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.

These top 10 antibodies were purified and analyzed by PRNTs using live SARS-CoV on the permissive Vero E6 cell line. The results are summarized in Fig. 4 and show that one of the humanized clones (61G4) achieved 80% neutralization of the SARS virus at a 3.5 -4-fold lower concentration compared to the mouse -human chimera (WT) and a second humanized clone (61H4) was equal to WT. Clones not shown in Fig. 4C had 80% neutralization capabilities less than wild-type (WT) (i.e. 6.25 mg/ml). Thus, after screening $3200 clones in duplicate, we found two humanized antibodies that either maintained functional activity or showed an enhancement of activity. The fact that some clones exhibited lower neutralization activity than WT, although showing enhanced binding to the spike protein, is not surprising, as one should not expect a perfect correlation to exist between the spike protein ELISA and the SARS viral neutralization assay.