Analysis of the binding affinity of 2B10 and 2E4 scFvs by ELISA. Different dilutions of BG505:SOSIP.664 gp140 (10–800 nM) were incubated with fixed concentration of the two scFvs and unbound antibody was detected by ELISA. The experiment was repeated at least twice. Saturation binding curve was plotted between free antigen Vs specific binding through non-linear regression analysis.