ( Figure 1A) . Three mAbs, HJ16, HGN194 and HK20, stood out for their breadth of neutralizing activity, neutralizing 10, 11 and 17 out of the 20 pseudoviruses, respectively ( Figure 1A) . These mAbs were further characterized in the same assay for their potency ( Figure 1B) . HJ16 showed high neutralizing activity, while HGN194 and HK20 were less potent. In addition, while most antibodies preferentially neutralized Tier-1 isolates, HJ16 preferentially neutralized Tier-2 isolates ( Figure 1A-B) .