FIG. 6.

Pre- and postattachment neutralization assays. (A) For preattachment neutralization, pseudovirions were incubated with the indicated dilutions of monoclonal antibodies for 1 h at 4°C and subsequently added to COS7 cells. Infection was monitored for 72 h after the pseudovirions were replaced by supplemented DMEM. (B) For postattachment neutralization, pseudovirions were bound to COS7 cells for 1 h at 4°C, and cell-bound virions were exposed to antibodies at the indicated dilutions. Antibodies were removed after 1 h at 37°C. A value of 100% infectivity corresponds to 72 infected cells. Antibody H33.J3, but not antibody H33.B6, displays different capacities in pre- and postattachment neutralization assays.