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.

The purified antibodies were tested in plaque reduction neutralization tests (PRNTs) using a live SARS virus on the permissive Vero E6 cell line. The results are summarized in Table I and showed five antibodies exhibiting 50% neutralization activity at concentrations ranging from 0.59 to 21 mg/ml. All three of the antibodies that had blocked spike binding to Vero E6 cells (i.e. 4049Fab14, 3889Fab33, 3889Fab35) also showed neutralization in the PRNTs. Two additional antibodies that had not blocked spike binding did neutralize SARS infection, suggesting an inhibitory mechanism other than direct blockage of receptor binding epitopes. One of these antibodies, 4049Fab28, was discovered using viral isolates as the antigen. 4049Fab14 and 3889Fab33 showed 80% neutralization at concentrations of ,0.7 and 4.75 mg/ml, respectively. 4049Fab14 exhibited the best neutralization activity and was chosen for the subsequent optimization studies.