Rapid discovery and optimization of therapeutic antibodies against emerging infectious diseases

Rogers, J.; Schoepp, R.J.; Schröder, O.; Clements, T.L.; Holland, T.F.; Li, J.Q.; Li, J.; Lewis, L.M.; Dirmeier, R.P.; Frey, G.J.; Tan, X.; Wong, K.; Woodnutt, G.; Keller, M.; Reed, D.S.; Kimmel, B.E.; Tozer, E.C.

In the PRNT, all of the variants achieved 80% neutralization of the SARS virus at concentrations equal to or lower than the WT chimera. The best antibody (i.e. 2978/10) achieved 80% neutralization at an 8-fold lower concentration than WT (Fig. 5 ). Those variants with equal ability to the WT antibody are not shown. To determine whether the enhanced neutralization efficiency correlated with increased affinity, the kinetics of the 2978/10 and WT antibodies were measured. A 40-fold improvement in affinity was observed for 2978/10 compared to the WT chimera (K D ¼ 0.967 versus 38.5 nM, respectively) ( Table III) . The 2978/10 variant contained the two mutations from the top two individual clones (51E7 and 52G3) placed in the light chain framework exhibiting the best activity (61G4) ( Table II) . No additive or synergistic effect was observed (2978/10 is somewhat less effective at neutralization than 51E7 alone), which could be due to the small library size and/or the simultaneous change to just two possible human frameworks.